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/iosys-map.h>
17 #include <linux/file.h>
18 #include <linux/err.h>
19 #include <linux/scatterlist.h>
20 #include <linux/list.h>
21 #include <linux/dma-mapping.h>
22 #include <linux/fs.h>
23 #include <linux/dma-fence.h>
24 #include <linux/wait.h>
25
26 struct device;
27 struct dma_buf;
28 struct dma_buf_attachment;
29
30 /**
31 * struct dma_buf_ops - operations possible on struct dma_buf
32 * @vmap: [optional] creates a virtual mapping for the buffer into kernel
33 * address space. Same restrictions as for vmap and friends apply.
34 * @vunmap: [optional] unmaps a vmap from the buffer
35 */
36 struct dma_buf_ops {
37 /**
38 * @cache_sgt_mapping:
39 *
40 * If true the framework will cache the first mapping made for each
41 * attachment. This avoids creating mappings for attachments multiple
42 * times.
43 */
44 bool cache_sgt_mapping;
45
46 /**
47 * @attach:
48 *
49 * This is called from dma_buf_attach() to make sure that a given
50 * &dma_buf_attachment.dev can access the provided &dma_buf. Exporters
51 * which support buffer objects in special locations like VRAM or
52 * device-specific carveout areas should check whether the buffer could
53 * be move to system memory (or directly accessed by the provided
54 * device), and otherwise need to fail the attach operation.
55 *
56 * The exporter should also in general check whether the current
57 * allocation fulfills the DMA constraints of the new device. If this
58 * is not the case, and the allocation cannot be moved, it should also
59 * fail the attach operation.
60 *
61 * Any exporter-private housekeeping data can be stored in the
62 * &dma_buf_attachment.priv pointer.
63 *
64 * This callback is optional.
65 *
66 * Returns:
67 *
68 * 0 on success, negative error code on failure. It might return -EBUSY
69 * to signal that backing storage is already allocated and incompatible
70 * with the requirements of requesting device.
71 */
72 int (*attach)(struct dma_buf *, struct dma_buf_attachment *);
73
74 /**
75 * @detach:
76 *
77 * This is called by dma_buf_detach() to release a &dma_buf_attachment.
78 * Provided so that exporters can clean up any housekeeping for an
79 * &dma_buf_attachment.
80 *
81 * This callback is optional.
82 */
83 void (*detach)(struct dma_buf *, struct dma_buf_attachment *);
84
85 /**
86 * @pin:
87 *
88 * This is called by dma_buf_pin() and lets the exporter know that the
89 * DMA-buf can't be moved any more. Ideally, the exporter should
90 * pin the buffer so that it is generally accessible by all
91 * devices.
92 *
93 * This is called with the &dmabuf.resv object locked and is mutual
94 * exclusive with @cache_sgt_mapping.
95 *
96 * This is called automatically for non-dynamic importers from
97 * dma_buf_attach().
98 *
99 * Note that similar to non-dynamic exporters in their @map_dma_buf
100 * callback the driver must guarantee that the memory is available for
101 * use and cleared of any old data by the time this function returns.
102 * Drivers which pipeline their buffer moves internally must wait for
103 * all moves and clears to complete.
104 *
105 * Returns:
106 *
107 * 0 on success, negative error code on failure.
108 */
109 int (*pin)(struct dma_buf_attachment *attach);
110
111 /**
112 * @unpin:
113 *
114 * This is called by dma_buf_unpin() and lets the exporter know that the
115 * DMA-buf can be moved again.
116 *
117 * This is called with the dmabuf->resv object locked and is mutual
118 * exclusive with @cache_sgt_mapping.
119 *
120 * This callback is optional.
121 */
122 void (*unpin)(struct dma_buf_attachment *attach);
123
124 /**
125 * @map_dma_buf:
126 *
127 * This is called by dma_buf_map_attachment() and is used to map a
128 * shared &dma_buf into device address space, and it is mandatory. It
129 * can only be called if @attach has been called successfully.
