1 | /* |
2 | * Framework for buffer objects that can be shared across devices/subsystems. |
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 | |
25 | #include <linux/fs.h> |
26 | #include <linux/slab.h> |
27 | #include <linux/dma-buf.h> |
28 | #include <linux/dma-fence.h> |
29 | #include <linux/anon_inodes.h> |
30 | #include <linux/export.h> |
31 | #include <linux/debugfs.h> |
32 | #include <linux/module.h> |
33 | #include <linux/seq_file.h> |
34 | #include <linux/poll.h> |
35 | #include <linux/reservation.h> |
36 | #include <linux/mm.h> |
37 | |
38 | #include <uapi/linux/dma-buf.h> |
39 | |
40 | static inline int is_dma_buf_file(struct file *); |
41 | |
42 | struct dma_buf_list { |
43 | struct list_head head; |
44 | struct mutex lock; |
45 | }; |
46 | |
47 | static struct dma_buf_list db_list; |
48 | |
49 | static int dma_buf_release(struct inode *inode, struct file *file) |
50 | { |
51 | struct dma_buf *dmabuf; |
52 | |
53 | if (!is_dma_buf_file(file)) |
54 | return -EINVAL; |
55 | |
56 | dmabuf = file->private_data; |
57 | |
58 | BUG_ON(dmabuf->vmapping_counter); |
59 | |
60 | /* |
61 | * Any fences that a dma-buf poll can wait on should be signaled |
62 | * before releasing dma-buf. This is the responsibility of each |
63 | * driver that uses the reservation objects. |
64 | * |
65 | * If you hit this BUG() it means someone dropped their ref to the |
66 | * dma-buf while still having pending operation to the buffer. |
67 | */ |
68 | BUG_ON(dmabuf->cb_shared.active || dmabuf->cb_excl.active); |
69 | |
70 | dmabuf->ops->release(dmabuf); |
71 | |
72 | mutex_lock(&db_list.lock); |
73 | list_del(&dmabuf->list_node); |
74 | mutex_unlock(&db_list.lock); |
75 | |
76 | if (dmabuf->resv == (struct reservation_object *)&dmabuf[1]) |
77 | reservation_object_fini(dmabuf->resv); |
78 | |
79 | module_put(dmabuf->owner); |
80 | kfree(dmabuf); |
81 | return 0; |
82 | } |
83 | |
84 | static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma) |
85 | { |
86 | struct dma_buf *dmabuf; |
87 | |
88 | if (!is_dma_buf_file(file)) |
89 | return -EINVAL; |
90 | |
91 | dmabuf = file->private_data; |
92 | |
93 | /* check for overflowing the buffer's size */ |
94 | if (vma->vm_pgoff + vma_pages(vma) > |
95 | dmabuf->size >> PAGE_SHIFT) |
96 | return -EINVAL; |
97 | |
98 | return dmabuf->ops->mmap(dmabuf, vma); |
99 | } |
100 | |
101 | static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence) |
102 | { |
103 | struct dma_buf *dmabuf; |
104 | loff_t base; |
105 | |
106 | if (!is_dma_buf_file(file)) |
107 | return -EBADF; |
108 | |
109 | dmabuf = file->private_data; |
110 | |
111 | /* only support discovering the end of the buffer, |
112 | but also allow SEEK_SET to maintain the idiomatic |
113 | SEEK_END(0), SEEK_CUR(0) pattern */ |
114 | if (whence == SEEK_END) |
115 | base = dmabuf->size; |
116 | else if (whence == SEEK_SET) |
117 | base = 0; |
118 | else |
119 | return -EINVAL; |
120 | |
121 | if (offset != 0) |
122 | return -EINVAL; |
123 | |
124 | return base + offset; |
125 | } |
126 | |
127 | /** |
128 | * DOC: fence polling |
129 | * |
130 | * To support cross-device and cross-driver synchronization of buffer access |
131 | * implicit fences (represented internally in the kernel with &struct fence) can |
132 | * be attached to a &dma_buf. The glue for that and a few related things are |
133 | * provided in the &reservation_object structure. |
134 | * |
135 | * Userspace can query the state of these implicitly tracked fences using poll() |
136 | * and related system calls: |
137 | * |
138 | * - Checking for EPOLLIN, i.e. read access, can be use to query the state of the |
139 | * most recent write or exclusive fence. |
140 | * |
141 | * - Checking for EPOLLOUT, i.e. write access, can be used to query the state of |
142 | * all attached fences, shared and exclusive ones. |
143 | * |
144 | * Note that this only signals the completion of the respective fences, i.e. the |
145 | * DMA transfers are complete. Cache flushing and any other necessary |
146 | * preparations before CPU access can begin still need to happen. |
147 | */ |
148 | |
149 | static void dma_buf_poll_cb(struct dma_fence *fence, struct dma_fence_cb *cb) |
150 | { |
151 | struct dma_buf_poll_cb_t *dcb = (struct dma_buf_poll_cb_t *)cb; |
152 | unsigned long flags; |
153 | |
154 | spin_lock_irqsave(&dcb->poll->lock, flags); |
155 | wake_up_locked_poll(dcb->poll, dcb->active); |
156 | dcb->active = 0; |
157 | spin_unlock_irqrestore(&dcb->poll->lock, flags); |
158 | } |
159 | |
160 | static __poll_t dma_buf_poll(struct file *file, poll_table *poll) |
161 | { |
162 | struct dma_buf *dmabuf; |
163 | struct reservation_object *resv; |
164 | struct reservation_object_list *fobj; |
165 | struct dma_fence *fence_excl; |
166 | __poll_t events; |
167 | unsigned shared_count, seq; |
168 | |
169 | dmabuf = file->private_data; |
170 | if (!dmabuf || !dmabuf->resv) |
171 | return EPOLLERR; |
172 | |
173 | resv = dmabuf->resv; |
