1 /*
2 * Header file for dma buffer sharing framework.
3 *
4 * Copyright(C) 2011 Linaro Limited. All rights reserved.
5 * Author: Sumit Semwal <sumit.semwal@ti.com>
6 *
7 * Many thanks to linaro-mm-sig list, and specially
8 * Arnd Bergmann <arnd@arndb.de>, Rob Clark <rob@ti.com> and
9 * Daniel Vetter <daniel@ffwll.ch> for their support in creation and
10 * refining of this idea.
11 *
12 * This program is free software; you can redistribute it and/or modify it
13 * under the terms of the GNU General Public License version 2 as published by
14 * the Free Software Foundation.
15 *
16 * This program is distributed in the hope that it will be useful, but WITHOUT
17 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
18 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
19 * more details.
20 *
21 * You should have received a copy of the GNU General Public License along with
22 * this program. If not, see <http://www.gnu.org/licenses/>.
23 */
24 #ifndef __DMA_BUF_H__
25 #define __DMA_BUF_H__
26
27 #include <linux/file.h>
28 #include <linux/err.h>
29 #include <linux/scatterlist.h>
30 #include <linux/list.h>
31 #include <linux/dma-mapping.h>
32 #include <linux/fs.h>
33 #include <linux/dma-fence.h>
34 #include <linux/wait.h>
35
36 struct device;
37 struct dma_buf;
38 struct dma_buf_attachment;
39
40 /**
41 * struct dma_buf_ops - operations possible on struct dma_buf
42 * @map_atomic: [optional] maps a page from the buffer into kernel address
43 * space, users may not block until the subsequent unmap call.
44 * This callback must not sleep.
45 * @unmap_atomic: [optional] unmaps a atomically mapped page from the buffer.
46 * This Callback must not sleep.
47 * @map: [optional] maps a page from the buffer into kernel address space.
48 * @unmap: [optional] unmaps a page from the buffer.
49 * @vmap: [optional] creates a virtual mapping for the buffer into kernel
50 * address space. Same restrictions as for vmap and friends apply.
51 * @vunmap: [optional] unmaps a vmap from the buffer
52 */
53 struct dma_buf_ops {
54 /**
55 * @attach:
56 *
57 * This is called from dma_buf_attach() to make sure that a given
58 * &dma_buf_attachment.dev can access the provided &dma_buf. Exporters
59 * which support buffer objects in special locations like VRAM or
60 * device-specific carveout areas should check whether the buffer could
61 * be move to system memory (or directly accessed by the provided
62 * device), and otherwise need to fail the attach operation.
63 *
64 * The exporter should also in general check whether the current
65 * allocation fullfills the DMA constraints of the new device. If this
66 * is not the case, and the allocation cannot be moved, it should also
67 * fail the attach operation.
68 *
69 * Any exporter-private housekeeping data can be stored in the
70 * &dma_buf_attachment.priv pointer.
71 *
72 * This callback is optional.
73 *
74 * Returns:
75 *
76 * 0 on success, negative error code on failure. It might return -EBUSY
77 * to signal that backing storage is already allocated and incompatible
78 * with the requirements of requesting device.
79 */
80 int (*attach)(struct dma_buf *, struct dma_buf_attachment *);
81
82 /**
83 * @detach:
84 *
85 * This is called by dma_buf_detach() to release a &dma_buf_attachment.
86 * Provided so that exporters can clean up any housekeeping for an
87 * &dma_buf_attachment.
88 *
89 * This callback is optional.
90 */
91 void (*detach)(struct dma_buf *, struct dma_buf_attachment *);
92
93 /**
94 * @map_dma_buf:
95 *
96 * This is called by dma_buf_map_attachment() and is used to map a
97 * shared &dma_buf into device address space, and it is mandatory. It
98 * can only be called if @attach has been called successfully. This
99 * essentially pins the DMA buffer into place, and it cannot be moved
100 * any more
101 *
102 * This call may sleep, e.g. when the backing storage first needs to be
103 * allocated, or moved to a location suitable for all currently attached
104 * devices.