130 *
131 * This call may sleep, e.g. when the backing storage first needs to be
132 * allocated, or moved to a location suitable for all currently attached
133 * devices.
134 *
135 * Note that any specific buffer attributes required for this function
136 * should get added to device_dma_parameters accessible via
137 * &device.dma_params from the &dma_buf_attachment. The @attach callback
138 * should also check these constraints.
139 *
140 * If this is being called for the first time, the exporter can now
141 * choose to scan through the list of attachments for this buffer,
142 * collate the requirements of the attached devices, and choose an
143 * appropriate backing storage for the buffer.
144 *
145 * Based on enum dma_data_direction, it might be possible to have
146 * multiple users accessing at the same time (for reading, maybe), or
147 * any other kind of sharing that the exporter might wish to make
148 * available to buffer-users.
149 *
150 * This is always called with the dmabuf->resv object locked when
151 * the dynamic_mapping flag is true.
152 *
153 * Note that for non-dynamic exporters the driver must guarantee that
154 * that the memory is available for use and cleared of any old data by
155 * the time this function returns. Drivers which pipeline their buffer
156 * moves internally must wait for all moves and clears to complete.
157 * Dynamic exporters do not need to follow this rule: For non-dynamic
158 * importers the buffer is already pinned through @pin, which has the
159 * same requirements. Dynamic importers otoh are required to obey the
160 * dma_resv fences.
161 *
162 * Returns:
163 *
164 * A &sg_table scatter list of the backing storage of the DMA buffer,
165 * already mapped into the device address space of the &device attached
166 * with the provided &dma_buf_attachment. The addresses and lengths in
167 * the scatter list are PAGE_SIZE aligned.
168 *
169 * On failure, returns a negative error value wrapped into a pointer.
170 * May also return -EINTR when a signal was received while being
171 * blocked.
172 *
173 * Note that exporters should not try to cache the scatter list, or
174 * return the same one for multiple calls. Caching is done either by the
175 * DMA-BUF code (for non-dynamic importers) or the importer. Ownership
176 * of the scatter list is transferred to the caller, and returned by
177 * @unmap_dma_buf.
178 */
179 struct sg_table * (*map_dma_buf)(struct dma_buf_attachment *,
180 enum dma_data_direction);
181 /**
182 * @unmap_dma_buf:
183 *
184 * This is called by dma_buf_unmap_attachment() and should unmap and
185 * release the &sg_table allocated in @map_dma_buf, and it is mandatory.
186 * For static dma_buf handling this might also unpin the backing
187 * storage if this is the last mapping of the DMA buffer.
188 */
189 void (*unmap_dma_buf)(struct dma_buf_attachment *,
190 struct sg_table *,
191 enum dma_data_direction);
192
193 /* TODO: Add try_map_dma_buf version, to return immed with -EBUSY
194 * if the call would block.
195 */
196
197 /**
198 * @release:
199 *
200 * Called after the last dma_buf_put to release the &dma_buf, and
201 * mandatory.
202 */
203 void (*release)(struct dma_buf *);
204
205 /**
206 * @begin_cpu_access:
207 *
208 * This is called from dma_buf_begin_cpu_access() and allows the
209 * exporter to ensure that the memory is actually coherent for cpu
210 * access. The exporter also needs to ensure that cpu access is coherent
211 * for the access direction. The direction can be used by the exporter
212 * to optimize the cache flushing, i.e. access with a different
213 * direction (read instead of write) might return stale or even bogus
214 * data (e.g. when the exporter needs to copy the data to temporary
215 * storage).
216 *
217 * Note that this is both called through the DMA_BUF_IOCTL_SYNC IOCTL
218 * command for userspace mappings established through @mmap, and also
219 * for kernel mappings established with @vmap.
220 *
221 * This callback is optional.
