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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 : : * @dynamic_mapping:
47 : : *
48 : : * If true the framework makes sure that the map/unmap_dma_buf
49 : : * callbacks are always called with the dma_resv object locked.
50 : : *
51 : : * If false the framework makes sure that the map/unmap_dma_buf
52 : : * callbacks are always called without the dma_resv object locked.
53 : : * Mutual exclusive with @cache_sgt_mapping.
54 : : */
55 : : bool dynamic_mapping;
56 : :
57 : : /**
58 : : * @attach:
59 : : *
60 : : * This is called from dma_buf_attach() to make sure that a given
61 : : * &dma_buf_attachment.dev can access the provided &dma_buf. Exporters
62 : : * which support buffer objects in special locations like VRAM or
63 : : * device-specific carveout areas should check whether the buffer could
64 : : * be move to system memory (or directly accessed by the provided
65 : : * device), and otherwise need to fail the attach operation.
66 : : *
67 : : * The exporter should also in general check whether the current
68 : : * allocation fullfills the DMA constraints of the new device. If this
69 : : * is not the case, and the allocation cannot be moved, it should also
70 : : * fail the attach operation.
71 : : *
72 : : * Any exporter-private housekeeping data can be stored in the
73 : : * &dma_buf_attachment.priv pointer.
74 : : *
75 : : * This callback is optional.
76 : : *
77 : : * Returns:
78 : : *
79 : : * 0 on success, negative error code on failure. It might return -EBUSY
80 : : * to signal that backing storage is already allocated and incompatible
81 : : * with the requirements of requesting device.
82 : : */
83 : : int (*attach)(struct dma_buf *, struct dma_buf_attachment *);
84 : :
85 : : /**
86 : : * @detach:
87 : : *
88 : : * This is called by dma_buf_detach() to release a &dma_buf_attachment.
89 : : * Provided so that exporters can clean up any housekeeping for an
90 : : * &dma_buf_attachment.
91 : : *
92 : : * This callback is optional.
93 : : */
94 : : void (*detach)(struct dma_buf *, struct dma_buf_attachment *);
95 : :
96 : : /**
97 : : * @map_dma_buf:
98 : : *
99 : : * This is called by dma_buf_map_attachment() and is used to map a
100 : : * shared &dma_buf into device address space, and it is mandatory. It
101 : : * can only be called if @attach has been called successfully. This
102 : : * essentially pins the DMA buffer into place, and it cannot be moved
103 : : * any more
104 : : *
105 : : * This call may sleep, e.g. when the backing storage first needs to be
106 : : * allocated, or moved to a location suitable for all currently attached
107 : : * devices.
108 : : *
109 : : * Note that any specific buffer attributes required for this function
110 : : * should get added to device_dma_parameters accessible via
111 : : * &device.dma_params from the &dma_buf_attachment. The @attach callback
112 : : * should also check these constraints.
113 : : *
114 : : * If this is being called for the first time, the exporter can now
115 : : * choose to scan through the list of attachments for this buffer,
116 : : * collate the requirements of the attached devices, and choose an
117 : : * appropriate backing storage for the buffer.
118 : : *
119 : : * Based on enum dma_data_direction, it might be possible to have
120 : : * multiple users accessing at the same time (for reading, maybe), or
121 : : * any other kind of sharing that the exporter might wish to make
122 : : * available to buffer-users.
123 : : *
124 : : * This is always called with the dmabuf->resv object locked when
125 : : * the dynamic_mapping flag is true.
126 : : *
127 : : * Returns:
128 : : *
129 : : * A &sg_table scatter list of or the backing storage of the DMA buffer,
130 : : * already mapped into the device address space of the &device attached
131 : : * with the provided &dma_buf_attachment.
132 : : *
133 : : * On failure, returns a negative error value wrapped into a pointer.
134 : : * May also return -EINTR when a signal was received while being
135 : : * blocked.
136 : : */
137 : : struct sg_table * (*map_dma_buf)(struct dma_buf_attachment *,
138 : : enum dma_data_direction);
139 : : /**
140 : : * @unmap_dma_buf:
141 : : *
142 : : * This is called by dma_buf_unmap_attachment() and should unmap and
143 : : * release the &sg_table allocated in @map_dma_buf, and it is mandatory.
144 : : * It should also unpin the backing storage if this is the last mapping
145 : : * of the DMA buffer, it the exporter supports backing storage
146 : : * migration.
