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#include <linux/pci-p2pdma.h>
26
27struct device;
28struct dma_buf;
29struct dma_buf_attachment;
30
31/**
32 * struct dma_buf_ops - operations possible on struct dma_buf
33 * @vmap: [optional] creates a virtual mapping for the buffer into kernel
34 * address space. Same restrictions as for vmap and friends apply.
35 * @vunmap: [optional] unmaps a vmap from the buffer
36 */
37struct dma_buf_ops {
38 /**
39 * @attach:
40 *
41 * This is called from dma_buf_attach() to make sure that a given
42 * &dma_buf_attachment.dev can access the provided &dma_buf. Exporters
43 * which support buffer objects in special locations like VRAM or
44 * device-specific carveout areas should check whether the buffer could
45 * be move to system memory (or directly accessed by the provided
46 * device), and otherwise need to fail the attach operation.
47 *
48 * The exporter should also in general check whether the current
49 * allocation fulfills the DMA constraints of the new device. If this
50 * is not the case, and the allocation cannot be moved, it should also
51 * fail the attach operation.
52 *
53 * Any exporter-private housekeeping data can be stored in the
54 * &dma_buf_attachment.priv pointer.
55 *
56 * This callback is optional.
57 *
58 * Returns:
59 *
60 * 0 on success, negative error code on failure. It might return -EBUSY
61 * to signal that backing storage is already allocated and incompatible
62 * with the requirements of requesting device.
63 */
64 int (*attach)(struct dma_buf *, struct dma_buf_attachment *);
65
66 /**
67 * @detach:
68 *
69 * This is called by dma_buf_detach() to release a &dma_buf_attachment.
70 * Provided so that exporters can clean up any housekeeping for an
71 * &dma_buf_attachment.
72 *
73 * This callback is optional.
74 */
75 void (*detach)(struct dma_buf *, struct dma_buf_attachment *);
76
77 /**
78 * @pin:
79 *
80 * This is called by dma_buf_pin() and lets the exporter know that the
81 * DMA-buf can't be moved any more. Ideally, the exporter should
82 * pin the buffer so that it is generally accessible by all
83 * devices.
84 *
85 * This is called with the &dmabuf.resv object locked and is mutual
86 * exclusive with @cache_sgt_mapping.
87 *
88 * This is called automatically for non-dynamic importers from
89 * dma_buf_attach().
90 *
91 * Note that similar to non-dynamic exporters in their @map_dma_buf
92 * callback the driver must guarantee that the memory is available for
93 * use and cleared of any old data by the time this function returns.
94 * Drivers which pipeline their buffer moves internally must wait for
95 * all moves and clears to complete.
96 *
97 * Returns:
98 *
99 * 0 on success, negative error code on failure.
100 */
101 int (*pin)(struct dma_buf_attachment *attach);
102
103 /**
104 * @unpin:
105 *
106 * This is called by dma_buf_unpin() and lets the exporter know that the
107 * DMA-buf can be moved again.
108 *
109 * This is called with the dmabuf->resv object locked and is mutual
110 * exclusive with @cache_sgt_mapping.
111 *
112 * This callback is optional.
113 */
114 void (*unpin)(struct dma_buf_attachment *attach);
115
116 /**
117 * @map_dma_buf:
118 *
119 * This is called by dma_buf_map_attachment() and is used to map a
120 * shared &dma_buf into device address space, and it is mandatory. It
121 * can only be called if @attach has been called successfully.
122 *
123 * This call may sleep, e.g. when the backing storage first needs to be
124 * allocated, or moved to a location suitable for all currently attached
125 * devices.
126 *
127 * Note that any specific buffer attributes required for this function
128 * should get added to device_dma_parameters accessible via
129 * &device.dma_params from the &dma_buf_attachment. The @attach callback
130 * should also check these constraints.
131 *
132 * If this is being called for the first time, the exporter can now
133 * choose to scan through the list of attachments for this buffer,
134 * collate the requirements of the attached devices, and choose an
135 * appropriate backing storage for the buffer.
136 *
137 * Based on enum dma_data_direction, it might be possible to have
138 * multiple users accessing at the same time (for reading, maybe), or
139 * any other kind of sharing that the exporter might wish to make
140 * available to buffer-users.
141 *
142 * This is always called with the dmabuf->resv object locked when
143 * the dynamic_mapping flag is true.
144 *
145 * Note that for non-dynamic exporters the driver must guarantee that
146 * that the memory is available for use and cleared of any old data by
147 * the time this function returns. Drivers which pipeline their buffer
148 * moves internally must wait for all moves and clears to complete.