222 *
223 * Returns:
224 *
225 * 0 on success or a negative error code on failure. This can for
226 * example fail when the backing storage can't be allocated. Can also
227 * return -ERESTARTSYS or -EINTR when the call has been interrupted and
228 * needs to be restarted.
229 */
230 int (*begin_cpu_access)(struct dma_buf *, enum dma_data_direction);
231
232 /**
233 * @end_cpu_access:
234 *
235 * This is called from dma_buf_end_cpu_access() when the importer is
236 * done accessing the CPU. The exporter can use this to flush caches and
237 * undo anything else done in @begin_cpu_access.
238 *
239 * This callback is optional.
240 *
241 * Returns:
242 *
243 * 0 on success or a negative error code on failure. Can return
244 * -ERESTARTSYS or -EINTR when the call has been interrupted and needs
245 * to be restarted.
246 */
247 int (*end_cpu_access)(struct dma_buf *, enum dma_data_direction);
248
249 /**
250 * @mmap:
251 *
252 * This callback is used by the dma_buf_mmap() function
253 *
254 * Note that the mapping needs to be incoherent, userspace is expected
255 * to bracket CPU access using the DMA_BUF_IOCTL_SYNC interface.
256 *
257 * Because dma-buf buffers have invariant size over their lifetime, the
258 * dma-buf core checks whether a vma is too large and rejects such
259 * mappings. The exporter hence does not need to duplicate this check.
260 * Drivers do not need to check this themselves.
261 *
262 * If an exporter needs to manually flush caches and hence needs to fake
263 * coherency for mmap support, it needs to be able to zap all the ptes
264 * pointing at the backing storage. Now linux mm needs a struct
265 * address_space associated with the struct file stored in vma->vm_file
266 * to do that with the function unmap_mapping_range. But the dma_buf
267 * framework only backs every dma_buf fd with the anon_file struct file,
268 * i.e. all dma_bufs share the same file.
269 *
270 * Hence exporters need to setup their own file (and address_space)
271 * association by setting vma->vm_file and adjusting vma->vm_pgoff in
272 * the dma_buf mmap callback. In the specific case of a gem driver the
273 * exporter could use the shmem file already provided by gem (and set
274 * vm_pgoff = 0). Exporters can then zap ptes by unmapping the
275 * corresponding range of the struct address_space associated with their
276 * own file.
277 *
278 * This callback is optional.
279 *
280 * Returns:
281 *
282 * 0 on success or a negative error code on failure.
283 */
284 int (*mmap)(struct dma_buf *, struct vm_area_struct *vma);
285
286 int (*vmap)(struct dma_buf *dmabuf, struct iosys_map *map);
287 void (*vunmap)(struct dma_buf *dmabuf, struct iosys_map *map);
288 };
289
290 /**
291 * struct dma_buf - shared buffer object
292 *
293 * This represents a shared buffer, created by calling dma_buf_export(). The
294 * userspace representation is a normal file descriptor, which can be created by
295 * calling dma_buf_fd().
296 *
297 * Shared dma buffers are reference counted using dma_buf_put() and
298 * get_dma_buf().
299 *
300 * Device DMA access is handled by the separate &struct dma_buf_attachment.
301 */
302 struct dma_buf {
303 /**
304 * @size:
305 *
306 * Size of the buffer; invariant over the lifetime of the buffer.
307 */
308 size_t size;
309
310 /**
311 * @file:
312 *
313 * File pointer used for sharing buffers across, and for refcounting.
314 * See dma_buf_get() and dma_buf_put().
315 */
316 struct file *file;
317
318 /**
319 * @attachments:
320 *
321 * List of dma_buf_attachment that denotes all devices attached,
322 * protected by &dma_resv lock @resv.
323 */
324 struct list_head attachments;
325
326 /** @ops: dma_buf_ops associated with this buffer object. */
327 const struct dma_buf_ops *ops;
328
329 /**
330 * @vmapping_counter:
331 *
332 * Used internally to refcnt the vmaps returned by dma_buf_vmap().
333 * Protected by @lock.