174 | |
175 | poll_wait(file, &dmabuf->poll, poll); |
176 | |
177 | events = poll_requested_events(poll) & (EPOLLIN | EPOLLOUT); |
178 | if (!events) |
179 | return 0; |
180 | |
181 | retry: |
182 | seq = read_seqcount_begin(&resv->seq); |
183 | rcu_read_lock(); |
184 | |
185 | fobj = rcu_dereference(resv->fence); |
186 | if (fobj) |
187 | shared_count = fobj->shared_count; |
188 | else |
189 | shared_count = 0; |
190 | fence_excl = rcu_dereference(resv->fence_excl); |
191 | if (read_seqcount_retry(&resv->seq, seq)) { |
192 | rcu_read_unlock(); |
193 | goto retry; |
194 | } |
195 | |
196 | if (fence_excl && (!(events & EPOLLOUT) || shared_count == 0)) { |
197 | struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_excl; |
198 | __poll_t pevents = EPOLLIN; |
199 | |
200 | if (shared_count == 0) |
201 | pevents |= EPOLLOUT; |
202 | |
203 | spin_lock_irq(&dmabuf->poll.lock); |
204 | if (dcb->active) { |
205 | dcb->active |= pevents; |
206 | events &= ~pevents; |
207 | } else |
208 | dcb->active = pevents; |
209 | spin_unlock_irq(&dmabuf->poll.lock); |
210 | |
211 | if (events & pevents) { |
212 | if (!dma_fence_get_rcu(fence_excl)) { |
213 | /* force a recheck */ |
214 | events &= ~pevents; |
215 | dma_buf_poll_cb(NULL, &dcb->cb); |
216 | } else if (!dma_fence_add_callback(fence_excl, &dcb->cb, |
217 | dma_buf_poll_cb)) { |
218 | events &= ~pevents; |
219 | dma_fence_put(fence_excl); |
220 | } else { |
221 | /* |
222 | * No callback queued, wake up any additional |
223 | * waiters. |
224 | */ |
225 | dma_fence_put(fence_excl); |
226 | dma_buf_poll_cb(NULL, &dcb->cb); |
227 | } |
228 | } |
229 | } |
230 | |
231 | if ((events & EPOLLOUT) && shared_count > 0) { |
232 | struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_shared; |
233 | int i; |
234 | |
235 | /* Only queue a new callback if no event has fired yet */ |
236 | spin_lock_irq(&dmabuf->poll.lock); |
237 | if (dcb->active) |
238 | events &= ~EPOLLOUT; |
239 | else |
240 | dcb->active = EPOLLOUT; |
241 | spin_unlock_irq(&dmabuf->poll.lock); |
242 | |
243 | if (!(events & EPOLLOUT)) |
244 | goto out; |
245 | |
246 | for (i = 0; i < shared_count; ++i) { |
247 | struct dma_fence *fence = rcu_dereference(fobj->shared[i]); |
248 | |
249 | if (!dma_fence_get_rcu(fence)) { |
250 | /* |
251 | * fence refcount dropped to zero, this means |
252 | * that fobj has been freed |
253 | * |
254 | * call dma_buf_poll_cb and force a recheck! |
255 | */ |
256 | events &= ~EPOLLOUT; |
257 | dma_buf_poll_cb(NULL, &dcb->cb); |
258 | break; |
259 | } |
260 | if (!dma_fence_add_callback(fence, &dcb->cb, |
261 | dma_buf_poll_cb)) { |
262 | dma_fence_put(fence); |
263 | events &= ~EPOLLOUT; |
264 | break; |
265 | } |
266 | dma_fence_put(fence); |
267 | } |
268 | |
269 | /* No callback queued, wake up any additional waiters. */ |
270 | if (i == shared_count) |
271 | dma_buf_poll_cb(NULL, &dcb->cb); |
272 | } |
273 | |
274 | out: |
275 | rcu_read_unlock(); |
276 | return events; |
277 | } |
278 | |
279 | static long dma_buf_ioctl(struct file *file, |
280 | unsigned int cmd, unsigned long arg) |
281 | { |
282 | struct dma_buf *dmabuf; |
283 | struct dma_buf_sync sync; |
284 | enum dma_data_direction direction; |
285 | int ret; |
286 | |
287 | dmabuf = file->private_data; |
288 | |
289 | switch (cmd) { |
290 | case DMA_BUF_IOCTL_SYNC: |
291 | if (copy_from_user(&sync, (void __user *) arg, sizeof(sync))) |
292 | return -EFAULT; |
293 | |
294 | if (sync.flags & ~DMA_BUF_SYNC_VALID_FLAGS_MASK) |
295 | return -EINVAL; |
296 | |
297 | switch (sync.flags & DMA_BUF_SYNC_RW) { |
298 | case DMA_BUF_SYNC_READ: |
299 | direction = DMA_FROM_DEVICE; |
300 | break; |
301 | case DMA_BUF_SYNC_WRITE: |
302 | direction = DMA_TO_DEVICE; |
303 | break; |
304 | case DMA_BUF_SYNC_RW: |
305 | direction = DMA_BIDIRECTIONAL; |
306 | break; |
307 | default: |
308 | return -EINVAL; |
309 | } |
310 | |
311 | if (sync.flags & DMA_BUF_SYNC_END) |
312 | ret = dma_buf_end_cpu_access(dmabuf, direction); |
313 | else |
314 | ret = dma_buf_begin_cpu_access(dmabuf, direction); |
315 | |
316 | return ret; |
317 | default: |
318 | return -ENOTTY; |
319 | } |
320 | } |
321 | |
322 | static const struct file_operations dma_buf_fops = { |
323 | .release = dma_buf_release, |
324 | .mmap = dma_buf_mmap_internal, |
325 | .llseek = dma_buf_llseek, |
326 | .poll = dma_buf_poll, |
327 | .unlocked_ioctl = dma_buf_ioctl, |
328 | #ifdef CONFIG_COMPAT |
329 | .compat_ioctl = dma_buf_ioctl, |
330 | #endif |
331 | }; |
332 | |
333 | /* |
334 | * is_dma_buf_file - Check if struct file* is associated with dma_buf |
335 | */ |
336 | static inline int is_dma_buf_file(struct file *file) |
337 | { |
338 | return file->f_op == &dma_buf_fops; |
339 | } |
340 | |
341 | /** |
342 | * DOC: dma buf device access |
343 | * |
344 | * For device DMA access to a shared DMA buffer the usual sequence of operations |
345 | * is fairly simple: |
346 | * |
347 | * 1. The exporter defines his exporter instance using |