149 * Dynamic exporters do not need to follow this rule: For non-dynamic
150 * importers the buffer is already pinned through @pin, which has the
151 * same requirements. Dynamic importers otoh are required to obey the
152 * dma_resv fences.
153 *
154 * Returns:
155 *
156 * A &sg_table scatter list of the backing storage of the DMA buffer,
157 * already mapped into the device address space of the &device attached
158 * with the provided &dma_buf_attachment. The addresses and lengths in
159 * the scatter list are PAGE_SIZE aligned.
160 *
161 * On failure, returns a negative error value wrapped into a pointer.
162 * May also return -EINTR when a signal was received while being
163 * blocked.
164 *
165 * Note that exporters should not try to cache the scatter list, or
166 * return the same one for multiple calls. Caching is done either by the
167 * DMA-BUF code (for non-dynamic importers) or the importer. Ownership
168 * of the scatter list is transferred to the caller, and returned by
169 * @unmap_dma_buf.
170 */
171 struct sg_table * (*map_dma_buf)(struct dma_buf_attachment *,
172 enum dma_data_direction);
173 /**
174 * @unmap_dma_buf:
175 *
176 * This is called by dma_buf_unmap_attachment() and should unmap and
177 * release the &sg_table allocated in @map_dma_buf, and it is mandatory.
178 * For static dma_buf handling this might also unpin the backing
179 * storage if this is the last mapping of the DMA buffer.
180 */
181 void (*unmap_dma_buf)(struct dma_buf_attachment *,
182 struct sg_table *,
183 enum dma_data_direction);
184
185 /* TODO: Add try_map_dma_buf version, to return immed with -EBUSY
186 * if the call would block.
187 */
188
189 /**
190 * @release:
191 *
192 * Called after the last dma_buf_put to release the &dma_buf, and
193 * mandatory.
194 */
195 void (*release)(struct dma_buf *);
196
197 /**
198 * @begin_cpu_access:
199 *
200 * This is called from dma_buf_begin_cpu_access() and allows the
201 * exporter to ensure that the memory is actually coherent for cpu
202 * access. The exporter also needs to ensure that cpu access is coherent
203 * for the access direction. The direction can be used by the exporter
204 * to optimize the cache flushing, i.e. access with a different
205 * direction (read instead of write) might return stale or even bogus
206 * data (e.g. when the exporter needs to copy the data to temporary
207 * storage).
208 *
209 * Note that this is both called through the DMA_BUF_IOCTL_SYNC IOCTL
210 * command for userspace mappings established through @mmap, and also
211 * for kernel mappings established with @vmap.
212 *
213 * This callback is optional.
214 *
215 * Returns:
216 *
217 * 0 on success or a negative error code on failure. This can for
218 * example fail when the backing storage can't be allocated. Can also
219 * return -ERESTARTSYS or -EINTR when the call has been interrupted and
220 * needs to be restarted.
221 */
222 int (*begin_cpu_access)(struct dma_buf *, enum dma_data_direction);
223
224 /**
225 * @end_cpu_access:
226 *
227 * This is called from dma_buf_end_cpu_access() when the importer is
228 * done accessing the CPU. The exporter can use this to flush caches and
229 * undo anything else done in @begin_cpu_access.
230 *
231 * This callback is optional.
232 *
233 * Returns:
234 *
235 * 0 on success or a negative error code on failure. Can return
236 * -ERESTARTSYS or -EINTR when the call has been interrupted and needs
237 * to be restarted.
238 */
239 int (*end_cpu_access)(struct dma_buf *, enum dma_data_direction);
240
241 /**
242 * @mmap:
243 *
244 * This callback is used by the dma_buf_mmap() function
245 *
246 * Note that the mapping needs to be incoherent, userspace is expected
247 * to bracket CPU access using the DMA_BUF_IOCTL_SYNC interface.
248 *
249 * Because dma-buf buffers have invariant size over their lifetime, the
250 * dma-buf core checks whether a vma is too large and rejects such
251 * mappings. The exporter hence does not need to duplicate this check.
252 * Drivers do not need to check this themselves.
253 *
254 * If an exporter needs to manually flush caches and hence needs to fake
255 * coherency for mmap support, it needs to be able to zap all the ptes
256 * pointing at the backing storage. Now linux mm needs a struct
257 * address_space associated with the struct file stored in vma->vm_file
258 * to do that with the function unmap_mapping_range. But the dma_buf
259 * framework only backs every dma_buf fd with the anon_file struct file,
260 * i.e. all dma_bufs share the same file.
