1 // SPDX-License-Identifier: GPL-2.0-only
3 * Framework for buffer objects that can be shared across devices/subsystems.
5 * Copyright(C) 2011 Linaro Limited. All rights reserved.
6 * Author: Sumit Semwal <sumit.semwal@ti.com>
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.
15 #include <linux/slab.h>
16 #include <linux/dma-buf.h>
17 #include <linux/dma-fence.h>
18 #include <linux/anon_inodes.h>
19 #include <linux/export.h>
20 #include <linux/debugfs.h>
21 #include <linux/module.h>
22 #include <linux/seq_file.h>
23 #include <linux/poll.h>
24 #include <linux/dma-resv.h>
26 #include <linux/mount.h>
27 #include <linux/pseudo_fs.h>
29 #include <uapi/linux/dma-buf.h>
30 #include <uapi/linux/magic.h>
32 static inline int is_dma_buf_file(struct file *);
35 struct list_head head;
39 static struct dma_buf_list db_list;
41 static char *dmabuffs_dname(struct dentry *dentry, char *buffer, int buflen)
43 struct dma_buf *dmabuf;
44 char name[DMA_BUF_NAME_LEN];
47 dmabuf = dentry->d_fsdata;
48 spin_lock(&dmabuf->name_lock);
50 ret = strlcpy(name, dmabuf->name, DMA_BUF_NAME_LEN);
51 spin_unlock(&dmabuf->name_lock);
53 return dynamic_dname(dentry, buffer, buflen, "/%s:%s",
54 dentry->d_name.name, ret > 0 ? name : "");
57 static void dma_buf_release(struct dentry *dentry)
59 struct dma_buf *dmabuf;
61 dmabuf = dentry->d_fsdata;
62 if (unlikely(!dmabuf))
65 BUG_ON(dmabuf->vmapping_counter);
68 * Any fences that a dma-buf poll can wait on should be signaled
69 * before releasing dma-buf. This is the responsibility of each
70 * driver that uses the reservation objects.
72 * If you hit this BUG() it means someone dropped their ref to the
73 * dma-buf while still having pending operation to the buffer.
75 BUG_ON(dmabuf->cb_shared.active || dmabuf->cb_excl.active);
77 dmabuf->ops->release(dmabuf);
79 mutex_lock(&db_list.lock);
80 list_del(&dmabuf->list_node);
81 mutex_unlock(&db_list.lock);
83 if (dmabuf->resv == (struct dma_resv *)&dmabuf[1])
84 dma_resv_fini(dmabuf->resv);
86 module_put(dmabuf->owner);
91 static const struct dentry_operations dma_buf_dentry_ops = {
92 .d_dname = dmabuffs_dname,
93 .d_release = dma_buf_release,
96 static struct vfsmount *dma_buf_mnt;
98 static int dma_buf_fs_init_context(struct fs_context *fc)
100 struct pseudo_fs_context *ctx;
102 ctx = init_pseudo(fc, DMA_BUF_MAGIC);
105 ctx->dops = &dma_buf_dentry_ops;
109 static struct file_system_type dma_buf_fs_type = {
111 .init_fs_context = dma_buf_fs_init_context,
112 .kill_sb = kill_anon_super,
115 static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
117 struct dma_buf *dmabuf;
119 if (!is_dma_buf_file(file))
122 dmabuf = file->private_data;
124 /* check if buffer supports mmap */
125 if (!dmabuf->ops->mmap)
128 /* check for overflowing the buffer's size */
129 if (vma->vm_pgoff + vma_pages(vma) >
130 dmabuf->size >> PAGE_SHIFT)
133 return dmabuf->ops->mmap(dmabuf, vma);
136 static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence)
138 struct dma_buf *dmabuf;
141 if (!is_dma_buf_file(file))
144 dmabuf = file->private_data;
146 /* only support discovering the end of the buffer,
147 but also allow SEEK_SET to maintain the idiomatic
148 SEEK_END(0), SEEK_CUR(0) pattern */
149 if (whence == SEEK_END)
151 else if (whence == SEEK_SET)
159 return base + offset;
163 * DOC: implicit fence polling
165 * To support cross-device and cross-driver synchronization of buffer access
166 * implicit fences (represented internally in the kernel with &struct dma_fence)
167 * can be attached to a &dma_buf. The glue for that and a few related things are
168 * provided in the &dma_resv structure.
170 * Userspace can query the state of these implicitly tracked fences using poll()
171 * and related system calls:
173 * - Checking for EPOLLIN, i.e. read access, can be use to query the state of the
174 * most recent write or exclusive fence.
176 * - Checking for EPOLLOUT, i.e. write access, can be used to query the state of
177 * all attached fences, shared and exclusive ones.
179 * Note that this only signals the completion of the respective fences, i.e. the
180 * DMA transfers are complete. Cache flushing and any other necessary
181 * preparations before CPU access can begin still need to happen.
