1 /* -*- Mode: C; indent-tabs-mode:t ; c-basic-offset:8 -*- */
2 /*
3 * I/O functions for libusb
4 * Copyright © 2007-2009 Daniel Drake <dsd@gentoo.org>
5 * Copyright © 2001 Johannes Erdfelt <johannes@erdfelt.com>
6 *
7 * This library is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * This library is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with this library; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22 #include <config.h>
23
24 #include <assert.h>
25 #include <errno.h>
26 #include <stdint.h>
27 #include <stdlib.h>
28 #include <string.h>
29 #include <time.h>
30 #ifdef HAVE_SIGNAL_H
31 #include <signal.h>
32 #endif
33 #ifdef HAVE_SYS_TIME_H
34 #include <sys/time.h>
35 #endif
36 #ifdef USBI_TIMERFD_AVAILABLE
37 #include <sys/timerfd.h>
38 #endif
39
40 #include "libusbi.h"
41 #include "hotplug.h"
42
43 /**
44 * \page libusb_io Synchronous and asynchronous device I/O
45 *
46 * \section io_intro Introduction
47 *
48 * If you're using libusb in your application, you're probably wanting to
49 * perform I/O with devices - you want to perform USB data transfers.
50 *
51 * libusb offers two separate interfaces for device I/O. This page aims to
52 * introduce the two in order to help you decide which one is more suitable
53 * for your application. You can also choose to use both interfaces in your
54 * application by considering each transfer on a case-by-case basis.
55 *
56 * Once you have read through the following discussion, you should consult the
57 * detailed API documentation pages for the details:
58 * - \ref libusb_syncio
59 * - \ref libusb_asyncio
60 *
61 * \section theory Transfers at a logical level
62 *
63 * At a logical level, USB transfers typically happen in two parts. For
64 * example, when reading data from a endpoint:
65 * -# A request for data is sent to the device
66 * -# Some time later, the incoming data is received by the host
67 *
68 * or when writing data to an endpoint:
69 *
70 * -# The data is sent to the device
71 * -# Some time later, the host receives acknowledgement from the device that
72 * the data has been transferred.
73 *
74 * There may be an indefinite delay between the two steps. Consider a
75 * fictional USB input device with a button that the user can press. In order
76 * to determine when the button is pressed, you would likely submit a request
77 * to read data on a bulk or interrupt endpoint and wait for data to arrive.
78 * Data will arrive when the button is pressed by the user, which is
79 * potentially hours later.
80 *
81 * libusb offers both a synchronous and an asynchronous interface to performing
82 * USB transfers. The main difference is that the synchronous interface
83 * combines both steps indicated above into a single function call, whereas
84 * the asynchronous interface separates them.
85 *
86 * \section sync The synchronous interface
87 *
88 * The synchronous I/O interface allows you to perform a USB transfer with
89 * a single function call. When the function call returns, the transfer has
90 * completed and you can parse the results.
91 *
92 * If you have used the libusb-0.1 before, this I/O style will seem familar to
93 * you. libusb-0.1 only offered a synchronous interface.
94 *
95 * In our input device example, to read button presses you might write code
96 * in the following style:
97 \code
98 unsigned char data[4];
99 int actual_length;
100 int r = libusb_bulk_transfer(dev_handle, LIBUSB_ENDPOINT_IN, data, sizeof(data), &actual_length, 0);
101 if (r == 0 && actual_length == sizeof(data)) {
102 // results of the transaction can now be found in the data buffer
103 // parse them here and report button press
104 } else {
105 error();
106 }
107 \endcode
108 *
109 * The main advantage of this model is simplicity: you did everything with
110 * a single simple function call.
111 *
112 * However, this interface has its limitations. Your application will sleep
113 * inside libusb_bulk_transfer() until the transaction has completed. If it
114 * takes the user 3 hours to press the button, your application will be
115 * sleeping for that long. Execution will be tied up inside the library -
116 * the entire thread will be useless for that duration.
117 *
118 * Another issue is that by tieing up the thread with that single transaction
119 * there is no possibility of performing I/O with multiple endpoints and/or
120 * multiple devices simultaneously, unless you resort to creating one thread
121 * per transaction.
122 *
123 * Additionally, there is no opportunity to cancel the transfer after the
124 * request has been submitted.
125 *
126 * For details on how to use the synchronous API, see the
127 * \ref libusb_syncio "synchronous I/O API documentation" pages.
128 *
129 * \section async The asynchronous interface
130 *
131 * Asynchronous I/O is the most significant new feature in libusb-1.0.
132 * Although it is a more complex interface, it solves all the issues detailed
133 * above.
134 *
135 * Instead of providing which functions that block until the I/O has complete,
136 * libusb's asynchronous interface presents non-blocking functions which
137 * begin a transfer and then return immediately. Your application passes a
138 * callback function pointer to this non-blocking function, which libusb will
139 * call with the results of the transaction when it has completed.
140 *
141 * Transfers which have been submitted through the non-blocking functions
142 * can be cancelled with a separate function call.
143 *
144 * The non-blocking nature of this interface allows you to be simultaneously
145 * performing I/O to multiple endpoints on multiple devices, without having
146 * to use threads.
147 *
148 * This added flexibility does come with some complications though:
149 * - In the interest of being a lightweight library, libusb does not create
150 * threads and can only operate when your application is calling into it. Your
151 * application must call into libusb from it's main loop when events are ready
152 * to be handled, or you must use some other scheme to allow libusb to
153 * undertake whatever work needs to be done.
154 * - libusb also needs to be called into at certain fixed points in time in
155 * order to accurately handle transfer timeouts.
156 * - Memory handling becomes more complex. You cannot use stack memory unless
157 * the function with that stack is guaranteed not to return until the transfer
158 * callback has finished executing.
159 * - You generally lose some linearity from your code flow because submitting
160 * the transfer request is done in a separate function from where the transfer
161 * results are handled. This becomes particularly obvious when you want to
162 * submit a second transfer based on the results of an earlier transfer.
163 *
164 * Internally, libusb's synchronous interface is expressed in terms of function
165 * calls to the asynchronous interface.
166 *
167 * For details on how to use the asynchronous API, see the
168 * \ref libusb_asyncio "asynchronous I/O API" documentation pages.
169 */
170
171
172 /**
173 * \page libusb_packetoverflow Packets and overflows
174 *
175 * \section packets Packet abstraction
176 *
177 * The USB specifications describe how data is transmitted in packets, with
178 * constraints on packet size defined by endpoint descriptors. The host must
179 * not send data payloads larger than the endpoint's maximum packet size.
180 *
181 * libusb and the underlying OS abstract out the packet concept, allowing you
182 * to request transfers of any size. Internally, the request will be divided
183 * up into correctly-sized packets. You do not have to be concerned with
184 * packet sizes, but there is one exception when considering overflows.
185 *
186 * \section overflow Bulk/interrupt transfer overflows
187 *
188 * When requesting data on a bulk endpoint, libusb requires you to supply a
189 * buffer and the maximum number of bytes of data that libusb can put in that
190 * buffer. However, the size of the buffer is not communicated to the device -
191 * the device is just asked to send any amount of data.
192 *
193 * There is no problem if the device sends an amount of data that is less than
194 * or equal to the buffer size. libusb reports this condition to you through
195 * the \ref libusb_transfer::actual_length "libusb_transfer.actual_length"
196 * field.
197 *
198 * Problems may occur if the device attempts to send more data than can fit in
199 * the buffer. libusb reports LIBUSB_TRANSFER_OVERFLOW for this condition but
200 * other behaviour is largely undefined: actual_length may or may not be
201 * accurate, the chunk of data that can fit in the buffer (before overflow)
202 * may or may not have been transferred.
203 *
204 * Overflows are nasty, but can be avoided. Even though you were told to
205 * ignore packets above, think about the lower level details: each transfer is
206 * split into packets (typically small, with a maximum size of 512 bytes).
207 * Overflows can only happen if the final packet in an incoming data transfer
208 * is smaller than the actual packet that the device wants to transfer.
209 * Therefore, you will never see an overflow if your transfer buffer size is a
210 * multiple of the endpoint's packet size: the final packet will either
211 * fill up completely or will be only partially filled.
212 */
213
214 /**
215 * @defgroup libusb_asyncio Asynchronous device I/O
216 *
217 * This page details libusb's asynchronous (non-blocking) API for USB device
218 * I/O. This interface is very powerful but is also quite complex - you will
219 * need to read this page carefully to understand the necessary considerations
220 * and issues surrounding use of this interface. Simplistic applications
221 * may wish to consider the \ref libusb_syncio "synchronous I/O API" instead.
222 *
223 * The asynchronous interface is built around the idea of separating transfer
224 * submission and handling of transfer completion (the synchronous model
225 * combines both of these into one). There may be a long delay between
226 * submission and completion, however the asynchronous submission function
227 * is non-blocking so will return control to your application during that
228 * potentially long delay.
229 *
230 * \section asyncabstraction Transfer abstraction
231 *
232 * For the asynchronous I/O, libusb implements the concept of a generic
233 * transfer entity for all types of I/O (control, bulk, interrupt,
234 * isochronous). The generic transfer object must be treated slightly
235 * differently depending on which type of I/O you are performing with it.
236 *
237 * This is represented by the public libusb_transfer structure type.
238 *
239 * \section asynctrf Asynchronous transfers
240 *
241 * We can view asynchronous I/O as a 5 step process:
242 * -# <b>Allocation</b>: allocate a libusb_transfer
243 * -# <b>Filling</b>: populate the libusb_transfer instance with information
244 * about the transfer you wish to perform
245 * -# <b>Submission</b>: ask libusb to submit the transfer
246 * -# <b>Completion handling</b>: examine transfer results in the
247 * libusb_transfer structure
248 * -# <b>Deallocation</b>: clean up resources
249 *
250 *
251 * \subsection asyncalloc Allocation
252 *
253 * This step involves allocating memory for a USB transfer. This is the
254 * generic transfer object mentioned above. At this stage, the transfer
255 * is "blank" with no details about what type of I/O it will be used for.
256 *
257 * Allocation is done with the libusb_alloc_transfer() function. You must use
258 * this function rather than allocating your own transfers.
259 *
260 * \subsection asyncfill Filling
261 *
262 * This step is where you take a previously allocated transfer and fill it
263 * with information to determine the message type and direction, data buffer,
264 * callback function, etc.
265 *
266 * You can either fill the required fields yourself or you can use the
267 * helper functions: libusb_fill_control_transfer(), libusb_fill_bulk_transfer()
268 * and libusb_fill_interrupt_transfer().
269 *
270 * \subsection asyncsubmit Submission
271 *
272 * When you have allocated a transfer and filled it, you can submit it using
273 * libusb_submit_transfer(). This function returns immediately but can be
274 * regarded as firing off the I/O request in the background.
275 *
276 * \subsection asynccomplete Completion handling
277 *
278 * After a transfer has been submitted, one of four things can happen to it:
279 *
280 * - The transfer completes (i.e. some data was transferred)
281 * - The transfer has a timeout and the timeout expires before all data is
282 * transferred
283 * - The transfer fails due to an error
284 * - The transfer is cancelled
285 *
286 * Each of these will cause the user-specified transfer callback function to
287 * be invoked. It is up to the callback function to determine which of the
288 * above actually happened and to act accordingly.
289 *
290 * The user-specified callback is passed a pointer to the libusb_transfer
291 * structure which was used to setup and submit the transfer. At completion
292 * time, libusb has populated this structure with results of the transfer:
293 * success or failure reason, number of bytes of data transferred, etc. See
294 * the libusb_transfer structure documentation for more information.
295 *
296 * <b>Important Note</b>: The user-specified callback is called from an event
297 * handling context. It is therefore important that no calls are made into
298 * libusb that will attempt to perform any event handling. Examples of such
299 * functions are any listed in the \ref libusb_syncio "synchronous API" and any of
300 * the blocking functions that retrieve \ref libusb_desc "USB descriptors".
301 *
302 * \subsection Deallocation
303 *
304 * When a transfer has completed (i.e. the callback function has been invoked),
305 * you are advised to free the transfer (unless you wish to resubmit it, see
306 * below). Transfers are deallocated with libusb_free_transfer().
307 *
308 * It is undefined behaviour to free a transfer which has not completed.
309 *
310 * \section asyncresubmit Resubmission
311 *
312 * You may be wondering why allocation, filling, and submission are all
313 * separated above where they could reasonably be combined into a single
314 * operation.
315 *
316 * The reason for separation is to allow you to resubmit transfers without
317 * having to allocate new ones every time. This is especially useful for
318 * common situations dealing with interrupt endpoints - you allocate one
319 * transfer, fill and submit it, and when it returns with results you just
320 * resubmit it for the next interrupt.
321 *
322 * \section asynccancel Cancellation
323 *
324 * Another advantage of using the asynchronous interface is that you have
325 * the ability to cancel transfers which have not yet completed. This is
326 * done by calling the libusb_cancel_transfer() function.
327 *
328 * libusb_cancel_transfer() is asynchronous/non-blocking in itself. When the
329 * cancellation actually completes, the transfer's callback function will
330 * be invoked, and the callback function should check the transfer status to
331 * determine that it was cancelled.
332 *
333 * Freeing the transfer after it has been cancelled but before cancellation
334 * has completed will result in undefined behaviour.
335 *
336 * When a transfer is cancelled, some of the data may have been transferred.
337 * libusb will communicate this to you in the transfer callback. Do not assume
338 * that no data was transferred.
339 *
340 * \section bulk_overflows Overflows on device-to-host bulk/interrupt endpoints
341 *
342 * If your device does not have predictable transfer sizes (or it misbehaves),
343 * your application may submit a request for data on an IN endpoint which is
344 * smaller than the data that the device wishes to send. In some circumstances
345 * this will cause an overflow, which is a nasty condition to deal with. See
346 * the \ref libusb_packetoverflow page for discussion.
347 *
348 * \section asyncctrl Considerations for control transfers
349 *
350 * The <tt>libusb_transfer</tt> structure is generic and hence does not
351 * include specific fields for the control-specific setup packet structure.
352 *
353 * In order to perform a control transfer, you must place the 8-byte setup
354 * packet at the start of the data buffer. To simplify this, you could
355 * cast the buffer pointer to type struct libusb_control_setup, or you can
356 * use the helper function libusb_fill_control_setup().
357 *
358 * The wLength field placed in the setup packet must be the length you would
359 * expect to be sent in the setup packet: the length of the payload that
360 * follows (or the expected maximum number of bytes to receive). However,
361 * the length field of the libusb_transfer object must be the length of
362 * the data buffer - i.e. it should be wLength <em>plus</em> the size of
363 * the setup packet (LIBUSB_CONTROL_SETUP_SIZE).
364 *
365 * If you use the helper functions, this is simplified for you:
366 * -# Allocate a buffer of size LIBUSB_CONTROL_SETUP_SIZE plus the size of the
367 * data you are sending/requesting.
368 * -# Call libusb_fill_control_setup() on the data buffer, using the transfer
369 * request size as the wLength value (i.e. do not include the extra space you
370 * allocated for the control setup).
371 * -# If this is a host-to-device transfer, place the data to be transferred
372 * in the data buffer, starting at offset LIBUSB_CONTROL_SETUP_SIZE.
