1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3 * Header file for dma buffer sharing framework.
4 *
5 * Copyright(C) 2011 Linaro Limited. All rights reserved.
6 * Author: Sumit Semwal <sumit.semwal@ti.com>
7 *
8 * Many thanks to linaro-mm-sig list, and specially
9 * Arnd Bergmann <arnd@arndb.de>, Rob Clark <rob@ti.com> and
10 * Daniel Vetter <daniel@ffwll.ch> for their support in creation and
11 * refining of this idea.
12 */
13 #ifndef __DMA_BUF_H__
14 #define __DMA_BUF_H__
15
16 #include <linux/file.h>
17 #include <linux/err.h>
18 #include <linux/scatterlist.h>
19 #include <linux/list.h>
20 #include <linux/dma-mapping.h>
21 #include <linux/fs.h>
22 #include <linux/dma-fence.h>
23 #include <linux/wait.h>
24
25 struct device;
26 struct dma_buf;
27 struct dma_buf_attachment;
28
29 /**
30 * struct dma_buf_ops - operations possible on struct dma_buf
31 * @vmap: [optional] creates a virtual mapping for the buffer into kernel
32 * address space. Same restrictions as for vmap and friends apply.
33 * @vunmap: [optional] unmaps a vmap from the buffer
34 */
35 struct dma_buf_ops {
36 /**
37 * @cache_sgt_mapping:
38 *
39 * If true the framework will cache the first mapping made for each
40 * attachment. This avoids creating mappings for attachments multiple
41 * times.
42 */
43 bool cache_sgt_mapping;
44
45 /**
46 * @attach:
47 *
48 * This is called from dma_buf_attach() to make sure that a given
49 * &dma_buf_attachment.dev can access the provided &dma_buf. Exporters
50 * which support buffer objects in special locations like VRAM or
51 * device-specific carveout areas should check whether the buffer could
52 * be move to system memory (or directly accessed by the provided
53 * device), and otherwise need to fail the attach operation.
54 *
55 * The exporter should also in general check whether the current
56 * allocation fullfills the DMA constraints of the new device. If this
57 * is not the case, and the allocation cannot be moved, it should also
58 * fail the attach operation.
59 *
60 * Any exporter-private housekeeping data can be stored in the
61 * &dma_buf_attachment.priv pointer.
62 *
63 * This callback is optional.
64 *
65 * Returns:
66 *
67 * 0 on success, negative error code on failure. It might return -EBUSY
68 * to signal that backing storage is already allocated and incompatible
69 * with the requirements of requesting device.
70 */
71 int (*attach)(struct dma_buf *, struct dma_buf_attachment *);
72
73 /**
74 * @detach:
75 *
76 * This is called by dma_buf_detach() to release a &dma_buf_attachment.
77 * Provided so that exporters can clean up any housekeeping for an
78 * &dma_buf_attachment.
79 *
80 * This callback is optional.
81 */
82 void (*detach)(struct dma_buf *, struct dma_buf_attachment *);
83
84 /**
85 * @pin:
86 *
87 * This is called by dma_buf_pin and lets the exporter know that the
88 * DMA-buf can't be moved any more.
89 *
90 * This is called with the dmabuf->resv object locked and is mutual
91 * exclusive with @cache_sgt_mapping.
92 *
93 * This callback is optional and should only be used in limited use
94 * cases like scanout and not for temporary pin operations.
95 *
96 * Returns:
97 *
98 * 0 on success, negative error code on failure.
99 */
100 int (*pin)(struct dma_buf_attachment *attach);
101
102 /**
103 * @unpin:
104 *
105 * This is called by dma_buf_unpin and lets the exporter know that the
106 * DMA-buf can be moved again.
107 *
108 * This is called with the dmabuf->resv object locked and is mutual
109 * exclusive with @cache_sgt_mapping.
110 *
111 * This callback is optional.
112 */
113 void (*unpin)(struct dma_buf_attachment *attach);
114
115 /**
116 * @map_dma_buf:
117 *
118 * This is called by dma_buf_map_attachment() and is used to map a
119 * shared &dma_buf into device address space, and it is mandatory. It
120 * can only be called if @attach has been called successfully.