184 static void dma_buf_poll_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
186 struct dma_buf_poll_cb_t *dcb = (struct dma_buf_poll_cb_t *)cb;
189 spin_lock_irqsave(&dcb->poll->lock, flags);
190 wake_up_locked_poll(dcb->poll, dcb->active);
192 spin_unlock_irqrestore(&dcb->poll->lock, flags);
195 static __poll_t dma_buf_poll(struct file *file, poll_table *poll)
197 struct dma_buf *dmabuf;
198 struct dma_resv *resv;
199 struct dma_resv_list *fobj;
200 struct dma_fence *fence_excl;
202 unsigned shared_count, seq;
204 dmabuf = file->private_data;
205 if (!dmabuf || !dmabuf->resv)
210 poll_wait(file, &dmabuf->poll, poll);
212 events = poll_requested_events(poll) & (EPOLLIN | EPOLLOUT);
217 seq = read_seqcount_begin(&resv->seq);
220 fobj = rcu_dereference(resv->fence);
222 shared_count = fobj->shared_count;
225 fence_excl = rcu_dereference(resv->fence_excl);
226 if (read_seqcount_retry(&resv->seq, seq)) {
231 if (fence_excl && (!(events & EPOLLOUT) || shared_count == 0)) {
232 struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_excl;
233 __poll_t pevents = EPOLLIN;
235 if (shared_count == 0)
238 spin_lock_irq(&dmabuf->poll.lock);
240 dcb->active |= pevents;
243 dcb->active = pevents;
244 spin_unlock_irq(&dmabuf->poll.lock);
246 if (events & pevents) {
247 if (!dma_fence_get_rcu(fence_excl)) {
248 /* force a recheck */
250 dma_buf_poll_cb(NULL, &dcb->cb);
251 } else if (!dma_fence_add_callback(fence_excl, &dcb->cb,
254 dma_fence_put(fence_excl);
257 * No callback queued, wake up any additional
260 dma_fence_put(fence_excl);
261 dma_buf_poll_cb(NULL, &dcb->cb);
266 if ((events & EPOLLOUT) && shared_count > 0) {
267 struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_shared;
270 /* Only queue a new callback if no event has fired yet */
271 spin_lock_irq(&dmabuf->poll.lock);
275 dcb->active = EPOLLOUT;
276 spin_unlock_irq(&dmabuf->poll.lock);
278 if (!(events & EPOLLOUT))
281 for (i = 0; i < shared_count; ++i) {
282 struct dma_fence *fence = rcu_dereference(fobj->shared[i]);
284 if (!dma_fence_get_rcu(fence)) {
286 * fence refcount dropped to zero, this means
287 * that fobj has been freed
289 * call dma_buf_poll_cb and force a recheck!
292 dma_buf_poll_cb(NULL, &dcb->cb);
295 if (!dma_fence_add_callback(fence, &dcb->cb,
297 dma_fence_put(fence);
301 dma_fence_put(fence);
304 /* No callback queued, wake up any additional waiters. */
305 if (i == shared_count)
306 dma_buf_poll_cb(NULL, &dcb->cb);
315 * dma_buf_set_name - Set a name to a specific dma_buf to track the usage.
316 * The name of the dma-buf buffer can only be set when the dma-buf is not
317 * attached to any devices. It could theoritically support changing the
318 * name of the dma-buf if the same piece of memory is used for multiple
319 * purpose between different devices.
321 * @dmabuf: [in] dmabuf buffer that will be renamed.
322 * @buf: [in] A piece of userspace memory that contains the name of
325 * Returns 0 on success. If the dma-buf buffer is already attached to
326 * devices, return -EBUSY.
329 static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf)
331 char *name = strndup_user(buf, DMA_BUF_NAME_LEN);
335 return PTR_ERR(name);
337 dma_resv_lock(dmabuf->resv, NULL);
338 if (!list_empty(&dmabuf->attachments)) {
343 spin_lock(&dmabuf->name_lock);
346 spin_unlock(&dmabuf->name_lock);
349 dma_resv_unlock(dmabuf->resv);
353 static long dma_buf_ioctl(struct file *file,
354 unsigned int cmd, unsigned long arg)
356 struct dma_buf *dmabuf;
357 struct dma_buf_sync sync;
358 enum dma_data_direction direction;
361 dmabuf = file->private_data;
364 case DMA_BUF_IOCTL_SYNC:
365 if (copy_from_user(&sync, (void __user *) arg, sizeof(sync)))
368 if (sync.flags & ~DMA_BUF_SYNC_VALID_FLAGS_MASK)
371 switch (sync.flags & DMA_BUF_SYNC_RW) {
372 case DMA_BUF_SYNC_READ:
373 direction = DMA_FROM_DEVICE;
375 case DMA_BUF_SYNC_WRITE:
376 direction = DMA_TO_DEVICE;
378 case DMA_BUF_SYNC_RW:
379 direction = DMA_BIDIRECTIONAL;
385 if (sync.flags & DMA_BUF_SYNC_END)
386 ret = dma_buf_end_cpu_access(dmabuf, direction);
388 ret = dma_buf_begin_cpu_access(dmabuf, direction);
392 case DMA_BUF_SET_NAME_A:
393 case DMA_BUF_SET_NAME_B:
394 return dma_buf_set_name(dmabuf, (const char __user *)arg);
401 static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file)
403 struct dma_buf *dmabuf = file->private_data;
405 seq_printf(m, "size:\t%zu\n", dmabuf->size);
406 /* Don't count the temporary reference taken inside procfs seq_show */
407 seq_printf(m, "count:\t%ld\n", file_count(dmabuf->file) - 1);
408 seq_printf(m, "exp_name:\t%s\n", dmabuf->exp_name);
409 spin_lock(&dmabuf->name_lock);
