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;
63 BUG_ON(dmabuf->vmapping_counter);
66 * Any fences that a dma-buf poll can wait on should be signaled
67 * before releasing dma-buf. This is the responsibility of each
68 * driver that uses the reservation objects.
70 * If you hit this BUG() it means someone dropped their ref to the
71 * dma-buf while still having pending operation to the buffer.
73 BUG_ON(dmabuf->cb_shared.active || dmabuf->cb_excl.active);
75 dmabuf->ops->release(dmabuf);
77 mutex_lock(&db_list.lock);
78 list_del(&dmabuf->list_node);
79 mutex_unlock(&db_list.lock);
81 if (dmabuf->resv == (struct dma_resv *)&dmabuf[1])
82 dma_resv_fini(dmabuf->resv);
84 module_put(dmabuf->owner);
89 static const struct dentry_operations dma_buf_dentry_ops = {
90 .d_dname = dmabuffs_dname,
91 .d_release = dma_buf_release,
94 static struct vfsmount *dma_buf_mnt;
96 static int dma_buf_fs_init_context(struct fs_context *fc)
98 struct pseudo_fs_context *ctx;
100 ctx = init_pseudo(fc, DMA_BUF_MAGIC);
103 ctx->dops = &dma_buf_dentry_ops;
107 static struct file_system_type dma_buf_fs_type = {
109 .init_fs_context = dma_buf_fs_init_context,
110 .kill_sb = kill_anon_super,
113 static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
115 struct dma_buf *dmabuf;
117 if (!is_dma_buf_file(file))
120 dmabuf = file->private_data;
122 /* check if buffer supports mmap */
123 if (!dmabuf->ops->mmap)
126 /* check for overflowing the buffer's size */
127 if (vma->vm_pgoff + vma_pages(vma) >
128 dmabuf->size >> PAGE_SHIFT)
131 return dmabuf->ops->mmap(dmabuf, vma);
134 static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence)
136 struct dma_buf *dmabuf;
139 if (!is_dma_buf_file(file))
142 dmabuf = file->private_data;
144 /* only support discovering the end of the buffer,
145 but also allow SEEK_SET to maintain the idiomatic
146 SEEK_END(0), SEEK_CUR(0) pattern */
147 if (whence == SEEK_END)
149 else if (whence == SEEK_SET)
157 return base + offset;
161 * DOC: implicit fence polling
163 * To support cross-device and cross-driver synchronization of buffer access
164 * implicit fences (represented internally in the kernel with &struct dma_fence)
165 * can be attached to a &dma_buf. The glue for that and a few related things are
166 * provided in the &dma_resv structure.
168 * Userspace can query the state of these implicitly tracked fences using poll()
169 * and related system calls:
171 * - Checking for EPOLLIN, i.e. read access, can be use to query the state of the
172 * most recent write or exclusive fence.
174 * - Checking for EPOLLOUT, i.e. write access, can be used to query the state of
175 * all attached fences, shared and exclusive ones.
177 * Note that this only signals the completion of the respective fences, i.e. the
178 * DMA transfers are complete. Cache flushing and any other necessary
179 * preparations before CPU access can begin still need to happen.
182 static void dma_buf_poll_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
184 struct dma_buf_poll_cb_t *dcb = (struct dma_buf_poll_cb_t *)cb;
187 spin_lock_irqsave(&dcb->poll->lock, flags);
188 wake_up_locked_poll(dcb->poll, dcb->active);
190 spin_unlock_irqrestore(&dcb->poll->lock, flags);
193 static __poll_t dma_buf_poll(struct file *file, poll_table *poll)
195 struct dma_buf *dmabuf;
196 struct dma_resv *resv;
197 struct dma_resv_list *fobj;
198 struct dma_fence *fence_excl;
200 unsigned shared_count, seq;
202 dmabuf = file->private_data;
203 if (!dmabuf || !dmabuf->resv)
208 poll_wait(file, &dmabuf->poll, poll);
210 events = poll_requested_events(poll) & (EPOLLIN | EPOLLOUT);
215 seq = read_seqcount_begin(&resv->seq);
218 fobj = rcu_dereference(resv->fence);
220 shared_count = fobj->shared_count;
223 fence_excl = rcu_dereference(resv->fence_excl);
224 if (read_seqcount_retry(&resv->seq, seq)) {
229 if (fence_excl && (!(events & EPOLLOUT) || shared_count == 0)) {
230 struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_excl;
231 __poll_t pevents = EPOLLIN;
233 if (shared_count == 0)
236 spin_lock_irq(&dmabuf->poll.lock);
238 dcb->active |= pevents;
241 dcb->active = pevents;
242 spin_unlock_irq(&dmabuf->poll.lock);
244 if (events & pevents) {
245 if (!dma_fence_get_rcu(fence_excl)) {
246 /* force a recheck */
248 dma_buf_poll_cb(NULL, &dcb->cb);
249 } else if (!dma_fence_add_callback(fence_excl, &dcb->cb,
252 dma_fence_put(fence_excl);
255 * No callback queued, wake up any additional
258 dma_fence_put(fence_excl);
259 dma_buf_poll_cb(NULL, &dcb->cb);
264 if ((events & EPOLLOUT) && shared_count > 0) {
265 struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_shared;
268 /* Only queue a new callback if no event has fired yet */
269 spin_lock_irq(&dmabuf->poll.lock);
273 dcb->active = EPOLLOUT;
274 spin_unlock_irq(&dmabuf->poll.lock);
276 if (!(events & EPOLLOUT))
279 for (i = 0; i < shared_count; ++i) {
280 struct dma_fence *fence = rcu_dereference(fobj->shared[i]);
282 if (!dma_fence_get_rcu(fence)) {
284 * fence refcount dropped to zero, this means
285 * that fobj has been freed
287 * call dma_buf_poll_cb and force a recheck!
