1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * USB Skeleton driver - 2.2
4 *
5 * Copyright (C) 2001-2004 Greg Kroah-Hartman (greg@kroah.com)
6 *
7 * This driver is based on the 2.6.3 version of drivers/usb/usb-skeleton.c
8 * but has been rewritten to be easier to read and use.
9 */
10
11 #include <linux/kernel.h>
12 #include <linux/errno.h>
13 #include <linux/slab.h>
14 #include <linux/module.h>
15 #include <linux/kref.h>
16 #include <linux/uaccess.h>
17 #include <linux/usb.h>
18 #include <linux/mutex.h>
19
20
21 /* Define these values to match your devices */
22 #define USB_SKEL_VENDOR_ID 0xfff0
23 #define USB_SKEL_PRODUCT_ID 0xfff0
24
25 /* table of devices that work with this driver */
26 static const struct usb_device_id skel_table[] = {
27 { USB_DEVICE(USB_SKEL_VENDOR_ID, USB_SKEL_PRODUCT_ID) },
28 { } /* Terminating entry */
29 };
30 MODULE_DEVICE_TABLE(usb, skel_table);
31
32
33 /* Get a minor range for your devices from the usb maintainer */
34 #define USB_SKEL_MINOR_BASE 192
35
36 /* our private defines. if this grows any larger, use your own .h file */
37 #define MAX_TRANSFER (PAGE_SIZE - 512)
38 /* MAX_TRANSFER is chosen so that the VM is not stressed by
39 allocations > PAGE_SIZE and the number of packets in a page
40 is an integer 512 is the largest possible packet on EHCI */
41 #define WRITES_IN_FLIGHT 8
42 /* arbitrarily chosen */
43
44 /* Structure to hold all of our device specific stuff */
45 struct usb_skel {
46 struct usb_device *udev; /* the usb device for this device */
47 struct usb_interface *interface; /* the interface for this device */
48 struct semaphore limit_sem; /* limiting the number of writes in progress */
49 struct usb_anchor submitted; /* in case we need to retract our submissions */
50 struct urb *bulk_in_urb; /* the urb to read data with */
51 unsigned char *bulk_in_buffer; /* the buffer to receive data */
52 size_t bulk_in_size; /* the size of the receive buffer */
53 size_t bulk_in_filled; /* number of bytes in the buffer */
54 size_t bulk_in_copied; /* already copied to user space */
55 __u8 bulk_in_endpointAddr; /* the address of the bulk in endpoint */
56 __u8 bulk_out_endpointAddr; /* the address of the bulk out endpoint */
57 int errors; /* the last request tanked */
58 bool ongoing_read; /* a read is going on */
59 spinlock_t err_lock; /* lock for errors */
60 struct kref kref;
61 struct mutex io_mutex; /* synchronize I/O with disconnect */
62 unsigned long disconnected:1;
63 wait_queue_head_t bulk_in_wait; /* to wait for an ongoing read */
64 };
65 #define to_skel_dev(d) container_of(d, struct usb_skel, kref)
66
67 static struct usb_driver skel_driver;
68 static void skel_draw_down(struct usb_skel *dev);
69
skel_delete(struct kref * kref)70 static void skel_delete(struct kref *kref)
71 {
72 struct usb_skel *dev = to_skel_dev(kref);
73
74 usb_free_urb(dev->bulk_in_urb);
75 usb_put_intf(dev->interface);
76 usb_put_dev(dev->udev);
77 kfree(dev->bulk_in_buffer);
78 kfree(dev);
79 }
80
skel_open(struct inode * inode,struct file * file)81 static int skel_open(struct inode *inode, struct file *file)
82 {
83 struct usb_skel *dev;
84 struct usb_interface *interface;
85 int subminor;
86 int retval = 0;
87
88 subminor = iminor(inode);
89
90 interface = usb_find_interface(&skel_driver, subminor);
91 if (!interface) {
92 pr_err("%s - error, can't find device for minor %d\n",
93 __func__, subminor);
94 retval = -ENODEV;
95 goto exit;
96 }
97
98 dev = usb_get_intfdata(interface);
99 if (!dev) {
100 retval = -ENODEV;
101 goto exit;
102 }
103
104 retval = usb_autopm_get_interface(interface);
