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1 /* SPDX-License-Identifier: GPL-2.0-only */
3 * Header file for dma buffer sharing framework.
5 * Copyright(C) 2011 Linaro Limited. All rights reserved.
6 * Author: Sumit Semwal <sumit.semwal@ti.com>
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.
16 #include <linux/dma-buf-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>
23 #include <linux/dma-fence.h>
24 #include <linux/wait.h>
28 struct dma_buf_attachment
;
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
40 * If true the framework will cache the first mapping made for each
41 * attachment. This avoids creating mappings for attachments multiple
44 bool cache_sgt_mapping
;
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.
56 * The exporter should also in general check whether the current
57 * allocation fullfills 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.
61 * Any exporter-private housekeeping data can be stored in the
62 * &dma_buf_attachment.priv pointer.
64 * This callback is optional.
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.
72 int (*attach
)(struct dma_buf
*, struct dma_buf_attachment
*);
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.
81 * This callback is optional.
83 void (*detach
)(struct dma_buf
*, struct dma_buf_attachment
*);
88 * This is called by dma_buf_pin() and lets the exporter know that the
89 * DMA-buf can't be moved any more. The exporter should pin the buffer
90 * into system memory to make sure it is generally accessible by other
93 * This is called with the &dmabuf.resv object locked and is mutual
94 * exclusive with @cache_sgt_mapping.
96 * This is called automatically for non-dynamic importers from
101 * 0 on success, negative error code on failure.
103 int (*pin
)(struct dma_buf_attachment
*attach
);
108 * This is called by dma_buf_unpin() and lets the exporter know that the
109 * DMA-buf can be moved again.
111 * This is called with the dmabuf->resv object locked and is mutual
112 * exclusive with @cache_sgt_mapping.
114 * This callback is optional.
116 void (*unpin
)(struct dma_buf_attachment
*attach
);
121 * This is called by dma_buf_map_attachment() and is used to map a
122 * shared &dma_buf into device address space, and it is mandatory. It
123 * can only be called if @attach has been called successfully.
125 * This call may sleep, e.g. when the backing storage first needs to be
126 * allocated, or moved to a location suitable for all currently attached
129 * Note that any specific buffer attributes required for this function
130 * should get added to device_dma_parameters accessible via
131 * &device.dma_params from the &dma_buf_attachment. The @attach callback
132 * should also check these constraints.
134 * If this is being called for the first time, the exporter can now
135 * choose to scan through the list of attachments for this buffer,
136 * collate the requirements of the attached devices, and choose an
137 * appropriate backing storage for the buffer.
139 * Based on enum dma_data_direction, it might be possible to have
140 * multiple users accessing at the same time (for reading, maybe), or
141 * any other kind of sharing that the exporter might wish to make
142 * available to buffer-users.
144 * This is always called with the dmabuf->resv object locked when
145 * the dynamic_mapping flag is true.
149 * A &sg_table scatter list of or the backing storage of the DMA buffer,
150 * already mapped into the device address space of the &device attached
151 * with the provided &dma_buf_attachment. The addresses and lengths in
152 * the scatter list are PAGE_SIZE aligned.
154 * On failure, returns a negative error value wrapped into a pointer.
155 * May also return -EINTR when a signal was received while being
158 * Note that exporters should not try to cache the scatter list, or
159 * return the same one for multiple calls. Caching is done either by the
160 * DMA-BUF code (for non-dynamic importers) or the importer. Ownership
161 * of the scatter list is transferred to the caller, and returned by
164 struct sg_table
* (*map_dma_buf
)(struct dma_buf_attachment
*,
165 enum dma_data_direction
);
169 * This is called by dma_buf_unmap_attachment() and should unmap and
170 * release the &sg_table allocated in @map_dma_buf, and it is mandatory.
171 * For static dma_buf handling this might also unpins the backing
172 * storage if this is the last mapping of the DMA buffer.
174 void (*unmap_dma_buf
)(struct dma_buf_attachment
*,
176 enum dma_data_direction
);
178 /* TODO: Add try_map_dma_buf version, to return immed with -EBUSY
179 * if the call would block.