147 : : */
148 : : void (*unmap_dma_buf)(struct dma_buf_attachment *,
149 : : struct sg_table *,
150 : : enum dma_data_direction);
151 : :
152 : : /* TODO: Add try_map_dma_buf version, to return immed with -EBUSY
153 : : * if the call would block.
154 : : */
155 : :
156 : : /**
157 : : * @release:
158 : : *
159 : : * Called after the last dma_buf_put to release the &dma_buf, and
160 : : * mandatory.
161 : : */
162 : : void (*release)(struct dma_buf *);
163 : :
164 : : /**
165 : : * @begin_cpu_access:
166 : : *
167 : : * This is called from dma_buf_begin_cpu_access() and allows the
168 : : * exporter to ensure that the memory is actually available for cpu
169 : : * access - the exporter might need to allocate or swap-in and pin the
170 : : * backing storage. The exporter also needs to ensure that cpu access is
171 : : * coherent for the access direction. The direction can be used by the
172 : : * exporter to optimize the cache flushing, i.e. access with a different
173 : : * direction (read instead of write) might return stale or even bogus
174 : : * data (e.g. when the exporter needs to copy the data to temporary
175 : : * storage).
176 : : *
177 : : * This callback is optional.
178 : : *
179 : : * FIXME: This is both called through the DMA_BUF_IOCTL_SYNC command
180 : : * from userspace (where storage shouldn't be pinned to avoid handing
181 : : * de-factor mlock rights to userspace) and for the kernel-internal
182 : : * users of the various kmap interfaces, where the backing storage must
183 : : * be pinned to guarantee that the atomic kmap calls can succeed. Since
184 : : * there's no in-kernel users of the kmap interfaces yet this isn't a
185 : : * real problem.
186 : : *
187 : : * Returns:
188 : : *
189 : : * 0 on success or a negative error code on failure. This can for
190 : : * example fail when the backing storage can't be allocated. Can also
191 : : * return -ERESTARTSYS or -EINTR when the call has been interrupted and
192 : : * needs to be restarted.
193 : : */
194 : : int (*begin_cpu_access)(struct dma_buf *, enum dma_data_direction);
195 : :
196 : : /**
197 : : * @end_cpu_access:
198 : : *
199 : : * This is called from dma_buf_end_cpu_access() when the importer is
200 : : * done accessing the CPU. The exporter can use this to flush caches and
201 : : * unpin any resources pinned in @begin_cpu_access.
202 : : * The result of any dma_buf kmap calls after end_cpu_access is
203 : : * undefined.
204 : : *
205 : : * This callback is optional.
206 : : *
207 : : * Returns:
208 : : *
209 : : * 0 on success or a negative error code on failure. Can return
210 : : * -ERESTARTSYS or -EINTR when the call has been interrupted and needs
211 : : * to be restarted.
212 : : */
213 : : int (*end_cpu_access)(struct dma_buf *, enum dma_data_direction);
214 : :
215 : : /**
216 : : * @mmap:
217 : : *
218 : : * This callback is used by the dma_buf_mmap() function
219 : : *
220 : : * Note that the mapping needs to be incoherent, userspace is expected
221 : : * to braket CPU access using the DMA_BUF_IOCTL_SYNC interface.
222 : : *
223 : : * Because dma-buf buffers have invariant size over their lifetime, the
224 : : * dma-buf core checks whether a vma is too large and rejects such
225 : : * mappings. The exporter hence does not need to duplicate this check.
226 : : * Drivers do not need to check this themselves.
227 : : *
228 : : * If an exporter needs to manually flush caches and hence needs to fake
229 : : * coherency for mmap support, it needs to be able to zap all the ptes
230 : : * pointing at the backing storage. Now linux mm needs a struct
231 : : * address_space associated with the struct file stored in vma->vm_file
232 : : * to do that with the function unmap_mapping_range. But the dma_buf
233 : : * framework only backs every dma_buf fd with the anon_file struct file,
234 : : * i.e. all dma_bufs share the same file.
235 : : *
236 : : * Hence exporters need to setup their own file (and address_space)
237 : : * association by setting vma->vm_file and adjusting vma->vm_pgoff in
238 : : * the dma_buf mmap callback. In the specific case of a gem driver the
239 : : * exporter could use the shmem file already provided by gem (and set
240 : : * vm_pgoff = 0). Exporters can then zap ptes by unmapping the
241 : : * corresponding range of the struct address_space associated with their
242 : : * own file.
243 : : *
244 : : * This callback is optional.
245 : : *
246 : : * Returns:
247 : : *
248 : : * 0 on success or a negative error code on failure.