348 | * DEFINE_DMA_BUF_EXPORT_INFO() and calls dma_buf_export() to wrap a private |
349 | * buffer object into a &dma_buf. It then exports that &dma_buf to userspace |
350 | * as a file descriptor by calling dma_buf_fd(). |
351 | * |
352 | * 2. Userspace passes this file-descriptors to all drivers it wants this buffer |
353 | * to share with: First the filedescriptor is converted to a &dma_buf using |
354 | * dma_buf_get(). Then the buffer is attached to the device using |
355 | * dma_buf_attach(). |
356 | * |
357 | * Up to this stage the exporter is still free to migrate or reallocate the |
358 | * backing storage. |
359 | * |
360 | * 3. Once the buffer is attached to all devices userspace can initiate DMA |
361 | * access to the shared buffer. In the kernel this is done by calling |
362 | * dma_buf_map_attachment() and dma_buf_unmap_attachment(). |
363 | * |
364 | * 4. Once a driver is done with a shared buffer it needs to call |
365 | * dma_buf_detach() (after cleaning up any mappings) and then release the |
366 | * reference acquired with dma_buf_get by calling dma_buf_put(). |
367 | * |
368 | * For the detailed semantics exporters are expected to implement see |
369 | * &dma_buf_ops. |
370 | */ |
371 | |
372 | /** |
373 | * dma_buf_export - Creates a new dma_buf, and associates an anon file |
374 | * with this buffer, so it can be exported. |
375 | * Also connect the allocator specific data and ops to the buffer. |
376 | * Additionally, provide a name string for exporter; useful in debugging. |
377 | * |
378 | * @exp_info: [in] holds all the export related information provided |
379 | * by the exporter. see &struct dma_buf_export_info |
380 | * for further details. |
381 | * |
382 | * Returns, on success, a newly created dma_buf object, which wraps the |
383 | * supplied private data and operations for dma_buf_ops. On either missing |
384 | * ops, or error in allocating struct dma_buf, will return negative error. |
385 | * |
386 | * For most cases the easiest way to create @exp_info is through the |
387 | * %DEFINE_DMA_BUF_EXPORT_INFO macro. |
388 | */ |
389 | struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info) |
390 | { |
391 | struct dma_buf *dmabuf; |
392 | struct reservation_object *resv = exp_info->resv; |
393 | struct file *file; |
394 | size_t alloc_size = sizeof(struct dma_buf); |
395 | int ret; |
396 | |
397 | if (!exp_info->resv) |
398 | alloc_size += sizeof(struct reservation_object); |
399 | else |
400 | /* prevent &dma_buf[1] == dma_buf->resv */ |
401 | alloc_size += 1; |
402 | |
403 | if (WARN_ON(!exp_info->priv |
404 | || !exp_info->ops |
405 | || !exp_info->ops->map_dma_buf |
406 | || !exp_info->ops->unmap_dma_buf |
407 | || !exp_info->ops->release |
408 | || !exp_info->ops->mmap)) { |
409 | return ERR_PTR(-EINVAL); |
410 | } |
411 | |
412 | if (!try_module_get(exp_info->owner)) |
413 | return ERR_PTR(-ENOENT); |
414 | |
415 | dmabuf = kzalloc(alloc_size, GFP_KERNEL); |
416 | if (!dmabuf) { |
417 | ret = -ENOMEM; |
418 | goto err_module; |
419 | } |
420 | |
421 | dmabuf->priv = exp_info->priv; |
422 | dmabuf->ops = exp_info->ops; |
423 | dmabuf->size = exp_info->size; |
424 | dmabuf->exp_name = exp_info->exp_name; |
425 | dmabuf->owner = exp_info->owner; |
426 | init_waitqueue_head(&dmabuf->poll); |
427 | dmabuf->cb_excl.poll = dmabuf->cb_shared.poll = &dmabuf->poll; |
428 | dmabuf->cb_excl.active = dmabuf->cb_shared.active = 0; |
429 | |
430 | if (!resv) { |
431 | resv = (struct reservation_object *)&dmabuf[1]; |
432 | reservation_object_init(resv); |
433 | } |
434 | dmabuf->resv = resv; |
435 | |
436 | file = anon_inode_getfile("dmabuf" , &dma_buf_fops, dmabuf, |
437 | exp_info->flags); |
438 | if (IS_ERR(file)) { |
439 | ret = PTR_ERR(file); |
440 | goto err_dmabuf; |
441 | } |
442 | |
443 | file->f_mode |= FMODE_LSEEK; |
444 | dmabuf->file = file; |
445 | |
446 | mutex_init(&dmabuf->lock); |
447 | INIT_LIST_HEAD(&dmabuf->attachments); |
448 | |
449 | mutex_lock(&db_list.lock); |
450 | list_add(&dmabuf->list_node, &db_list.head); |
451 | mutex_unlock(&db_list.lock); |
452 | |
453 | return dmabuf; |
454 | |
455 | err_dmabuf: |
456 | kfree(dmabuf); |
457 | err_module: |
458 | module_put(exp_info->owner); |
459 | return ERR_PTR(ret); |
460 | } |
461 | EXPORT_SYMBOL_GPL(dma_buf_export); |
462 | |
463 | /** |
464 | * dma_buf_fd - returns a file descriptor for the given dma_buf |
465 | * @dmabuf: [in] pointer to dma_buf for which fd is required. |
466 | * @flags: [in] flags to give to fd |
467 | * |
468 | * On success, returns an associated 'fd'. Else, returns error. |
469 | */ |
470 | int dma_buf_fd(struct dma_buf *dmabuf, int flags) |
471 | { |
472 | int fd; |
473 | |
474 | if (!dmabuf || !dmabuf->file) |
475 | return -EINVAL; |
476 | |
477 | fd = get_unused_fd_flags(flags); |
478 | if (fd < 0) |
479 | return fd; |
480 | |
481 | fd_install(fd, dmabuf->file); |
482 | |
483 | return fd; |
484 | } |