373 * -# Call libusb_fill_control_transfer() to associate the data buffer with
374 * the transfer (and to set the remaining details such as callback and timeout).
375 * - Note that there is no parameter to set the length field of the transfer.
376 * The length is automatically inferred from the wLength field of the setup
377 * packet.
378 * -# Submit the transfer.
379 *
380 * The multi-byte control setup fields (wValue, wIndex and wLength) must
381 * be given in little-endian byte order (the endianness of the USB bus).
382 * Endianness conversion is transparently handled by
383 * libusb_fill_control_setup() which is documented to accept host-endian
384 * values.
385 *
386 * Further considerations are needed when handling transfer completion in
387 * your callback function:
388 * - As you might expect, the setup packet will still be sitting at the start
389 * of the data buffer.
390 * - If this was a device-to-host transfer, the received data will be sitting
391 * at offset LIBUSB_CONTROL_SETUP_SIZE into the buffer.
392 * - The actual_length field of the transfer structure is relative to the
393 * wLength of the setup packet, rather than the size of the data buffer. So,
394 * if your wLength was 4, your transfer's <tt>length</tt> was 12, then you
395 * should expect an <tt>actual_length</tt> of 4 to indicate that the data was
396 * transferred in entirity.
397 *
398 * To simplify parsing of setup packets and obtaining the data from the
399 * correct offset, you may wish to use the libusb_control_transfer_get_data()
400 * and libusb_control_transfer_get_setup() functions within your transfer
401 * callback.
402 *
403 * Even though control endpoints do not halt, a completed control transfer
404 * may have a LIBUSB_TRANSFER_STALL status code. This indicates the control
405 * request was not supported.
406 *
407 * \section asyncintr Considerations for interrupt transfers
408 *
409 * All interrupt transfers are performed using the polling interval presented
410 * by the bInterval value of the endpoint descriptor.
411 *
412 * \section asynciso Considerations for isochronous transfers
413 *
414 * Isochronous transfers are more complicated than transfers to
415 * non-isochronous endpoints.
416 *
417 * To perform I/O to an isochronous endpoint, allocate the transfer by calling
418 * libusb_alloc_transfer() with an appropriate number of isochronous packets.
419 *
420 * During filling, set \ref libusb_transfer::type "type" to
421 * \ref libusb_transfer_type::LIBUSB_TRANSFER_TYPE_ISOCHRONOUS
422 * "LIBUSB_TRANSFER_TYPE_ISOCHRONOUS", and set
423 * \ref libusb_transfer::num_iso_packets "num_iso_packets" to a value less than
424 * or equal to the number of packets you requested during allocation.
425 * libusb_alloc_transfer() does not set either of these fields for you, given
426 * that you might not even use the transfer on an isochronous endpoint.
427 *
428 * Next, populate the length field for the first num_iso_packets entries in
429 * the \ref libusb_transfer::iso_packet_desc "iso_packet_desc" array. Section
430 * 5.6.3 of the USB2 specifications describe how the maximum isochronous
431 * packet length is determined by the wMaxPacketSize field in the endpoint
432 * descriptor.
433 * Two functions can help you here:
434 *
435 * - libusb_get_max_iso_packet_size() is an easy way to determine the max
436 * packet size for an isochronous endpoint. Note that the maximum packet
437 * size is actually the maximum number of bytes that can be transmitted in
438 * a single microframe, therefore this function multiplies the maximum number
439 * of bytes per transaction by the number of transaction opportunities per
440 * microframe.
441 * - libusb_set_iso_packet_lengths() assigns the same length to all packets
442 * within a transfer, which is usually what you want.
443 *
444 * For outgoing transfers, you'll obviously fill the buffer and populate the
445 * packet descriptors in hope that all the data gets transferred. For incoming
446 * transfers, you must ensure the buffer has sufficient capacity for
447 * the situation where all packets transfer the full amount of requested data.
448 *
449 * Completion handling requires some extra consideration. The
450 * \ref libusb_transfer::actual_length "actual_length" field of the transfer
451 * is meaningless and should not be examined; instead you must refer to the
452 * \ref libusb_iso_packet_descriptor::actual_length "actual_length" field of
453 * each individual packet.
454 *
455 * The \ref libusb_transfer::status "status" field of the transfer is also a
456 * little misleading:
457 * - If the packets were submitted and the isochronous data microframes
458 * completed normally, status will have value
459 * \ref libusb_transfer_status::LIBUSB_TRANSFER_COMPLETED
460 * "LIBUSB_TRANSFER_COMPLETED". Note that bus errors and software-incurred
461 * delays are not counted as transfer errors; the transfer.status field may
462 * indicate COMPLETED even if some or all of the packets failed. Refer to
463 * the \ref libusb_iso_packet_descriptor::status "status" field of each
464 * individual packet to determine packet failures.
465 * - The status field will have value
466 * \ref libusb_transfer_status::LIBUSB_TRANSFER_ERROR
467 * "LIBUSB_TRANSFER_ERROR" only when serious errors were encountered.
468 * - Other transfer status codes occur with normal behaviour.
469 *
470 * The data for each packet will be found at an offset into the buffer that
471 * can be calculated as if each prior packet completed in full. The
472 * libusb_get_iso_packet_buffer() and libusb_get_iso_packet_buffer_simple()
473 * functions may help you here.
474 *
475 * <b>Note</b>: Some operating systems (e.g. Linux) may impose limits on the
476 * length of individual isochronous packets and/or the total length of the
477 * isochronous transfer. Such limits can be difficult for libusb to detect,
478 * so the library will simply try and submit the transfer as set up by you.
479 * If the transfer fails to submit because it is too large,
480 * libusb_submit_transfer() will return
481 * \ref libusb_error::LIBUSB_ERROR_INVALID_PARAM "LIBUSB_ERROR_INVALID_PARAM".
482 *
483 * \section asyncmem Memory caveats
484 *
485 * In most circumstances, it is not safe to use stack memory for transfer
486 * buffers. This is because the function that fired off the asynchronous
487 * transfer may return before libusb has finished using the buffer, and when
488 * the function returns it's stack gets destroyed. This is true for both
489 * host-to-device and device-to-host transfers.
490 *
491 * The only case in which it is safe to use stack memory is where you can
492 * guarantee that the function owning the stack space for the buffer does not
493 * return until after the transfer's callback function has completed. In every
494 * other case, you need to use heap memory instead.
495 *
496 * \section asyncflags Fine control
497 *
498 * Through using this asynchronous interface, you may find yourself repeating
499 * a few simple operations many times. You can apply a bitwise OR of certain
500 * flags to a transfer to simplify certain things:
501 * - \ref libusb_transfer_flags::LIBUSB_TRANSFER_SHORT_NOT_OK
502 * "LIBUSB_TRANSFER_SHORT_NOT_OK" results in transfers which transferred
503 * less than the requested amount of data being marked with status
504 * \ref libusb_transfer_status::LIBUSB_TRANSFER_ERROR "LIBUSB_TRANSFER_ERROR"
505 * (they would normally be regarded as COMPLETED)
506 * - \ref libusb_transfer_flags::LIBUSB_TRANSFER_FREE_BUFFER
507 * "LIBUSB_TRANSFER_FREE_BUFFER" allows you to ask libusb to free the transfer
508 * buffer when freeing the transfer.
509 * - \ref libusb_transfer_flags::LIBUSB_TRANSFER_FREE_TRANSFER
510 * "LIBUSB_TRANSFER_FREE_TRANSFER" causes libusb to automatically free the
511 * transfer after the transfer callback returns.
512 *
513 * \section asyncevent Event handling
514 *
515 * An asynchronous model requires that libusb perform work at various
516 * points in time - namely processing the results of previously-submitted
517 * transfers and invoking the user-supplied callback function.
518 *
519 * This gives rise to the libusb_handle_events() function which your
520 * application must call into when libusb has work do to. This gives libusb
521 * the opportunity to reap pending transfers, invoke callbacks, etc.
522 *
523 * There are 2 different approaches to dealing with libusb_handle_events:
524 *
525 * -# Repeatedly call libusb_handle_events() in blocking mode from a dedicated
526 * thread.
527 * -# Integrate libusb with your application's main event loop. libusb
528 * exposes a set of file descriptors which allow you to do this.
529 *
530 * The first approach has the big advantage that it will also work on Windows
531 * were libusb' poll API for select / poll integration is not available. So
532 * if you want to support Windows and use the async API, you must use this
533 * approach, see the \ref eventthread "Using an event handling thread" section
534 * below for details.
535 *
536 * If you prefer a single threaded approach with a single central event loop,
537 * see the \ref libusb_poll "polling and timing" section for how to integrate libusb
538 * into your application's main event loop.
539 *
540 * \section eventthread Using an event handling thread
541 *
542 * Lets begin with stating the obvious: If you're going to use a separate
543 * thread for libusb event handling, your callback functions MUST be
544 * threadsafe.
545 *
546 * Other then that doing event handling from a separate thread, is mostly
547 * simple. You can use an event thread function as follows:
548 \code
549 void *event_thread_func(void *ctx)
550 {
551 while (event_thread_run)
552 libusb_handle_events(ctx);
553
554 return NULL;
555 }
556 \endcode
557 *
558 * There is one caveat though, stopping this thread requires setting the
559 * event_thread_run variable to 0, and after that libusb_handle_events() needs
560 * to return control to event_thread_func. But unless some event happens,
561 * libusb_handle_events() will not return.
562 *
563 * There are 2 different ways of dealing with this, depending on if your
564 * application uses libusb' \ref libusb_hotplug "hotplug" support or not.
565 *
566 * Applications which do not use hotplug support, should not start the event
567 * thread until after their first call to libusb_open(), and should stop the
568 * thread when closing the last open device as follows:
569 \code
570 void my_close_handle(libusb_device_handle *dev_handle)
571 {
572 if (open_devs == 1)
573 event_thread_run = 0;
574
575 libusb_close(dev_handle); // This wakes up libusb_handle_events()
576
577 if (open_devs == 1)
578 pthread_join(event_thread);
579
580 open_devs--;
581 }
582 \endcode
583 *
584 * Applications using hotplug support should start the thread at program init,
585 * after having successfully called libusb_hotplug_register_callback(), and
586 * should stop the thread at program exit as follows:
587 \code
588 void my_libusb_exit(void)
589 {
590 event_thread_run = 0;
591 libusb_hotplug_deregister_callback(ctx, hotplug_cb_handle); // This wakes up libusb_handle_events()
592 pthread_join(event_thread);
593 libusb_exit(ctx);
594 }
595 \endcode
596 */
597
598 /**
599 * @defgroup libusb_poll Polling and timing
600 *
601 * This page documents libusb's functions for polling events and timing.
602 * These functions are only necessary for users of the
603 * \ref libusb_asyncio "asynchronous API". If you are only using the simpler
604 * \ref libusb_syncio "synchronous API" then you do not need to ever call these
605 * functions.
606 *
607 * The justification for the functionality described here has already been
608 * discussed in the \ref asyncevent "event handling" section of the
609 * asynchronous API documentation. In summary, libusb does not create internal
610 * threads for event processing and hence relies on your application calling
611 * into libusb at certain points in time so that pending events can be handled.
612 *
613 * Your main loop is probably already calling poll() or select() or a
614 * variant on a set of file descriptors for other event sources (e.g. keyboard
615 * button presses, mouse movements, network sockets, etc). You then add
616 * libusb's file descriptors to your poll()/select() calls, and when activity
617 * is detected on such descriptors you know it is time to call
618 * libusb_handle_events().
619 *
620 * There is one final event handling complication. libusb supports
621 * asynchronous transfers which time out after a specified time period.
622 *
623 * On some platforms a timerfd is used, so the timeout handling is just another
624 * fd, on other platforms this requires that libusb is called into at or after
625 * the timeout to handle it. So, in addition to considering libusb's file
626 * descriptors in your main event loop, you must also consider that libusb
627 * sometimes needs to be called into at fixed points in time even when there
628 * is no file descriptor activity, see \ref polltime details.
629 *
630 * In order to know precisely when libusb needs to be called into, libusb
631 * offers you a set of pollable file descriptors and information about when
632 * the next timeout expires.
633 *
634 * If you are using the asynchronous I/O API, you must take one of the two
635 * following options, otherwise your I/O will not complete.
636 *
637 * \section pollsimple The simple option
638 *
639 * If your application revolves solely around libusb and does not need to
640 * handle other event sources, you can have a program structure as follows:
641 \code
642 // initialize libusb
643 // find and open device
644 // maybe fire off some initial async I/O
645
646 while (user_has_not_requested_exit)
647 libusb_handle_events(ctx);
648
649 // clean up and exit
650 \endcode
651 *
652 * With such a simple main loop, you do not have to worry about managing
653 * sets of file descriptors or handling timeouts. libusb_handle_events() will
654 * handle those details internally.
655 *
656 * \section libusb_pollmain The more advanced option
657 *
658 * \note This functionality is currently only available on Unix-like platforms.
659 * On Windows, libusb_get_pollfds() simply returns NULL. Applications which
660 * want to support Windows are advised to use an \ref eventthread
661 * "event handling thread" instead.
662 *
663 * In more advanced applications, you will already have a main loop which
664 * is monitoring other event sources: network sockets, X11 events, mouse
665 * movements, etc. Through exposing a set of file descriptors, libusb is
666 * designed to cleanly integrate into such main loops.
667 *
668 * In addition to polling file descriptors for the other event sources, you
669 * take a set of file descriptors from libusb and monitor those too. When you
670 * detect activity on libusb's file descriptors, you call
671 * libusb_handle_events_timeout() in non-blocking mode.
672 *
673 * What's more, libusb may also need to handle events at specific moments in
674 * time. No file descriptor activity is generated at these times, so your
675 * own application needs to be continually aware of when the next one of these
676 * moments occurs (through calling libusb_get_next_timeout()), and then it
677 * needs to call libusb_handle_events_timeout() in non-blocking mode when
678 * these moments occur. This means that you need to adjust your
679 * poll()/select() timeout accordingly.
680 *
681 * libusb provides you with a set of file descriptors to poll and expects you
682 * to poll all of them, treating them as a single entity. The meaning of each
683 * file descriptor in the set is an internal implementation detail,
684 * platform-dependent and may vary from release to release. Don't try and
685 * interpret the meaning of the file descriptors, just do as libusb indicates,
686 * polling all of them at once.
687 *
688 * In pseudo-code, you want something that looks like:
689 \code
690 // initialise libusb
691
692 libusb_get_pollfds(ctx)
693 while (user has not requested application exit) {
694 libusb_get_next_timeout(ctx);
695 poll(on libusb file descriptors plus any other event sources of interest,
696 using a timeout no larger than the value libusb just suggested)
697 if (poll() indicated activity on libusb file descriptors)
698 libusb_handle_events_timeout(ctx, &zero_tv);
699 if (time has elapsed to or beyond the libusb timeout)
700 libusb_handle_events_timeout(ctx, &zero_tv);
701 // handle events from other sources here
702 }
703
704 // clean up and exit
705 \endcode
706 *
707 * \subsection polltime Notes on time-based events
708 *
709 * The above complication with having to track time and call into libusb at
710 * specific moments is a bit of a headache. For maximum compatibility, you do
711 * need to write your main loop as above, but you may decide that you can
712 * restrict the supported platforms of your application and get away with
713 * a more simplistic scheme.