411 seq_printf(m, "name:\t%s\n", dmabuf->name);
412 spin_unlock(&dmabuf->name_lock);
415 static const struct file_operations dma_buf_fops = {
416 .mmap = dma_buf_mmap_internal,
417 .llseek = dma_buf_llseek,
418 .poll = dma_buf_poll,
419 .unlocked_ioctl = dma_buf_ioctl,
420 .compat_ioctl = compat_ptr_ioctl,
421 .show_fdinfo = dma_buf_show_fdinfo,
425 * is_dma_buf_file - Check if struct file* is associated with dma_buf
427 static inline int is_dma_buf_file(struct file *file)
429 return file->f_op == &dma_buf_fops;
432 static struct file *dma_buf_getfile(struct dma_buf *dmabuf, int flags)
435 struct inode *inode = alloc_anon_inode(dma_buf_mnt->mnt_sb);
438 return ERR_CAST(inode);
440 inode->i_size = dmabuf->size;
441 inode_set_bytes(inode, dmabuf->size);
443 file = alloc_file_pseudo(inode, dma_buf_mnt, "dmabuf",
444 flags, &dma_buf_fops);
447 file->f_flags = flags & (O_ACCMODE | O_NONBLOCK);
448 file->private_data = dmabuf;
449 file->f_path.dentry->d_fsdata = dmabuf;
459 * DOC: dma buf device access
461 * For device DMA access to a shared DMA buffer the usual sequence of operations
464 * 1. The exporter defines his exporter instance using
465 * DEFINE_DMA_BUF_EXPORT_INFO() and calls dma_buf_export() to wrap a private
466 * buffer object into a &dma_buf. It then exports that &dma_buf to userspace
467 * as a file descriptor by calling dma_buf_fd().
469 * 2. Userspace passes this file-descriptors to all drivers it wants this buffer
470 * to share with: First the filedescriptor is converted to a &dma_buf using
471 * dma_buf_get(). Then the buffer is attached to the device using
474 * Up to this stage the exporter is still free to migrate or reallocate the
477 * 3. Once the buffer is attached to all devices userspace can initiate DMA
478 * access to the shared buffer. In the kernel this is done by calling
479 * dma_buf_map_attachment() and dma_buf_unmap_attachment().
481 * 4. Once a driver is done with a shared buffer it needs to call
482 * dma_buf_detach() (after cleaning up any mappings) and then release the
483 * reference acquired with dma_buf_get by calling dma_buf_put().
485 * For the detailed semantics exporters are expected to implement see
490 * dma_buf_export - Creates a new dma_buf, and associates an anon file
491 * with this buffer, so it can be exported.
492 * Also connect the allocator specific data and ops to the buffer.
493 * Additionally, provide a name string for exporter; useful in debugging.
495 * @exp_info: [in] holds all the export related information provided
496 * by the exporter. see &struct dma_buf_export_info
497 * for further details.
499 * Returns, on success, a newly created dma_buf object, which wraps the
500 * supplied private data and operations for dma_buf_ops. On either missing
501 * ops, or error in allocating struct dma_buf, will return negative error.
503 * For most cases the easiest way to create @exp_info is through the
504 * %DEFINE_DMA_BUF_EXPORT_INFO macro.
506 struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
508 struct dma_buf *dmabuf;
509 struct dma_resv *resv = exp_info->resv;
511 size_t alloc_size = sizeof(struct dma_buf);
515 alloc_size += sizeof(struct dma_resv);
517 /* prevent &dma_buf[1] == dma_buf->resv */
520 if (WARN_ON(!exp_info->priv
522 || !exp_info->ops->map_dma_buf
523 || !exp_info->ops->unmap_dma_buf
524 || !exp_info->ops->release)) {
525 return ERR_PTR(-EINVAL);
528 if (WARN_ON(exp_info->ops->cache_sgt_mapping &&
529 (exp_info->ops->pin || exp_info->ops->unpin)))
530 return ERR_PTR(-EINVAL);
532 if (WARN_ON(!exp_info->ops->pin != !exp_info->ops->unpin))
533 return ERR_PTR(-EINVAL);
535 if (!try_module_get(exp_info->owner))
536 return ERR_PTR(-ENOENT);
538 dmabuf = kzalloc(alloc_size, GFP_KERNEL);
544 dmabuf->priv = exp_info->priv;
545 dmabuf->ops = exp_info->ops;
546 dmabuf->size = exp_info->size;
547 dmabuf->exp_name = exp_info->exp_name;
548 dmabuf->owner = exp_info->owner;
549 spin_lock_init(&dmabuf->name_lock);
550 init_waitqueue_head(&dmabuf->poll);
551 dmabuf->cb_excl.poll = dmabuf->cb_shared.poll = &dmabuf->poll;
552 dmabuf->cb_excl.active = dmabuf->cb_shared.active = 0;
555 resv = (struct dma_resv *)&dmabuf[1];
560 file = dma_buf_getfile(dmabuf, exp_info->flags);
566 file->f_mode |= FMODE_LSEEK;
569 mutex_init(&dmabuf->lock);
570 INIT_LIST_HEAD(&dmabuf->attachments);
572 mutex_lock(&db_list.lock);
573 list_add(&dmabuf->list_node, &db_list.head);
574 mutex_unlock(&db_list.lock);
581 module_put(exp_info->owner);
584 EXPORT_SYMBOL_GPL(dma_buf_export);
587 * dma_buf_fd - returns a file descriptor for the given dma_buf
588 * @dmabuf: [in] pointer to dma_buf for which fd is required.