485 | EXPORT_SYMBOL_GPL(dma_buf_fd); |
486 | |
487 | /** |
488 | * dma_buf_get - returns the dma_buf structure related to an fd |
489 | * @fd: [in] fd associated with the dma_buf to be returned |
490 | * |
491 | * On success, returns the dma_buf structure associated with an fd; uses |
492 | * file's refcounting done by fget to increase refcount. returns ERR_PTR |
493 | * otherwise. |
494 | */ |
495 | struct dma_buf *dma_buf_get(int fd) |
496 | { |
497 | struct file *file; |
498 | |
499 | file = fget(fd); |
500 | |
501 | if (!file) |
502 | return ERR_PTR(-EBADF); |
503 | |
504 | if (!is_dma_buf_file(file)) { |
505 | fput(file); |
506 | return ERR_PTR(-EINVAL); |
507 | } |
508 | |
509 | return file->private_data; |
510 | } |
511 | EXPORT_SYMBOL_GPL(dma_buf_get); |
512 | |
513 | /** |
514 | * dma_buf_put - decreases refcount of the buffer |
515 | * @dmabuf: [in] buffer to reduce refcount of |
516 | * |
517 | * Uses file's refcounting done implicitly by fput(). |
518 | * |
519 | * If, as a result of this call, the refcount becomes 0, the 'release' file |
520 | * operation related to this fd is called. It calls &dma_buf_ops.release vfunc |
521 | * in turn, and frees the memory allocated for dmabuf when exported. |
522 | */ |
523 | void dma_buf_put(struct dma_buf *dmabuf) |
524 | { |
525 | if (WARN_ON(!dmabuf || !dmabuf->file)) |
526 | return; |
527 | |
528 | fput(dmabuf->file); |
529 | } |
530 | EXPORT_SYMBOL_GPL(dma_buf_put); |
531 | |
532 | /** |
533 | * dma_buf_attach - Add the device to dma_buf's attachments list; optionally, |
534 | * calls attach() of dma_buf_ops to allow device-specific attach functionality |
535 | * @dmabuf: [in] buffer to attach device to. |
536 | * @dev: [in] device to be attached. |
537 | * |
538 | * Returns struct dma_buf_attachment pointer for this attachment. Attachments |
539 | * must be cleaned up by calling dma_buf_detach(). |
540 | * |
541 | * Returns: |
542 | * |
543 | * A pointer to newly created &dma_buf_attachment on success, or a negative |
544 | * error code wrapped into a pointer on failure. |
545 | * |
546 | * Note that this can fail if the backing storage of @dmabuf is in a place not |
547 | * accessible to @dev, and cannot be moved to a more suitable place. This is |
548 | * indicated with the error code -EBUSY. |
549 | */ |
550 | struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf, |
551 | struct device *dev) |
552 | { |
553 | struct dma_buf_attachment *attach; |
554 | int ret; |
555 | |
556 | if (WARN_ON(!dmabuf || !dev)) |
557 | return ERR_PTR(-EINVAL); |
558 | |
559 | attach = kzalloc(sizeof(*attach), GFP_KERNEL); |
560 | if (!attach) |
561 | return ERR_PTR(-ENOMEM); |
562 | |
563 | attach->dev = dev; |
564 | attach->dmabuf = dmabuf; |
565 | |
566 | mutex_lock(&dmabuf->lock); |
567 | |
568 | if (dmabuf->ops->attach) { |
569 | ret = dmabuf->ops->attach(dmabuf, attach); |
570 | if (ret) |
571 | goto err_attach; |
572 | } |
573 | list_add(&attach->node, &dmabuf->attachments); |
574 | |
575 | mutex_unlock(&dmabuf->lock); |
576 | return attach; |
577 | |
578 | err_attach: |
579 | kfree(attach); |
580 | mutex_unlock(&dmabuf->lock); |
581 | return ERR_PTR(ret); |
582 | } |
583 | EXPORT_SYMBOL_GPL(dma_buf_attach); |
584 | |
585 | /** |
586 | * dma_buf_detach - Remove the given attachment from dmabuf's attachments list; |
587 | * optionally calls detach() of dma_buf_ops for device-specific detach |
588 | * @dmabuf: [in] buffer to detach from. |
589 | * @attach: [in] attachment to be detached; is free'd after this call. |
590 | * |
591 | * Clean up a device attachment obtained by calling dma_buf_attach(). |
592 | */ |
593 | void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach) |
594 | { |
595 | if (WARN_ON(!dmabuf || !attach)) |
596 | return; |
597 | |
598 | mutex_lock(&dmabuf->lock); |
599 | list_del(&attach->node); |
600 | if (dmabuf->ops->detach) |
601 | dmabuf->ops->detach(dmabuf, attach); |
602 | |
603 | mutex_unlock(&dmabuf->lock); |
604 | kfree(attach); |
605 | } |
606 | EXPORT_SYMBOL_GPL(dma_buf_detach); |
607 | |
608 | /** |
609 | * dma_buf_map_attachment - Returns the scatterlist table of the attachment; |
610 | * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the |
611 | * dma_buf_ops. |
612 | * @attach: [in] attachment whose scatterlist is to be returned |
613 | * @direction: [in] direction of DMA transfer |
614 | * |
615 | * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR |
616 | * on error. May return -EINTR if it is interrupted by a signal. |
617 | * |
618 | * A mapping must be unmapped by using dma_buf_unmap_attachment(). Note that |
619 | * the underlying backing storage is pinned for as long as a mapping exists, |
620 | * therefore users/importers should not hold onto a mapping for undue amounts of |
621 | * time. |
622 | */ |
623 | struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach, |
624 | enum dma_data_direction direction) |
625 | { |
626 | struct sg_table *sg_table; |
627 | |
628 | might_sleep(); |