714 *
715 * These time-based event complications are \b not required on the following
716 * platforms:
717 * - Darwin
718 * - Linux, provided that the following version requirements are satisfied:
719 * - Linux v2.6.27 or newer, compiled with timerfd support
720 * - glibc v2.9 or newer
721 * - libusb v1.0.5 or newer
722 *
723 * Under these configurations, libusb_get_next_timeout() will \em always return
724 * 0, so your main loop can be simplified to:
725 \code
726 // initialise libusb
727
728 libusb_get_pollfds(ctx)
729 while (user has not requested application exit) {
730 poll(on libusb file descriptors plus any other event sources of interest,
731 using any timeout that you like)
732 if (poll() indicated activity on libusb file descriptors)
733 libusb_handle_events_timeout(ctx, &zero_tv);
734 // handle events from other sources here
735 }
736
737 // clean up and exit
738 \endcode
739 *
740 * Do remember that if you simplify your main loop to the above, you will
741 * lose compatibility with some platforms (including legacy Linux platforms,
742 * and <em>any future platforms supported by libusb which may have time-based
743 * event requirements</em>). The resultant problems will likely appear as
744 * strange bugs in your application.
745 *
746 * You can use the libusb_pollfds_handle_timeouts() function to do a runtime
747 * check to see if it is safe to ignore the time-based event complications.
748 * If your application has taken the shortcut of ignoring libusb's next timeout
749 * in your main loop, then you are advised to check the return value of
750 * libusb_pollfds_handle_timeouts() during application startup, and to abort
751 * if the platform does suffer from these timing complications.
752 *
753 * \subsection fdsetchange Changes in the file descriptor set
754 *
755 * The set of file descriptors that libusb uses as event sources may change
756 * during the life of your application. Rather than having to repeatedly
757 * call libusb_get_pollfds(), you can set up notification functions for when
758 * the file descriptor set changes using libusb_set_pollfd_notifiers().
759 *
760 * \subsection mtissues Multi-threaded considerations
761 *
762 * Unfortunately, the situation is complicated further when multiple threads
763 * come into play. If two threads are monitoring the same file descriptors,
764 * the fact that only one thread will be woken up when an event occurs causes
765 * some headaches.
766 *
767 * The events lock, event waiters lock, and libusb_handle_events_locked()
768 * entities are added to solve these problems. You do not need to be concerned
769 * with these entities otherwise.
770 *
771 * See the extra documentation: \ref libusb_mtasync
772 */
773
774 /** \page libusb_mtasync Multi-threaded applications and asynchronous I/O
775 *
776 * libusb is a thread-safe library, but extra considerations must be applied
777 * to applications which interact with libusb from multiple threads.
778 *
779 * The underlying issue that must be addressed is that all libusb I/O
780 * revolves around monitoring file descriptors through the poll()/select()
781 * system calls. This is directly exposed at the
782 * \ref libusb_asyncio "asynchronous interface" but it is important to note that the
783 * \ref libusb_syncio "synchronous interface" is implemented on top of the
784 * asynchonrous interface, therefore the same considerations apply.
785 *
786 * The issue is that if two or more threads are concurrently calling poll()
787 * or select() on libusb's file descriptors then only one of those threads
788 * will be woken up when an event arrives. The others will be completely
789 * oblivious that anything has happened.
790 *
791 * Consider the following pseudo-code, which submits an asynchronous transfer
792 * then waits for its completion. This style is one way you could implement a
793 * synchronous interface on top of the asynchronous interface (and libusb
794 * does something similar, albeit more advanced due to the complications
795 * explained on this page).
796 *
797 \code
798 void cb(struct libusb_transfer *transfer)
799 {
800 int *completed = transfer->user_data;
801 *completed = 1;
802 }
803
804 void myfunc() {
805 struct libusb_transfer *transfer;
806 unsigned char buffer[LIBUSB_CONTROL_SETUP_SIZE] __attribute__ ((aligned (2)));
807 int completed = 0;
808
809 transfer = libusb_alloc_transfer(0);
810 libusb_fill_control_setup(buffer,
811 LIBUSB_REQUEST_TYPE_VENDOR | LIBUSB_ENDPOINT_OUT, 0x04, 0x01, 0, 0);
812 libusb_fill_control_transfer(transfer, dev, buffer, cb, &completed, 1000);
813 libusb_submit_transfer(transfer);
814
815 while (!completed) {
816 poll(libusb file descriptors, 120*1000);
817 if (poll indicates activity)
818 libusb_handle_events_timeout(ctx, &zero_tv);
819 }
820 printf("completed!");
821 // other code here
822 }
823 \endcode
824 *
825 * Here we are <em>serializing</em> completion of an asynchronous event
826 * against a condition - the condition being completion of a specific transfer.
827 * The poll() loop has a long timeout to minimize CPU usage during situations
828 * when nothing is happening (it could reasonably be unlimited).
829 *
830 * If this is the only thread that is polling libusb's file descriptors, there
831 * is no problem: there is no danger that another thread will swallow up the
832 * event that we are interested in. On the other hand, if there is another
833 * thread polling the same descriptors, there is a chance that it will receive
834 * the event that we were interested in. In this situation, <tt>myfunc()</tt>
835 * will only realise that the transfer has completed on the next iteration of
836 * the loop, <em>up to 120 seconds later.</em> Clearly a two-minute delay is
837 * undesirable, and don't even think about using short timeouts to circumvent
838 * this issue!
839 *
840 * The solution here is to ensure that no two threads are ever polling the
841 * file descriptors at the same time. A naive implementation of this would
842 * impact the capabilities of the library, so libusb offers the scheme
843 * documented below to ensure no loss of functionality.
844 *
845 * Before we go any further, it is worth mentioning that all libusb-wrapped
846 * event handling procedures fully adhere to the scheme documented below.
847 * This includes libusb_handle_events() and its variants, and all the
848 * synchronous I/O functions - libusb hides this headache from you.
849 *
850 * \section Using libusb_handle_events() from multiple threads
851 *
852 * Even when only using libusb_handle_events() and synchronous I/O functions,
853 * you can still have a race condition. You might be tempted to solve the
854 * above with libusb_handle_events() like so:
855 *
856 \code
857 libusb_submit_transfer(transfer);
858
859 while (!completed) {
860 libusb_handle_events(ctx);
861 }
862 printf("completed!");
863 \endcode
864 *
865 * This however has a race between the checking of completed and
866 * libusb_handle_events() acquiring the events lock, so another thread
867 * could have completed the transfer, resulting in this thread hanging
868 * until either a timeout or another event occurs. See also commit
869 * 6696512aade99bb15d6792af90ae329af270eba6 which fixes this in the
870 * synchronous API implementation of libusb.
871 *
872 * Fixing this race requires checking the variable completed only after
873 * taking the event lock, which defeats the concept of just calling
874 * libusb_handle_events() without worrying about locking. This is why
875 * libusb-1.0.9 introduces the new libusb_handle_events_timeout_completed()
876 * and libusb_handle_events_completed() functions, which handles doing the
877 * completion check for you after they have acquired the lock:
878 *
879 \code
880 libusb_submit_transfer(transfer);
881
882 while (!completed) {
883 libusb_handle_events_completed(ctx, &completed);
884 }
885 printf("completed!");
886 \endcode
887 *
888 * This nicely fixes the race in our example. Note that if all you want to
889 * do is submit a single transfer and wait for its completion, then using
890 * one of the synchronous I/O functions is much easier.
891 *
892 * \section eventlock The events lock
893 *
894 * The problem is when we consider the fact that libusb exposes file
895 * descriptors to allow for you to integrate asynchronous USB I/O into
896 * existing main loops, effectively allowing you to do some work behind
897 * libusb's back. If you do take libusb's file descriptors and pass them to
898 * poll()/select() yourself, you need to be aware of the associated issues.
899 *
900 * The first concept to be introduced is the events lock. The events lock
901 * is used to serialize threads that want to handle events, such that only
902 * one thread is handling events at any one time.
903 *
904 * You must take the events lock before polling libusb file descriptors,
905 * using libusb_lock_events(). You must release the lock as soon as you have
906 * aborted your poll()/select() loop, using libusb_unlock_events().
907 *
908 * \section threadwait Letting other threads do the work for you
909 *
910 * Although the events lock is a critical part of the solution, it is not
911 * enough on it's own. You might wonder if the following is sufficient...
912 \code
913 libusb_lock_events(ctx);
914 while (!completed) {
915 poll(libusb file descriptors, 120*1000);
916 if (poll indicates activity)
917 libusb_handle_events_timeout(ctx, &zero_tv);
918 }
919 libusb_unlock_events(ctx);
920 \endcode
921 * ...and the answer is that it is not. This is because the transfer in the
922 * code shown above may take a long time (say 30 seconds) to complete, and
923 * the lock is not released until the transfer is completed.
924 *
925 * Another thread with similar code that wants to do event handling may be
926 * working with a transfer that completes after a few milliseconds. Despite
927 * having such a quick completion time, the other thread cannot check that
928 * status of its transfer until the code above has finished (30 seconds later)
929 * due to contention on the lock.
930 *
931 * To solve this, libusb offers you a mechanism to determine when another
932 * thread is handling events. It also offers a mechanism to block your thread
933 * until the event handling thread has completed an event (and this mechanism
934 * does not involve polling of file descriptors).
935 *
936 * After determining that another thread is currently handling events, you
937 * obtain the <em>event waiters</em> lock using libusb_lock_event_waiters().
938 * You then re-check that some other thread is still handling events, and if
939 * so, you call libusb_wait_for_event().
940 *
941 * libusb_wait_for_event() puts your application to sleep until an event
942 * occurs, or until a thread releases the events lock. When either of these
943 * things happen, your thread is woken up, and should re-check the condition
944 * it was waiting on. It should also re-check that another thread is handling
945 * events, and if not, it should start handling events itself.
946 *
947 * This looks like the following, as pseudo-code:
948 \code
949 retry:
950 if (libusb_try_lock_events(ctx) == 0) {
951 // we obtained the event lock: do our own event handling
952 while (!completed) {
953 if (!libusb_event_handling_ok(ctx)) {
954 libusb_unlock_events(ctx);
955 goto retry;
956 }
957 poll(libusb file descriptors, 120*1000);
958 if (poll indicates activity)
959 libusb_handle_events_locked(ctx, 0);
960 }
961 libusb_unlock_events(ctx);
962 } else {
963 // another thread is doing event handling. wait for it to signal us that
964 // an event has completed
965 libusb_lock_event_waiters(ctx);
966
967 while (!completed) {
968 // now that we have the event waiters lock, double check that another
969 // thread is still handling events for us. (it may have ceased handling
970 // events in the time it took us to reach this point)
971 if (!libusb_event_handler_active(ctx)) {
972 // whoever was handling events is no longer doing so, try again
973 libusb_unlock_event_waiters(ctx);
974 goto retry;
975 }
976
977 libusb_wait_for_event(ctx, NULL);
978 }
979 libusb_unlock_event_waiters(ctx);
980 }
981 printf("completed!\n");
982 \endcode
983 *
984 * A naive look at the above code may suggest that this can only support
985 * one event waiter (hence a total of 2 competing threads, the other doing
986 * event handling), because the event waiter seems to have taken the event
987 * waiters lock while waiting for an event. However, the system does support
988 * multiple event waiters, because libusb_wait_for_event() actually drops
989 * the lock while waiting, and reaquires it before continuing.
990 *
991 * We have now implemented code which can dynamically handle situations where
992 * nobody is handling events (so we should do it ourselves), and it can also
993 * handle situations where another thread is doing event handling (so we can
994 * piggyback onto them). It is also equipped to handle a combination of
995 * the two, for example, another thread is doing event handling, but for
996 * whatever reason it stops doing so before our condition is met, so we take
997 * over the event handling.
998 *
999 * Four functions were introduced in the above pseudo-code. Their importance
1000 * should be apparent from the code shown above.
1001 * -# libusb_try_lock_events() is a non-blocking function which attempts
1002 * to acquire the events lock but returns a failure code if it is contended.
1003 * -# libusb_event_handling_ok() checks that libusb is still happy for your
1004 * thread to be performing event handling. Sometimes, libusb needs to
1005 * interrupt the event handler, and this is how you can check if you have
1006 * been interrupted. If this function returns 0, the correct behaviour is
1007 * for you to give up the event handling lock, and then to repeat the cycle.
1008 * The following libusb_try_lock_events() will fail, so you will become an
1009 * events waiter. For more information on this, read \ref fullstory below.
1010 * -# libusb_handle_events_locked() is a variant of
1011 * libusb_handle_events_timeout() that you can call while holding the
1012 * events lock. libusb_handle_events_timeout() itself implements similar
1013 * logic to the above, so be sure not to call it when you are
1014 * "working behind libusb's back", as is the case here.
1015 * -# libusb_event_handler_active() determines if someone is currently
1016 * holding the events lock
1017 *
1018 * You might be wondering why there is no function to wake up all threads
1019 * blocked on libusb_wait_for_event(). This is because libusb can do this
1020 * internally: it will wake up all such threads when someone calls
1021 * libusb_unlock_events() or when a transfer completes (at the point after its
1022 * callback has returned).
1023 *
1024 * \subsection fullstory The full story
1025 *
1026 * The above explanation should be enough to get you going, but if you're
1027 * really thinking through the issues then you may be left with some more
1028 * questions regarding libusb's internals. If you're curious, read on, and if
1029 * not, skip to the next section to avoid confusing yourself!
1030 *
1031 * The immediate question that may spring to mind is: what if one thread
1032 * modifies the set of file descriptors that need to be polled while another
1033 * thread is doing event handling?
1034 *
1035 * There are 2 situations in which this may happen.
1036 * -# libusb_open() will add another file descriptor to the poll set,
1037 * therefore it is desirable to interrupt the event handler so that it
1038 * restarts, picking up the new descriptor.
1039 * -# libusb_close() will remove a file descriptor from the poll set. There
1040 * are all kinds of race conditions that could arise here, so it is
1041 * important that nobody is doing event handling at this time.
1042 *
1043 * libusb handles these issues internally, so application developers do not
1044 * have to stop their event handlers while opening/closing devices. Here's how
1045 * it works, focusing on the libusb_close() situation first:
1046 *
1047 * -# During initialization, libusb opens an internal pipe, and it adds the read
1048 * end of this pipe to the set of file descriptors to be polled.
1049 * -# During libusb_close(), libusb writes some dummy data on this event pipe.
1050 * This immediately interrupts the event handler. libusb also records
1051 * internally that it is trying to interrupt event handlers for this
1052 * high-priority event.
1053 * -# At this point, some of the functions described above start behaving
1054 * differently:
1055 * - libusb_event_handling_ok() starts returning 1, indicating that it is NOT
1056 * OK for event handling to continue.
1057 * - libusb_try_lock_events() starts returning 1, indicating that another
1058 * thread holds the event handling lock, even if the lock is uncontended.
1059 * - libusb_event_handler_active() starts returning 1, indicating that
1060 * another thread is doing event handling, even if that is not true.
1061 * -# The above changes in behaviour result in the event handler stopping and
1062 * giving up the events lock very quickly, giving the high-priority
1063 * libusb_close() operation a "free ride" to acquire the events lock. All
1064 * threads that are competing to do event handling become event waiters.