105 if (retval)
106 goto exit;
107
108 /* increment our usage count for the device */
109 kref_get(&dev->kref);
110
111 /* save our object in the file's private structure */
112 file->private_data = dev;
113
114 exit:
115 return retval;
116 }
117
skel_release(struct inode * inode,struct file * file)118 static int skel_release(struct inode *inode, struct file *file)
119 {
120 struct usb_skel *dev;
121
122 dev = file->private_data;
123 if (dev == NULL)
124 return -ENODEV;
125
126 /* allow the device to be autosuspended */
127 usb_autopm_put_interface(dev->interface);
128
129 /* decrement the count on our device */
130 kref_put(&dev->kref, skel_delete);
131 return 0;
132 }
133
skel_flush(struct file * file,fl_owner_t id)134 static int skel_flush(struct file *file, fl_owner_t id)
135 {
136 struct usb_skel *dev;
137 int res;
138
139 dev = file->private_data;
140 if (dev == NULL)
141 return -ENODEV;
142
143 /* wait for io to stop */
144 mutex_lock(&dev->io_mutex);
145 skel_draw_down(dev);
146
147 /* read out errors, leave subsequent opens a clean slate */
148 spin_lock_irq(&dev->err_lock);
149 res = dev->errors ? (dev->errors == -EPIPE ? -EPIPE : -EIO) : 0;
150 dev->errors = 0;
151 spin_unlock_irq(&dev->err_lock);
152
153 mutex_unlock(&dev->io_mutex);
154
155 return res;
156 }
157
skel_read_bulk_callback(struct urb * urb)158 static void skel_read_bulk_callback(struct urb *urb)
159 {
160 struct usb_skel *dev;
161 unsigned long flags;
162
163 dev = urb->context;
164
165 spin_lock_irqsave(&dev->err_lock, flags);
166 /* sync/async unlink faults aren't errors */
167 if (urb->status) {
168 if (!(urb->status == -ENOENT ||
169 urb->status == -ECONNRESET ||
170 urb->status == -ESHUTDOWN))
171 dev_err(&dev->interface->dev,
172 "%s - nonzero write bulk status received: %d\n",
173 __func__, urb->status);
174
175 dev->errors = urb->status;
176 } else {
177 dev->bulk_in_filled = urb->actual_length;
178 }
179 dev->ongoing_read = 0;
180 spin_unlock_irqrestore(&dev->err_lock, flags);
181
182 wake_up_interruptible(&dev->bulk_in_wait);
183 }
184
skel_do_read_io(struct usb_skel * dev,size_t count)185 static int skel_do_read_io(struct usb_skel *dev, size_t count)
186 {
187 int rv;
188
189 /* prepare a read */
190 usb_fill_bulk_urb(dev->bulk_in_urb,
191 dev->udev,
192 usb_rcvbulkpipe(dev->udev,
193 dev->bulk_in_endpointAddr),
194 dev->bulk_in_buffer,
195 min(dev->bulk_in_size, count),
196 skel_read_bulk_callback,
197 dev);
198 /* tell everybody to leave the URB alone */
199 spin_lock_irq(&dev->err_lock);
200 dev->ongoing_read = 1;
201 spin_unlock_irq(&dev->err_lock);
202
203 /* submit bulk in urb, which means no data to deliver */
204 dev->bulk_in_filled = 0;
205 dev->bulk_in_copied = 0;
206
207 /* do it */
208 rv = usb_submit_urb(dev->bulk_in_urb, GFP_KERNEL);
209 if (rv < 0) {
210 dev_err(&dev->interface->dev,
211 "%s - failed submitting read urb, error %d\n",
212 __func__, rv);
213 rv = (rv == -ENOMEM) ? rv : -EIO;
214 spin_lock_irq(&dev->err_lock);
215 dev->ongoing_read = 0;
216 spin_unlock_irq(&dev->err_lock);
217 }
218
219 return rv;
220 }
221
skel_read(struct file * file,char * buffer,size_t count,loff_t * ppos)222 static ssize_t skel_read(struct file *file, char *buffer, size_t count,
223 loff_t *ppos)
224 {
225 struct usb_skel *dev;
226 int rv;
227 bool ongoing_io;
228
229 dev = file->private_data;
230
231 /* if we cannot read at all, return EOF */
232 if (!dev->bulk_in_urb || !count)
233 return 0;
234
235 /* no concurrent readers */
236 rv = mutex_lock_interruptible(&dev->io_mutex);
237 if (rv < 0)
238 return rv;
239