629 | |
630 | if (WARN_ON(!attach || !attach->dmabuf)) |
631 | return ERR_PTR(-EINVAL); |
632 | |
633 | sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction); |
634 | if (!sg_table) |
635 | sg_table = ERR_PTR(-ENOMEM); |
636 | |
637 | return sg_table; |
638 | } |
639 | EXPORT_SYMBOL_GPL(dma_buf_map_attachment); |
640 | |
641 | /** |
642 | * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might |
643 | * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of |
644 | * dma_buf_ops. |
645 | * @attach: [in] attachment to unmap buffer from |
646 | * @sg_table: [in] scatterlist info of the buffer to unmap |
647 | * @direction: [in] direction of DMA transfer |
648 | * |
649 | * This unmaps a DMA mapping for @attached obtained by dma_buf_map_attachment(). |
650 | */ |
651 | void dma_buf_unmap_attachment(struct dma_buf_attachment *attach, |
652 | struct sg_table *sg_table, |
653 | enum dma_data_direction direction) |
654 | { |
655 | might_sleep(); |
656 | |
657 | if (WARN_ON(!attach || !attach->dmabuf || !sg_table)) |
658 | return; |
659 | |
660 | attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, |
661 | direction); |
662 | } |
663 | EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment); |
664 | |
665 | /** |
666 | * DOC: cpu access |
667 | * |
668 | * There are mutliple reasons for supporting CPU access to a dma buffer object: |
669 | * |
670 | * - Fallback operations in the kernel, for example when a device is connected |
671 | * over USB and the kernel needs to shuffle the data around first before |
672 | * sending it away. Cache coherency is handled by braketing any transactions |
673 | * with calls to dma_buf_begin_cpu_access() and dma_buf_end_cpu_access() |
674 | * access. |
675 | * |
676 | * To support dma_buf objects residing in highmem cpu access is page-based |
677 | * using an api similar to kmap. Accessing a dma_buf is done in aligned chunks |
678 | * of PAGE_SIZE size. Before accessing a chunk it needs to be mapped, which |
679 | * returns a pointer in kernel virtual address space. Afterwards the chunk |
680 | * needs to be unmapped again. There is no limit on how often a given chunk |
681 | * can be mapped and unmapped, i.e. the importer does not need to call |
682 | * begin_cpu_access again before mapping the same chunk again. |
683 | * |
684 | * Interfaces:: |
685 | * void \*dma_buf_kmap(struct dma_buf \*, unsigned long); |
686 | * void dma_buf_kunmap(struct dma_buf \*, unsigned long, void \*); |
687 | * |
688 | * Implementing the functions is optional for exporters and for importers all |
689 | * the restrictions of using kmap apply. |
690 | * |
691 | * dma_buf kmap calls outside of the range specified in begin_cpu_access are |
692 | * undefined. If the range is not PAGE_SIZE aligned, kmap needs to succeed on |
693 | * the partial chunks at the beginning and end but may return stale or bogus |
694 | * data outside of the range (in these partial chunks). |
695 | * |
696 | * For some cases the overhead of kmap can be too high, a vmap interface |
697 | * is introduced. This interface should be used very carefully, as vmalloc |
698 | * space is a limited resources on many architectures. |
699 | * |
700 | * Interfaces:: |
701 | * void \*dma_buf_vmap(struct dma_buf \*dmabuf) |
702 | * void dma_buf_vunmap(struct dma_buf \*dmabuf, void \*vaddr) |
703 | * |
704 | * The vmap call can fail if there is no vmap support in the exporter, or if |
705 | * it runs out of vmalloc space. Fallback to kmap should be implemented. Note |
706 | * that the dma-buf layer keeps a reference count for all vmap access and |
707 | * calls down into the exporter's vmap function only when no vmapping exists, |
708 | * and only unmaps it once. Protection against concurrent vmap/vunmap calls is |
709 | * provided by taking the dma_buf->lock mutex. |
710 | * |
711 | * - For full compatibility on the importer side with existing userspace |
712 | * interfaces, which might already support mmap'ing buffers. This is needed in |
713 | * many processing pipelines (e.g. feeding a software rendered image into a |
714 | * hardware pipeline, thumbnail creation, snapshots, ...). Also, Android's ION |
715 | * framework already supported this and for DMA buffer file descriptors to |
716 | * replace ION buffers mmap support was needed. |
717 | * |
718 | * There is no special interfaces, userspace simply calls mmap on the dma-buf |
719 | * fd. But like for CPU access there's a need to braket the actual access, |
720 | * which is handled by the ioctl (DMA_BUF_IOCTL_SYNC). Note that |
721 | * DMA_BUF_IOCTL_SYNC can fail with -EAGAIN or -EINTR, in which case it must |
722 | * be restarted. |
723 | * |
724 | * Some systems might need some sort of cache coherency management e.g. when |
725 | * CPU and GPU domains are being accessed through dma-buf at the same time. |
726 | * To circumvent this problem there are begin/end coherency markers, that |