121 *
122 * This call may sleep, e.g. when the backing storage first needs to be
123 * allocated, or moved to a location suitable for all currently attached
124 * devices.
125 *
126 * Note that any specific buffer attributes required for this function
127 * should get added to device_dma_parameters accessible via
128 * &device.dma_params from the &dma_buf_attachment. The @attach callback
129 * should also check these constraints.
130 *
131 * If this is being called for the first time, the exporter can now
132 * choose to scan through the list of attachments for this buffer,
133 * collate the requirements of the attached devices, and choose an
134 * appropriate backing storage for the buffer.
135 *
136 * Based on enum dma_data_direction, it might be possible to have
137 * multiple users accessing at the same time (for reading, maybe), or
138 * any other kind of sharing that the exporter might wish to make
139 * available to buffer-users.
140 *
141 * This is always called with the dmabuf->resv object locked when
142 * the dynamic_mapping flag is true.
143 *
144 * Returns:
145 *
146 * A &sg_table scatter list of or the backing storage of the DMA buffer,
147 * already mapped into the device address space of the &device attached
148 * with the provided &dma_buf_attachment.
149 *
150 * On failure, returns a negative error value wrapped into a pointer.
151 * May also return -EINTR when a signal was received while being
152 * blocked.
153 */
154 struct sg_table * (*map_dma_buf)(struct dma_buf_attachment *,
155 enum dma_data_direction);
156 /**
157 * @unmap_dma_buf:
158 *
159 * This is called by dma_buf_unmap_attachment() and should unmap and
160 * release the &sg_table allocated in @map_dma_buf, and it is mandatory.
161 * For static dma_buf handling this might also unpins the backing
162 * storage if this is the last mapping of the DMA buffer.
163 */
164 void (*unmap_dma_buf)(struct dma_buf_attachment *,
165 struct sg_table *,
166 enum dma_data_direction);
167
168 /* TODO: Add try_map_dma_buf version, to return immed with -EBUSY
169 * if the call would block.
170 */
171
172 /**
173 * @release:
174 *
175 * Called after the last dma_buf_put to release the &dma_buf, and
176 * mandatory.
177 */
178 void (*release)(struct dma_buf *);
179
180 /**
181 * @begin_cpu_access:
182 *
183 * This is called from dma_buf_begin_cpu_access() and allows the
184 * exporter to ensure that the memory is actually available for cpu
185 * access - the exporter might need to allocate or swap-in and pin the
186 * backing storage. The exporter also needs to ensure that cpu access is
187 * coherent for the access direction. The direction can be used by the
188 * exporter to optimize the cache flushing, i.e. access with a different
189 * direction (read instead of write) might return stale or even bogus
190 * data (e.g. when the exporter needs to copy the data to temporary
191 * storage).
192 *
193 * This callback is optional.
194 *
195 * FIXME: This is both called through the DMA_BUF_IOCTL_SYNC command
196 * from userspace (where storage shouldn't be pinned to avoid handing
197 * de-factor mlock rights to userspace) and for the kernel-internal
198 * users of the various kmap interfaces, where the backing storage must
199 * be pinned to guarantee that the atomic kmap calls can succeed. Since
200 * there's no in-kernel users of the kmap interfaces yet this isn't a
201 * real problem.
202 *
203 * Returns:
204 *
205 * 0 on success or a negative error code on failure. This can for
206 * example fail when the backing storage can't be allocated. Can also
207 * return -ERESTARTSYS or -EINTR when the call has been interrupted and
208 * needs to be restarted.
209 */
210 int (*begin_cpu_access)(struct dma_buf *, enum dma_data_direction);
211
212 /**
213 * @end_cpu_access:
214 *
215 * This is called from dma_buf_end_cpu_access() when the importer is
216 * done accessing the CPU. The exporter can use this to flush caches and
217 * unpin any resources pinned in @begin_cpu_access.
218 * The result of any dma_buf kmap calls after end_cpu_access is
219 * undefined.
220 *
221 * This callback is optional.
222 *
223 * Returns:
224 *
225 * 0 on success or a negative error code on failure. Can return
226 * -ERESTARTSYS or -EINTR when the call has been interrupted and needs
227 * to be restarted.