249 : : */
250 : : int (*mmap)(struct dma_buf *, struct vm_area_struct *vma);
251 : :
252 : : void *(*vmap)(struct dma_buf *);
253 : : void (*vunmap)(struct dma_buf *, void *vaddr);
254 : : };
255 : :
256 : : /**
257 : : * struct dma_buf - shared buffer object
258 : : * @size: size of the buffer
259 : : * @file: file pointer used for sharing buffers across, and for refcounting.
260 : : * @attachments: list of dma_buf_attachment that denotes all devices attached,
261 : : * protected by dma_resv lock.
262 : : * @ops: dma_buf_ops associated with this buffer object.
263 : : * @lock: used internally to serialize list manipulation, attach/detach and
264 : : * vmap/unmap
265 : : * @vmapping_counter: used internally to refcnt the vmaps
266 : : * @vmap_ptr: the current vmap ptr if vmapping_counter > 0
267 : : * @exp_name: name of the exporter; useful for debugging.
268 : : * @name: userspace-provided name; useful for accounting and debugging,
269 : : * protected by @resv.
270 : : * @owner: pointer to exporter module; used for refcounting when exporter is a
271 : : * kernel module.
272 : : * @list_node: node for dma_buf accounting and debugging.
273 : : * @priv: exporter specific private data for this buffer object.
274 : : * @resv: reservation object linked to this dma-buf
275 : : * @poll: for userspace poll support
276 : : * @cb_excl: for userspace poll support
277 : : * @cb_shared: for userspace poll support
278 : : *
279 : : * This represents a shared buffer, created by calling dma_buf_export(). The
280 : : * userspace representation is a normal file descriptor, which can be created by
281 : : * calling dma_buf_fd().
282 : : *
283 : : * Shared dma buffers are reference counted using dma_buf_put() and
284 : : * get_dma_buf().
285 : : *
286 : : * Device DMA access is handled by the separate &struct dma_buf_attachment.
287 : : */
288 : : struct dma_buf {
289 : : size_t size;
290 : : struct file *file;
291 : : struct list_head attachments;
292 : : const struct dma_buf_ops *ops;
293 : : struct mutex lock;
294 : : unsigned vmapping_counter;
295 : : void *vmap_ptr;
296 : : const char *exp_name;
297 : : const char *name;
298 : : struct module *owner;
299 : : struct list_head list_node;
300 : : void *priv;
301 : : struct dma_resv *resv;
302 : :
303 : : /* poll support */
304 : : wait_queue_head_t poll;
305 : :
306 : : struct dma_buf_poll_cb_t {
307 : : struct dma_fence_cb cb;
308 : : wait_queue_head_t *poll;
309 : :
310 : : __poll_t active;
311 : : } cb_excl, cb_shared;
312 : : };
313 : :
314 : : /**
315 : : * struct dma_buf_attachment - holds device-buffer attachment data
316 : : * @dmabuf: buffer for this attachment.
317 : : * @dev: device attached to the buffer.
318 : : * @node: list of dma_buf_attachment, protected by dma_resv lock of the dmabuf.
319 : : * @sgt: cached mapping.
320 : : * @dir: direction of cached mapping.
321 : : * @priv: exporter specific attachment data.
322 : : * @dynamic_mapping: true if dma_buf_map/unmap_attachment() is called with the
323 : : * dma_resv lock held.
324 : : *
325 : : * This structure holds the attachment information between the dma_buf buffer
326 : : * and its user device(s). The list contains one attachment struct per device
327 : : * attached to the buffer.
328 : : *
329 : : * An attachment is created by calling dma_buf_attach(), and released again by
330 : : * calling dma_buf_detach(). The DMA mapping itself needed to initiate a
331 : : * transfer is created by dma_buf_map_attachment() and freed again by calling
332 : : * dma_buf_unmap_attachment().
333 : : */
334 : : struct dma_buf_attachment {
335 : : struct dma_buf *dmabuf;
336 : : struct device *dev;
337 : : struct list_head node;
338 : : struct sg_table *sgt;
339 : : enum dma_data_direction dir;
340 : : bool dynamic_mapping;
341 : : void *priv;
342 : : };
343 : :
344 : : /**
345 : : * struct dma_buf_export_info - holds information needed to export a dma_buf
346 : : * @exp_name: name of the exporter - useful for debugging.