290 dma_buf_poll_cb(NULL, &dcb->cb);
293 if (!dma_fence_add_callback(fence, &dcb->cb,
295 dma_fence_put(fence);
299 dma_fence_put(fence);
302 /* No callback queued, wake up any additional waiters. */
303 if (i == shared_count)
304 dma_buf_poll_cb(NULL, &dcb->cb);
313 * dma_buf_set_name - Set a name to a specific dma_buf to track the usage.
314 * The name of the dma-buf buffer can only be set when the dma-buf is not
315 * attached to any devices. It could theoritically support changing the
316 * name of the dma-buf if the same piece of memory is used for multiple
317 * purpose between different devices.
319 * @dmabuf [in] dmabuf buffer that will be renamed.
320 * @buf: [in] A piece of userspace memory that contains the name of
323 * Returns 0 on success. If the dma-buf buffer is already attached to
324 * devices, return -EBUSY.
327 static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf)
329 char *name = strndup_user(buf, DMA_BUF_NAME_LEN);
333 return PTR_ERR(name);
335 dma_resv_lock(dmabuf->resv, NULL);
336 if (!list_empty(&dmabuf->attachments)) {
341 spin_lock(&dmabuf->name_lock);
344 spin_unlock(&dmabuf->name_lock);
347 dma_resv_unlock(dmabuf->resv);
351 static long dma_buf_ioctl(struct file *file,
352 unsigned int cmd, unsigned long arg)
354 struct dma_buf *dmabuf;
355 struct dma_buf_sync sync;
356 enum dma_data_direction direction;
359 dmabuf = file->private_data;
362 case DMA_BUF_IOCTL_SYNC:
363 if (copy_from_user(&sync, (void __user *) arg, sizeof(sync)))
366 if (sync.flags & ~DMA_BUF_SYNC_VALID_FLAGS_MASK)
369 switch (sync.flags & DMA_BUF_SYNC_RW) {
370 case DMA_BUF_SYNC_READ:
371 direction = DMA_FROM_DEVICE;
373 case DMA_BUF_SYNC_WRITE:
374 direction = DMA_TO_DEVICE;
376 case DMA_BUF_SYNC_RW:
377 direction = DMA_BIDIRECTIONAL;
383 if (sync.flags & DMA_BUF_SYNC_END)
384 ret = dma_buf_end_cpu_access(dmabuf, direction);
386 ret = dma_buf_begin_cpu_access(dmabuf, direction);
390 case DMA_BUF_SET_NAME_A:
391 case DMA_BUF_SET_NAME_B:
392 return dma_buf_set_name(dmabuf, (const char __user *)arg);
399 static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file)
401 struct dma_buf *dmabuf = file->private_data;
403 seq_printf(m, "size:\t%zu\n", dmabuf->size);
404 /* Don't count the temporary reference taken inside procfs seq_show */
405 seq_printf(m, "count:\t%ld\n", file_count(dmabuf->file) - 1);
406 seq_printf(m, "exp_name:\t%s\n", dmabuf->exp_name);
407 spin_lock(&dmabuf->name_lock);
409 seq_printf(m, "name:\t%s\n", dmabuf->name);
410 spin_unlock(&dmabuf->name_lock);
413 static const struct file_operations dma_buf_fops = {
414 .mmap = dma_buf_mmap_internal,
415 .llseek = dma_buf_llseek,
416 .poll = dma_buf_poll,
417 .unlocked_ioctl = dma_buf_ioctl,
418 .compat_ioctl = compat_ptr_ioctl,
419 .show_fdinfo = dma_buf_show_fdinfo,
423 * is_dma_buf_file - Check if struct file* is associated with dma_buf
425 static inline int is_dma_buf_file(struct file *file)
427 return file->f_op == &dma_buf_fops;
430 static struct file *dma_buf_getfile(struct dma_buf *dmabuf, int flags)
433 struct inode *inode = alloc_anon_inode(dma_buf_mnt->mnt_sb);
436 return ERR_CAST(inode);
438 inode->i_size = dmabuf->size;
439 inode_set_bytes(inode, dmabuf->size);
441 file = alloc_file_pseudo(inode, dma_buf_mnt, "dmabuf",
442 flags, &dma_buf_fops);
445 file->f_flags = flags & (O_ACCMODE | O_NONBLOCK);
446 file->private_data = dmabuf;
447 file->f_path.dentry->d_fsdata = dmabuf;
457 * DOC: dma buf device access
459 * For device DMA access to a shared DMA buffer the usual sequence of operations
462 * 1. The exporter defines his exporter instance using
463 * DEFINE_DMA_BUF_EXPORT_INFO() and calls dma_buf_export() to wrap a private
464 * buffer object into a &dma_buf. It then exports that &dma_buf to userspace
465 * as a file descriptor by calling dma_buf_fd().