727 | * forward directly to existing dma-buf device drivers vfunc hooks. Userspace |
728 | * can make use of those markers through the DMA_BUF_IOCTL_SYNC ioctl. The |
729 | * sequence would be used like following: |
730 | * |
731 | * - mmap dma-buf fd |
732 | * - for each drawing/upload cycle in CPU 1. SYNC_START ioctl, 2. read/write |
733 | * to mmap area 3. SYNC_END ioctl. This can be repeated as often as you |
734 | * want (with the new data being consumed by say the GPU or the scanout |
735 | * device) |
736 | * - munmap once you don't need the buffer any more |
737 | * |
738 | * For correctness and optimal performance, it is always required to use |
739 | * SYNC_START and SYNC_END before and after, respectively, when accessing the |
740 | * mapped address. Userspace cannot rely on coherent access, even when there |
741 | * are systems where it just works without calling these ioctls. |
742 | * |
743 | * - And as a CPU fallback in userspace processing pipelines. |
744 | * |
745 | * Similar to the motivation for kernel cpu access it is again important that |
746 | * the userspace code of a given importing subsystem can use the same |
747 | * interfaces with a imported dma-buf buffer object as with a native buffer |
748 | * object. This is especially important for drm where the userspace part of |
749 | * contemporary OpenGL, X, and other drivers is huge, and reworking them to |
750 | * use a different way to mmap a buffer rather invasive. |
751 | * |
752 | * The assumption in the current dma-buf interfaces is that redirecting the |
753 | * initial mmap is all that's needed. A survey of some of the existing |
754 | * subsystems shows that no driver seems to do any nefarious thing like |
755 | * syncing up with outstanding asynchronous processing on the device or |
756 | * allocating special resources at fault time. So hopefully this is good |
757 | * enough, since adding interfaces to intercept pagefaults and allow pte |
758 | * shootdowns would increase the complexity quite a bit. |
759 | * |
760 | * Interface:: |
761 | * int dma_buf_mmap(struct dma_buf \*, struct vm_area_struct \*, |
762 | * unsigned long); |
763 | * |
764 | * If the importing subsystem simply provides a special-purpose mmap call to |
765 | * set up a mapping in userspace, calling do_mmap with dma_buf->file will |
766 | * equally achieve that for a dma-buf object. |
767 | */ |
768 | |
769 | static int __dma_buf_begin_cpu_access(struct dma_buf *dmabuf, |
770 | enum dma_data_direction direction) |
771 | { |
772 | bool write = (direction == DMA_BIDIRECTIONAL || |
773 | direction == DMA_TO_DEVICE); |
774 | struct reservation_object *resv = dmabuf->resv; |
775 | long ret; |
776 | |
777 | /* Wait on any implicit rendering fences */ |
778 | ret = reservation_object_wait_timeout_rcu(resv, write, true, |
779 | MAX_SCHEDULE_TIMEOUT); |
780 | if (ret < 0) |
781 | return ret; |
782 | |
783 | return 0; |
784 | } |
785 | |
786 | /** |
787 | * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the |
788 | * cpu in the kernel context. Calls begin_cpu_access to allow exporter-specific |
789 | * preparations. Coherency is only guaranteed in the specified range for the |
790 | * specified access direction. |
791 | * @dmabuf: [in] buffer to prepare cpu access for. |
792 | * @direction: [in] length of range for cpu access. |
793 | * |
794 | * After the cpu access is complete the caller should call |
795 | * dma_buf_end_cpu_access(). Only when cpu access is braketed by both calls is |
796 | * it guaranteed to be coherent with other DMA access. |
797 | * |
798 | * Can return negative error values, returns 0 on success. |
799 | */ |
800 | int dma_buf_begin_cpu_access(struct dma_buf *dmabuf, |
801 | enum dma_data_direction direction) |
802 | { |
803 | int ret = 0; |
804 | |
805 | if (WARN_ON(!dmabuf)) |
806 | return -EINVAL; |
807 | |
808 | if (dmabuf->ops->begin_cpu_access) |
809 | ret = dmabuf->ops->begin_cpu_access(dmabuf, direction); |
810 | |
811 | /* Ensure that all fences are waited upon - but we first allow |
812 | * the native handler the chance to do so more efficiently if it |
813 | * chooses. A double invocation here will be reasonably cheap no-op. |
814 | */ |
815 | if (ret == 0) |
816 | ret = __dma_buf_begin_cpu_access(dmabuf, direction); |
817 | |
818 | return ret; |
819 | } |
820 | EXPORT_SYMBOL_GPL(dma_buf_begin_cpu_access); |
821 | |
822 | /** |
823 | * dma_buf_end_cpu_access - Must be called after accessing a dma_buf from the |
824 | * cpu in the kernel context. Calls end_cpu_access to allow exporter-specific |
825 | * actions. Coherency is only guaranteed in the specified range for the |
826 | * specified access direction. |
827 | * @dmabuf: [in] buffer to complete cpu access for. |
828 | * @direction: [in] length of range for cpu access. |
829 | * |
830 | * This terminates CPU access started with dma_buf_begin_cpu_access(). |
831 | * |
832 | * Can return negative error values, returns 0 on success. |
833 | */ |