105 *
106 * Note that any specific buffer attributes required for this function
107 * should get added to device_dma_parameters accessible via
108 * &device.dma_params from the &dma_buf_attachment. The @attach callback
109 * should also check these constraints.
110 *
111 * If this is being called for the first time, the exporter can now
112 * choose to scan through the list of attachments for this buffer,
113 * collate the requirements of the attached devices, and choose an
114 * appropriate backing storage for the buffer.
115 *
116 * Based on enum dma_data_direction, it might be possible to have
117 * multiple users accessing at the same time (for reading, maybe), or
118 * any other kind of sharing that the exporter might wish to make
119 * available to buffer-users.
120 *
121 * Returns:
122 *
123 * A &sg_table scatter list of or the backing storage of the DMA buffer,
124 * already mapped into the device address space of the &device attached
125 * with the provided &dma_buf_attachment.
126 *
127 * On failure, returns a negative error value wrapped into a pointer.
128 * May also return -EINTR when a signal was received while being
129 * blocked.
130 */
131 struct sg_table * (*map_dma_buf)(struct dma_buf_attachment *,
132 enum dma_data_direction);
133 /**
134 * @unmap_dma_buf:
135 *
136 * This is called by dma_buf_unmap_attachment() and should unmap and
137 * release the &sg_table allocated in @map_dma_buf, and it is mandatory.
138 * It should also unpin the backing storage if this is the last mapping
139 * of the DMA buffer, it the exporter supports backing storage
140 * migration.
141 */
142 void (*unmap_dma_buf)(struct dma_buf_attachment *,
143 struct sg_table *,
144 enum dma_data_direction);
145
146 /* TODO: Add try_map_dma_buf version, to return immed with -EBUSY
147 * if the call would block.
148 */
149
150 /**
151 * @release:
152 *
153 * Called after the last dma_buf_put to release the &dma_buf, and
154 * mandatory.
155 */
156 void (*release)(struct dma_buf *);
157
158 /**
159 * @begin_cpu_access:
160 *
161 * This is called from dma_buf_begin_cpu_access() and allows the
162 * exporter to ensure that the memory is actually available for cpu
163 * access - the exporter might need to allocate or swap-in and pin the
164 * backing storage. The exporter also needs to ensure that cpu access is
165 * coherent for the access direction. The direction can be used by the
166 * exporter to optimize the cache flushing, i.e. access with a different
167 * direction (read instead of write) might return stale or even bogus
168 * data (e.g. when the exporter needs to copy the data to temporary
169 * storage).
170 *
171 * This callback is optional.
172 *
173 * FIXME: This is both called through the DMA_BUF_IOCTL_SYNC command
174 * from userspace (where storage shouldn't be pinned to avoid handing
175 * de-factor mlock rights to userspace) and for the kernel-internal
176 * users of the various kmap interfaces, where the backing storage must
177 * be pinned to guarantee that the atomic kmap calls can succeed. Since
178 * there's no in-kernel users of the kmap interfaces yet this isn't a
179 * real problem.
180 *
181 * Returns:
182 *
183 * 0 on success or a negative error code on failure. This can for
184 * example fail when the backing storage can't be allocated. Can also
185 * return -ERESTARTSYS or -EINTR when the call has been interrupted and
186 * needs to be restarted.
187 */
188 int (*begin_cpu_access)(struct dma_buf *, enum dma_data_direction);
189
190 /**
191 * @end_cpu_access:
192 *
193 * This is called from dma_buf_end_cpu_access() when the importer is
194 * done accessing the CPU. The exporter can use this to flush caches and
195 * unpin any resources pinned in @begin_cpu_access.
196 * The result of any dma_buf kmap calls after end_cpu_access is
197 * undefined.
198 *
199 * This callback is optional.
200 *
201 * Returns:
202 *
203 * 0 on success or a negative error code on failure. Can return
204 * -ERESTARTSYS or -EINTR when the call has been interrupted and needs
205 * to be restarted.