589 * @flags: [in] flags to give to fd
591 * On success, returns an associated 'fd'. Else, returns error.
593 int dma_buf_fd(struct dma_buf *dmabuf, int flags)
597 if (!dmabuf || !dmabuf->file)
600 fd = get_unused_fd_flags(flags);
604 fd_install(fd, dmabuf->file);
608 EXPORT_SYMBOL_GPL(dma_buf_fd);
611 * dma_buf_get - returns the dma_buf structure related to an fd
612 * @fd: [in] fd associated with the dma_buf to be returned
614 * On success, returns the dma_buf structure associated with an fd; uses
615 * file's refcounting done by fget to increase refcount. returns ERR_PTR
618 struct dma_buf *dma_buf_get(int fd)
625 return ERR_PTR(-EBADF);
627 if (!is_dma_buf_file(file)) {
629 return ERR_PTR(-EINVAL);
632 return file->private_data;
634 EXPORT_SYMBOL_GPL(dma_buf_get);
637 * dma_buf_put - decreases refcount of the buffer
638 * @dmabuf: [in] buffer to reduce refcount of
640 * Uses file's refcounting done implicitly by fput().
642 * If, as a result of this call, the refcount becomes 0, the 'release' file
643 * operation related to this fd is called. It calls &dma_buf_ops.release vfunc
644 * in turn, and frees the memory allocated for dmabuf when exported.
646 void dma_buf_put(struct dma_buf *dmabuf)
648 if (WARN_ON(!dmabuf || !dmabuf->file))
653 EXPORT_SYMBOL_GPL(dma_buf_put);
656 * dma_buf_dynamic_attach - Add the device to dma_buf's attachments list; optionally,
657 * calls attach() of dma_buf_ops to allow device-specific attach functionality
658 * @dmabuf: [in] buffer to attach device to.
659 * @dev: [in] device to be attached.
660 * @importer_ops: [in] importer operations for the attachment
661 * @importer_priv: [in] importer private pointer for the attachment
663 * Returns struct dma_buf_attachment pointer for this attachment. Attachments
664 * must be cleaned up by calling dma_buf_detach().
668 * A pointer to newly created &dma_buf_attachment on success, or a negative
669 * error code wrapped into a pointer on failure.
671 * Note that this can fail if the backing storage of @dmabuf is in a place not
672 * accessible to @dev, and cannot be moved to a more suitable place. This is
673 * indicated with the error code -EBUSY.
675 struct dma_buf_attachment *
676 dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
677 const struct dma_buf_attach_ops *importer_ops,
680 struct dma_buf_attachment *attach;
683 if (WARN_ON(!dmabuf || !dev))
684 return ERR_PTR(-EINVAL);
686 if (WARN_ON(importer_ops && !importer_ops->move_notify))
687 return ERR_PTR(-EINVAL);
689 attach = kzalloc(sizeof(*attach), GFP_KERNEL);
691 return ERR_PTR(-ENOMEM);
694 attach->dmabuf = dmabuf;
696 attach->peer2peer = importer_ops->allow_peer2peer;
697 attach->importer_ops = importer_ops;
698 attach->importer_priv = importer_priv;
700 if (dmabuf->ops->attach) {
701 ret = dmabuf->ops->attach(dmabuf, attach);
705 dma_resv_lock(dmabuf->resv, NULL);
706 list_add(&attach->node, &dmabuf->attachments);
707 dma_resv_unlock(dmabuf->resv);
709 /* When either the importer or the exporter can't handle dynamic
710 * mappings we cache the mapping here to avoid issues with the
711 * reservation object lock.
713 if (dma_buf_attachment_is_dynamic(attach) !=
714 dma_buf_is_dynamic(dmabuf)) {
715 struct sg_table *sgt;
717 if (dma_buf_is_dynamic(attach->dmabuf)) {
718 dma_resv_lock(attach->dmabuf->resv, NULL);
719 ret = dma_buf_pin(attach);
724 sgt = dmabuf->ops->map_dma_buf(attach, DMA_BIDIRECTIONAL);
726 sgt = ERR_PTR(-ENOMEM);
731 if (dma_buf_is_dynamic(attach->dmabuf))
732 dma_resv_unlock(attach->dmabuf->resv);
734 attach->dir = DMA_BIDIRECTIONAL;
744 if (dma_buf_is_dynamic(attach->dmabuf))
745 dma_buf_unpin(attach);
748 if (dma_buf_is_dynamic(attach->dmabuf))
749 dma_resv_unlock(attach->dmabuf->resv);
751 dma_buf_detach(dmabuf, attach);
754 EXPORT_SYMBOL_GPL(dma_buf_dynamic_attach);
757 * dma_buf_attach - Wrapper for dma_buf_dynamic_attach
758 * @dmabuf: [in] buffer to attach device to.
759 * @dev: [in] device to be attached.