240 if (dev->disconnected) { /* disconnect() was called */
241 rv = -ENODEV;
242 goto exit;
243 }
244
245 /* if IO is under way, we must not touch things */
246 retry:
247 spin_lock_irq(&dev->err_lock);
248 ongoing_io = dev->ongoing_read;
249 spin_unlock_irq(&dev->err_lock);
250
251 if (ongoing_io) {
252 /* nonblocking IO shall not wait */
253 if (file->f_flags & O_NONBLOCK) {
254 rv = -EAGAIN;
255 goto exit;
256 }
257 /*
258 * IO may take forever
259 * hence wait in an interruptible state
260 */
261 rv = wait_event_interruptible(dev->bulk_in_wait, (!dev->ongoing_read));
262 if (rv < 0)
263 goto exit;
264 }
265
266 /* errors must be reported */
267 rv = dev->errors;
268 if (rv < 0) {
269 /* any error is reported once */
270 dev->errors = 0;
271 /* to preserve notifications about reset */
272 rv = (rv == -EPIPE) ? rv : -EIO;
273 /* report it */
274 goto exit;
275 }
276
277 /*
278 * if the buffer is filled we may satisfy the read
279 * else we need to start IO
280 */
281
282 if (dev->bulk_in_filled) {
283 /* we had read data */
284 size_t available = dev->bulk_in_filled - dev->bulk_in_copied;
285 size_t chunk = min(available, count);
286
287 if (!available) {
288 /*
289 * all data has been used
290 * actual IO needs to be done
291 */
292 rv = skel_do_read_io(dev, count);
293 if (rv < 0)
294 goto exit;
295 else
296 goto retry;
297 }
298 /*
299 * data is available
300 * chunk tells us how much shall be copied
301 */
302
303 if (copy_to_user(buffer,
304 dev->bulk_in_buffer + dev->bulk_in_copied,
305 chunk))
306 rv = -EFAULT;
307 else
308 rv = chunk;
309
310 dev->bulk_in_copied += chunk;
311
312 /*
313 * if we are asked for more than we have,
314 * we start IO but don't wait
315 */
316 if (available < count)
317 skel_do_read_io(dev, count - chunk);
318 } else {
319 /* no data in the buffer */
320 rv = skel_do_read_io(dev, count);
321 if (rv < 0)
322 goto exit;
323 else
324 goto retry;
325 }
326 exit:
327 mutex_unlock(&dev->io_mutex);
328 return rv;
329 }
330
skel_write_bulk_callback(struct urb * urb)331 static void skel_write_bulk_callback(struct urb *urb)
332 {
333 struct usb_skel *dev;
334 unsigned long flags;
335
336 dev = urb->context;
337
338 /* sync/async unlink faults aren't errors */
339 if (urb->status) {
340 if (!(urb->status == -ENOENT ||
341 urb->status == -ECONNRESET ||
342 urb->status == -ESHUTDOWN))
343 dev_err(&dev->interface->dev,
344 "%s - nonzero write bulk status received: %d\n",
345 __func__, urb->status);
346
347 spin_lock_irqsave(&dev->err_lock, flags);
348 dev->errors = urb->status;
349 spin_unlock_irqrestore(&dev->err_lock, flags);
350 }
351
352 /* free up our allocated buffer */
353 usb_free_coherent(urb->dev, urb->transfer_buffer_length,
354 urb->transfer_buffer, urb->transfer_dma);
355 up(&dev->limit_sem);
356 }
357
skel_write(struct file * file,const char * user_buffer,size_t count,loff_t * ppos)358 static ssize_t skel_write(struct file *file, const char *user_buffer,
359 size_t count, loff_t *ppos)
360 {
361 struct usb_skel *dev;
362 int retval = 0;
363 struct urb *urb = NULL;
364 char *buf = NULL;
365 size_t writesize = min(count, (size_t)MAX_TRANSFER);
366
367 dev = file->private_data;
368
369 /* verify that we actually have some data to write */
370 if (count == 0)
371 goto exit;
372
373 /*
374 * limit the number of URBs in flight to stop a user from using up all
375 * RAM
376 */
377 if (!(file->f_flags & O_NONBLOCK)) {
378 if (down_interruptible(&dev->limit_sem)) {
379 retval = -ERESTARTSYS;
380 goto exit;
381 }
382 } else {
383 if (down_trylock(&dev->limit_sem)) {
384 retval = -EAGAIN;
385 goto exit;
386 }
387 }