334 */
335 unsigned vmapping_counter;
336
337 /**
338 * @vmap_ptr:
339 * The current vmap ptr if @vmapping_counter > 0. Protected by @lock.
340 */
341 struct iosys_map vmap_ptr;
342
343 /**
344 * @exp_name:
345 *
346 * Name of the exporter; useful for debugging. Must not be NULL
347 */
348 const char *exp_name;
349
350 /**
351 * @name:
352 *
353 * Userspace-provided name. Default value is NULL. If not NULL,
354 * length cannot be longer than DMA_BUF_NAME_LEN, including NIL
355 * char. Useful for accounting and debugging. Read/Write accesses
356 * are protected by @name_lock
357 *
358 * See the IOCTLs DMA_BUF_SET_NAME or DMA_BUF_SET_NAME_A/B
359 */
360 const char *name;
361
362 /** @name_lock: Spinlock to protect name access for read access. */
363 spinlock_t name_lock;
364
365 /**
366 * @owner:
367 *
368 * Pointer to exporter module; used for refcounting when exporter is a
369 * kernel module.
370 */
371 struct module *owner;
372
373 #if IS_ENABLED(CONFIG_DEBUG_FS)
374 /** @list_node: node for dma_buf accounting and debugging. */
375 struct list_head list_node;
376 #endif
377
378 /** @priv: exporter specific private data for this buffer object. */
379 void *priv;
380
381 /**
382 * @resv:
383 *
384 * Reservation object linked to this dma-buf.
385 *
386 * IMPLICIT SYNCHRONIZATION RULES:
387 *
388 * Drivers which support implicit synchronization of buffer access as
389 * e.g. exposed in `Implicit Fence Poll Support`_ must follow the
390 * below rules.
391 *
392 * - Drivers must add a read fence through dma_resv_add_fence() with the
393 * DMA_RESV_USAGE_READ flag for anything the userspace API considers a
394 * read access. This highly depends upon the API and window system.
395 *
396 * - Similarly drivers must add a write fence through
397 * dma_resv_add_fence() with the DMA_RESV_USAGE_WRITE flag for
398 * anything the userspace API considers write access.
399 *
400 * - Drivers may just always add a write fence, since that only
401 * causes unnecessary synchronization, but no correctness issues.
402 *
403 * - Some drivers only expose a synchronous userspace API with no
404 * pipelining across drivers. These do not set any fences for their
405 * access. An example here is v4l.
406 *
407 * - Driver should use dma_resv_usage_rw() when retrieving fences as
408 * dependency for implicit synchronization.
409 *
410 * DYNAMIC IMPORTER RULES:
411 *
412 * Dynamic importers, see dma_buf_attachment_is_dynamic(), have
413 * additional constraints on how they set up fences:
414 *
415 * - Dynamic importers must obey the write fences and wait for them to
416 * signal before allowing access to the buffer's underlying storage
417 * through the device.
418 *
419 * - Dynamic importers should set fences for any access that they can't
420 * disable immediately from their &dma_buf_attach_ops.move_notify
421 * callback.
422 *
423 * IMPORTANT:
424 *
425 * All drivers and memory management related functions must obey the
426 * struct dma_resv rules, specifically the rules for updating and
427 * obeying fences. See enum dma_resv_usage for further descriptions.
428 */
429 struct dma_resv *resv;
430
431 /** @poll: for userspace poll support */
432 wait_queue_head_t poll;
433
434 /** @cb_in: for userspace poll support */
435 /** @cb_out: for userspace poll support */
436 struct dma_buf_poll_cb_t {
437 struct dma_fence_cb cb;
438 wait_queue_head_t *poll;
439
440 __poll_t active;
441 } cb_in, cb_out;
442 #ifdef CONFIG_DMABUF_SYSFS_STATS
443 /**
444 * @sysfs_entry:
445 *
446 * For exposing information about this buffer in sysfs. See also
447 * `DMA-BUF statistics`_ for the uapi this enables.