834 | int dma_buf_end_cpu_access(struct dma_buf *dmabuf, |
835 | enum dma_data_direction direction) |
836 | { |
837 | int ret = 0; |
838 | |
839 | WARN_ON(!dmabuf); |
840 | |
841 | if (dmabuf->ops->end_cpu_access) |
842 | ret = dmabuf->ops->end_cpu_access(dmabuf, direction); |
843 | |
844 | return ret; |
845 | } |
846 | EXPORT_SYMBOL_GPL(dma_buf_end_cpu_access); |
847 | |
848 | /** |
849 | * dma_buf_kmap - Map a page of the buffer object into kernel address space. The |
850 | * same restrictions as for kmap and friends apply. |
851 | * @dmabuf: [in] buffer to map page from. |
852 | * @page_num: [in] page in PAGE_SIZE units to map. |
853 | * |
854 | * This call must always succeed, any necessary preparations that might fail |
855 | * need to be done in begin_cpu_access. |
856 | */ |
857 | void *dma_buf_kmap(struct dma_buf *dmabuf, unsigned long page_num) |
858 | { |
859 | WARN_ON(!dmabuf); |
860 | |
861 | if (!dmabuf->ops->map) |
862 | return NULL; |
863 | return dmabuf->ops->map(dmabuf, page_num); |
864 | } |
865 | EXPORT_SYMBOL_GPL(dma_buf_kmap); |
866 | |
867 | /** |
868 | * dma_buf_kunmap - Unmap a page obtained by dma_buf_kmap. |
869 | * @dmabuf: [in] buffer to unmap page from. |
870 | * @page_num: [in] page in PAGE_SIZE units to unmap. |
871 | * @vaddr: [in] kernel space pointer obtained from dma_buf_kmap. |
872 | * |
873 | * This call must always succeed. |
874 | */ |
875 | void dma_buf_kunmap(struct dma_buf *dmabuf, unsigned long page_num, |
876 | void *vaddr) |
877 | { |
878 | WARN_ON(!dmabuf); |
879 | |
880 | if (dmabuf->ops->unmap) |
881 | dmabuf->ops->unmap(dmabuf, page_num, vaddr); |
882 | } |
883 | EXPORT_SYMBOL_GPL(dma_buf_kunmap); |
884 | |
885 | |
886 | /** |
887 | * dma_buf_mmap - Setup up a userspace mmap with the given vma |
888 | * @dmabuf: [in] buffer that should back the vma |
889 | * @vma: [in] vma for the mmap |
890 | * @pgoff: [in] offset in pages where this mmap should start within the |
891 | * dma-buf buffer. |
892 | * |
893 | * This function adjusts the passed in vma so that it points at the file of the |
894 | * dma_buf operation. It also adjusts the starting pgoff and does bounds |
895 | * checking on the size of the vma. Then it calls the exporters mmap function to |
896 | * set up the mapping. |
897 | * |
898 | * Can return negative error values, returns 0 on success. |
899 | */ |
900 | int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma, |
901 | unsigned long pgoff) |
902 | { |
903 | struct file *oldfile; |
904 | int ret; |
905 | |
906 | if (WARN_ON(!dmabuf || !vma)) |
907 | return -EINVAL; |
908 | |
909 | /* check for offset overflow */ |
910 | if (pgoff + vma_pages(vma) < pgoff) |
911 | return -EOVERFLOW; |
912 | |
913 | /* check for overflowing the buffer's size */ |
914 | if (pgoff + vma_pages(vma) > |
915 | dmabuf->size >> PAGE_SHIFT) |
916 | return -EINVAL; |
917 | |
918 | /* readjust the vma */ |
919 | get_file(dmabuf->file); |
920 | oldfile = vma->vm_file; |
921 | vma->vm_file = dmabuf->file; |
922 | vma->vm_pgoff = pgoff; |
923 | |
924 | ret = dmabuf->ops->mmap(dmabuf, vma); |
925 | if (ret) { |
926 | /* restore old parameters on failure */ |
927 | vma->vm_file = oldfile; |
928 | fput(dmabuf->file); |
929 | } else { |
930 | if (oldfile) |
931 | fput(oldfile); |
932 | } |
933 | return ret; |
934 | |
935 | } |
936 | EXPORT_SYMBOL_GPL(dma_buf_mmap); |
937 | |
938 | /** |
939 | * dma_buf_vmap - Create virtual mapping for the buffer object into kernel |
940 | * address space. Same restrictions as for vmap and friends apply. |
941 | * @dmabuf: [in] buffer to vmap |
942 | * |
943 | * This call may fail due to lack of virtual mapping address space. |
944 | * These calls are optional in drivers. The intended use for them |
945 | * is for mapping objects linear in kernel space for high use objects. |
946 | * Please attempt to use kmap/kunmap before thinking about these interfaces. |
947 | * |
948 | * Returns NULL on error. |
949 | */ |
950 | void *dma_buf_vmap(struct dma_buf *dmabuf) |
951 | { |
952 | void *ptr; |
953 | |
954 | if (WARN_ON(!dmabuf)) |
955 | return NULL; |
956 | |
957 | if (!dmabuf->ops->vmap) |
958 | return NULL; |
959 | |
960 | mutex_lock(&dmabuf->lock); |
961 | if (dmabuf->vmapping_counter) { |
962 | dmabuf->vmapping_counter++; |
963 | BUG_ON(!dmabuf->vmap_ptr); |
964 | ptr = dmabuf->vmap_ptr; |
965 | goto out_unlock; |
966 | } |
967 | |
968 | BUG_ON(dmabuf->vmap_ptr); |
969 | |
970 | ptr = dmabuf->ops->vmap(dmabuf); |
971 | if (WARN_ON_ONCE(IS_ERR(ptr))) |
972 | ptr = NULL; |
973 | if (!ptr) |
974 | goto out_unlock; |
975 | |
976 | dmabuf->vmap_ptr = ptr; |
977 | dmabuf->vmapping_counter = 1; |
978 | |
979 | out_unlock: |
980 | mutex_unlock(&dmabuf->lock); |
981 | return ptr; |
982 | } |
983 | EXPORT_SYMBOL_GPL(dma_buf_vmap); |
984 | |
985 | /** |
986 | * dma_buf_vunmap - Unmap a vmap obtained by dma_buf_vmap. |
987 | * @dmabuf: [in] buffer to vunmap |
988 | * @vaddr: [in] vmap to vunmap |
989 | */ |