185 * Called after the last dma_buf_put to release the &dma_buf, and
188 void (*release
)(struct dma_buf
*);
193 * This is called from dma_buf_begin_cpu_access() and allows the
194 * exporter to ensure that the memory is actually coherent for cpu
195 * access. The exporter also needs to ensure that cpu access is coherent
196 * for the access direction. The direction can be used by the exporter
197 * to optimize the cache flushing, i.e. access with a different
198 * direction (read instead of write) might return stale or even bogus
199 * data (e.g. when the exporter needs to copy the data to temporary
202 * Note that this is both called through the DMA_BUF_IOCTL_SYNC IOCTL
203 * command for userspace mappings established through @mmap, and also
204 * for kernel mappings established with @vmap.
206 * This callback is optional.
210 * 0 on success or a negative error code on failure. This can for
211 * example fail when the backing storage can't be allocated. Can also
212 * return -ERESTARTSYS or -EINTR when the call has been interrupted and
213 * needs to be restarted.
215 int (*begin_cpu_access
)(struct dma_buf
*, enum dma_data_direction
);
220 * This is called from dma_buf_end_cpu_access() when the importer is
221 * done accessing the CPU. The exporter can use this to flush caches and
222 * undo anything else done in @begin_cpu_access.
224 * This callback is optional.
228 * 0 on success or a negative error code on failure. Can return
229 * -ERESTARTSYS or -EINTR when the call has been interrupted and needs
232 int (*end_cpu_access
)(struct dma_buf
*, enum dma_data_direction
);
237 * This callback is used by the dma_buf_mmap() function
239 * Note that the mapping needs to be incoherent, userspace is expected
240 * to braket CPU access using the DMA_BUF_IOCTL_SYNC interface.
242 * Because dma-buf buffers have invariant size over their lifetime, the
243 * dma-buf core checks whether a vma is too large and rejects such
244 * mappings. The exporter hence does not need to duplicate this check.
245 * Drivers do not need to check this themselves.
247 * If an exporter needs to manually flush caches and hence needs to fake
248 * coherency for mmap support, it needs to be able to zap all the ptes
249 * pointing at the backing storage. Now linux mm needs a struct
250 * address_space associated with the struct file stored in vma->vm_file
251 * to do that with the function unmap_mapping_range. But the dma_buf
252 * framework only backs every dma_buf fd with the anon_file struct file,
253 * i.e. all dma_bufs share the same file.
255 * Hence exporters need to setup their own file (and address_space)
256 * association by setting vma->vm_file and adjusting vma->vm_pgoff in
257 * the dma_buf mmap callback. In the specific case of a gem driver the
258 * exporter could use the shmem file already provided by gem (and set
259 * vm_pgoff = 0). Exporters can then zap ptes by unmapping the
260 * corresponding range of the struct address_space associated with their
263 * This callback is optional.
267 * 0 on success or a negative error code on failure.
269 int (*mmap
)(struct dma_buf
*, struct vm_area_struct
*vma
);
271 int (*vmap
)(struct dma_buf
*dmabuf
, struct dma_buf_map
*map
);
272 void (*vunmap
)(struct dma_buf
*dmabuf
, struct dma_buf_map
*map
);
276 * struct dma_buf - shared buffer object
277 * @size: size of the buffer; invariant over the lifetime of the buffer.
278 * @file: file pointer used for sharing buffers across, and for refcounting.
279 * @attachments: list of dma_buf_attachment that denotes all devices attached,
280 * protected by dma_resv lock.
281 * @ops: dma_buf_ops associated with this buffer object.
282 * @lock: used internally to serialize list manipulation, attach/detach and
284 * @vmapping_counter: used internally to refcnt the vmaps
285 * @vmap_ptr: the current vmap ptr if vmapping_counter > 0
286 * @exp_name: name of the exporter; useful for debugging.
287 * @name: userspace-provided name; useful for accounting and debugging,
288 * protected by @resv.