1065 * -# With the events lock held inside libusb_close(), libusb can safely remove
1066 * a file descriptor from the poll set, in the safety of knowledge that
1067 * nobody is polling those descriptors or trying to access the poll set.
1068 * -# After obtaining the events lock, the close operation completes very
1069 * quickly (usually a matter of milliseconds) and then immediately releases
1070 * the events lock.
1071 * -# At the same time, the behaviour of libusb_event_handling_ok() and friends
1072 * reverts to the original, documented behaviour.
1073 * -# The release of the events lock causes the threads that are waiting for
1074 * events to be woken up and to start competing to become event handlers
1075 * again. One of them will succeed; it will then re-obtain the list of poll
1076 * descriptors, and USB I/O will then continue as normal.
1077 *
1078 * libusb_open() is similar, and is actually a more simplistic case. Upon a
1079 * call to libusb_open():
1080 *
1081 * -# The device is opened and a file descriptor is added to the poll set.
1082 * -# libusb sends some dummy data on the event pipe, and records that it
1083 * is trying to modify the poll descriptor set.
1084 * -# The event handler is interrupted, and the same behaviour change as for
1085 * libusb_close() takes effect, causing all event handling threads to become
1086 * event waiters.
1087 * -# The libusb_open() implementation takes its free ride to the events lock.
1088 * -# Happy that it has successfully paused the events handler, libusb_open()
1089 * releases the events lock.
1090 * -# The event waiter threads are all woken up and compete to become event
1091 * handlers again. The one that succeeds will obtain the list of poll
1092 * descriptors again, which will include the addition of the new device.
1093 *
1094 * \subsection concl Closing remarks
1095 *
1096 * The above may seem a little complicated, but hopefully I have made it clear
1097 * why such complications are necessary. Also, do not forget that this only
1098 * applies to applications that take libusb's file descriptors and integrate
1099 * them into their own polling loops.
1100 *
1101 * You may decide that it is OK for your multi-threaded application to ignore
1102 * some of the rules and locks detailed above, because you don't think that
1103 * two threads can ever be polling the descriptors at the same time. If that
1104 * is the case, then that's good news for you because you don't have to worry.
1105 * But be careful here; remember that the synchronous I/O functions do event
1106 * handling internally. If you have one thread doing event handling in a loop
1107 * (without implementing the rules and locking semantics documented above)
1108 * and another trying to send a synchronous USB transfer, you will end up with
1109 * two threads monitoring the same descriptors, and the above-described
1110 * undesirable behaviour occurring. The solution is for your polling thread to
1111 * play by the rules; the synchronous I/O functions do so, and this will result
1112 * in them getting along in perfect harmony.
1113 *
1114 * If you do have a dedicated thread doing event handling, it is perfectly
1115 * legal for it to take the event handling lock for long periods of time. Any
1116 * synchronous I/O functions you call from other threads will transparently
1117 * fall back to the "event waiters" mechanism detailed above. The only
1118 * consideration that your event handling thread must apply is the one related
1119 * to libusb_event_handling_ok(): you must call this before every poll(), and
1120 * give up the events lock if instructed.
1121 */
1122
usbi_io_init(struct libusb_context * ctx)1123 int usbi_io_init(struct libusb_context *ctx)
1124 {
1125 int r;
1126
1127 usbi_mutex_init(&ctx->flying_transfers_lock);
1128 usbi_mutex_init(&ctx->events_lock);
1129 usbi_mutex_init(&ctx->event_waiters_lock);
1130 usbi_cond_init(&ctx->event_waiters_cond);
1131 usbi_mutex_init(&ctx->event_data_lock);
1132 usbi_tls_key_create(&ctx->event_handling_key);
1133 list_init(&ctx->flying_transfers);
1134 list_init(&ctx->ipollfds);
1135 list_init(&ctx->hotplug_msgs);
1136 list_init(&ctx->completed_transfers);
1137
1138 /* FIXME should use an eventfd on kernels that support it */
1139 r = usbi_pipe(ctx->event_pipe);
1140 if (r < 0) {
1141 r = LIBUSB_ERROR_OTHER;
1142 goto err;
1143 }
1144
1145 r = usbi_add_pollfd(ctx, ctx->event_pipe[0], POLLIN);
1146 if (r < 0)
1147 goto err_close_pipe;
1148
1149 #ifdef USBI_TIMERFD_AVAILABLE
1150 ctx->timerfd = timerfd_create(usbi_backend->get_timerfd_clockid(),
1151 TFD_NONBLOCK);
1152 if (ctx->timerfd >= 0) {
1153 usbi_dbg("using timerfd for timeouts");
1154 r = usbi_add_pollfd(ctx, ctx->timerfd, POLLIN);
1155 if (r < 0)
1156 goto err_close_timerfd;
1157 } else {
1158 usbi_dbg("timerfd not available (code %d error %d)", ctx->timerfd, errno);
1159 ctx->timerfd = -1;
1160 }
1161 #endif
1162
1163 return 0;
1164
1165 #ifdef USBI_TIMERFD_AVAILABLE
1166 err_close_timerfd:
1167 close(ctx->timerfd);
1168 usbi_remove_pollfd(ctx, ctx->event_pipe[0]);
1169 #endif
1170 err_close_pipe:
1171 usbi_close(ctx->event_pipe[0]);
1172 usbi_close(ctx->event_pipe[1]);
1173 err:
1174 usbi_mutex_destroy(&ctx->flying_transfers_lock);
1175 usbi_mutex_destroy(&ctx->events_lock);
1176 usbi_mutex_destroy(&ctx->event_waiters_lock);
1177 usbi_cond_destroy(&ctx->event_waiters_cond);
1178 usbi_mutex_destroy(&ctx->event_data_lock);
1179 usbi_tls_key_delete(ctx->event_handling_key);
1180 return r;
1181 }
1182
usbi_io_exit(struct libusb_context * ctx)1183 void usbi_io_exit(struct libusb_context *ctx)
1184 {
1185 usbi_remove_pollfd(ctx, ctx->event_pipe[0]);
1186 usbi_close(ctx->event_pipe[0]);
1187 usbi_close(ctx->event_pipe[1]);
1188 #ifdef USBI_TIMERFD_AVAILABLE
1189 if (usbi_using_timerfd(ctx)) {
1190 usbi_remove_pollfd(ctx, ctx->timerfd);
1191 close(ctx->timerfd);
1192 }
1193 #endif
1194 usbi_mutex_destroy(&ctx->flying_transfers_lock);
1195 usbi_mutex_destroy(&ctx->events_lock);
1196 usbi_mutex_destroy(&ctx->event_waiters_lock);
1197 usbi_cond_destroy(&ctx->event_waiters_cond);
1198 usbi_mutex_destroy(&ctx->event_data_lock);
1199 usbi_tls_key_delete(ctx->event_handling_key);
1200 if (ctx->pollfds)
1201 free(ctx->pollfds);
1202 }
1203
calculate_timeout(struct usbi_transfer * transfer)1204 static int calculate_timeout(struct usbi_transfer *transfer)
1205 {
1206 int r;
1207 struct timespec current_time;
1208 unsigned int timeout =
1209 USBI_TRANSFER_TO_LIBUSB_TRANSFER(transfer)->timeout;
1210
1211 if (!timeout)
1212 return 0;
1213
1214 r = usbi_backend->clock_gettime(USBI_CLOCK_MONOTONIC, ¤t_time);
1215 if (r < 0) {
1216 usbi_err(ITRANSFER_CTX(transfer),
1217 "failed to read monotonic clock, errno=%d", errno);
1218 return r;
1219 }
1220
1221 current_time.tv_sec += timeout / 1000;
1222 current_time.tv_nsec += (timeout % 1000) * 1000000;
1223
1224 while (current_time.tv_nsec >= 1000000000) {
1225 current_time.tv_nsec -= 1000000000;
1226 current_time.tv_sec++;
1227 }
1228
1229 TIMESPEC_TO_TIMEVAL(&transfer->timeout, ¤t_time);
1230 return 0;
1231 }
1232
1233 /** \ingroup libusb_asyncio
1234 * Allocate a libusb transfer with a specified number of isochronous packet
1235 * descriptors. The returned transfer is pre-initialized for you. When the new
1236 * transfer is no longer needed, it should be freed with
1237 * libusb_free_transfer().
1238 *
1239 * Transfers intended for non-isochronous endpoints (e.g. control, bulk,
1240 * interrupt) should specify an iso_packets count of zero.
1241 *
1242 * For transfers intended for isochronous endpoints, specify an appropriate
1243 * number of packet descriptors to be allocated as part of the transfer.
1244 * The returned transfer is not specially initialized for isochronous I/O;
1245 * you are still required to set the
1246 * \ref libusb_transfer::num_iso_packets "num_iso_packets" and
1247 * \ref libusb_transfer::type "type" fields accordingly.
1248 *
1249 * It is safe to allocate a transfer with some isochronous packets and then
1250 * use it on a non-isochronous endpoint. If you do this, ensure that at time
1251 * of submission, num_iso_packets is 0 and that type is set appropriately.
1252 *
1253 * \param iso_packets number of isochronous packet descriptors to allocate
1254 * \returns a newly allocated transfer, or NULL on error
1255 */
1256 DEFAULT_VISIBILITY
libusb_alloc_transfer(int iso_packets)1257 struct libusb_transfer * LIBUSB_CALL libusb_alloc_transfer(
1258 int iso_packets)
1259 {
1260 struct libusb_transfer *transfer;
1261 size_t os_alloc_size = usbi_backend->transfer_priv_size;
1262 size_t alloc_size = sizeof(struct usbi_transfer)
1263 + sizeof(struct libusb_transfer)
1264 + (sizeof(struct libusb_iso_packet_descriptor) * iso_packets)
1265 + os_alloc_size;
1266 struct usbi_transfer *itransfer = calloc(1, alloc_size);
1267 if (!itransfer)
1268 return NULL;
1269
1270 itransfer->num_iso_packets = iso_packets;
1271 usbi_mutex_init(&itransfer->lock);
1272 transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
1273 usbi_dbg("transfer %p", transfer);
1274 return transfer;
1275 }
1276
1277 /** \ingroup libusb_asyncio
1278 * Free a transfer structure. This should be called for all transfers
1279 * allocated with libusb_alloc_transfer().
1280 *
1281 * If the \ref libusb_transfer_flags::LIBUSB_TRANSFER_FREE_BUFFER
1282 * "LIBUSB_TRANSFER_FREE_BUFFER" flag is set and the transfer buffer is
1283 * non-NULL, this function will also free the transfer buffer using the
1284 * standard system memory allocator (e.g. free()).
1285 *
1286 * It is legal to call this function with a NULL transfer. In this case,
1287 * the function will simply return safely.
1288 *
1289 * It is not legal to free an active transfer (one which has been submitted
1290 * and has not yet completed).
1291 *
1292 * \param transfer the transfer to free
1293 */
libusb_free_transfer(struct libusb_transfer * transfer)1294 void API_EXPORTED libusb_free_transfer(struct libusb_transfer *transfer)
1295 {
1296 struct usbi_transfer *itransfer;
1297 if (!transfer)
1298 return;
1299
1300 usbi_dbg("transfer %p", transfer);
1301 if (transfer->flags & LIBUSB_TRANSFER_FREE_BUFFER && transfer->buffer)
1302 free(transfer->buffer);
1303
1304 itransfer = LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
1305 usbi_mutex_destroy(&itransfer->lock);
1306 free(itransfer);
1307 }
1308
1309 #ifdef USBI_TIMERFD_AVAILABLE
disarm_timerfd(struct libusb_context * ctx)1310 static int disarm_timerfd(struct libusb_context *ctx)
1311 {
1312 const struct itimerspec disarm_timer = { { 0, 0 }, { 0, 0 } };
1313 int r;
1314
1315 usbi_dbg("");
1316 r = timerfd_settime(ctx->timerfd, 0, &disarm_timer, NULL);
1317 if (r < 0)
1318 return LIBUSB_ERROR_OTHER;
1319 else
1320 return 0;
1321 }
1322
1323 /* iterates through the flying transfers, and rearms the timerfd based on the
1324 * next upcoming timeout.
1325 * must be called with flying_list locked.
1326 * returns 0 on success or a LIBUSB_ERROR code on failure.
1327 */
arm_timerfd_for_next_timeout(struct libusb_context * ctx)1328 static int arm_timerfd_for_next_timeout(struct libusb_context *ctx)
1329 {
1330 struct usbi_transfer *transfer;
1331
1332 list_for_each_entry(transfer, &ctx->flying_transfers, list, struct usbi_transfer) {
1333 struct timeval *cur_tv = &transfer->timeout;
1334
1335 /* if we've reached transfers of infinite timeout, then we have no
1336 * arming to do */
1337 if (!timerisset(cur_tv))
1338 goto disarm;
1339
1340 /* act on first transfer that has not already been handled */
1341 if (!(transfer->timeout_flags & (USBI_TRANSFER_TIMEOUT_HANDLED | USBI_TRANSFER_OS_HANDLES_TIMEOUT))) {
1342 int r;
1343 const struct itimerspec it = { {0, 0},
1344 { cur_tv->tv_sec, cur_tv->tv_usec * 1000 } };
1345 usbi_dbg("next timeout originally %dms", USBI_TRANSFER_TO_LIBUSB_TRANSFER(transfer)->timeout);
1346 r = timerfd_settime(ctx->timerfd, TFD_TIMER_ABSTIME, &it, NULL);
1347 if (r < 0)
1348 return LIBUSB_ERROR_OTHER;
1349 return 0;
1350 }
1351 }
1352
1353 disarm:
1354 return disarm_timerfd(ctx);
1355 }
1356 #else
arm_timerfd_for_next_timeout(struct libusb_context * ctx)1357 static int arm_timerfd_for_next_timeout(struct libusb_context *ctx)
1358 {
1359 UNUSED(ctx);
1360 return 0;
1361 }
1362 #endif
1363
1364 /* add a transfer to the (timeout-sorted) active transfers list.