761 * Wrapper to call dma_buf_dynamic_attach() for drivers which still use a static
764 struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
767 return dma_buf_dynamic_attach(dmabuf, dev, NULL, NULL);
769 EXPORT_SYMBOL_GPL(dma_buf_attach);
772 * dma_buf_detach - Remove the given attachment from dmabuf's attachments list;
773 * optionally calls detach() of dma_buf_ops for device-specific detach
774 * @dmabuf: [in] buffer to detach from.
775 * @attach: [in] attachment to be detached; is free'd after this call.
777 * Clean up a device attachment obtained by calling dma_buf_attach().
779 void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
781 if (WARN_ON(!dmabuf || !attach))
785 if (dma_buf_is_dynamic(attach->dmabuf))
786 dma_resv_lock(attach->dmabuf->resv, NULL);
788 dmabuf->ops->unmap_dma_buf(attach, attach->sgt, attach->dir);
790 if (dma_buf_is_dynamic(attach->dmabuf)) {
791 dma_buf_unpin(attach);
792 dma_resv_unlock(attach->dmabuf->resv);
796 dma_resv_lock(dmabuf->resv, NULL);
797 list_del(&attach->node);
798 dma_resv_unlock(dmabuf->resv);
799 if (dmabuf->ops->detach)
800 dmabuf->ops->detach(dmabuf, attach);
804 EXPORT_SYMBOL_GPL(dma_buf_detach);
807 * dma_buf_pin - Lock down the DMA-buf
809 * @attach: [in] attachment which should be pinned
812 * 0 on success, negative error code on failure.
814 int dma_buf_pin(struct dma_buf_attachment *attach)
816 struct dma_buf *dmabuf = attach->dmabuf;
819 dma_resv_assert_held(dmabuf->resv);
821 if (dmabuf->ops->pin)
822 ret = dmabuf->ops->pin(attach);
826 EXPORT_SYMBOL_GPL(dma_buf_pin);
829 * dma_buf_unpin - Remove lock from DMA-buf
831 * @attach: [in] attachment which should be unpinned
833 void dma_buf_unpin(struct dma_buf_attachment *attach)
835 struct dma_buf *dmabuf = attach->dmabuf;
837 dma_resv_assert_held(dmabuf->resv);
839 if (dmabuf->ops->unpin)
840 dmabuf->ops->unpin(attach);
842 EXPORT_SYMBOL_GPL(dma_buf_unpin);
845 * dma_buf_map_attachment - Returns the scatterlist table of the attachment;
846 * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the
848 * @attach: [in] attachment whose scatterlist is to be returned
849 * @direction: [in] direction of DMA transfer
851 * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
852 * on error. May return -EINTR if it is interrupted by a signal.
854 * On success, the DMA addresses and lengths in the returned scatterlist are
857 * A mapping must be unmapped by using dma_buf_unmap_attachment(). Note that
858 * the underlying backing storage is pinned for as long as a mapping exists,
859 * therefore users/importers should not hold onto a mapping for undue amounts of
862 struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
863 enum dma_data_direction direction)
865 struct sg_table *sg_table;
870 if (WARN_ON(!attach || !attach->dmabuf))
871 return ERR_PTR(-EINVAL);
873 if (dma_buf_attachment_is_dynamic(attach))
874 dma_resv_assert_held(attach->dmabuf->resv);
878 * Two mappings with different directions for the same
879 * attachment are not allowed.
881 if (attach->dir != direction &&
882 attach->dir != DMA_BIDIRECTIONAL)
883 return ERR_PTR(-EBUSY);
888 if (dma_buf_is_dynamic(attach->dmabuf)) {
889 dma_resv_assert_held(attach->dmabuf->resv);
890 if (!IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY)) {
891 r = dma_buf_pin(attach);
897 sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
899 sg_table = ERR_PTR(-ENOMEM);
901 if (IS_ERR(sg_table) && dma_buf_is_dynamic(attach->dmabuf) &&
902 !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY))
903 dma_buf_unpin(attach);
905 if (!IS_ERR(sg_table) && attach->dmabuf->ops->cache_sgt_mapping) {
906 attach->sgt = sg_table;
907 attach->dir = direction;
910 #ifdef CONFIG_DMA_API_DEBUG
911 if (!IS_ERR(sg_table)) {
912 struct scatterlist *sg;
917 for_each_sgtable_dma_sg(sg_table, sg, i) {
918 addr = sg_dma_address(sg);
919 len = sg_dma_len(sg);
920 if (!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(len)) {
921 pr_debug("%s: addr %llx or len %x is not page aligned!\n",
922 __func__, addr, len);
926 #endif /* CONFIG_DMA_API_DEBUG */
930 EXPORT_SYMBOL_GPL(dma_buf_map_attachment);
933 * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might
934 * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of
936 * @attach: [in] attachment to unmap buffer from
937 * @sg_table: [in] scatterlist info of the buffer to unmap
938 * @direction: [in] direction of DMA transfer
940 * This unmaps a DMA mapping for @attached obtained by dma_buf_map_attachment().