289 * @name_lock: spinlock to protect name access
290 * @owner: pointer to exporter module; used for refcounting when exporter is a
292 * @list_node: node for dma_buf accounting and debugging.
293 * @priv: exporter specific private data for this buffer object.
294 * @resv: reservation object linked to this dma-buf
295 * @poll: for userspace poll support
296 * @cb_excl: for userspace poll support
297 * @cb_shared: for userspace poll support
299 * This represents a shared buffer, created by calling dma_buf_export(). The
300 * userspace representation is a normal file descriptor, which can be created by
301 * calling dma_buf_fd().
303 * Shared dma buffers are reference counted using dma_buf_put() and
306 * Device DMA access is handled by the separate &struct dma_buf_attachment.
311 struct list_head attachments
;
312 const struct dma_buf_ops
*ops
;
314 unsigned vmapping_counter
;
315 struct dma_buf_map vmap_ptr
;
316 const char *exp_name
;
318 spinlock_t name_lock
;
319 struct module
*owner
;
320 struct list_head list_node
;
322 struct dma_resv
*resv
;
325 wait_queue_head_t poll
;
327 struct dma_buf_poll_cb_t
{
328 struct dma_fence_cb cb
;
329 wait_queue_head_t
*poll
;
332 } cb_excl
, cb_shared
;
336 * struct dma_buf_attach_ops - importer operations for an attachment
338 * Attachment operations implemented by the importer.
340 struct dma_buf_attach_ops
{
344 * If this is set to true the importer must be able to handle peer
345 * resources without struct pages.
347 bool allow_peer2peer
;
350 * @move_notify: [optional] notification that the DMA-buf is moving
352 * If this callback is provided the framework can avoid pinning the
353 * backing store while mappings exists.
355 * This callback is called with the lock of the reservation object
356 * associated with the dma_buf held and the mapping function must be
357 * called with this lock held as well. This makes sure that no mapping
358 * is created concurrently with an ongoing move operation.
360 * Mappings stay valid and are not directly affected by this callback.
361 * But the DMA-buf can now be in a different physical location, so all
362 * mappings should be destroyed and re-created as soon as possible.
364 * New mappings can be created after this callback returns, and will
365 * point to the new location of the DMA-buf.
367 void (*move_notify
)(struct dma_buf_attachment
*attach
);
371 * struct dma_buf_attachment - holds device-buffer attachment data
372 * @dmabuf: buffer for this attachment.
373 * @dev: device attached to the buffer.
374 * @node: list of dma_buf_attachment, protected by dma_resv lock of the dmabuf.
375 * @sgt: cached mapping.
376 * @dir: direction of cached mapping.
377 * @peer2peer: true if the importer can handle peer resources without pages.
378 * @priv: exporter specific attachment data.
379 * @importer_ops: importer operations for this attachment, if provided
380 * dma_buf_map/unmap_attachment() must be called with the dma_resv lock held.
381 * @importer_priv: importer specific attachment data.
383 * This structure holds the attachment information between the dma_buf buffer
384 * and its user device(s). The list contains one attachment struct per device
385 * attached to the buffer.
387 * An attachment is created by calling dma_buf_attach(), and released again by
388 * calling dma_buf_detach(). The DMA mapping itself needed to initiate a
389 * transfer is created by dma_buf_map_attachment() and freed again by calling
390 * dma_buf_unmap_attachment().
392 struct dma_buf_attachment
{
393 struct dma_buf
*dmabuf
;
395 struct list_head node
;
396 struct sg_table
*sgt
;
397 enum dma_data_direction dir
;
399 const struct dma_buf_attach_ops
*importer_ops
;
405 * struct dma_buf_export_info - holds information needed to export a dma_buf
406 * @exp_name: name of the exporter - useful for debugging.
407 * @owner: pointer to exporter module - used for refcounting kernel module
408 * @ops: Attach allocator-defined dma buf ops to the new buffer
409 * @size: Size of the buffer - invariant over the lifetime of the buffer
410 * @flags: mode flags for the file
411 * @resv: reservation-object, NULL to allocate default one
412 * @priv: Attach private data of allocator to this buffer
414 * This structure holds the information required to export the buffer. Used
415 * with dma_buf_export() only.