347 : : * @owner: pointer to exporter module - used for refcounting kernel module
348 : : * @ops: Attach allocator-defined dma buf ops to the new buffer
349 : : * @size: Size of the buffer
350 : : * @flags: mode flags for the file
351 : : * @resv: reservation-object, NULL to allocate default one
352 : : * @priv: Attach private data of allocator to this buffer
353 : : *
354 : : * This structure holds the information required to export the buffer. Used
355 : : * with dma_buf_export() only.
356 : : */
357 : : struct dma_buf_export_info {
358 : : const char *exp_name;
359 : : struct module *owner;
360 : : const struct dma_buf_ops *ops;
361 : : size_t size;
362 : : int flags;
363 : : struct dma_resv *resv;
364 : : void *priv;
365 : : };
366 : :
367 : : /**
368 : : * DEFINE_DMA_BUF_EXPORT_INFO - helper macro for exporters
369 : : * @name: export-info name
370 : : *
371 : : * DEFINE_DMA_BUF_EXPORT_INFO macro defines the &struct dma_buf_export_info,
372 : : * zeroes it out and pre-populates exp_name in it.
373 : : */
374 : : #define DEFINE_DMA_BUF_EXPORT_INFO(name) \
375 : : struct dma_buf_export_info name = { .exp_name = KBUILD_MODNAME, \
376 : : .owner = THIS_MODULE }
377 : :
378 : : /**
379 : : * get_dma_buf - convenience wrapper for get_file.
380 : : * @dmabuf: [in] pointer to dma_buf
381 : : *
382 : : * Increments the reference count on the dma-buf, needed in case of drivers
383 : : * that either need to create additional references to the dmabuf on the
384 : : * kernel side. For example, an exporter that needs to keep a dmabuf ptr
385 : : * so that subsequent exports don't create a new dmabuf.
386 : : */
387 : 0 : static inline void get_dma_buf(struct dma_buf *dmabuf)
388 : : {
389 : 0 : get_file(dmabuf->file);
390 : 0 : }
391 : :
392 : : /**
393 : : * dma_buf_is_dynamic - check if a DMA-buf uses dynamic mappings.
394 : : * @dmabuf: the DMA-buf to check
395 : : *
396 : : * Returns true if a DMA-buf exporter wants to be called with the dma_resv
397 : : * locked for the map/unmap callbacks, false if it doesn't wants to be called
398 : : * with the lock held.
399 : : */
400 : 0 : static inline bool dma_buf_is_dynamic(struct dma_buf *dmabuf)
401 : : {
402 [ # # # # : 0 : return dmabuf->ops->dynamic_mapping;
# # # # #
# # # ]
403 : : }
404 : :
405 : : /**
406 : : * dma_buf_attachment_is_dynamic - check if a DMA-buf attachment uses dynamic
407 : : * mappinsg
408 : : * @attach: the DMA-buf attachment to check
409 : : *
410 : : * Returns true if a DMA-buf importer wants to call the map/unmap functions with
411 : : * the dma_resv lock held.
412 : : */
413 : : static inline bool
414 : 0 : dma_buf_attachment_is_dynamic(struct dma_buf_attachment *attach)
415 : : {
416 [ # # # # : 0 : return attach->dynamic_mapping;
# # ]
417 : : }
418 : :
419 : : struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
420 : : struct device *dev);
421 : : struct dma_buf_attachment *
422 : : dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
423 : : bool dynamic_mapping);
424 : : void dma_buf_detach(struct dma_buf *dmabuf,
425 : : struct dma_buf_attachment *attach);
426 : :
427 : : struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info);
428 : :
429 : : int dma_buf_fd(struct dma_buf *dmabuf, int flags);
430 : : struct dma_buf *dma_buf_get(int fd);
431 : : void dma_buf_put(struct dma_buf *dmabuf);
432 : :
433 : : struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *,
434 : : enum dma_data_direction);
435 : : void dma_buf_unmap_attachment(struct dma_buf_attachment *, struct sg_table *,
436 : : enum dma_data_direction);
437 : : void dma_buf_move_notify(struct dma_buf *dma_buf);
438 : : int dma_buf_begin_cpu_access(struct dma_buf *dma_buf,
439 : : enum dma_data_direction dir);
440 : : int dma_buf_end_cpu_access(struct dma_buf *dma_buf,
441 : : enum dma_data_direction dir);
442 : :
443 : : int dma_buf_mmap(struct dma_buf *, struct vm_area_struct *,
444 : : unsigned long);
445 : : void *dma_buf_vmap(struct dma_buf *);
446 : : void dma_buf_vunmap(struct dma_buf *, void *vaddr);
447 : : #endif /* __DMA_BUF_H__ */
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