388
389 spin_lock_irq(&dev->err_lock);
390 retval = dev->errors;
391 if (retval < 0) {
392 /* any error is reported once */
393 dev->errors = 0;
394 /* to preserve notifications about reset */
395 retval = (retval == -EPIPE) ? retval : -EIO;
396 }
397 spin_unlock_irq(&dev->err_lock);
398 if (retval < 0)
399 goto error;
400
401 /* create a urb, and a buffer for it, and copy the data to the urb */
402 urb = usb_alloc_urb(0, GFP_KERNEL);
403 if (!urb) {
404 retval = -ENOMEM;
405 goto error;
406 }
407
408 buf = usb_alloc_coherent(dev->udev, writesize, GFP_KERNEL,
409 &urb->transfer_dma);
410 if (!buf) {
411 retval = -ENOMEM;
412 goto error;
413 }
414
415 if (copy_from_user(buf, user_buffer, writesize)) {
416 retval = -EFAULT;
417 goto error;
418 }
419
420 /* this lock makes sure we don't submit URBs to gone devices */
421 mutex_lock(&dev->io_mutex);
422 if (dev->disconnected) { /* disconnect() was called */
423 mutex_unlock(&dev->io_mutex);
424 retval = -ENODEV;
425 goto error;
426 }
427
428 /* initialize the urb properly */
429 usb_fill_bulk_urb(urb, dev->udev,
430 usb_sndbulkpipe(dev->udev, dev->bulk_out_endpointAddr),
431 buf, writesize, skel_write_bulk_callback, dev);
432 urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
433 usb_anchor_urb(urb, &dev->submitted);
434
435 /* send the data out the bulk port */
436 retval = usb_submit_urb(urb, GFP_KERNEL);
437 mutex_unlock(&dev->io_mutex);
438 if (retval) {
439 dev_err(&dev->interface->dev,
440 "%s - failed submitting write urb, error %d\n",
441 __func__, retval);
442 goto error_unanchor;
443 }
444
445 /*
446 * release our reference to this urb, the USB core will eventually free
447 * it entirely
448 */
449 usb_free_urb(urb);
450
451
452 return writesize;
453
454 error_unanchor:
455 usb_unanchor_urb(urb);
456 error:
457 if (urb) {
458 usb_free_coherent(dev->udev, writesize, buf, urb->transfer_dma);
459 usb_free_urb(urb);
460 }
461 up(&dev->limit_sem);
462
463 exit:
464 return retval;
465 }
466
467 static const struct file_operations skel_fops = {
468 .owner = THIS_MODULE,
469 .read = skel_read,
470 .write = skel_write,
471 .open = skel_open,
472 .release = skel_release,
473 .flush = skel_flush,
474 .llseek = noop_llseek,
475 };
476
477 /*
478 * usb class driver info in order to get a minor number from the usb core,
479 * and to have the device registered with the driver core
480 */
481 static struct usb_class_driver skel_class = {
482 .name = "skel%d",
483 .fops = &skel_fops,
484 .minor_base = USB_SKEL_MINOR_BASE,
485 };
486
skel_probe(struct usb_interface * interface,const struct usb_device_id * id)487 static int skel_probe(struct usb_interface *interface,
488 const struct usb_device_id *id)
489 {
490 struct usb_skel *dev;
491 struct usb_endpoint_descriptor *bulk_in, *bulk_out;
492 int retval;
493
494 /* allocate memory for our device state and initialize it */
495 dev = kzalloc(sizeof(*dev), GFP_KERNEL);
496 if (!dev)
497 return -ENOMEM;
498
499 kref_init(&dev->kref);
500 sema_init(&dev->limit_sem, WRITES_IN_FLIGHT);
501 mutex_init(&dev->io_mutex);
502 spin_lock_init(&dev->err_lock);
503 init_usb_anchor(&dev->submitted);
504 init_waitqueue_head(&dev->bulk_in_wait);
505
506 dev->udev = usb_get_dev(interface_to_usbdev(interface));
507 dev->interface = usb_get_intf(interface);
508
509 /* set up the endpoint information */
510 /* use only the first bulk-in and bulk-out endpoints */
511 retval = usb_find_common_endpoints(interface->cur_altsetting,
512 &bulk_in, &bulk_out, NULL, NULL);
513 if (retval) {
514 dev_err(&interface->dev,
515 "Could not find both bulk-in and bulk-out endpoints\n");
