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