228 */
229 int (*end_cpu_access)(struct dma_buf *, enum dma_data_direction);
230
231 /**
232 * @mmap:
233 *
234 * This callback is used by the dma_buf_mmap() function
235 *
236 * Note that the mapping needs to be incoherent, userspace is expected
237 * to braket CPU access using the DMA_BUF_IOCTL_SYNC interface.
238 *
239 * Because dma-buf buffers have invariant size over their lifetime, the
240 * dma-buf core checks whether a vma is too large and rejects such
241 * mappings. The exporter hence does not need to duplicate this check.
242 * Drivers do not need to check this themselves.
243 *
244 * If an exporter needs to manually flush caches and hence needs to fake
245 * coherency for mmap support, it needs to be able to zap all the ptes
246 * pointing at the backing storage. Now linux mm needs a struct
247 * address_space associated with the struct file stored in vma->vm_file
248 * to do that with the function unmap_mapping_range. But the dma_buf
249 * framework only backs every dma_buf fd with the anon_file struct file,
250 * i.e. all dma_bufs share the same file.
251 *
252 * Hence exporters need to setup their own file (and address_space)
253 * association by setting vma->vm_file and adjusting vma->vm_pgoff in
254 * the dma_buf mmap callback. In the specific case of a gem driver the
255 * exporter could use the shmem file already provided by gem (and set
256 * vm_pgoff = 0). Exporters can then zap ptes by unmapping the
257 * corresponding range of the struct address_space associated with their
258 * own file.
259 *
260 * This callback is optional.
261 *
262 * Returns:
263 *
264 * 0 on success or a negative error code on failure.
265 */
266 int (*mmap)(struct dma_buf *, struct vm_area_struct *vma);
267
268 void *(*vmap)(struct dma_buf *);
269 void (*vunmap)(struct dma_buf *, void *vaddr);
270 };
271
272 /**
273 * struct dma_buf - shared buffer object
274 * @size: size of the buffer
275 * @file: file pointer used for sharing buffers across, and for refcounting.
276 * @attachments: list of dma_buf_attachment that denotes all devices attached,
277 * protected by dma_resv lock.
278 * @ops: dma_buf_ops associated with this buffer object.
279 * @lock: used internally to serialize list manipulation, attach/detach and
280 * vmap/unmap
281 * @vmapping_counter: used internally to refcnt the vmaps
282 * @vmap_ptr: the current vmap ptr if vmapping_counter > 0
283 * @exp_name: name of the exporter; useful for debugging.
284 * @name: userspace-provided name; useful for accounting and debugging,
285 * protected by @resv.
286 * @name_lock: spinlock to protect name access
287 * @owner: pointer to exporter module; used for refcounting when exporter is a
288 * kernel module.
289 * @list_node: node for dma_buf accounting and debugging.
290 * @priv: exporter specific private data for this buffer object.
291 * @resv: reservation object linked to this dma-buf
292 * @exp_pid: pid of exporter task which created this obj
293 * @exp_task_comm: process name of exporter task which created this obj
294 * @poll: for userspace poll support
295 * @cb_excl: for userspace poll support
296 * @cb_shared: for userspace poll support
297 * @sysfs_entry: for exposing information about this buffer in sysfs.
298 * The attachment_uid member of @sysfs_entry is protected by dma_resv lock
299 * and is incremented on each attach.
300 *
301 * This represents a shared buffer, created by calling dma_buf_export(). The
302 * userspace representation is a normal file descriptor, which can be created by
303 * calling dma_buf_fd().
304 *
305 * Shared dma buffers are reference counted using dma_buf_put() and
306 * get_dma_buf().
307 *
308 * Device DMA access is handled by the separate &struct dma_buf_attachment.