417 struct dma_buf_export_info
{
418 const char *exp_name
;
419 struct module
*owner
;
420 const struct dma_buf_ops
*ops
;
423 struct dma_resv
*resv
;
428 * DEFINE_DMA_BUF_EXPORT_INFO - helper macro for exporters
429 * @name: export-info name
431 * DEFINE_DMA_BUF_EXPORT_INFO macro defines the &struct dma_buf_export_info,
432 * zeroes it out and pre-populates exp_name in it.
434 #define DEFINE_DMA_BUF_EXPORT_INFO(name) \
435 struct dma_buf_export_info name = { .exp_name = KBUILD_MODNAME, \
436 .owner = THIS_MODULE }
439 * get_dma_buf - convenience wrapper for get_file.
440 * @dmabuf: [in] pointer to dma_buf
442 * Increments the reference count on the dma-buf, needed in case of drivers
443 * that either need to create additional references to the dmabuf on the
444 * kernel side. For example, an exporter that needs to keep a dmabuf ptr
445 * so that subsequent exports don't create a new dmabuf.
447 static inline void get_dma_buf(struct dma_buf
*dmabuf
)
449 get_file(dmabuf
->file
);
453 * dma_buf_is_dynamic - check if a DMA-buf uses dynamic mappings.
454 * @dmabuf: the DMA-buf to check
456 * Returns true if a DMA-buf exporter wants to be called with the dma_resv
457 * locked for the map/unmap callbacks, false if it doesn't wants to be called
458 * with the lock held.
460 static inline bool dma_buf_is_dynamic(struct dma_buf
*dmabuf
)
462 return !!dmabuf
->ops
->pin
;
466 * dma_buf_attachment_is_dynamic - check if a DMA-buf attachment uses dynamic
468 * @attach: the DMA-buf attachment to check
470 * Returns true if a DMA-buf importer wants to call the map/unmap functions with
471 * the dma_resv lock held.
474 dma_buf_attachment_is_dynamic(struct dma_buf_attachment
*attach
)
476 return !!attach
->importer_ops
;
479 struct dma_buf_attachment
*dma_buf_attach(struct dma_buf
*dmabuf
,
481 struct dma_buf_attachment
*
482 dma_buf_dynamic_attach(struct dma_buf
*dmabuf
, struct device
*dev
,
483 const struct dma_buf_attach_ops
*importer_ops
,
484 void *importer_priv
);
485 void dma_buf_detach(struct dma_buf
*dmabuf
,
486 struct dma_buf_attachment
*attach
);
487 int dma_buf_pin(struct dma_buf_attachment
*attach
);
488 void dma_buf_unpin(struct dma_buf_attachment
*attach
);
490 struct dma_buf
*dma_buf_export(const struct dma_buf_export_info
*exp_info
);
492 int dma_buf_fd(struct dma_buf
*dmabuf
, int flags
);
493 struct dma_buf
*dma_buf_get(int fd
);
494 void dma_buf_put(struct dma_buf
*dmabuf
);
496 struct sg_table
*dma_buf_map_attachment(struct dma_buf_attachment
*,
497 enum dma_data_direction
);
498 void dma_buf_unmap_attachment(struct dma_buf_attachment
*, struct sg_table
*,
499 enum dma_data_direction
);
500 void dma_buf_move_notify(struct dma_buf
*dma_buf
);
501 int dma_buf_begin_cpu_access(struct dma_buf
*dma_buf
,
502 enum dma_data_direction dir
);
503 int dma_buf_end_cpu_access(struct dma_buf
*dma_buf
,
504 enum dma_data_direction dir
);
506 int dma_buf_mmap(struct dma_buf
*, struct vm_area_struct
*,
508 int dma_buf_vmap(struct dma_buf
*dmabuf
, struct dma_buf_map
*map
);
509 void dma_buf_vunmap(struct dma_buf
*dmabuf
, struct dma_buf_map
*map
);
510 #endif /* __DMA_BUF_H__ */