448 */
449 struct dma_buf_sysfs_entry {
450 struct kobject kobj;
451 struct dma_buf *dmabuf;
452 } *sysfs_entry;
453 #endif
454 };
455
456 /**
457 * struct dma_buf_attach_ops - importer operations for an attachment
458 *
459 * Attachment operations implemented by the importer.
460 */
461 struct dma_buf_attach_ops {
462 /**
463 * @allow_peer2peer:
464 *
465 * If this is set to true the importer must be able to handle peer
466 * resources without struct pages.
467 */
468 bool allow_peer2peer;
469
470 /**
471 * @move_notify: [optional] notification that the DMA-buf is moving
472 *
473 * If this callback is provided the framework can avoid pinning the
474 * backing store while mappings exists.
475 *
476 * This callback is called with the lock of the reservation object
477 * associated with the dma_buf held and the mapping function must be
478 * called with this lock held as well. This makes sure that no mapping
479 * is created concurrently with an ongoing move operation.
480 *
481 * Mappings stay valid and are not directly affected by this callback.
482 * But the DMA-buf can now be in a different physical location, so all
483 * mappings should be destroyed and re-created as soon as possible.
484 *
485 * New mappings can be created after this callback returns, and will
486 * point to the new location of the DMA-buf.
487 */
488 void (*move_notify)(struct dma_buf_attachment *attach);
489 };
490
491 /**
492 * struct dma_buf_attachment - holds device-buffer attachment data
493 * @dmabuf: buffer for this attachment.
494 * @dev: device attached to the buffer.
495 * @node: list of dma_buf_attachment, protected by dma_resv lock of the dmabuf.
496 * @sgt: cached mapping.
497 * @dir: direction of cached mapping.
498 * @peer2peer: true if the importer can handle peer resources without pages.
499 * @priv: exporter specific attachment data.
500 * @importer_ops: importer operations for this attachment, if provided
501 * dma_buf_map/unmap_attachment() must be called with the dma_resv lock held.
502 * @importer_priv: importer specific attachment data.
503 *
504 * This structure holds the attachment information between the dma_buf buffer
505 * and its user device(s). The list contains one attachment struct per device
506 * attached to the buffer.
507 *
508 * An attachment is created by calling dma_buf_attach(), and released again by
509 * calling dma_buf_detach(). The DMA mapping itself needed to initiate a
510 * transfer is created by dma_buf_map_attachment() and freed again by calling
511 * dma_buf_unmap_attachment().
512 */
513 struct dma_buf_attachment {
514 struct dma_buf *dmabuf;
515 struct device *dev;
516 struct list_head node;
517 struct sg_table *sgt;
518 enum dma_data_direction dir;
519 bool peer2peer;
520 const struct dma_buf_attach_ops *importer_ops;
521 void *importer_priv;
522 void *priv;
523 };
524
525 /**
526 * struct dma_buf_export_info - holds information needed to export a dma_buf
527 * @exp_name: name of the exporter - useful for debugging.
528 * @owner: pointer to exporter module - used for refcounting kernel module
529 * @ops: Attach allocator-defined dma buf ops to the new buffer
530 * @size: Size of the buffer - invariant over the lifetime of the buffer
531 * @flags: mode flags for the file
532 * @resv: reservation-object, NULL to allocate default one
533 * @priv: Attach private data of allocator to this buffer
534 *
535 * This structure holds the information required to export the buffer. Used
536 * with dma_buf_export() only.
537 */
538 struct dma_buf_export_info {
539 const char *exp_name;
540 struct module *owner;
541 const struct dma_buf_ops *ops;
542 size_t size;
543 int flags;
544 struct dma_resv *resv;
545 void *priv;
546 };
547
548 /**
549 * DEFINE_DMA_BUF_EXPORT_INFO - helper macro for exporters
550 * @name: export-info name
551 *
552 * DEFINE_DMA_BUF_EXPORT_INFO macro defines the &struct dma_buf_export_info,
553 * zeroes it out and pre-populates exp_name in it.