942 void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
943 struct sg_table *sg_table,
944 enum dma_data_direction direction)
948 if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
951 if (dma_buf_attachment_is_dynamic(attach))
952 dma_resv_assert_held(attach->dmabuf->resv);
954 if (attach->sgt == sg_table)
957 if (dma_buf_is_dynamic(attach->dmabuf))
958 dma_resv_assert_held(attach->dmabuf->resv);
960 attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, direction);
962 if (dma_buf_is_dynamic(attach->dmabuf) &&
963 !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY))
964 dma_buf_unpin(attach);
966 EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment);
969 * dma_buf_move_notify - notify attachments that DMA-buf is moving
971 * @dmabuf: [in] buffer which is moving
973 * Informs all attachmenst that they need to destroy and recreated all their
976 void dma_buf_move_notify(struct dma_buf *dmabuf)
978 struct dma_buf_attachment *attach;
980 dma_resv_assert_held(dmabuf->resv);
982 list_for_each_entry(attach, &dmabuf->attachments, node)
983 if (attach->importer_ops)
984 attach->importer_ops->move_notify(attach);
986 EXPORT_SYMBOL_GPL(dma_buf_move_notify);
991 * There are mutliple reasons for supporting CPU access to a dma buffer object:
993 * - Fallback operations in the kernel, for example when a device is connected
994 * over USB and the kernel needs to shuffle the data around first before
995 * sending it away. Cache coherency is handled by braketing any transactions
996 * with calls to dma_buf_begin_cpu_access() and dma_buf_end_cpu_access()
999 * Since for most kernel internal dma-buf accesses need the entire buffer, a
1000 * vmap interface is introduced. Note that on very old 32-bit architectures
1001 * vmalloc space might be limited and result in vmap calls failing.
1004 * void \*dma_buf_vmap(struct dma_buf \*dmabuf)
1005 * void dma_buf_vunmap(struct dma_buf \*dmabuf, void \*vaddr)
1007 * The vmap call can fail if there is no vmap support in the exporter, or if
1008 * it runs out of vmalloc space. Fallback to kmap should be implemented. Note
1009 * that the dma-buf layer keeps a reference count for all vmap access and
1010 * calls down into the exporter's vmap function only when no vmapping exists,
1011 * and only unmaps it once. Protection against concurrent vmap/vunmap calls is
1012 * provided by taking the dma_buf->lock mutex.
1014 * - For full compatibility on the importer side with existing userspace
1015 * interfaces, which might already support mmap'ing buffers. This is needed in
1016 * many processing pipelines (e.g. feeding a software rendered image into a
1017 * hardware pipeline, thumbnail creation, snapshots, ...). Also, Android's ION
1018 * framework already supported this and for DMA buffer file descriptors to
1019 * replace ION buffers mmap support was needed.
1021 * There is no special interfaces, userspace simply calls mmap on the dma-buf
1022 * fd. But like for CPU access there's a need to braket the actual access,
1023 * which is handled by the ioctl (DMA_BUF_IOCTL_SYNC). Note that
1024 * DMA_BUF_IOCTL_SYNC can fail with -EAGAIN or -EINTR, in which case it must
1027 * Some systems might need some sort of cache coherency management e.g. when
1028 * CPU and GPU domains are being accessed through dma-buf at the same time.
1029 * To circumvent this problem there are begin/end coherency markers, that
1030 * forward directly to existing dma-buf device drivers vfunc hooks. Userspace
1031 * can make use of those markers through the DMA_BUF_IOCTL_SYNC ioctl. The
1032 * sequence would be used like following:
1035 * - for each drawing/upload cycle in CPU 1. SYNC_START ioctl, 2. read/write
1036 * to mmap area 3. SYNC_END ioctl. This can be repeated as often as you
1037 * want (with the new data being consumed by say the GPU or the scanout
1039 * - munmap once you don't need the buffer any more
1041 * For correctness and optimal performance, it is always required to use
1042 * SYNC_START and SYNC_END before and after, respectively, when accessing the
1043 * mapped address. Userspace cannot rely on coherent access, even when there
1044 * are systems where it just works without calling these ioctls.
1046 * - And as a CPU fallback in userspace processing pipelines.
1048 * Similar to the motivation for kernel cpu access it is again important that
1049 * the userspace code of a given importing subsystem can use the same
1050 * interfaces with a imported dma-buf buffer object as with a native buffer
1051 * object. This is especially important for drm where the userspace part of
1052 * contemporary OpenGL, X, and other drivers is huge, and reworking them to
1053 * use a different way to mmap a buffer rather invasive.
1055 * The assumption in the current dma-buf interfaces is that redirecting the
1056 * initial mmap is all that's needed. A survey of some of the existing
1057 * subsystems shows that no driver seems to do any nefarious thing like
1058 * syncing up with outstanding asynchronous processing on the device or
1059 * allocating special resources at fault time. So hopefully this is good
1060 * enough, since adding interfaces to intercept pagefaults and allow pte
1061 * shootdowns would increase the complexity quite a bit.
1064 * int dma_buf_mmap(struct dma_buf \*, struct vm_area_struct \*,
1067 * If the importing subsystem simply provides a special-purpose mmap call to
1068 * set up a mapping in userspace, calling do_mmap with dma_buf->file will
1069 * equally achieve that for a dma-buf object.
1072 static int __dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
1073 enum dma_data_direction direction)
1075 bool write = (direction == DMA_BIDIRECTIONAL ||
1076 direction == DMA_TO_DEVICE);
1077 struct dma_resv *resv = dmabuf->resv;
1080 /* Wait on any implicit rendering fences */
1081 ret = dma_resv_wait_timeout_rcu(resv, write, true,
1082 MAX_SCHEDULE_TIMEOUT);
1090 * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the
1091 * cpu in the kernel context. Calls begin_cpu_access to allow exporter-specific
1092 * preparations. Coherency is only guaranteed in the specified range for the
1093 * specified access direction.
