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 struct module *owner;
307 struct list_head list_node;
308 void *priv;
309 struct dma_resv *resv;
310
311 /* poll support */
312 wait_queue_head_t poll;
313
314 struct dma_buf_poll_cb_t {
315 struct dma_fence_cb cb;
316 wait_queue_head_t *poll;
317
318 __poll_t active;
319 } cb_excl, cb_shared;
320 };
321
322 /**
323 * struct dma_buf_attachment - holds device-buffer attachment data
324 * @dmabuf: buffer for this attachment.
325 * @dev: device attached to the buffer.
326 * @node: list of dma_buf_attachment.
327 * @sgt: cached mapping.
328 * @dir: direction of cached mapping.
329 * @priv: exporter specific attachment data.
330 *
331 * This structure holds the attachment information between the dma_buf buffer
332 * and its user device(s). The list contains one attachment struct per device
333 * attached to the buffer.
334 *
335 * An attachment is created by calling dma_buf_attach(), and released again by
336 * calling dma_buf_detach(). The DMA mapping itself needed to initiate a
337 * transfer is created by dma_buf_map_attachment() and freed again by calling
338 * dma_buf_unmap_attachment().
339 */
340 struct dma_buf_attachment {
341 struct dma_buf *dmabuf;
342 struct device *dev;
343 struct list_head node;
344 struct sg_table *sgt;
345 enum dma_data_direction dir;
346 void *priv;
347 };
348
349 /**
350 * struct dma_buf_export_info - holds information needed to export a dma_buf
351 * @exp_name: name of the exporter - useful for debugging.
352 * @owner: pointer to exporter module - used for refcounting kernel module
353 * @ops: Attach allocator-defined dma buf ops to the new buffer
354 * @size: Size of the buffer
355 * @flags: mode flags for the file
356 * @resv: reservation-object, NULL to allocate default one
357 * @priv: Attach private data of allocator to this buffer
358 *
359 * This structure holds the information required to export the buffer. Used
360 * with dma_buf_export() only.
361 */
362 struct dma_buf_export_info {
363 const char *exp_name;
364 struct module *owner;
365 const struct dma_buf_ops *ops;
366 size_t size;
367 int flags;
368 struct dma_resv *resv;
369 void *priv;
370 };
371
372 /**
373 * DEFINE_DMA_BUF_EXPORT_INFO - helper macro for exporters
374 * @name: export-info name
375 *
376 * DEFINE_DMA_BUF_EXPORT_INFO macro defines the &struct dma_buf_export_info,
377 * zeroes it out and pre-populates exp_name in it.
378 */
379 #define DEFINE_DMA_BUF_EXPORT_INFO(name) \
380 struct dma_buf_export_info name = { .exp_name = KBUILD_MODNAME, \
381 .owner = THIS_MODULE }
382
383 /**
384 * get_dma_buf - convenience wrapper for get_file.
385 * @dmabuf: [in] pointer to dma_buf
386 *
387 * Increments the reference count on the dma-buf, needed in case of drivers
388 * that either need to create additional references to the dmabuf on the
389 * kernel side. For example, an exporter that needs to keep a dmabuf ptr
390 * so that subsequent exports don't create a new dmabuf.
391 */
392 static inline void get_dma_buf(struct dma_buf *dmabuf)
393 {
394 get_file(dmabuf->file);
395 }
396
397 struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
398 struct device *dev);
399 void dma_buf_detach(struct dma_buf *dmabuf,
400 struct dma_buf_attachment *dmabuf_attach);
401
402 struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info);
403
404 int dma_buf_fd(struct dma_buf *dmabuf, int flags);
405 struct dma_buf *dma_buf_get(int fd);
406 void dma_buf_put(struct dma_buf *dmabuf);
407
408 struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *,
409 enum dma_data_direction);
410 void dma_buf_unmap_attachment(struct dma_buf_attachment *, struct sg_table *,
411 enum dma_data_direction);
412 int dma_buf_begin_cpu_access(struct dma_buf *dma_buf,
413 enum dma_data_direction dir);
414 int dma_buf_end_cpu_access(struct dma_buf *dma_buf,
415 enum dma_data_direction dir);
416 void *dma_buf_kmap(struct dma_buf *, unsigned long);
417 void dma_buf_kunmap(struct dma_buf *, unsigned long, void *);
418
419 int dma_buf_mmap(struct dma_buf *, struct vm_area_struct *,
420 unsigned long);
421 void *dma_buf_vmap(struct dma_buf *);
422 void dma_buf_vunmap(struct dma_buf *, void *vaddr);
423 #endif /* __DMA_BUF_H__ */