261 *
262 * Hence exporters need to setup their own file (and address_space)
263 * association by setting vma->vm_file and adjusting vma->vm_pgoff in
264 * the dma_buf mmap callback. In the specific case of a gem driver the
265 * exporter could use the shmem file already provided by gem (and set
266 * vm_pgoff = 0). Exporters can then zap ptes by unmapping the
267 * corresponding range of the struct address_space associated with their
268 * own file.
269 *
270 * This callback is optional.
271 *
272 * Returns:
273 *
274 * 0 on success or a negative error code on failure.
275 */
276 int (*mmap)(struct dma_buf *, struct vm_area_struct *vma);
277
278 int (*vmap)(struct dma_buf *dmabuf, struct iosys_map *map);
279 void (*vunmap)(struct dma_buf *dmabuf, struct iosys_map *map);
280};
281
282/**
283 * struct dma_buf - shared buffer object
284 *
285 * This represents a shared buffer, created by calling dma_buf_export(). The
286 * userspace representation is a normal file descriptor, which can be created by
287 * calling dma_buf_fd().
288 *
289 * Shared dma buffers are reference counted using dma_buf_put() and
290 * get_dma_buf().
291 *
292 * Device DMA access is handled by the separate &struct dma_buf_attachment.
293 */
294struct dma_buf {
295 /**
296 * @size:
297 *
298 * Size of the buffer; invariant over the lifetime of the buffer.
299 */
300 size_t size;
301
302 /**
303 * @file:
304 *
305 * File pointer used for sharing buffers across, and for refcounting.
306 * See dma_buf_get() and dma_buf_put().
307 */
308 struct file *file;
309
310 /**
311 * @attachments:
312 *
313 * List of dma_buf_attachment that denotes all devices attached,
314 * protected by &dma_resv lock @resv.
315 */
316 struct list_head attachments;
317
318 /** @ops: dma_buf_ops associated with this buffer object. */
319 const struct dma_buf_ops *ops;
320
321 /**
322 * @vmapping_counter:
323 *
324 * Used internally to refcnt the vmaps returned by dma_buf_vmap().
325 * Protected by @lock.
326 */
327 unsigned vmapping_counter;
328
329 /**
330 * @vmap_ptr:
331 * The current vmap ptr if @vmapping_counter > 0. Protected by @lock.
332 */
333 struct iosys_map vmap_ptr;
334
335 /**
336 * @exp_name:
337 *
338 * Name of the exporter; useful for debugging. Must not be NULL
339 */
340 const char *exp_name;
341
342 /**
343 * @name:
344 *
345 * Userspace-provided name. Default value is NULL. If not NULL,
346 * length cannot be longer than DMA_BUF_NAME_LEN, including NIL
347 * char. Useful for accounting and debugging. Read/Write accesses
348 * are protected by @name_lock
349 *
350 * See the IOCTLs DMA_BUF_SET_NAME or DMA_BUF_SET_NAME_A/B
351 */
352 const char *name;
353
354 /** @name_lock: Spinlock to protect name access for read access. */
355 spinlock_t name_lock;
356
357 /**
358 * @owner:
359 *
360 * Pointer to exporter module; used for refcounting when exporter is a
361 * kernel module.
362 */
363 struct module *owner;
364
365 /** @list_node: node for dma_buf accounting and debugging. */
366 struct list_head list_node;
367
368 /** @priv: exporter specific private data for this buffer object. */
369 void *priv;
370
371 /**
372 * @resv:
373 *
374 * Reservation object linked to this dma-buf.
375 *
376 * IMPLICIT SYNCHRONIZATION RULES:
377 *
378 * Drivers which support implicit synchronization of buffer access as
379 * e.g. exposed in `Implicit Fence Poll Support`_ must follow the
380 * below rules.
381 *
382 * - Drivers must add a read fence through dma_resv_add_fence() with the
383 * DMA_RESV_USAGE_READ flag for anything the userspace API considers a
384 * read access. This highly depends upon the API and window system.
385 *
386 * - Similarly drivers must add a write fence through
387 * dma_resv_add_fence() with the DMA_RESV_USAGE_WRITE flag for
388 * anything the userspace API considers write access.
389 *
390 * - Drivers may just always add a write fence, since that only
391 * causes unnecessary synchronization, but no correctness issues.
392 *
393 * - Some drivers only expose a synchronous userspace API with no
394 * pipelining across drivers. These do not set any fences for their
395 * access. An example here is v4l.