1094 * @dmabuf: [in] buffer to prepare cpu access for.
1095 * @direction: [in] length of range for cpu access.
1097 * After the cpu access is complete the caller should call
1098 * dma_buf_end_cpu_access(). Only when cpu access is braketed by both calls is
1099 * it guaranteed to be coherent with other DMA access.
1101 * Can return negative error values, returns 0 on success.
1103 int dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
1104 enum dma_data_direction direction)
1108 if (WARN_ON(!dmabuf))
1111 if (dmabuf->ops->begin_cpu_access)
1112 ret = dmabuf->ops->begin_cpu_access(dmabuf, direction);
1114 /* Ensure that all fences are waited upon - but we first allow
1115 * the native handler the chance to do so more efficiently if it
1116 * chooses. A double invocation here will be reasonably cheap no-op.
1119 ret = __dma_buf_begin_cpu_access(dmabuf, direction);
1123 EXPORT_SYMBOL_GPL(dma_buf_begin_cpu_access);
1126 * dma_buf_end_cpu_access - Must be called after accessing a dma_buf from the
1127 * cpu in the kernel context. Calls end_cpu_access to allow exporter-specific
1128 * actions. Coherency is only guaranteed in the specified range for the
1129 * specified access direction.
1130 * @dmabuf: [in] buffer to complete cpu access for.
1131 * @direction: [in] length of range for cpu access.
1133 * This terminates CPU access started with dma_buf_begin_cpu_access().
1135 * Can return negative error values, returns 0 on success.
1137 int dma_buf_end_cpu_access(struct dma_buf *dmabuf,
1138 enum dma_data_direction direction)
1144 if (dmabuf->ops->end_cpu_access)
1145 ret = dmabuf->ops->end_cpu_access(dmabuf, direction);
1149 EXPORT_SYMBOL_GPL(dma_buf_end_cpu_access);
1153 * dma_buf_mmap - Setup up a userspace mmap with the given vma
1154 * @dmabuf: [in] buffer that should back the vma
1155 * @vma: [in] vma for the mmap
1156 * @pgoff: [in] offset in pages where this mmap should start within the
1159 * This function adjusts the passed in vma so that it points at the file of the
1160 * dma_buf operation. It also adjusts the starting pgoff and does bounds
1161 * checking on the size of the vma. Then it calls the exporters mmap function to
1162 * set up the mapping.
1164 * Can return negative error values, returns 0 on success.
1166 int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
1167 unsigned long pgoff)
1169 struct file *oldfile;
1172 if (WARN_ON(!dmabuf || !vma))
1175 /* check if buffer supports mmap */
1176 if (!dmabuf->ops->mmap)
1179 /* check for offset overflow */
1180 if (pgoff + vma_pages(vma) < pgoff)
1183 /* check for overflowing the buffer's size */
1184 if (pgoff + vma_pages(vma) >
1185 dmabuf->size >> PAGE_SHIFT)
1188 /* readjust the vma */
1189 get_file(dmabuf->file);
1190 oldfile = vma->vm_file;
1191 vma->vm_file = dmabuf->file;
1192 vma->vm_pgoff = pgoff;
1194 ret = dmabuf->ops->mmap(dmabuf, vma);
1196 /* restore old parameters on failure */
1197 vma->vm_file = oldfile;
1206 EXPORT_SYMBOL_GPL(dma_buf_mmap);
1209 * dma_buf_vmap - Create virtual mapping for the buffer object into kernel
1210 * address space. Same restrictions as for vmap and friends apply.
1211 * @dmabuf: [in] buffer to vmap
1212 * @map: [out] returns the vmap pointer
1214 * This call may fail due to lack of virtual mapping address space.
1215 * These calls are optional in drivers. The intended use for them
1216 * is for mapping objects linear in kernel space for high use objects.
1217 * Please attempt to use kmap/kunmap before thinking about these interfaces.
1219 * Returns 0 on success, or a negative errno code otherwise.
1221 int dma_buf_vmap(struct dma_buf *dmabuf, struct dma_buf_map *map)
1223 struct dma_buf_map ptr;
1226 dma_buf_map_clear(map);
1228 if (WARN_ON(!dmabuf))
1231 if (!dmabuf->ops->vmap)
1234 mutex_lock(&dmabuf->lock);
1235 if (dmabuf->vmapping_counter) {
1236 dmabuf->vmapping_counter++;
1237 BUG_ON(dma_buf_map_is_null(&dmabuf->vmap_ptr));
1238 *map = dmabuf->vmap_ptr;
1242 BUG_ON(dma_buf_map_is_set(&dmabuf->vmap_ptr));
1244 ret = dmabuf->ops->vmap(dmabuf, &ptr);
1245 if (WARN_ON_ONCE(ret))
1248 dmabuf->vmap_ptr = ptr;
1249 dmabuf->vmapping_counter = 1;
1251 *map = dmabuf->vmap_ptr;
1254 mutex_unlock(&dmabuf->lock);
1257 EXPORT_SYMBOL_GPL(dma_buf_vmap);
1260 * dma_buf_vunmap - Unmap a vmap obtained by dma_buf_vmap.