206 */
207 int (*end_cpu_access)(struct dma_buf *, enum dma_data_direction);
208 void *(*map)(struct dma_buf *, unsigned long);
209 void (*unmap)(struct dma_buf *, unsigned long, void *);
210
211 /**
212 * @mmap:
213 *
214 * This callback is used by the dma_buf_mmap() function
215 *
216 * Note that the mapping needs to be incoherent, userspace is expected
217 * to braket CPU access using the DMA_BUF_IOCTL_SYNC interface.
218 *
219 * Because dma-buf buffers have invariant size over their lifetime, the
220 * dma-buf core checks whether a vma is too large and rejects such
221 * mappings. The exporter hence does not need to duplicate this check.
222 * Drivers do not need to check this themselves.
223 *
224 * If an exporter needs to manually flush caches and hence needs to fake
225 * coherency for mmap support, it needs to be able to zap all the ptes
226 * pointing at the backing storage. Now linux mm needs a struct
227 * address_space associated with the struct file stored in vma->vm_file
228 * to do that with the function unmap_mapping_range. But the dma_buf
229 * framework only backs every dma_buf fd with the anon_file struct file,
230 * i.e. all dma_bufs share the same file.
231 *
232 * Hence exporters need to setup their own file (and address_space)
233 * association by setting vma->vm_file and adjusting vma->vm_pgoff in
234 * the dma_buf mmap callback. In the specific case of a gem driver the
235 * exporter could use the shmem file already provided by gem (and set
236 * vm_pgoff = 0). Exporters can then zap ptes by unmapping the
237 * corresponding range of the struct address_space associated with their
238 * own file.
239 *
240 * This callback is optional.
241 *
242 * Returns:
243 *
244 * 0 on success or a negative error code on failure.
245 */
246 int (*mmap)(struct dma_buf *, struct vm_area_struct *vma);
247
248 void *(*vmap)(struct dma_buf *);
249 void (*vunmap)(struct dma_buf *, void *vaddr);
250 };
251
252 /**
253 * struct dma_buf - shared buffer object
254 * @size: size of the buffer
255 * @file: file pointer used for sharing buffers across, and for refcounting.
256 * @attachments: list of dma_buf_attachment that denotes all devices attached.
257 * @ops: dma_buf_ops associated with this buffer object.
258 * @lock: used internally to serialize list manipulation, attach/detach and vmap/unmap
259 * @vmapping_counter: used internally to refcnt the vmaps
260 * @vmap_ptr: the current vmap ptr if vmapping_counter > 0
261 * @exp_name: name of the exporter; useful for debugging.
262 * @owner: pointer to exporter module; used for refcounting when exporter is a
263 * kernel module.
264 * @list_node: node for dma_buf accounting and debugging.
265 * @priv: exporter specific private data for this buffer object.
266 * @resv: reservation object linked to this dma-buf
267 * @poll: for userspace poll support
268 * @cb_excl: for userspace poll support
269 * @cb_shared: for userspace poll support
270 *
271 * This represents a shared buffer, created by calling dma_buf_export(). The
272 * userspace representation is a normal file descriptor, which can be created by
273 * calling dma_buf_fd().
274 *
275 * Shared dma buffers are reference counted using dma_buf_put() and
276 * get_dma_buf().
277 *
278 * Device DMA access is handled by the separate &struct dma_buf_attachment.
279 */
280 struct dma_buf {
281 size_t size;
282 struct file *file;
283 struct list_head attachments;
284 const struct dma_buf_ops *ops;
285 struct mutex lock;
286 unsigned vmapping_counter;
287 void *vmap_ptr;
288 const char *exp_name;
289 struct module *owner;
290 struct list_head list_node;
291 void *priv;
292 struct reservation_object *resv;
293
294 /* poll support */
295 wait_queue_head_t poll;
296
297 struct dma_buf_poll_cb_t {
298 struct dma_fence_cb cb;
299 wait_queue_head_t *poll;
300
301 __poll_t active;
302 } cb_excl, cb_shared;
303 };
304
305 /**
306 * struct dma_buf_attachment - holds device-buffer attachment data
307 * @dmabuf: buffer for this attachment.