1365 * This function will return non 0 if fails to update the timer,
1366 * in which case the transfer is *not* on the flying_transfers list. */
add_to_flying_list(struct usbi_transfer * transfer)1367 static int add_to_flying_list(struct usbi_transfer *transfer)
1368 {
1369 struct usbi_transfer *cur;
1370 struct timeval *timeout = &transfer->timeout;
1371 struct libusb_context *ctx = ITRANSFER_CTX(transfer);
1372 int r;
1373 int first = 1;
1374
1375 r = calculate_timeout(transfer);
1376 if (r)
1377 return r;
1378
1379 /* if we have no other flying transfers, start the list with this one */
1380 if (list_empty(&ctx->flying_transfers)) {
1381 list_add(&transfer->list, &ctx->flying_transfers);
1382 goto out;
1383 }
1384
1385 /* if we have infinite timeout, append to end of list */
1386 if (!timerisset(timeout)) {
1387 list_add_tail(&transfer->list, &ctx->flying_transfers);
1388 /* first is irrelevant in this case */
1389 goto out;
1390 }
1391
1392 /* otherwise, find appropriate place in list */
1393 list_for_each_entry(cur, &ctx->flying_transfers, list, struct usbi_transfer) {
1394 /* find first timeout that occurs after the transfer in question */
1395 struct timeval *cur_tv = &cur->timeout;
1396
1397 if (!timerisset(cur_tv) || (cur_tv->tv_sec > timeout->tv_sec) ||
1398 (cur_tv->tv_sec == timeout->tv_sec &&
1399 cur_tv->tv_usec > timeout->tv_usec)) {
1400 list_add_tail(&transfer->list, &cur->list);
1401 goto out;
1402 }
1403 first = 0;
1404 }
1405 /* first is 0 at this stage (list not empty) */
1406
1407 /* otherwise we need to be inserted at the end */
1408 list_add_tail(&transfer->list, &ctx->flying_transfers);
1409 out:
1410 #ifdef USBI_TIMERFD_AVAILABLE
1411 if (first && usbi_using_timerfd(ctx) && timerisset(timeout)) {
1412 /* if this transfer has the lowest timeout of all active transfers,
1413 * rearm the timerfd with this transfer's timeout */
1414 const struct itimerspec it = { {0, 0},
1415 { timeout->tv_sec, timeout->tv_usec * 1000 } };
1416 usbi_dbg("arm timerfd for timeout in %dms (first in line)",
1417 USBI_TRANSFER_TO_LIBUSB_TRANSFER(transfer)->timeout);
1418 r = timerfd_settime(ctx->timerfd, TFD_TIMER_ABSTIME, &it, NULL);
1419 if (r < 0) {
1420 usbi_warn(ctx, "failed to arm first timerfd (errno %d)", errno);
1421 r = LIBUSB_ERROR_OTHER;
1422 }
1423 }
1424 #else
1425 UNUSED(first);
1426 #endif
1427
1428 if (r)
1429 list_del(&transfer->list);
1430
1431 return r;
1432 }
1433
1434 /* remove a transfer from the active transfers list.
1435 * This function will *always* remove the transfer from the
1436 * flying_transfers list. It will return a LIBUSB_ERROR code
1437 * if it fails to update the timer for the next timeout. */
remove_from_flying_list(struct usbi_transfer * transfer)1438 static int remove_from_flying_list(struct usbi_transfer *transfer)
1439 {
1440 struct libusb_context *ctx = ITRANSFER_CTX(transfer);
1441 int rearm_timerfd;
1442 int r = 0;
1443
1444 usbi_mutex_lock(&ctx->flying_transfers_lock);
1445 rearm_timerfd = (timerisset(&transfer->timeout) &&
1446 list_first_entry(&ctx->flying_transfers, struct usbi_transfer, list) == transfer);
1447 list_del(&transfer->list);
1448 if (usbi_using_timerfd(ctx) && rearm_timerfd)
1449 r = arm_timerfd_for_next_timeout(ctx);
1450 usbi_mutex_unlock(&ctx->flying_transfers_lock);
1451
1452 return r;
1453 }
1454
1455 /** \ingroup libusb_asyncio
1456 * Submit a transfer. This function will fire off the USB transfer and then
1457 * return immediately.
1458 *
1459 * \param transfer the transfer to submit
1460 * \returns 0 on success
1461 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1462 * \returns LIBUSB_ERROR_BUSY if the transfer has already been submitted.
1463 * \returns LIBUSB_ERROR_NOT_SUPPORTED if the transfer flags are not supported
1464 * by the operating system.
1465 * \returns LIBUSB_ERROR_INVALID_PARAM if the transfer size is larger than
1466 * the operating system and/or hardware can support
1467 * \returns another LIBUSB_ERROR code on other failure
1468 */
libusb_submit_transfer(struct libusb_transfer * transfer)1469 int API_EXPORTED libusb_submit_transfer(struct libusb_transfer *transfer)
1470 {
1471 struct usbi_transfer *itransfer =
1472 LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
1473 struct libusb_context *ctx = TRANSFER_CTX(transfer);
1474 int r;
1475
1476 usbi_dbg("transfer %p", transfer);
1477
1478 /*
1479 * Important note on locking, this function takes / releases locks
1480 * in the following order:
1481 * take flying_transfers_lock
1482 * take itransfer->lock
1483 * clear transfer
1484 * add to flying_transfers list
1485 * release flying_transfers_lock
1486 * submit transfer
1487 * release itransfer->lock
1488 * if submit failed:
1489 * take flying_transfers_lock
1490 * remove from flying_transfers list
1491 * release flying_transfers_lock
1492 *
1493 * Note that it takes locks in the order a-b and then releases them
1494 * in the same order a-b. This is somewhat unusual but not wrong,
1495 * release order is not important as long as *all* locks are released
1496 * before re-acquiring any locks.
1497 *
1498 * This means that the ordering of first releasing itransfer->lock
1499 * and then re-acquiring the flying_transfers_list on error is
1500 * important and must not be changed!
1501 *
1502 * This is done this way because when we take both locks we must always
1503 * take flying_transfers_lock first to avoid ab-ba style deadlocks with
1504 * the timeout handling and usbi_handle_disconnect paths.
1505 *
1506 * And we cannot release itransfer->lock before the submission is
1507 * complete otherwise timeout handling for transfers with short
1508 * timeouts may run before submission.
1509 */
1510 usbi_mutex_lock(&ctx->flying_transfers_lock);
1511 usbi_mutex_lock(&itransfer->lock);
1512 if (itransfer->state_flags & USBI_TRANSFER_IN_FLIGHT) {
1513 usbi_mutex_unlock(&ctx->flying_transfers_lock);
1514 usbi_mutex_unlock(&itransfer->lock);
1515 return LIBUSB_ERROR_BUSY;
1516 }
1517 itransfer->transferred = 0;
1518 itransfer->state_flags = 0;
1519 itransfer->timeout_flags = 0;
1520 r = add_to_flying_list(itransfer);
1521 if (r) {
1522 usbi_mutex_unlock(&ctx->flying_transfers_lock);
1523 usbi_mutex_unlock(&itransfer->lock);
1524 return r;
1525 }
1526 /*
1527 * We must release the flying transfers lock here, because with
1528 * some backends the submit_transfer method is synchroneous.
1529 */
1530 usbi_mutex_unlock(&ctx->flying_transfers_lock);
1531
1532 r = usbi_backend->submit_transfer(itransfer);
1533 if (r == LIBUSB_SUCCESS) {
1534 itransfer->state_flags |= USBI_TRANSFER_IN_FLIGHT;
1535 /* keep a reference to this device */
1536 libusb_ref_device(transfer->dev_handle->dev);
1537 }
1538 usbi_mutex_unlock(&itransfer->lock);
1539
1540 if (r != LIBUSB_SUCCESS)
1541 remove_from_flying_list(itransfer);
1542
1543 return r;
1544 }
1545
1546 /** \ingroup libusb_asyncio
1547 * Asynchronously cancel a previously submitted transfer.
1548 * This function returns immediately, but this does not indicate cancellation
1549 * is complete. Your callback function will be invoked at some later time
1550 * with a transfer status of
1551 * \ref libusb_transfer_status::LIBUSB_TRANSFER_CANCELLED
1552 * "LIBUSB_TRANSFER_CANCELLED."
1553 *
1554 * \param transfer the transfer to cancel
1555 * \returns 0 on success
1556 * \returns LIBUSB_ERROR_NOT_FOUND if the transfer is not in progress,
1557 * already complete, or already cancelled.
1558 * \returns a LIBUSB_ERROR code on failure
1559 */
libusb_cancel_transfer(struct libusb_transfer * transfer)1560 int API_EXPORTED libusb_cancel_transfer(struct libusb_transfer *transfer)
1561 {
1562 struct usbi_transfer *itransfer =
1563 LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
1564 int r;
1565
1566 usbi_dbg("transfer %p", transfer );
1567 usbi_mutex_lock(&itransfer->lock);
1568 if (!(itransfer->state_flags & USBI_TRANSFER_IN_FLIGHT)
1569 || (itransfer->state_flags & USBI_TRANSFER_CANCELLING)) {
1570 r = LIBUSB_ERROR_NOT_FOUND;
1571 goto out;
1572 }
1573 r = usbi_backend->cancel_transfer(itransfer);
1574 if (r < 0) {
1575 if (r != LIBUSB_ERROR_NOT_FOUND &&
1576 r != LIBUSB_ERROR_NO_DEVICE)
1577 usbi_err(TRANSFER_CTX(transfer),
1578 "cancel transfer failed error %d", r);
1579 else
1580 usbi_dbg("cancel transfer failed error %d", r);
1581
1582 if (r == LIBUSB_ERROR_NO_DEVICE)
1583 itransfer->state_flags |= USBI_TRANSFER_DEVICE_DISAPPEARED;
1584 }
1585
1586 itransfer->state_flags |= USBI_TRANSFER_CANCELLING;
1587
1588 out:
1589 usbi_mutex_unlock(&itransfer->lock);
1590 return r;
1591 }
1592
1593 /** \ingroup libusb_asyncio
1594 * Set a transfers bulk stream id. Note users are advised to use
1595 * libusb_fill_bulk_stream_transfer() instead of calling this function
1596 * directly.
1597 *
1598 * Since version 1.0.19, \ref LIBUSB_API_VERSION >= 0x01000103
1599 *
1600 * \param transfer the transfer to set the stream id for
1601 * \param stream_id the stream id to set
1602 * \see libusb_alloc_streams()
1603 */
libusb_transfer_set_stream_id(struct libusb_transfer * transfer,uint32_t stream_id)1604 void API_EXPORTED libusb_transfer_set_stream_id(
1605 struct libusb_transfer *transfer, uint32_t stream_id)
1606 {
1607 struct usbi_transfer *itransfer =
1608 LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
1609
1610 itransfer->stream_id = stream_id;
1611 }
1612
1613 /** \ingroup libusb_asyncio
1614 * Get a transfers bulk stream id.
1615 *
1616 * Since version 1.0.19, \ref LIBUSB_API_VERSION >= 0x01000103
1617 *
1618 * \param transfer the transfer to get the stream id for
1619 * \returns the stream id for the transfer
1620 */
libusb_transfer_get_stream_id(struct libusb_transfer * transfer)1621 uint32_t API_EXPORTED libusb_transfer_get_stream_id(
1622 struct libusb_transfer *transfer)
1623 {
1624 struct usbi_transfer *itransfer =
1625 LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
1626
1627 return itransfer->stream_id;
1628 }
1629
1630 /* Handle completion of a transfer (completion might be an error condition).
1631 * This will invoke the user-supplied callback function, which may end up
1632 * freeing the transfer. Therefore you cannot use the transfer structure
1633 * after calling this function, and you should free all backend-specific
1634 * data before calling it.
1635 * Do not call this function with the usbi_transfer lock held. User-specified
1636 * callback functions may attempt to directly resubmit the transfer, which
1637 * will attempt to take the lock. */
usbi_handle_transfer_completion(struct usbi_transfer * itransfer,enum libusb_transfer_status status)1638 int usbi_handle_transfer_completion(struct usbi_transfer *itransfer,
1639 enum libusb_transfer_status status)
1640 {
1641 struct libusb_transfer *transfer =
1642 USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
1643 struct libusb_device_handle *dev_handle = transfer->dev_handle;
1644 uint8_t flags;
1645 int r;
1646
1647 r = remove_from_flying_list(itransfer);
1648 if (r < 0)
1649 usbi_err(ITRANSFER_CTX(itransfer), "failed to set timer for next timeout, errno=%d", errno);
1650
1651 usbi_mutex_lock(&itransfer->lock);
1652 itransfer->state_flags &= ~USBI_TRANSFER_IN_FLIGHT;
1653 usbi_mutex_unlock(&itransfer->lock);
1654
1655 if (status == LIBUSB_TRANSFER_COMPLETED
1656 && transfer->flags & LIBUSB_TRANSFER_SHORT_NOT_OK) {
1657 int rqlen = transfer->length;
1658 if (transfer->type == LIBUSB_TRANSFER_TYPE_CONTROL)
1659 rqlen -= LIBUSB_CONTROL_SETUP_SIZE;
1660 if (rqlen != itransfer->transferred) {
1661 usbi_dbg("interpreting short transfer as error");
1662 status = LIBUSB_TRANSFER_ERROR;
1663 }
1664 }
1665
1666 flags = transfer->flags;
1667 transfer->status = status;
1668 transfer->actual_length = itransfer->transferred;
1669 usbi_dbg("transfer %p has callback %p", transfer, transfer->callback);
1670 if (transfer->callback)
1671 transfer->callback(transfer);
1672 /* transfer might have been freed by the above call, do not use from
1673 * this point. */
1674 if (flags & LIBUSB_TRANSFER_FREE_TRANSFER)
1675 libusb_free_transfer(transfer);
1676 libusb_unref_device(dev_handle->dev);
1677 return r;
1678 }
1679
1680 /* Similar to usbi_handle_transfer_completion() but exclusively for transfers
1681 * that were asynchronously cancelled. The same concerns w.r.t. freeing of
1682 * transfers exist here.
1683 * Do not call this function with the usbi_transfer lock held. User-specified
1684 * callback functions may attempt to directly resubmit the transfer, which
1685 * will attempt to take the lock. */
usbi_handle_transfer_cancellation(struct usbi_transfer * transfer)1686 int usbi_handle_transfer_cancellation(struct usbi_transfer *transfer)
1687 {
1688 struct libusb_context *ctx = ITRANSFER_CTX(transfer);
1689 uint8_t timed_out;
1690
1691 usbi_mutex_lock(&ctx->flying_transfers_lock);
1692 timed_out = transfer->timeout_flags & USBI_TRANSFER_TIMED_OUT;
1693 usbi_mutex_unlock(&ctx->flying_transfers_lock);
1694
1695 /* if the URB was cancelled due to timeout, report timeout to the user */
1696 if (timed_out) {
1697 usbi_dbg("detected timeout cancellation");
1698 return usbi_handle_transfer_completion(transfer, LIBUSB_TRANSFER_TIMED_OUT);
1699 }
1700
1701 /* otherwise its a normal async cancel */
1702 return usbi_handle_transfer_completion(transfer, LIBUSB_TRANSFER_CANCELLED);
1703 }
1704
1705 /* Add a completed transfer to the completed_transfers list of the
1706 * context and signal the event. The backend's handle_transfer_completion()
1707 * function will be called the next time an event handler runs. */
usbi_signal_transfer_completion(struct usbi_transfer * transfer)1708 void usbi_signal_transfer_completion(struct usbi_transfer *transfer)
1709 {
1710 struct libusb_context *ctx = ITRANSFER_CTX(transfer);
1711 int pending_events;
1712
1713 usbi_mutex_lock(&ctx->event_data_lock);
1714 pending_events = usbi_pending_events(ctx);
1715 list_add_tail(&transfer->completed_list, &ctx->completed_transfers);
1716 if (!pending_events)
1717 usbi_signal_event(ctx);
1718 usbi_mutex_unlock(&ctx->event_data_lock);
1719 }
1720
1721 /** \ingroup libusb_poll
1722 * Attempt to acquire the event handling lock. This lock is used to ensure that
1723 * only one thread is monitoring libusb event sources at any one time.
1724 *
1725 * You only need to use this lock if you are developing an application
1726 * which calls poll() or select() on libusb's file descriptors directly.
1727 * If you stick to libusb's event handling loop functions (e.g.
1728 * libusb_handle_events()) then you do not need to be concerned with this
1729 * locking.
1730 *
1731 * While holding this lock, you are trusted to actually be handling events.
1732 * If you are no longer handling events, you must call libusb_unlock_events()
1733 * as soon as possible.