309 */
310 struct dma_buf {
311 size_t size;
312 struct file *file;
313 struct list_head attachments;
314 const struct dma_buf_ops *ops;
315 struct mutex lock;
316 unsigned vmapping_counter;
317 void *vmap_ptr;
318 const char *exp_name;
319 const char *name;
320 spinlock_t name_lock;
321 struct module *owner;
322 struct list_head list_node;
323 void *priv;
324 struct dma_resv *resv;
325 #ifdef CONFIG_DMABUF_PROCESS_INFO
326 pid_t exp_pid;
327 char exp_task_comm[TASK_COMM_LEN];
328 #endif
329
330 /* poll support */
331 wait_queue_head_t poll;
332
333 struct dma_buf_poll_cb_t {
334 struct dma_fence_cb cb;
335 wait_queue_head_t *poll;
336
337 __poll_t active;
338 } cb_excl, cb_shared;
339 #ifdef CONFIG_DMABUF_SYSFS_STATS
340 /* for sysfs stats */
341 struct dma_buf_sysfs_entry {
342 struct kobject kobj;
343 struct dma_buf *dmabuf;
344 } *sysfs_entry;
345 #endif
346 };
347
348 /**
349 * struct dma_buf_attach_ops - importer operations for an attachment
350 *
351 * Attachment operations implemented by the importer.
352 */
353 struct dma_buf_attach_ops {
354 /**
355 * @allow_peer2peer:
356 *
357 * If this is set to true the importer must be able to handle peer
358 * resources without struct pages.
359 */
360 bool allow_peer2peer;
361
362 /**
363 * @move_notify: [optional] notification that the DMA-buf is moving
364 *
365 * If this callback is provided the framework can avoid pinning the
366 * backing store while mappings exists.
367 *
368 * This callback is called with the lock of the reservation object
369 * associated with the dma_buf held and the mapping function must be
370 * called with this lock held as well. This makes sure that no mapping
371 * is created concurrently with an ongoing move operation.
372 *
373 * Mappings stay valid and are not directly affected by this callback.
374 * But the DMA-buf can now be in a different physical location, so all
375 * mappings should be destroyed and re-created as soon as possible.
376 *
377 * New mappings can be created after this callback returns, and will
378 * point to the new location of the DMA-buf.
379 */
380 void (*move_notify)(struct dma_buf_attachment *attach);
381 };
382
383 /**
384 * struct dma_buf_attachment - holds device-buffer attachment data
385 * @dmabuf: buffer for this attachment.
386 * @dev: device attached to the buffer.
387 * @node: list of dma_buf_attachment, protected by dma_resv lock of the dmabuf.
388 * @sgt: cached mapping.
389 * @dir: direction of cached mapping.
390 * @peer2peer: true if the importer can handle peer resources without pages.
391 * @priv: exporter specific attachment data.
392 * @importer_ops: importer operations for this attachment, if provided
393 * dma_buf_map/unmap_attachment() must be called with the dma_resv lock held.
394 * @importer_priv: importer specific attachment data.
395 *
396 * This structure holds the attachment information between the dma_buf buffer
397 * and its user device(s). The list contains one attachment struct per device
398 * attached to the buffer.
399 *
400 * An attachment is created by calling dma_buf_attach(), and released again by
401 * calling dma_buf_detach(). The DMA mapping itself needed to initiate a
402 * transfer is created by dma_buf_map_attachment() and freed again by calling
403 * dma_buf_unmap_attachment().
404 */
405 struct dma_buf_attachment {
406 struct dma_buf *dmabuf;
407 struct device *dev;
408 struct list_head node;
409 struct sg_table *sgt;
410 enum dma_data_direction dir;
411 bool peer2peer;
412 const struct dma_buf_attach_ops *importer_ops;
413 void *importer_priv;
414 void *priv;
415 };
416
417 /**
418 * struct dma_buf_export_info - holds information needed to export a dma_buf
419 * @exp_name: name of the exporter - useful for debugging.
420 * @owner: pointer to exporter module - used for refcounting kernel module
421 * @ops: Attach allocator-defined dma buf ops to the new buffer
422 * @size: Size of the buffer
423 * @flags: mode flags for the file
424 * @resv: reservation-object, NULL to allocate default one
425 * @priv: Attach private data of allocator to this buffer
426 *
427 * This structure holds the information required to export the buffer. Used
428 * with dma_buf_export() only.
429 */
430 struct dma_buf_export_info {
431 const char *exp_name;
432 struct module *owner;
433 const struct dma_buf_ops *ops;
434 size_t size;
435 int flags;
436 struct dma_resv *resv;
437 void *priv;
438 };
439
440 /**
441 * DEFINE_DMA_BUF_EXPORT_INFO - helper macro for exporters
442 * @name: export-info name
443 *
444 * DEFINE_DMA_BUF_EXPORT_INFO macro defines the &struct dma_buf_export_info,
445 * zeroes it out and pre-populates exp_name in it.