308 * @dev: device attached to the buffer.
309 * @node: list of dma_buf_attachment.
310 * @priv: exporter specific attachment data.
311 *
312 * This structure holds the attachment information between the dma_buf buffer
313 * and its user device(s). The list contains one attachment struct per device
314 * attached to the buffer.
315 *
316 * An attachment is created by calling dma_buf_attach(), and released again by
317 * calling dma_buf_detach(). The DMA mapping itself needed to initiate a
318 * transfer is created by dma_buf_map_attachment() and freed again by calling
319 * dma_buf_unmap_attachment().
320 */
321 struct dma_buf_attachment {
322 struct dma_buf *dmabuf;
323 struct device *dev;
324 struct list_head node;
325 void *priv;
326 };
327
328 /**
329 * struct dma_buf_export_info - holds information needed to export a dma_buf
330 * @exp_name: name of the exporter - useful for debugging.
331 * @owner: pointer to exporter module - used for refcounting kernel module
332 * @ops: Attach allocator-defined dma buf ops to the new buffer
333 * @size: Size of the buffer
334 * @flags: mode flags for the file
335 * @resv: reservation-object, NULL to allocate default one
336 * @priv: Attach private data of allocator to this buffer
337 *
338 * This structure holds the information required to export the buffer. Used
339 * with dma_buf_export() only.
340 */
341 struct dma_buf_export_info {
342 const char *exp_name;
343 struct module *owner;
344 const struct dma_buf_ops *ops;
345 size_t size;
346 int flags;
347 struct reservation_object *resv;
348 void *priv;
349 };
350
351 /**
352 * DEFINE_DMA_BUF_EXPORT_INFO - helper macro for exporters
353 * @name: export-info name
354 *
355 * DEFINE_DMA_BUF_EXPORT_INFO macro defines the &struct dma_buf_export_info,
356 * zeroes it out and pre-populates exp_name in it.
357 */
358 #define DEFINE_DMA_BUF_EXPORT_INFO(name) \
359 struct dma_buf_export_info name = { .exp_name = KBUILD_MODNAME, \
360 .owner = THIS_MODULE }
361
362 /**
363 * get_dma_buf - convenience wrapper for get_file.
364 * @dmabuf: [in] pointer to dma_buf
365 *
366 * Increments the reference count on the dma-buf, needed in case of drivers
367 * that either need to create additional references to the dmabuf on the
368 * kernel side. For example, an exporter that needs to keep a dmabuf ptr
369 * so that subsequent exports don't create a new dmabuf.
370 */
get_dma_buf(struct dma_buf * dmabuf)371 static inline void get_dma_buf(struct dma_buf *dmabuf)
372 {
373 get_file(dmabuf->file);
374 }
375
376 struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
377 struct device *dev);
378 void dma_buf_detach(struct dma_buf *dmabuf,
379 struct dma_buf_attachment *dmabuf_attach);
380
381 struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info);
382
383 int dma_buf_fd(struct dma_buf *dmabuf, int flags);
384 struct dma_buf *dma_buf_get(int fd);
385 void dma_buf_put(struct dma_buf *dmabuf);
386
387 struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *,
388 enum dma_data_direction);
389 void dma_buf_unmap_attachment(struct dma_buf_attachment *, struct sg_table *,
390 enum dma_data_direction);
391 int dma_buf_begin_cpu_access(struct dma_buf *dma_buf,
392 enum dma_data_direction dir);
393 int dma_buf_end_cpu_access(struct dma_buf *dma_buf,
394 enum dma_data_direction dir);
395 void *dma_buf_kmap(struct dma_buf *, unsigned long);
396 void dma_buf_kunmap(struct dma_buf *, unsigned long, void *);
397
398 int dma_buf_mmap(struct dma_buf *, struct vm_area_struct *,
399 unsigned long);
400 void *dma_buf_vmap(struct dma_buf *);
401 void dma_buf_vunmap(struct dma_buf *, void *vaddr);
402 #endif /* __DMA_BUF_H__ */
403