516 goto error;
517 }
518
519 dev->bulk_in_size = usb_endpoint_maxp(bulk_in);
520 dev->bulk_in_endpointAddr = bulk_in->bEndpointAddress;
521 dev->bulk_in_buffer = kmalloc(dev->bulk_in_size, GFP_KERNEL);
522 if (!dev->bulk_in_buffer) {
523 retval = -ENOMEM;
524 goto error;
525 }
526 dev->bulk_in_urb = usb_alloc_urb(0, GFP_KERNEL);
527 if (!dev->bulk_in_urb) {
528 retval = -ENOMEM;
529 goto error;
530 }
531
532 dev->bulk_out_endpointAddr = bulk_out->bEndpointAddress;
533
534 /* save our data pointer in this interface device */
535 usb_set_intfdata(interface, dev);
536
537 /* we can register the device now, as it is ready */
538 retval = usb_register_dev(interface, &skel_class);
539 if (retval) {
540 /* something prevented us from registering this driver */
541 dev_err(&interface->dev,
542 "Not able to get a minor for this device.\n");
543 usb_set_intfdata(interface, NULL);
544 goto error;
545 }
546
547 /* let the user know what node this device is now attached to */
548 dev_info(&interface->dev,
549 "USB Skeleton device now attached to USBSkel-%d",
550 interface->minor);
551 return 0;
552
553 error:
554 /* this frees allocated memory */
555 kref_put(&dev->kref, skel_delete);
556
557 return retval;
558 }
559
skel_disconnect(struct usb_interface * interface)560 static void skel_disconnect(struct usb_interface *interface)
561 {
562 struct usb_skel *dev;
563 int minor = interface->minor;
564
565 dev = usb_get_intfdata(interface);
566 usb_set_intfdata(interface, NULL);
567
568 /* give back our minor */
569 usb_deregister_dev(interface, &skel_class);
570
571 /* prevent more I/O from starting */
572 mutex_lock(&dev->io_mutex);
573 dev->disconnected = 1;
574 mutex_unlock(&dev->io_mutex);
575
576 usb_kill_anchored_urbs(&dev->submitted);
577
578 /* decrement our usage count */
579 kref_put(&dev->kref, skel_delete);
580
581 dev_info(&interface->dev, "USB Skeleton #%d now disconnected", minor);
582 }
583
skel_draw_down(struct usb_skel * dev)584 static void skel_draw_down(struct usb_skel *dev)
585 {
586 int time;
587
588 time = usb_wait_anchor_empty_timeout(&dev->submitted, 1000);
589 if (!time)
590 usb_kill_anchored_urbs(&dev->submitted);
591 usb_kill_urb(dev->bulk_in_urb);
592 }
593
skel_suspend(struct usb_interface * intf,pm_message_t message)594 static int skel_suspend(struct usb_interface *intf, pm_message_t message)
595 {
596 struct usb_skel *dev = usb_get_intfdata(intf);
597
598 if (!dev)
599 return 0;
600 skel_draw_down(dev);
601 return 0;
602 }
603
skel_resume(struct usb_interface * intf)604 static int skel_resume(struct usb_interface *intf)
605 {
606 return 0;
607 }
608
skel_pre_reset(struct usb_interface * intf)609 static int skel_pre_reset(struct usb_interface *intf)
610 {
611 struct usb_skel *dev = usb_get_intfdata(intf);
612
613 mutex_lock(&dev->io_mutex);
614 skel_draw_down(dev);
615
616 return 0;
617 }
618
skel_post_reset(struct usb_interface * intf)619 static int skel_post_reset(struct usb_interface *intf)
620 {
621 struct usb_skel *dev = usb_get_intfdata(intf);
622
623 /* we are sure no URBs are active - no locking needed */
624 dev->errors = -EPIPE;
625 mutex_unlock(&dev->io_mutex);
626
627 return 0;
628 }
629
630 static struct usb_driver skel_driver = {
631 .name = "skeleton",
632 .probe = skel_probe,
633 .disconnect = skel_disconnect,
634 .suspend = skel_suspend,
635 .resume = skel_resume,
636 .pre_reset = skel_pre_reset,
637 .post_reset = skel_post_reset,
638 .id_table = skel_table,
639 .supports_autosuspend = 1,
640 };
641
642 module_usb_driver(skel_driver);
643
644 MODULE_LICENSE("GPL v2");
645