1261 * @dmabuf: [in] buffer to vunmap
1262 * @map: [in] vmap pointer to vunmap
1264 void dma_buf_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map)
1266 if (WARN_ON(!dmabuf))
1269 BUG_ON(dma_buf_map_is_null(&dmabuf->vmap_ptr));
1270 BUG_ON(dmabuf->vmapping_counter == 0);
1271 BUG_ON(!dma_buf_map_is_equal(&dmabuf->vmap_ptr, map));
1273 mutex_lock(&dmabuf->lock);
1274 if (--dmabuf->vmapping_counter == 0) {
1275 if (dmabuf->ops->vunmap)
1276 dmabuf->ops->vunmap(dmabuf, map);
1277 dma_buf_map_clear(&dmabuf->vmap_ptr);
1279 mutex_unlock(&dmabuf->lock);
1281 EXPORT_SYMBOL_GPL(dma_buf_vunmap);
1283 #ifdef CONFIG_DEBUG_FS
1284 static int dma_buf_debug_show(struct seq_file *s, void *unused)
1287 struct dma_buf *buf_obj;
1288 struct dma_buf_attachment *attach_obj;
1289 struct dma_resv *robj;
1290 struct dma_resv_list *fobj;
1291 struct dma_fence *fence;
1293 int count = 0, attach_count, shared_count, i;
1296 ret = mutex_lock_interruptible(&db_list.lock);
1301 seq_puts(s, "\nDma-buf Objects:\n");
1302 seq_printf(s, "%-8s\t%-8s\t%-8s\t%-8s\texp_name\t%-8s\n",
1303 "size", "flags", "mode", "count", "ino");
1305 list_for_each_entry(buf_obj, &db_list.head, list_node) {
1307 ret = dma_resv_lock_interruptible(buf_obj->resv, NULL);
1311 seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\t%08lu\t%s\n",
1313 buf_obj->file->f_flags, buf_obj->file->f_mode,
1314 file_count(buf_obj->file),
1316 file_inode(buf_obj->file)->i_ino,
1317 buf_obj->name ?: "");
1319 robj = buf_obj->resv;
1321 seq = read_seqcount_begin(&robj->seq);
1323 fobj = rcu_dereference(robj->fence);
1324 shared_count = fobj ? fobj->shared_count : 0;
1325 fence = rcu_dereference(robj->fence_excl);
1326 if (!read_seqcount_retry(&robj->seq, seq))
1332 seq_printf(s, "\tExclusive fence: %s %s %ssignalled\n",
1333 fence->ops->get_driver_name(fence),
1334 fence->ops->get_timeline_name(fence),
1335 dma_fence_is_signaled(fence) ? "" : "un");
1336 for (i = 0; i < shared_count; i++) {
1337 fence = rcu_dereference(fobj->shared[i]);
1338 if (!dma_fence_get_rcu(fence))
1340 seq_printf(s, "\tShared fence: %s %s %ssignalled\n",
1341 fence->ops->get_driver_name(fence),
1342 fence->ops->get_timeline_name(fence),
1343 dma_fence_is_signaled(fence) ? "" : "un");
1344 dma_fence_put(fence);
1348 seq_puts(s, "\tAttached Devices:\n");
1351 list_for_each_entry(attach_obj, &buf_obj->attachments, node) {
1352 seq_printf(s, "\t%s\n", dev_name(attach_obj->dev));
1355 dma_resv_unlock(buf_obj->resv);
1357 seq_printf(s, "Total %d devices attached\n\n",
1361 size += buf_obj->size;
1364 seq_printf(s, "\nTotal %d objects, %zu bytes\n", count, size);
1366 mutex_unlock(&db_list.lock);
1370 mutex_unlock(&db_list.lock);
1374 DEFINE_SHOW_ATTRIBUTE(dma_buf_debug);
1376 static struct dentry *dma_buf_debugfs_dir;
1378 static int dma_buf_init_debugfs(void)
1383 d = debugfs_create_dir("dma_buf", NULL);
1387 dma_buf_debugfs_dir = d;
1389 d = debugfs_create_file("bufinfo", S_IRUGO, dma_buf_debugfs_dir,
1390 NULL, &dma_buf_debug_fops);
1392 pr_debug("dma_buf: debugfs: failed to create node bufinfo\n");
1393 debugfs_remove_recursive(dma_buf_debugfs_dir);
1394 dma_buf_debugfs_dir = NULL;
1401 static void dma_buf_uninit_debugfs(void)
1403 debugfs_remove_recursive(dma_buf_debugfs_dir);
1406 static inline int dma_buf_init_debugfs(void)
1410 static inline void dma_buf_uninit_debugfs(void)
1415 static int __init dma_buf_init(void)
1417 dma_buf_mnt = kern_mount(&dma_buf_fs_type);
1418 if (IS_ERR(dma_buf_mnt))
1419 return PTR_ERR(dma_buf_mnt);
1421 mutex_init(&db_list.lock);
1422 INIT_LIST_HEAD(&db_list.head);
1423 dma_buf_init_debugfs();
1426 subsys_initcall(dma_buf_init);
1428 static void __exit dma_buf_deinit(void)
1430 dma_buf_uninit_debugfs();
1431 kern_unmount(dma_buf_mnt);
1433 __exitcall(dma_buf_deinit);