396 *
397 * - Driver should use dma_resv_usage_rw() when retrieving fences as
398 * dependency for implicit synchronization.
399 *
400 * DYNAMIC IMPORTER RULES:
401 *
402 * Dynamic importers, see dma_buf_attachment_is_dynamic(), have
403 * additional constraints on how they set up fences:
404 *
405 * - Dynamic importers must obey the write fences and wait for them to
406 * signal before allowing access to the buffer's underlying storage
407 * through the device.
408 *
409 * - Dynamic importers should set fences for any access that they can't
410 * disable immediately from their &dma_buf_attach_ops.move_notify
411 * callback.
412 *
413 * IMPORTANT:
414 *
415 * All drivers and memory management related functions must obey the
416 * struct dma_resv rules, specifically the rules for updating and
417 * obeying fences. See enum dma_resv_usage for further descriptions.
418 */
419 struct dma_resv *resv;
420
421 /** @poll: for userspace poll support */
422 wait_queue_head_t poll;
423
424 /** @cb_in: for userspace poll support */
425 /** @cb_out: for userspace poll support */
426 struct dma_buf_poll_cb_t {
427 struct dma_fence_cb cb;
428 wait_queue_head_t *poll;
429
430 __poll_t active;
431 } cb_in, cb_out;
432#ifdef CONFIG_DMABUF_SYSFS_STATS
433 /**
434 * @sysfs_entry:
435 *
436 * For exposing information about this buffer in sysfs. See also
437 * `DMA-BUF statistics`_ for the uapi this enables.
438 */
439 struct dma_buf_sysfs_entry {
440 struct kobject kobj;
441 struct dma_buf *dmabuf;
442 } *sysfs_entry;
443#endif
444};
445
446/**
447 * struct dma_buf_attach_ops - importer operations for an attachment
448 *
449 * Attachment operations implemented by the importer.
450 */
451struct dma_buf_attach_ops {
452 /**
453 * @allow_peer2peer:
454 *
455 * If this is set to true the importer must be able to handle peer
456 * resources without struct pages.
457 */
458 bool allow_peer2peer;
459
460 /**
461 * @move_notify: [optional] notification that the DMA-buf is moving
462 *
463 * If this callback is provided the framework can avoid pinning the
464 * backing store while mappings exists.
465 *
466 * This callback is called with the lock of the reservation object
467 * associated with the dma_buf held and the mapping function must be
468 * called with this lock held as well. This makes sure that no mapping
469 * is created concurrently with an ongoing move operation.
470 *
471 * Mappings stay valid and are not directly affected by this callback.
472 * But the DMA-buf can now be in a different physical location, so all
473 * mappings should be destroyed and re-created as soon as possible.
474 *
475 * New mappings can be created after this callback returns, and will
476 * point to the new location of the DMA-buf.
477 */
478 void (*move_notify)(struct dma_buf_attachment *attach);
479};
480
481/**
482 * struct dma_buf_attachment - holds device-buffer attachment data
483 * @dmabuf: buffer for this attachment.
484 * @dev: device attached to the buffer.
485 * @node: list of dma_buf_attachment, protected by dma_resv lock of the dmabuf.
486 * @peer2peer: true if the importer can handle peer resources without pages.
487 * @priv: exporter specific attachment data.
488 * @importer_ops: importer operations for this attachment, if provided
489 * dma_buf_map/unmap_attachment() must be called with the dma_resv lock held.
490 * @importer_priv: importer specific attachment data.
491 *
492 * This structure holds the attachment information between the dma_buf buffer
493 * and its user device(s). The list contains one attachment struct per device
494 * attached to the buffer.
495 *
496 * An attachment is created by calling dma_buf_attach(), and released again by
497 * calling dma_buf_detach(). The DMA mapping itself needed to initiate a
498 * transfer is created by dma_buf_map_attachment() and freed again by calling
499 * dma_buf_unmap_attachment().
500 */
501struct dma_buf_attachment {
502 struct dma_buf *dmabuf;
503 struct device *dev;
504 struct list_head node;
505 bool peer2peer;
506 const struct dma_buf_attach_ops *importer_ops;
507 void *importer_priv;
508 void *priv;
509};
510
511/**
512 * struct dma_buf_export_info - holds information needed to export a dma_buf
513 * @exp_name: name of the exporter - useful for debugging.
514 * @owner: pointer to exporter module - used for refcounting kernel module
515 * @ops: Attach allocator-defined dma buf ops to the new buffer
516 * @size: Size of the buffer - invariant over the lifetime of the buffer
517 * @flags: mode flags for the file
518 * @resv: reservation-object, NULL to allocate default one
519 * @priv: Attach private data of allocator to this buffer
520 *
521 * This structure holds the information required to export the buffer. Used
522 * with dma_buf_export() only.