446 */
447 #define DEFINE_DMA_BUF_EXPORT_INFO(name) \
448 struct dma_buf_export_info name = { .exp_name = KBUILD_MODNAME, \
449 .owner = THIS_MODULE }
450
451 /**
452 * get_dma_buf - convenience wrapper for get_file.
453 * @dmabuf: [in] pointer to dma_buf
454 *
455 * Increments the reference count on the dma-buf, needed in case of drivers
456 * that either need to create additional references to the dmabuf on the
457 * kernel side. For example, an exporter that needs to keep a dmabuf ptr
458 * so that subsequent exports don't create a new dmabuf.
459 */
get_dma_buf(struct dma_buf * dmabuf)460 static inline void get_dma_buf(struct dma_buf *dmabuf)
461 {
462 get_file(dmabuf->file);
463 }
464
465 /**
466 * dma_buf_is_dynamic - check if a DMA-buf uses dynamic mappings.
467 * @dmabuf: the DMA-buf to check
468 *
469 * Returns true if a DMA-buf exporter wants to be called with the dma_resv
470 * locked for the map/unmap callbacks, false if it doesn't wants to be called
471 * with the lock held.
472 */
dma_buf_is_dynamic(struct dma_buf * dmabuf)473 static inline bool dma_buf_is_dynamic(struct dma_buf *dmabuf)
474 {
475 return !!dmabuf->ops->pin;
476 }
477
478 /**
479 * dma_buf_attachment_is_dynamic - check if a DMA-buf attachment uses dynamic
480 * mappinsg
481 * @attach: the DMA-buf attachment to check
482 *
483 * Returns true if a DMA-buf importer wants to call the map/unmap functions with
484 * the dma_resv lock held.
485 */
486 static inline bool
dma_buf_attachment_is_dynamic(struct dma_buf_attachment * attach)487 dma_buf_attachment_is_dynamic(struct dma_buf_attachment *attach)
488 {
489 return !!attach->importer_ops;
490 }
491
492 struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
493 struct device *dev);
494 struct dma_buf_attachment *
495 dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
496 const struct dma_buf_attach_ops *importer_ops,
497 void *importer_priv);
498 void dma_buf_detach(struct dma_buf *dmabuf,
499 struct dma_buf_attachment *attach);
500 int dma_buf_pin(struct dma_buf_attachment *attach);
501 void dma_buf_unpin(struct dma_buf_attachment *attach);
502
503 struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info);
504
505 int dma_buf_fd(struct dma_buf *dmabuf, int flags);
506 struct dma_buf *dma_buf_get(int fd);
507 void dma_buf_put(struct dma_buf *dmabuf);
508
509 struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *,
510 enum dma_data_direction);
511 void dma_buf_unmap_attachment(struct dma_buf_attachment *, struct sg_table *,
512 enum dma_data_direction);
513 void dma_buf_move_notify(struct dma_buf *dma_buf);
514 int dma_buf_begin_cpu_access(struct dma_buf *dma_buf,
515 enum dma_data_direction dir);
516 int dma_buf_end_cpu_access(struct dma_buf *dma_buf,
517 enum dma_data_direction dir);
518
519 int dma_buf_mmap(struct dma_buf *, struct vm_area_struct *,
520 unsigned long);
521 void *dma_buf_vmap(struct dma_buf *);
522 void dma_buf_vunmap(struct dma_buf *, void *vaddr);
523
524 #ifdef CONFIG_DMABUF_PROCESS_INFO
525 /**
526 * get_dma_buf_from_file - Get struct dma_buf* from struct file*
527 * @f: [in] pointer to struct file, which is associated with a
528 * dma_buf object.
529 *
530 * If @f IS_ERR_OR_NULL, return NULL.
531 * If @f is not a file associated with dma_buf, return NULL.
532 */
533 struct dma_buf *get_dma_buf_from_file(struct file *f);
534 #endif /* CONFIG_DMABUF_PROCESS_INFO */
535 #endif /* __DMA_BUF_H__ */
536