1734 *
1735 * \param ctx the context to operate on, or NULL for the default context
1736 * \returns 0 if the lock was obtained successfully
1737 * \returns 1 if the lock was not obtained (i.e. another thread holds the lock)
1738 * \ref libusb_mtasync
1739 */
libusb_try_lock_events(libusb_context * ctx)1740 int API_EXPORTED libusb_try_lock_events(libusb_context *ctx)
1741 {
1742 int r;
1743 unsigned int ru;
1744 USBI_GET_CONTEXT(ctx);
1745
1746 /* is someone else waiting to close a device? if so, don't let this thread
1747 * start event handling */
1748 usbi_mutex_lock(&ctx->event_data_lock);
1749 ru = ctx->device_close;
1750 usbi_mutex_unlock(&ctx->event_data_lock);
1751 if (ru) {
1752 usbi_dbg("someone else is closing a device");
1753 return 1;
1754 }
1755
1756 r = usbi_mutex_trylock(&ctx->events_lock);
1757 if (r)
1758 return 1;
1759
1760 ctx->event_handler_active = 1;
1761 return 0;
1762 }
1763
1764 /** \ingroup libusb_poll
1765 * Acquire the event handling lock, blocking until successful acquisition if
1766 * it is contended. This lock is used to ensure that only one thread is
1767 * monitoring libusb event sources at any one time.
1768 *
1769 * You only need to use this lock if you are developing an application
1770 * which calls poll() or select() on libusb's file descriptors directly.
1771 * If you stick to libusb's event handling loop functions (e.g.
1772 * libusb_handle_events()) then you do not need to be concerned with this
1773 * locking.
1774 *
1775 * While holding this lock, you are trusted to actually be handling events.
1776 * If you are no longer handling events, you must call libusb_unlock_events()
1777 * as soon as possible.
1778 *
1779 * \param ctx the context to operate on, or NULL for the default context
1780 * \ref libusb_mtasync
1781 */
libusb_lock_events(libusb_context * ctx)1782 void API_EXPORTED libusb_lock_events(libusb_context *ctx)
1783 {
1784 USBI_GET_CONTEXT(ctx);
1785 usbi_mutex_lock(&ctx->events_lock);
1786 ctx->event_handler_active = 1;
1787 }
1788
1789 /** \ingroup libusb_poll
1790 * Release the lock previously acquired with libusb_try_lock_events() or
1791 * libusb_lock_events(). Releasing this lock will wake up any threads blocked
1792 * on libusb_wait_for_event().
1793 *
1794 * \param ctx the context to operate on, or NULL for the default context
1795 * \ref libusb_mtasync
1796 */
libusb_unlock_events(libusb_context * ctx)1797 void API_EXPORTED libusb_unlock_events(libusb_context *ctx)
1798 {
1799 USBI_GET_CONTEXT(ctx);
1800 ctx->event_handler_active = 0;
1801 usbi_mutex_unlock(&ctx->events_lock);
1802
1803 /* FIXME: perhaps we should be a bit more efficient by not broadcasting
1804 * the availability of the events lock when we are modifying pollfds
1805 * (check ctx->device_close)? */
1806 usbi_mutex_lock(&ctx->event_waiters_lock);
1807 usbi_cond_broadcast(&ctx->event_waiters_cond);
1808 usbi_mutex_unlock(&ctx->event_waiters_lock);
1809 }
1810
1811 /** \ingroup libusb_poll
1812 * Determine if it is still OK for this thread to be doing event handling.
1813 *
1814 * Sometimes, libusb needs to temporarily pause all event handlers, and this
1815 * is the function you should use before polling file descriptors to see if
1816 * this is the case.
1817 *
1818 * If this function instructs your thread to give up the events lock, you
1819 * should just continue the usual logic that is documented in \ref libusb_mtasync.
1820 * On the next iteration, your thread will fail to obtain the events lock,
1821 * and will hence become an event waiter.
1822 *
1823 * This function should be called while the events lock is held: you don't
1824 * need to worry about the results of this function if your thread is not
1825 * the current event handler.
1826 *
1827 * \param ctx the context to operate on, or NULL for the default context
1828 * \returns 1 if event handling can start or continue
1829 * \returns 0 if this thread must give up the events lock
1830 * \ref fullstory "Multi-threaded I/O: the full story"
1831 */
libusb_event_handling_ok(libusb_context * ctx)1832 int API_EXPORTED libusb_event_handling_ok(libusb_context *ctx)
1833 {
1834 unsigned int r;
1835 USBI_GET_CONTEXT(ctx);
1836
1837 /* is someone else waiting to close a device? if so, don't let this thread
1838 * continue event handling */
1839 usbi_mutex_lock(&ctx->event_data_lock);
1840 r = ctx->device_close;
1841 usbi_mutex_unlock(&ctx->event_data_lock);
1842 if (r) {
1843 usbi_dbg("someone else is closing a device");
1844 return 0;
1845 }
1846
1847 return 1;
1848 }
1849
1850
1851 /** \ingroup libusb_poll
1852 * Determine if an active thread is handling events (i.e. if anyone is holding
1853 * the event handling lock).
1854 *
1855 * \param ctx the context to operate on, or NULL for the default context
1856 * \returns 1 if a thread is handling events
1857 * \returns 0 if there are no threads currently handling events
1858 * \ref libusb_mtasync
1859 */
libusb_event_handler_active(libusb_context * ctx)1860 int API_EXPORTED libusb_event_handler_active(libusb_context *ctx)
1861 {
1862 unsigned int r;
1863 USBI_GET_CONTEXT(ctx);
1864
1865 /* is someone else waiting to close a device? if so, don't let this thread
1866 * start event handling -- indicate that event handling is happening */
1867 usbi_mutex_lock(&ctx->event_data_lock);
1868 r = ctx->device_close;
1869 usbi_mutex_unlock(&ctx->event_data_lock);
1870 if (r) {
1871 usbi_dbg("someone else is closing a device");
1872 return 1;
1873 }
1874
1875 return ctx->event_handler_active;
1876 }
1877
1878 /** \ingroup libusb_poll
1879 * Interrupt any active thread that is handling events. This is mainly useful
1880 * for interrupting a dedicated event handling thread when an application
1881 * wishes to call libusb_exit().
1882 *
1883 * Since version 1.0.21, \ref LIBUSB_API_VERSION >= 0x01000105
1884 *
1885 * \param ctx the context to operate on, or NULL for the default context
1886 * \ref libusb_mtasync
1887 */
libusb_interrupt_event_handler(libusb_context * ctx)1888 void API_EXPORTED libusb_interrupt_event_handler(libusb_context *ctx)
1889 {
1890 USBI_GET_CONTEXT(ctx);
1891
1892 usbi_dbg("");
1893 usbi_mutex_lock(&ctx->event_data_lock);
1894 if (!usbi_pending_events(ctx)) {
1895 ctx->event_flags |= USBI_EVENT_USER_INTERRUPT;
1896 usbi_signal_event(ctx);
1897 }
1898 usbi_mutex_unlock(&ctx->event_data_lock);
1899 }
1900
1901 /** \ingroup libusb_poll
1902 * Acquire the event waiters lock. This lock is designed to be obtained under
1903 * the situation where you want to be aware when events are completed, but
1904 * some other thread is event handling so calling libusb_handle_events() is not
1905 * allowed.
1906 *
1907 * You then obtain this lock, re-check that another thread is still handling
1908 * events, then call libusb_wait_for_event().
1909 *
1910 * You only need to use this lock if you are developing an application
1911 * which calls poll() or select() on libusb's file descriptors directly,
1912 * <b>and</b> may potentially be handling events from 2 threads simultaenously.
1913 * If you stick to libusb's event handling loop functions (e.g.
1914 * libusb_handle_events()) then you do not need to be concerned with this
1915 * locking.
1916 *
1917 * \param ctx the context to operate on, or NULL for the default context
1918 * \ref libusb_mtasync
1919 */
libusb_lock_event_waiters(libusb_context * ctx)1920 void API_EXPORTED libusb_lock_event_waiters(libusb_context *ctx)
1921 {
1922 USBI_GET_CONTEXT(ctx);
1923 usbi_mutex_lock(&ctx->event_waiters_lock);
1924 }
1925
1926 /** \ingroup libusb_poll
1927 * Release the event waiters lock.
1928 * \param ctx the context to operate on, or NULL for the default context
1929 * \ref libusb_mtasync
1930 */
libusb_unlock_event_waiters(libusb_context * ctx)1931 void API_EXPORTED libusb_unlock_event_waiters(libusb_context *ctx)
1932 {
1933 USBI_GET_CONTEXT(ctx);
1934 usbi_mutex_unlock(&ctx->event_waiters_lock);
1935 }
1936
1937 /** \ingroup libusb_poll
1938 * Wait for another thread to signal completion of an event. Must be called
1939 * with the event waiters lock held, see libusb_lock_event_waiters().
1940 *
1941 * This function will block until any of the following conditions are met:
1942 * -# The timeout expires
1943 * -# A transfer completes
1944 * -# A thread releases the event handling lock through libusb_unlock_events()
1945 *
1946 * Condition 1 is obvious. Condition 2 unblocks your thread <em>after</em>
1947 * the callback for the transfer has completed. Condition 3 is important
1948 * because it means that the thread that was previously handling events is no
1949 * longer doing so, so if any events are to complete, another thread needs to
1950 * step up and start event handling.
1951 *
1952 * This function releases the event waiters lock before putting your thread
1953 * to sleep, and reacquires the lock as it is being woken up.
1954 *
1955 * \param ctx the context to operate on, or NULL for the default context
1956 * \param tv maximum timeout for this blocking function. A NULL value
1957 * indicates unlimited timeout.
1958 * \returns 0 after a transfer completes or another thread stops event handling
1959 * \returns 1 if the timeout expired
1960 * \ref libusb_mtasync
1961 */
libusb_wait_for_event(libusb_context * ctx,struct timeval * tv)1962 int API_EXPORTED libusb_wait_for_event(libusb_context *ctx, struct timeval *tv)
1963 {
1964 int r;
1965
1966 USBI_GET_CONTEXT(ctx);
1967 if (tv == NULL) {
1968 usbi_cond_wait(&ctx->event_waiters_cond, &ctx->event_waiters_lock);
1969 return 0;
1970 }
1971
1972 r = usbi_cond_timedwait(&ctx->event_waiters_cond,
1973 &ctx->event_waiters_lock, tv);
1974
1975 if (r < 0)
1976 return r;
1977 else
1978 return (r == ETIMEDOUT);
1979 }
1980
handle_timeout(struct usbi_transfer * itransfer)1981 static void handle_timeout(struct usbi_transfer *itransfer)
1982 {
1983 struct libusb_transfer *transfer =
1984 USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
1985 int r;
1986
1987 itransfer->timeout_flags |= USBI_TRANSFER_TIMEOUT_HANDLED;
1988 r = libusb_cancel_transfer(transfer);
1989 if (r == LIBUSB_SUCCESS)
1990 itransfer->timeout_flags |= USBI_TRANSFER_TIMED_OUT;
1991 else
1992 usbi_warn(TRANSFER_CTX(transfer),
1993 "async cancel failed %d errno=%d", r, errno);
1994 }
1995
handle_timeouts_locked(struct libusb_context * ctx)1996 static int handle_timeouts_locked(struct libusb_context *ctx)
1997 {
1998 int r;
1999 struct timespec systime_ts;
2000 struct timeval systime;
2001 struct usbi_transfer *transfer;
2002
2003 if (list_empty(&ctx->flying_transfers))
2004 return 0;
2005
2006 /* get current time */
2007 r = usbi_backend->clock_gettime(USBI_CLOCK_MONOTONIC, &systime_ts);
2008 if (r < 0)
2009 return r;
2010
2011 TIMESPEC_TO_TIMEVAL(&systime, &systime_ts);
2012
2013 /* iterate through flying transfers list, finding all transfers that
2014 * have expired timeouts */
2015 list_for_each_entry(transfer, &ctx->flying_transfers, list, struct usbi_transfer) {
2016 struct timeval *cur_tv = &transfer->timeout;
2017
2018 /* if we've reached transfers of infinite timeout, we're all done */
2019 if (!timerisset(cur_tv))
2020 return 0;
2021
2022 /* ignore timeouts we've already handled */
2023 if (transfer->timeout_flags & (USBI_TRANSFER_TIMEOUT_HANDLED | USBI_TRANSFER_OS_HANDLES_TIMEOUT))
2024 continue;
2025
2026 /* if transfer has non-expired timeout, nothing more to do */
2027 if ((cur_tv->tv_sec > systime.tv_sec) ||
2028 (cur_tv->tv_sec == systime.tv_sec &&
2029 cur_tv->tv_usec > systime.tv_usec))
2030 return 0;
2031
2032 /* otherwise, we've got an expired timeout to handle */
2033 handle_timeout(transfer);
2034 }
2035 return 0;
2036 }
2037
handle_timeouts(struct libusb_context * ctx)2038 static int handle_timeouts(struct libusb_context *ctx)
2039 {
2040 int r;
2041 USBI_GET_CONTEXT(ctx);
2042 usbi_mutex_lock(&ctx->flying_transfers_lock);
2043 r = handle_timeouts_locked(ctx);
2044 usbi_mutex_unlock(&ctx->flying_transfers_lock);
2045 return r;
2046 }
2047
2048 #ifdef USBI_TIMERFD_AVAILABLE
handle_timerfd_trigger(struct libusb_context * ctx)2049 static int handle_timerfd_trigger(struct libusb_context *ctx)
2050 {
2051 int r;
2052
2053 usbi_mutex_lock(&ctx->flying_transfers_lock);
2054
2055 /* process the timeout that just happened */
2056 r = handle_timeouts_locked(ctx);
2057 if (r < 0)
2058 goto out;
2059
2060 /* arm for next timeout*/
2061 r = arm_timerfd_for_next_timeout(ctx);
2062
2063 out:
2064 usbi_mutex_unlock(&ctx->flying_transfers_lock);
2065 return r;
2066 }
2067 #endif
2068
2069 /* do the actual event handling. assumes that no other thread is concurrently
2070 * doing the same thing. */
handle_events(struct libusb_context * ctx,struct timeval * tv)2071 static int handle_events(struct libusb_context *ctx, struct timeval *tv)
2072 {
2073 int r;
2074 struct usbi_pollfd *ipollfd;
2075 POLL_NFDS_TYPE nfds = 0;
2076 POLL_NFDS_TYPE internal_nfds;
2077 struct pollfd *fds = NULL;
2078 int i = -1;
2079 int timeout_ms;
2080 int special_event;
2081
2082 /* prevent attempts to recursively handle events (e.g. calling into
2083 * libusb_handle_events() from within a hotplug or transfer callback) */
2084 if (usbi_handling_events(ctx))
2085 return LIBUSB_ERROR_BUSY;
2086 usbi_start_event_handling(ctx);
2087
2088 /* there are certain fds that libusb uses internally, currently:
2089 *
2090 * 1) event pipe
2091 * 2) timerfd
2092 *
2093 * the backend will never need to attempt to handle events on these fds, so
2094 * we determine how many fds are in use internally for this context and when
2095 * handle_events() is called in the backend, the pollfd list and count will
2096 * be adjusted to skip over these internal fds */
2097 if (usbi_using_timerfd(ctx))