523 */
524struct dma_buf_export_info {
525 const char *exp_name;
526 struct module *owner;
527 const struct dma_buf_ops *ops;
528 size_t size;
529 int flags;
530 struct dma_resv *resv;
531 void *priv;
532};
533
534/**
535 * struct dma_buf_phys_vec - describe continuous chunk of memory
536 * @paddr: physical address of that chunk
537 * @len: Length of this chunk
538 */
539struct dma_buf_phys_vec {
540 phys_addr_t paddr;
541 size_t len;
542};
543
544/**
545 * DEFINE_DMA_BUF_EXPORT_INFO - helper macro for exporters
546 * @name: export-info name
547 *
548 * DEFINE_DMA_BUF_EXPORT_INFO macro defines the &struct dma_buf_export_info,
549 * zeroes it out and pre-populates exp_name in it.
550 */
551#define DEFINE_DMA_BUF_EXPORT_INFO(name) \
552 struct dma_buf_export_info name = { .exp_name = KBUILD_MODNAME, \
553 .owner = THIS_MODULE }
554
555/**
556 * get_dma_buf - convenience wrapper for get_file.
557 * @dmabuf: [in] pointer to dma_buf
558 *
559 * Increments the reference count on the dma-buf, needed in case of drivers
560 * that either need to create additional references to the dmabuf on the
561 * kernel side. For example, an exporter that needs to keep a dmabuf ptr
562 * so that subsequent exports don't create a new dmabuf.
563 */
564static inline void get_dma_buf(struct dma_buf *dmabuf)
565{
566 get_file(f: dmabuf->file);
567}
568
569/**
570 * dma_buf_is_dynamic - check if a DMA-buf uses dynamic mappings.
571 * @dmabuf: the DMA-buf to check
572 *
573 * Returns true if a DMA-buf exporter wants to be called with the dma_resv
574 * locked for the map/unmap callbacks, false if it doesn't wants to be called
575 * with the lock held.
576 */
577static inline bool dma_buf_is_dynamic(struct dma_buf *dmabuf)
578{
579 return !!dmabuf->ops->pin;
580}
581
582struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
583 struct device *dev);
584struct dma_buf_attachment *
585dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
586 const struct dma_buf_attach_ops *importer_ops,
587 void *importer_priv);
588void dma_buf_detach(struct dma_buf *dmabuf,
589 struct dma_buf_attachment *attach);
590int dma_buf_pin(struct dma_buf_attachment *attach);
591void dma_buf_unpin(struct dma_buf_attachment *attach);
592
593struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info);
594
595int dma_buf_fd(struct dma_buf *dmabuf, int flags);
596struct dma_buf *dma_buf_get(int fd);
597void dma_buf_put(struct dma_buf *dmabuf);
598
599struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *,
600 enum dma_data_direction);
601void dma_buf_unmap_attachment(struct dma_buf_attachment *, struct sg_table *,
602 enum dma_data_direction);
603void dma_buf_move_notify(struct dma_buf *dma_buf);
604int dma_buf_begin_cpu_access(struct dma_buf *dma_buf,
605 enum dma_data_direction dir);
606int dma_buf_end_cpu_access(struct dma_buf *dma_buf,
607 enum dma_data_direction dir);
608struct sg_table *
609dma_buf_map_attachment_unlocked(struct dma_buf_attachment *attach,
610 enum dma_data_direction direction);
611void dma_buf_unmap_attachment_unlocked(struct dma_buf_attachment *attach,
612 struct sg_table *sg_table,
613 enum dma_data_direction direction);
614
615int dma_buf_mmap(struct dma_buf *, struct vm_area_struct *,
616 unsigned long);
617int dma_buf_vmap(struct dma_buf *dmabuf, struct iosys_map *map);
618void dma_buf_vunmap(struct dma_buf *dmabuf, struct iosys_map *map);
619int dma_buf_vmap_unlocked(struct dma_buf *dmabuf, struct iosys_map *map);
620void dma_buf_vunmap_unlocked(struct dma_buf *dmabuf, struct iosys_map *map);
621struct dma_buf *dma_buf_iter_begin(void);
622struct dma_buf *dma_buf_iter_next(struct dma_buf *dmbuf);
623#endif /* __DMA_BUF_H__ */
624

source code of linux/include/linux/dma-buf.h