554 */
555 #define DEFINE_DMA_BUF_EXPORT_INFO(name) \
556 struct dma_buf_export_info name = { .exp_name = KBUILD_MODNAME, \
557 .owner = THIS_MODULE }
558
559 /**
560 * get_dma_buf - convenience wrapper for get_file.
561 * @dmabuf: [in] pointer to dma_buf
562 *
563 * Increments the reference count on the dma-buf, needed in case of drivers
564 * that either need to create additional references to the dmabuf on the
565 * kernel side. For example, an exporter that needs to keep a dmabuf ptr
566 * so that subsequent exports don't create a new dmabuf.
567 */
568 static inline void get_dma_buf(struct dma_buf *dmabuf)
569 {
570 get_file(dmabuf->file);
571 }
572
573 /**
574 * dma_buf_is_dynamic - check if a DMA-buf uses dynamic mappings.
575 * @dmabuf: the DMA-buf to check
576 *
577 * Returns true if a DMA-buf exporter wants to be called with the dma_resv
578 * locked for the map/unmap callbacks, false if it doesn't wants to be called
579 * with the lock held.
580 */
581 static inline bool dma_buf_is_dynamic(struct dma_buf *dmabuf)
582 {
583 return !!dmabuf->ops->pin;
584 }
585
586 /**
587 * dma_buf_attachment_is_dynamic - check if a DMA-buf attachment uses dynamic
588 * mappings
589 * @attach: the DMA-buf attachment to check
590 *
591 * Returns true if a DMA-buf importer wants to call the map/unmap functions with
592 * the dma_resv lock held.
593 */
594 static inline bool
595 dma_buf_attachment_is_dynamic(struct dma_buf_attachment *attach)
596 {
597 return !!attach->importer_ops;
598 }
599
600 struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
601 struct device *dev);
602 struct dma_buf_attachment *
603 dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
604 const struct dma_buf_attach_ops *importer_ops,
605 void *importer_priv);
606 void dma_buf_detach(struct dma_buf *dmabuf,
607 struct dma_buf_attachment *attach);
608 int dma_buf_pin(struct dma_buf_attachment *attach);
609 void dma_buf_unpin(struct dma_buf_attachment *attach);
610
611 struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info);
612
613 int dma_buf_fd(struct dma_buf *dmabuf, int flags);
614 struct dma_buf *dma_buf_get(int fd);
615 void dma_buf_put(struct dma_buf *dmabuf);
616
617 struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *,
618 enum dma_data_direction);
619 void dma_buf_unmap_attachment(struct dma_buf_attachment *, struct sg_table *,
620 enum dma_data_direction);
621 void dma_buf_move_notify(struct dma_buf *dma_buf);
622 int dma_buf_begin_cpu_access(struct dma_buf *dma_buf,
623 enum dma_data_direction dir);
624 int dma_buf_end_cpu_access(struct dma_buf *dma_buf,
625 enum dma_data_direction dir);
626 struct sg_table *
627 dma_buf_map_attachment_unlocked(struct dma_buf_attachment *attach,
628 enum dma_data_direction direction);
629 void dma_buf_unmap_attachment_unlocked(struct dma_buf_attachment *attach,
630 struct sg_table *sg_table,
631 enum dma_data_direction direction);
632
633 int dma_buf_mmap(struct dma_buf *, struct vm_area_struct *,
634 unsigned long);
635 int dma_buf_vmap(struct dma_buf *dmabuf, struct iosys_map *map);
636 void dma_buf_vunmap(struct dma_buf *dmabuf, struct iosys_map *map);
637 int dma_buf_vmap_unlocked(struct dma_buf *dmabuf, struct iosys_map *map);
638 void dma_buf_vunmap_unlocked(struct dma_buf *dmabuf, struct iosys_map *map);
639 #endif /* __DMA_BUF_H__ */
640
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