990 | void dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr) |
991 | { |
992 | if (WARN_ON(!dmabuf)) |
993 | return; |
994 | |
995 | BUG_ON(!dmabuf->vmap_ptr); |
996 | BUG_ON(dmabuf->vmapping_counter == 0); |
997 | BUG_ON(dmabuf->vmap_ptr != vaddr); |
998 | |
999 | mutex_lock(&dmabuf->lock); |
1000 | if (--dmabuf->vmapping_counter == 0) { |
1001 | if (dmabuf->ops->vunmap) |
1002 | dmabuf->ops->vunmap(dmabuf, vaddr); |
1003 | dmabuf->vmap_ptr = NULL; |
1004 | } |
1005 | mutex_unlock(&dmabuf->lock); |
1006 | } |
1007 | EXPORT_SYMBOL_GPL(dma_buf_vunmap); |
1008 | |
1009 | #ifdef CONFIG_DEBUG_FS |
1010 | static int dma_buf_debug_show(struct seq_file *s, void *unused) |
1011 | { |
1012 | int ret; |
1013 | struct dma_buf *buf_obj; |
1014 | struct dma_buf_attachment *attach_obj; |
1015 | struct reservation_object *robj; |
1016 | struct reservation_object_list *fobj; |
1017 | struct dma_fence *fence; |
1018 | unsigned seq; |
1019 | int count = 0, attach_count, shared_count, i; |
1020 | size_t size = 0; |
1021 | |
1022 | ret = mutex_lock_interruptible(&db_list.lock); |
1023 | |
1024 | if (ret) |
1025 | return ret; |
1026 | |
1027 | seq_puts(s, "\nDma-buf Objects:\n" ); |
1028 | seq_printf(s, "%-8s\t%-8s\t%-8s\t%-8s\texp_name\n" , |
1029 | "size" , "flags" , "mode" , "count" ); |
1030 | |
1031 | list_for_each_entry(buf_obj, &db_list.head, list_node) { |
1032 | ret = mutex_lock_interruptible(&buf_obj->lock); |
1033 | |
1034 | if (ret) { |
1035 | seq_puts(s, |
1036 | "\tERROR locking buffer object: skipping\n" ); |
1037 | continue; |
1038 | } |
1039 | |
1040 | seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\n" , |
1041 | buf_obj->size, |
1042 | buf_obj->file->f_flags, buf_obj->file->f_mode, |
1043 | file_count(buf_obj->file), |
1044 | buf_obj->exp_name); |
1045 | |
1046 | robj = buf_obj->resv; |
1047 | while (true) { |
1048 | seq = read_seqcount_begin(&robj->seq); |
1049 | rcu_read_lock(); |
1050 | fobj = rcu_dereference(robj->fence); |
1051 | shared_count = fobj ? fobj->shared_count : 0; |
1052 | fence = rcu_dereference(robj->fence_excl); |
1053 | if (!read_seqcount_retry(&robj->seq, seq)) |
1054 | break; |
1055 | rcu_read_unlock(); |
1056 | } |
1057 | |
1058 | if (fence) |
1059 | seq_printf(s, "\tExclusive fence: %s %s %ssignalled\n" , |
1060 | fence->ops->get_driver_name(fence), |
1061 | fence->ops->get_timeline_name(fence), |
1062 | dma_fence_is_signaled(fence) ? "" : "un" ); |
1063 | for (i = 0; i < shared_count; i++) { |
1064 | fence = rcu_dereference(fobj->shared[i]); |
1065 | if (!dma_fence_get_rcu(fence)) |
1066 | continue; |
1067 | seq_printf(s, "\tShared fence: %s %s %ssignalled\n" , |
1068 | fence->ops->get_driver_name(fence), |
1069 | fence->ops->get_timeline_name(fence), |
1070 | dma_fence_is_signaled(fence) ? "" : "un" ); |
1071 | } |
1072 | rcu_read_unlock(); |
1073 | |
1074 | seq_puts(s, "\tAttached Devices:\n" ); |
1075 | attach_count = 0; |
1076 | |
1077 | list_for_each_entry(attach_obj, &buf_obj->attachments, node) { |
1078 | seq_printf(s, "\t%s\n" , dev_name(attach_obj->dev)); |
1079 | attach_count++; |
1080 | } |
1081 | |
1082 | seq_printf(s, "Total %d devices attached\n\n" , |
1083 | attach_count); |
1084 | |
1085 | count++; |
1086 | size += buf_obj->size; |
1087 | mutex_unlock(&buf_obj->lock); |
1088 | } |
1089 | |
1090 | seq_printf(s, "\nTotal %d objects, %zu bytes\n" , count, size); |
1091 | |
1092 | mutex_unlock(&db_list.lock); |
1093 | return 0; |
1094 | } |
1095 | |
1096 | DEFINE_SHOW_ATTRIBUTE(dma_buf_debug); |
1097 | |
1098 | static struct dentry *dma_buf_debugfs_dir; |
1099 | |
1100 | static int dma_buf_init_debugfs(void) |
1101 | { |
1102 | struct dentry *d; |
1103 | int err = 0; |
1104 | |
1105 | d = debugfs_create_dir("dma_buf" , NULL); |
1106 | if (IS_ERR(d)) |
1107 | return PTR_ERR(d); |
1108 | |
1109 | dma_buf_debugfs_dir = d; |
1110 | |
1111 | d = debugfs_create_file("bufinfo" , S_IRUGO, dma_buf_debugfs_dir, |
1112 | NULL, &dma_buf_debug_fops); |
1113 | if (IS_ERR(d)) { |
1114 | pr_debug("dma_buf: debugfs: failed to create node bufinfo\n" ); |
1115 | debugfs_remove_recursive(dma_buf_debugfs_dir); |
1116 | dma_buf_debugfs_dir = NULL; |
1117 | err = PTR_ERR(d); |
1118 | } |
1119 | |
1120 | return err; |
1121 | } |
1122 | |
1123 | static void dma_buf_uninit_debugfs(void) |
1124 | { |
1125 | debugfs_remove_recursive(dma_buf_debugfs_dir); |
1126 | } |
1127 | #else |
1128 | static inline int dma_buf_init_debugfs(void) |
1129 | { |
1130 | return 0; |
1131 | } |
1132 | static inline void dma_buf_uninit_debugfs(void) |
1133 | { |
1134 | } |
1135 | #endif |
1136 | |
1137 | static int __init dma_buf_init(void) |
1138 | { |
1139 | mutex_init(&db_list.lock); |
1140 | INIT_LIST_HEAD(&db_list.head); |
1141 | dma_buf_init_debugfs(); |
1142 | return 0; |
1143 | } |
1144 | subsys_initcall(dma_buf_init); |
1145 | |
1146 | static void __exit dma_buf_deinit(void) |
1147 | { |
1148 | dma_buf_uninit_debugfs(); |
1149 | } |
1150 | __exitcall(dma_buf_deinit); |
1151 | |