2098 internal_nfds = 2;
2099 else
2100 internal_nfds = 1;
2101
2102 /* only reallocate the poll fds when the list of poll fds has been modified
2103 * since the last poll, otherwise reuse them to save the additional overhead */
2104 usbi_mutex_lock(&ctx->event_data_lock);
2105 if (ctx->event_flags & USBI_EVENT_POLLFDS_MODIFIED) {
2106 usbi_dbg("poll fds modified, reallocating");
2107
2108 if (ctx->pollfds) {
2109 free(ctx->pollfds);
2110 ctx->pollfds = NULL;
2111 }
2112
2113 /* sanity check - it is invalid for a context to have fewer than the
2114 * required internal fds (memory corruption?) */
2115 assert(ctx->pollfds_cnt >= internal_nfds);
2116
2117 ctx->pollfds = calloc(ctx->pollfds_cnt, sizeof(*ctx->pollfds));
2118 if (!ctx->pollfds) {
2119 usbi_mutex_unlock(&ctx->event_data_lock);
2120 r = LIBUSB_ERROR_NO_MEM;
2121 goto done;
2122 }
2123
2124 list_for_each_entry(ipollfd, &ctx->ipollfds, list, struct usbi_pollfd) {
2125 struct libusb_pollfd *pollfd = &ipollfd->pollfd;
2126 i++;
2127 ctx->pollfds[i].fd = pollfd->fd;
2128 ctx->pollfds[i].events = pollfd->events;
2129 }
2130
2131 /* reset the flag now that we have the updated list */
2132 ctx->event_flags &= ~USBI_EVENT_POLLFDS_MODIFIED;
2133
2134 /* if no further pending events, clear the event pipe so that we do
2135 * not immediately return from poll */
2136 if (!usbi_pending_events(ctx))
2137 usbi_clear_event(ctx);
2138 }
2139 fds = ctx->pollfds;
2140 nfds = ctx->pollfds_cnt;
2141 usbi_mutex_unlock(&ctx->event_data_lock);
2142
2143 timeout_ms = (int)(tv->tv_sec * 1000) + (tv->tv_usec / 1000);
2144
2145 /* round up to next millisecond */
2146 if (tv->tv_usec % 1000)
2147 timeout_ms++;
2148
2149 redo_poll:
2150 usbi_dbg("poll() %d fds with timeout in %dms", nfds, timeout_ms);
2151 r = usbi_poll(fds, nfds, timeout_ms);
2152 usbi_dbg("poll() returned %d", r);
2153 if (r == 0) {
2154 r = handle_timeouts(ctx);
2155 goto done;
2156 }
2157 else if (r == -1 && errno == EINTR) {
2158 r = LIBUSB_ERROR_INTERRUPTED;
2159 goto done;
2160 }
2161 else if (r < 0) {
2162 usbi_err(ctx, "poll failed %d err=%d", r, errno);
2163 r = LIBUSB_ERROR_IO;
2164 goto done;
2165 }
2166
2167 special_event = 0;
2168
2169 /* fds[0] is always the event pipe */
2170 if (fds[0].revents) {
2171 libusb_hotplug_message *message = NULL;
2172 struct usbi_transfer *itransfer;
2173 int ret = 0;
2174
2175 usbi_dbg("caught a fish on the event pipe");
2176
2177 /* take the the event data lock while processing events */
2178 usbi_mutex_lock(&ctx->event_data_lock);
2179
2180 /* check if someone added a new poll fd */
2181 if (ctx->event_flags & USBI_EVENT_POLLFDS_MODIFIED)
2182 usbi_dbg("someone updated the poll fds");
2183
2184 if (ctx->event_flags & USBI_EVENT_USER_INTERRUPT) {
2185 usbi_dbg("someone purposely interrupted");
2186 ctx->event_flags &= ~USBI_EVENT_USER_INTERRUPT;
2187 }
2188
2189 /* check if someone is closing a device */
2190 if (ctx->device_close)
2191 usbi_dbg("someone is closing a device");
2192
2193 /* check for any pending hotplug messages */
2194 if (!list_empty(&ctx->hotplug_msgs)) {
2195 usbi_dbg("hotplug message received");
2196 special_event = 1;
2197 message = list_first_entry(&ctx->hotplug_msgs, libusb_hotplug_message, list);
2198 list_del(&message->list);
2199 }
2200
2201 /* complete any pending transfers */
2202 while (ret == 0 && !list_empty(&ctx->completed_transfers)) {
2203 itransfer = list_first_entry(&ctx->completed_transfers, struct usbi_transfer, completed_list);
2204 list_del(&itransfer->completed_list);
2205 usbi_mutex_unlock(&ctx->event_data_lock);
2206 ret = usbi_backend->handle_transfer_completion(itransfer);
2207 if (ret)
2208 usbi_err(ctx, "backend handle_transfer_completion failed with error %d", ret);
2209 usbi_mutex_lock(&ctx->event_data_lock);
2210 }
2211
2212 /* if no further pending events, clear the event pipe */
2213 if (!usbi_pending_events(ctx))
2214 usbi_clear_event(ctx);
2215
2216 usbi_mutex_unlock(&ctx->event_data_lock);
2217
2218 /* process the hotplug message, if any */
2219 if (message) {
2220 usbi_hotplug_match(ctx, message->device, message->event);
2221
2222 /* the device left, dereference the device */
2223 if (LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT == message->event)
2224 libusb_unref_device(message->device);
2225
2226 free(message);
2227 }
2228
2229 if (ret) {
2230 /* return error code */
2231 r = ret;
2232 goto done;
2233 }
2234
2235 if (0 == --r)
2236 goto handled;
2237 }
2238
2239 #ifdef USBI_TIMERFD_AVAILABLE
2240 /* on timerfd configurations, fds[1] is the timerfd */
2241 if (usbi_using_timerfd(ctx) && fds[1].revents) {
2242 /* timerfd indicates that a timeout has expired */
2243 int ret;
2244 usbi_dbg("timerfd triggered");
2245 special_event = 1;
2246
2247 ret = handle_timerfd_trigger(ctx);
2248 if (ret < 0) {
2249 /* return error code */
2250 r = ret;
2251 goto done;
2252 }
2253
2254 if (0 == --r)
2255 goto handled;
2256 }
2257 #endif
2258
2259 r = usbi_backend->handle_events(ctx, fds + internal_nfds, nfds - internal_nfds, r);
2260 if (r)
2261 usbi_err(ctx, "backend handle_events failed with error %d", r);
2262
2263 handled:
2264 if (r == 0 && special_event) {
2265 timeout_ms = 0;
2266 goto redo_poll;
2267 }
2268
2269 done:
2270 usbi_end_event_handling(ctx);
2271 return r;
2272 }
2273
2274 /* returns the smallest of:
2275 * 1. timeout of next URB
2276 * 2. user-supplied timeout
2277 * returns 1 if there is an already-expired timeout, otherwise returns 0
2278 * and populates out
2279 */
get_next_timeout(libusb_context * ctx,struct timeval * tv,struct timeval * out)2280 static int get_next_timeout(libusb_context *ctx, struct timeval *tv,
2281 struct timeval *out)
2282 {
2283 struct timeval timeout;
2284 int r = libusb_get_next_timeout(ctx, &timeout);
2285 if (r) {
2286 /* timeout already expired? */
2287 if (!timerisset(&timeout))
2288 return 1;
2289
2290 /* choose the smallest of next URB timeout or user specified timeout */
2291 if (timercmp(&timeout, tv, <))
2292 *out = timeout;
2293 else
2294 *out = *tv;
2295 } else {
2296 *out = *tv;
2297 }
2298 return 0;
2299 }
2300
2301 /** \ingroup libusb_poll
2302 * Handle any pending events.
2303 *
2304 * libusb determines "pending events" by checking if any timeouts have expired
2305 * and by checking the set of file descriptors for activity.
2306 *
2307 * If a zero timeval is passed, this function will handle any already-pending
2308 * events and then immediately return in non-blocking style.
2309 *
2310 * If a non-zero timeval is passed and no events are currently pending, this
2311 * function will block waiting for events to handle up until the specified
2312 * timeout. If an event arrives or a signal is raised, this function will
2313 * return early.
2314 *
2315 * If the parameter completed is not NULL then <em>after obtaining the event
2316 * handling lock</em> this function will return immediately if the integer
2317 * pointed to is not 0. This allows for race free waiting for the completion
2318 * of a specific transfer.
2319 *
2320 * \param ctx the context to operate on, or NULL for the default context
2321 * \param tv the maximum time to block waiting for events, or an all zero
2322 * timeval struct for non-blocking mode
2323 * \param completed pointer to completion integer to check, or NULL
2324 * \returns 0 on success, or a LIBUSB_ERROR code on failure
2325 * \ref libusb_mtasync
2326 */
libusb_handle_events_timeout_completed(libusb_context * ctx,struct timeval * tv,int * completed)2327 int API_EXPORTED libusb_handle_events_timeout_completed(libusb_context *ctx,
2328 struct timeval *tv, int *completed)
2329 {
2330 int r;
2331 struct timeval poll_timeout;
2332
2333 USBI_GET_CONTEXT(ctx);
2334 r = get_next_timeout(ctx, tv, &poll_timeout);
2335 if (r) {
2336 /* timeout already expired */
2337 return handle_timeouts(ctx);
2338 }
2339
2340 retry:
2341 if (libusb_try_lock_events(ctx) == 0) {
2342 if (completed == NULL || !*completed) {
2343 /* we obtained the event lock: do our own event handling */
2344 usbi_dbg("doing our own event handling");
2345 r = handle_events(ctx, &poll_timeout);
2346 }
2347 libusb_unlock_events(ctx);
2348 return r;
2349 }
2350
2351 /* another thread is doing event handling. wait for thread events that
2352 * notify event completion. */
2353 libusb_lock_event_waiters(ctx);
2354
2355 if (completed && *completed)
2356 goto already_done;
2357
2358 if (!libusb_event_handler_active(ctx)) {
2359 /* we hit a race: whoever was event handling earlier finished in the
2360 * time it took us to reach this point. try the cycle again. */
2361 libusb_unlock_event_waiters(ctx);
2362 usbi_dbg("event handler was active but went away, retrying");
2363 goto retry;
2364 }
2365
2366 usbi_dbg("another thread is doing event handling");
2367 r = libusb_wait_for_event(ctx, &poll_timeout);
2368
2369 already_done:
2370 libusb_unlock_event_waiters(ctx);
2371
2372 if (r < 0)
2373 return r;
2374 else if (r == 1)
2375 return handle_timeouts(ctx);
2376 else
2377 return 0;
2378 }
2379
2380 /** \ingroup libusb_poll
2381 * Handle any pending events
2382 *
2383 * Like libusb_handle_events_timeout_completed(), but without the completed
2384 * parameter, calling this function is equivalent to calling
2385 * libusb_handle_events_timeout_completed() with a NULL completed parameter.
2386 *
2387 * This function is kept primarily for backwards compatibility.
2388 * All new code should call libusb_handle_events_completed() or
2389 * libusb_handle_events_timeout_completed() to avoid race conditions.
2390 *
2391 * \param ctx the context to operate on, or NULL for the default context
2392 * \param tv the maximum time to block waiting for events, or an all zero
2393 * timeval struct for non-blocking mode
2394 * \returns 0 on success, or a LIBUSB_ERROR code on failure
2395 */
libusb_handle_events_timeout(libusb_context * ctx,struct timeval * tv)2396 int API_EXPORTED libusb_handle_events_timeout(libusb_context *ctx,
2397 struct timeval *tv)
2398 {
2399 return libusb_handle_events_timeout_completed(ctx, tv, NULL);
2400 }
2401
2402 /** \ingroup libusb_poll
2403 * Handle any pending events in blocking mode. There is currently a timeout
2404 * hardcoded at 60 seconds but we plan to make it unlimited in future. For
2405 * finer control over whether this function is blocking or non-blocking, or
2406 * for control over the timeout, use libusb_handle_events_timeout_completed()
2407 * instead.
2408 *
2409 * This function is kept primarily for backwards compatibility.
2410 * All new code should call libusb_handle_events_completed() or
2411 * libusb_handle_events_timeout_completed() to avoid race conditions.
2412 *
2413 * \param ctx the context to operate on, or NULL for the default context
2414 * \returns 0 on success, or a LIBUSB_ERROR code on failure
2415 */
libusb_handle_events(libusb_context * ctx)2416 int API_EXPORTED libusb_handle_events(libusb_context *ctx)
2417 {
2418 struct timeval tv;
2419 tv.tv_sec = 60;
2420 tv.tv_usec = 0;
2421 return libusb_handle_events_timeout_completed(ctx, &tv, NULL);
2422 }
2423
2424 /** \ingroup libusb_poll
2425 * Handle any pending events in blocking mode.
2426 *
2427 * Like libusb_handle_events(), with the addition of a completed parameter
2428 * to allow for race free waiting for the completion of a specific transfer.
2429 *
2430 * See libusb_handle_events_timeout_completed() for details on the completed
2431 * parameter.
2432 *
2433 * \param ctx the context to operate on, or NULL for the default context
2434 * \param completed pointer to completion integer to check, or NULL
2435 * \returns 0 on success, or a LIBUSB_ERROR code on failure
2436 * \ref libusb_mtasync
2437 */
libusb_handle_events_completed(libusb_context * ctx,int * completed)2438 int API_EXPORTED libusb_handle_events_completed(libusb_context *ctx,
2439 int *completed)
2440 {
2441 struct timeval tv;
2442 tv.tv_sec = 60;
2443 tv.tv_usec = 0;
2444 return libusb_handle_events_timeout_completed(ctx, &tv, completed);
2445 }
2446
2447 /** \ingroup libusb_poll
2448 * Handle any pending events by polling file descriptors, without checking if
2449 * any other threads are already doing so. Must be called with the event lock
2450 * held, see libusb_lock_events().
2451 *
2452 * This function is designed to be called under the situation where you have
2453 * taken the event lock and are calling poll()/select() directly on libusb's
2454 * file descriptors (as opposed to using libusb_handle_events() or similar).
2455 * You detect events on libusb's descriptors, so you then call this function
2456 * with a zero timeout value (while still holding the event lock).
2457 *
2458 * \param ctx the context to operate on, or NULL for the default context
2459 * \param tv the maximum time to block waiting for events, or zero for
2460 * non-blocking mode
2461 * \returns 0 on success, or a LIBUSB_ERROR code on failure
2462 * \ref libusb_mtasync
2463 */
libusb_handle_events_locked(libusb_context * ctx,struct timeval * tv)2464 int API_EXPORTED libusb_handle_events_locked(libusb_context *ctx,
2465 struct timeval *tv)
2466 {
2467 int r;
2468 struct timeval poll_timeout;
2469
2470 USBI_GET_CONTEXT(ctx);
2471 r = get_next_timeout(ctx, tv, &poll_timeout);
2472 if (r) {
2473 /* timeout already expired */
2474 return handle_timeouts(ctx);
2475 }
2476
2477 return handle_events(ctx, &poll_timeout);
2478 }
2479
2480 /** \ingroup libusb_poll
2481 * Determines whether your application must apply special timing considerations
2482 * when monitoring libusb's file descriptors.
2483 *
2484 * This function is only useful for applications which retrieve and poll
2485 * libusb's file descriptors in their own main loop (\ref libusb_pollmain).
2486 *
2487 * Ordinarily, libusb's event handler needs to be called into at specific
2488 * moments in time (in addition to times when there is activity on the file
2489 * descriptor set). The usual approach is to use libusb_get_next_timeout()
2490 * to learn about when the next timeout occurs, and to adjust your
2491 * poll()/select() timeout accordingly so that you can make a call into the
2492 * library at that time.
2493 *
2494 * Some platforms supported by libusb do not come with this baggage - any
2495 * events relevant to timing will be represented by activity on the file
2496 * descriptor set, and libusb_get_next_timeout() will always return 0.
2497 * This function allows you to detect whether you are running on such a
2498 * platform.
2499 *
2500 * Since v1.0.5.
2501 *
2502 * \param ctx the context to operate on, or NULL for the default context
2503 * \returns 0 if you must call into libusb at times determined by
2504 * libusb_get_next_timeout(), or 1 if all timeout events are handled internally
2505 * or through regular activity on the file descriptors.
2506 * \ref libusb_pollmain "Polling libusb file descriptors for event handling"
2507 */
libusb_pollfds_handle_timeouts(libusb_context * ctx)2508 int API_EXPORTED libusb_pollfds_handle_timeouts(libusb_context *ctx)
2509 {
2510 #if defined(USBI_TIMERFD_AVAILABLE)
2511 USBI_GET_CONTEXT(ctx);
2512 return usbi_using_timerfd(ctx);
2513 #else
2514 UNUSED(ctx);
2515 return 0;
2516 #endif
2517 }
2518
2519 /** \ingroup libusb_poll
2520 * Determine the next internal timeout that libusb needs to handle. You only
2521 * need to use this function if you are calling poll() or select() or similar
2522 * on libusb's file descriptors yourself - you do not need to use it if you
2523 * are calling libusb_handle_events() or a variant directly.
2524 *
2525 * You should call this function in your main loop in order to determine how
2526 * long to wait for select() or poll() to return results. libusb needs to be
2527 * called into at this timeout, so you should use it as an upper bound on
2528 * your select() or poll() call.
2529 *
2530 * When the timeout has expired, call into libusb_handle_events_timeout()
2531 * (perhaps in non-blocking mode) so that libusb can handle the timeout.
2532 *
2533 * This function may return 1 (success) and an all-zero timeval. If this is
2534 * the case, it indicates that libusb has a timeout that has already expired
2535 * so you should call libusb_handle_events_timeout() or similar immediately.
2536 * A return code of 0 indicates that there are no pending timeouts.
2537 *
2538 * On some platforms, this function will always returns 0 (no pending
2539 * timeouts). See \ref polltime.
2540 *
2541 * \param ctx the context to operate on, or NULL for the default context
2542 * \param tv output location for a relative time against the current
2543 * clock in which libusb must be called into in order to process timeout events
2544 * \returns 0 if there are no pending timeouts, 1 if a timeout was returned,
2545 * or LIBUSB_ERROR_OTHER on failure
2546 */
libusb_get_next_timeout(libusb_context * ctx,struct timeval * tv)2547 int API_EXPORTED libusb_get_next_timeout(libusb_context *ctx,
2548 struct timeval *tv)
2549 {
2550 struct usbi_transfer *transfer;
2551 struct timespec cur_ts;
2552 struct timeval cur_tv;
2553 struct timeval next_timeout = { 0, 0 };
2554 int r;
2555
2556 USBI_GET_CONTEXT(ctx);
2557 if (usbi_using_timerfd(ctx))
2558 return 0;
2559
2560 usbi_mutex_lock(&ctx->flying_transfers_lock);
2561 if (list_empty(&ctx->flying_transfers)) {
2562 usbi_mutex_unlock(&ctx->flying_transfers_lock);
2563 usbi_dbg("no URBs, no timeout!");
2564 return 0;
2565 }
2566
2567 /* find next transfer which hasn't already been processed as timed out */
2568 list_for_each_entry(transfer, &ctx->flying_transfers, list, struct usbi_transfer) {
2569 if (transfer->timeout_flags & (USBI_TRANSFER_TIMEOUT_HANDLED | USBI_TRANSFER_OS_HANDLES_TIMEOUT))
2570 continue;
2571
2572 /* if we've reached transfers of infinte timeout, we're done looking */
2573 if (!timerisset(&transfer->timeout))
2574 break;
2575
2576 next_timeout = transfer->timeout;
2577 break;
2578 }
2579 usbi_mutex_unlock(&ctx->flying_transfers_lock);
2580
2581 if (!timerisset(&next_timeout)) {
2582 usbi_dbg("no URB with timeout or all handled by OS; no timeout!");
2583 return 0;
2584 }
2585
2586 r = usbi_backend->clock_gettime(USBI_CLOCK_MONOTONIC, &cur_ts);
2587 if (r < 0) {
2588 usbi_err(ctx, "failed to read monotonic clock, errno=%d", errno);
2589 return 0;
2590 }
2591 TIMESPEC_TO_TIMEVAL(&cur_tv, &cur_ts);
2592
2593 if (!timercmp(&cur_tv, &next_timeout, <)) {
2594 usbi_dbg("first timeout already expired");
2595 timerclear(tv);
2596 } else {
2597 timersub(&next_timeout, &cur_tv, tv);
2598 usbi_dbg("next timeout in %d.%06ds", tv->tv_sec, tv->tv_usec);
2599 }
2600
2601 return 1;
2602 }
2603
2604 /** \ingroup libusb_poll
2605 * Register notification functions for file descriptor additions/removals.
2606 * These functions will be invoked for every new or removed file descriptor
2607 * that libusb uses as an event source.
2608 *
2609 * To remove notifiers, pass NULL values for the function pointers.
2610 *
2611 * Note that file descriptors may have been added even before you register
2612 * these notifiers (e.g. at libusb_init() time).
2613 *
2614 * Additionally, note that the removal notifier may be called during
2615 * libusb_exit() (e.g. when it is closing file descriptors that were opened
2616 * and added to the poll set at libusb_init() time). If you don't want this,
2617 * remove the notifiers immediately before calling libusb_exit().
2618 *
2619 * \param ctx the context to operate on, or NULL for the default context
2620 * \param added_cb pointer to function for addition notifications
2621 * \param removed_cb pointer to function for removal notifications
2622 * \param user_data User data to be passed back to callbacks (useful for
2623 * passing context information)
2624 */
libusb_set_pollfd_notifiers(libusb_context * ctx,libusb_pollfd_added_cb added_cb,libusb_pollfd_removed_cb removed_cb,void * user_data)2625 void API_EXPORTED libusb_set_pollfd_notifiers(libusb_context *ctx,
2626 libusb_pollfd_added_cb added_cb, libusb_pollfd_removed_cb removed_cb,
2627 void *user_data)
2628 {
2629 USBI_GET_CONTEXT(ctx);
2630 ctx->fd_added_cb = added_cb;
2631 ctx->fd_removed_cb = removed_cb;
2632 ctx->fd_cb_user_data = user_data;
2633 }
2634
2635 /*
2636 * Interrupt the iteration of the event handling thread, so that it picks
2637 * up the fd change. Callers of this function must hold the event_data_lock.
2638 */
usbi_fd_notification(struct libusb_context * ctx)2639 static void usbi_fd_notification(struct libusb_context *ctx)
2640 {
2641 int pending_events;
2642
2643 /* Record that there is a new poll fd.
2644 * Only signal an event if there are no prior pending events. */
2645 pending_events = usbi_pending_events(ctx);
2646 ctx->event_flags |= USBI_EVENT_POLLFDS_MODIFIED;
2647 if (!pending_events)
2648 usbi_signal_event(ctx);
2649 }
2650
2651 /* Add a file descriptor to the list of file descriptors to be monitored.
2652 * events should be specified as a bitmask of events passed to poll(), e.g.
2653 * POLLIN and/or POLLOUT. */
usbi_add_pollfd(struct libusb_context * ctx,int fd,short events)2654 int usbi_add_pollfd(struct libusb_context *ctx, int fd, short events)
2655 {
2656 struct usbi_pollfd *ipollfd = malloc(sizeof(*ipollfd));
2657 if (!ipollfd)
2658 return LIBUSB_ERROR_NO_MEM;
2659
2660 usbi_dbg("add fd %d events %d", fd, events);
2661 ipollfd->pollfd.fd = fd;
2662 ipollfd->pollfd.events = events;
2663 usbi_mutex_lock(&ctx->event_data_lock);
2664 list_add_tail(&ipollfd->list, &ctx->ipollfds);
2665 ctx->pollfds_cnt++;
2666 usbi_fd_notification(ctx);
2667 usbi_mutex_unlock(&ctx->event_data_lock);
2668
2669 if (ctx->fd_added_cb)
2670 ctx->fd_added_cb(fd, events, ctx->fd_cb_user_data);
2671 return 0;
2672 }
2673
2674 /* Remove a file descriptor from the list of file descriptors to be polled. */
usbi_remove_pollfd(struct libusb_context * ctx,int fd)2675 void usbi_remove_pollfd(struct libusb_context *ctx, int fd)
2676 {
2677 struct usbi_pollfd *ipollfd;
2678 int found = 0;
2679
2680 usbi_dbg("remove fd %d", fd);
2681 usbi_mutex_lock(&ctx->event_data_lock);
2682 list_for_each_entry(ipollfd, &ctx->ipollfds, list, struct usbi_pollfd)
2683 if (ipollfd->pollfd.fd == fd) {
2684 found = 1;
2685 break;
2686 }
2687
2688 if (!found) {
2689 usbi_dbg("couldn't find fd %d to remove", fd);
2690 usbi_mutex_unlock(&ctx->event_data_lock);
2691 return;
2692 }
2693
2694 list_del(&ipollfd->list);
2695 ctx->pollfds_cnt--;
2696 usbi_fd_notification(ctx);
2697 usbi_mutex_unlock(&ctx->event_data_lock);
2698 free(ipollfd);
2699 if (ctx->fd_removed_cb)
2700 ctx->fd_removed_cb(fd, ctx->fd_cb_user_data);
2701 }
2702
2703 /** \ingroup libusb_poll
2704 * Retrieve a list of file descriptors that should be polled by your main loop
2705 * as libusb event sources.
2706 *
2707 * The returned list is NULL-terminated and should be freed with libusb_free_pollfds()
2708 * when done. The actual list contents must not be touched.
2709 *
2710 * As file descriptors are a Unix-specific concept, this function is not
2711 * available on Windows and will always return NULL.
2712 *
2713 * \param ctx the context to operate on, or NULL for the default context
2714 * \returns a NULL-terminated list of libusb_pollfd structures
2715 * \returns NULL on error
2716 * \returns NULL on platforms where the functionality is not available
2717 */
2718 DEFAULT_VISIBILITY
libusb_get_pollfds(libusb_context * ctx)2719 const struct libusb_pollfd ** LIBUSB_CALL libusb_get_pollfds(
2720 libusb_context *ctx)
2721 {
2722 #ifndef OS_WINDOWS
2723 struct libusb_pollfd **ret = NULL;
2724 struct usbi_pollfd *ipollfd;
2725 size_t i = 0;
2726 USBI_GET_CONTEXT(ctx);
2727
2728 usbi_mutex_lock(&ctx->event_data_lock);
2729
2730 ret = calloc(ctx->pollfds_cnt + 1, sizeof(struct libusb_pollfd *));
2731 if (!ret)
2732 goto out;
2733
2734 list_for_each_entry(ipollfd, &ctx->ipollfds, list, struct usbi_pollfd)
2735 ret[i++] = (struct libusb_pollfd *) ipollfd;
2736 ret[ctx->pollfds_cnt] = NULL;
2737
2738 out:
2739 usbi_mutex_unlock(&ctx->event_data_lock);
2740 return (const struct libusb_pollfd **) ret;
2741 #else
2742 usbi_err(ctx, "external polling of libusb's internal descriptors "\
2743 "is not yet supported on Windows platforms");
2744 return NULL;
2745 #endif
2746 }
2747
2748 /** \ingroup libusb_poll
2749 * Free a list of libusb_pollfd structures. This should be called for all
2750 * pollfd lists allocated with libusb_get_pollfds().
2751 *
2752 * Since version 1.0.20, \ref LIBUSB_API_VERSION >= 0x01000104
2753 *
2754 * It is legal to call this function with a NULL pollfd list. In this case,
2755 * the function will simply return safely.
2756 *
2757 * \param pollfds the list of libusb_pollfd structures to free
2758 */
libusb_free_pollfds(const struct libusb_pollfd ** pollfds)2759 void API_EXPORTED libusb_free_pollfds(const struct libusb_pollfd **pollfds)
2760 {
2761 if (!pollfds)
2762 return;
2763
2764 free((void *)pollfds);
2765 }
2766
2767 /* Backends may call this from handle_events to report disconnection of a
2768 * device. This function ensures transfers get cancelled appropriately.
2769 * Callers of this function must hold the events_lock.
2770 */
usbi_handle_disconnect(struct libusb_device_handle * dev_handle)2771 void usbi_handle_disconnect(struct libusb_device_handle *dev_handle)
2772 {
2773 struct usbi_transfer *cur;
2774 struct usbi_transfer *to_cancel;
2775
2776 usbi_dbg("device %d.%d",
2777 dev_handle->dev->bus_number, dev_handle->dev->device_address);
2778
2779 /* terminate all pending transfers with the LIBUSB_TRANSFER_NO_DEVICE
2780 * status code.
2781 *
2782 * when we find a transfer for this device on the list, there are two
2783 * possible scenarios:
2784 * 1. the transfer is currently in-flight, in which case we terminate the
2785 * transfer here
2786 * 2. the transfer has been added to the flying transfer list by
2787 * libusb_submit_transfer, has failed to submit and
2788 * libusb_submit_transfer is waiting for us to release the
2789 * flying_transfers_lock to remove it, so we ignore it
2790 */
2791
2792 while (1) {
2793 to_cancel = NULL;
2794 usbi_mutex_lock(&HANDLE_CTX(dev_handle)->flying_transfers_lock);
2795 list_for_each_entry(cur, &HANDLE_CTX(dev_handle)->flying_transfers, list, struct usbi_transfer)
2796 if (USBI_TRANSFER_TO_LIBUSB_TRANSFER(cur)->dev_handle == dev_handle) {
2797 usbi_mutex_lock(&cur->lock);
2798 if (cur->state_flags & USBI_TRANSFER_IN_FLIGHT)
2799 to_cancel = cur;
2800 usbi_mutex_unlock(&cur->lock);
2801
2802 if (to_cancel)
2803 break;
2804 }
2805 usbi_mutex_unlock(&HANDLE_CTX(dev_handle)->flying_transfers_lock);
2806
2807 if (!to_cancel)
2808 break;
2809
2810 usbi_dbg("cancelling transfer %p from disconnect",
2811 USBI_TRANSFER_TO_LIBUSB_TRANSFER(to_cancel));
2812
2813 usbi_mutex_lock(&to_cancel->lock);
2814 usbi_backend->clear_transfer_priv(to_cancel);
2815 usbi_mutex_unlock(&to_cancel->lock);
2816 usbi_handle_transfer_completion(to_cancel, LIBUSB_TRANSFER_NO_DEVICE);
2817 }
2818
2819 }
2820