467 * 2. Userspace passes this file-descriptors to all drivers it wants this buffer
468 * to share with: First the filedescriptor is converted to a &dma_buf using
469 * dma_buf_get(). Then the buffer is attached to the device using
472 * Up to this stage the exporter is still free to migrate or reallocate the
475 * 3. Once the buffer is attached to all devices userspace can initiate DMA
476 * access to the shared buffer. In the kernel this is done by calling
477 * dma_buf_map_attachment() and dma_buf_unmap_attachment().
479 * 4. Once a driver is done with a shared buffer it needs to call
480 * dma_buf_detach() (after cleaning up any mappings) and then release the
481 * reference acquired with dma_buf_get by calling dma_buf_put().
483 * For the detailed semantics exporters are expected to implement see
488 * dma_buf_export - Creates a new dma_buf, and associates an anon file
489 * with this buffer, so it can be exported.
490 * Also connect the allocator specific data and ops to the buffer.
491 * Additionally, provide a name string for exporter; useful in debugging.
493 * @exp_info: [in] holds all the export related information provided
494 * by the exporter. see &struct dma_buf_export_info
495 * for further details.
497 * Returns, on success, a newly created dma_buf object, which wraps the
498 * supplied private data and operations for dma_buf_ops. On either missing
499 * ops, or error in allocating struct dma_buf, will return negative error.
501 * For most cases the easiest way to create @exp_info is through the
502 * %DEFINE_DMA_BUF_EXPORT_INFO macro.
504 struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
506 struct dma_buf *dmabuf;
507 struct dma_resv *resv = exp_info->resv;
509 size_t alloc_size = sizeof(struct dma_buf);
513 alloc_size += sizeof(struct dma_resv);
515 /* prevent &dma_buf[1] == dma_buf->resv */
518 if (WARN_ON(!exp_info->priv
520 || !exp_info->ops->map_dma_buf
521 || !exp_info->ops->unmap_dma_buf
522 || !exp_info->ops->release)) {
523 return ERR_PTR(-EINVAL);
526 if (WARN_ON(exp_info->ops->cache_sgt_mapping &&
527 (exp_info->ops->pin || exp_info->ops->unpin)))
528 return ERR_PTR(-EINVAL);
530 if (WARN_ON(!exp_info->ops->pin != !exp_info->ops->unpin))
531 return ERR_PTR(-EINVAL);
533 if (!try_module_get(exp_info->owner))
534 return ERR_PTR(-ENOENT);
536 dmabuf = kzalloc(alloc_size, GFP_KERNEL);
542 dmabuf->priv = exp_info->priv;
543 dmabuf->ops = exp_info->ops;
544 dmabuf->size = exp_info->size;
545 dmabuf->exp_name = exp_info->exp_name;
546 dmabuf->owner = exp_info->owner;
547 spin_lock_init(&dmabuf->name_lock);
548 init_waitqueue_head(&dmabuf->poll);
549 dmabuf->cb_excl.poll = dmabuf->cb_shared.poll = &dmabuf->poll;
550 dmabuf->cb_excl.active = dmabuf->cb_shared.active = 0;
553 resv = (struct dma_resv *)&dmabuf[1];
558 file = dma_buf_getfile(dmabuf, exp_info->flags);
564 file->f_mode |= FMODE_LSEEK;
567 mutex_init(&dmabuf->lock);
568 INIT_LIST_HEAD(&dmabuf->attachments);
570 mutex_lock(&db_list.lock);
571 list_add(&dmabuf->list_node, &db_list.head);
572 mutex_unlock(&db_list.lock);
579 module_put(exp_info->owner);
582 EXPORT_SYMBOL_GPL(dma_buf_export);
585 * dma_buf_fd - returns a file descriptor for the given dma_buf
586 * @dmabuf: [in] pointer to dma_buf for which fd is required.
587 * @flags: [in] flags to give to fd
589 * On success, returns an associated 'fd'. Else, returns error.
591 int dma_buf_fd(struct dma_buf *dmabuf, int flags)
595 if (!dmabuf || !dmabuf->file)
598 fd = get_unused_fd_flags(flags);
602 fd_install(fd, dmabuf->file);
606 EXPORT_SYMBOL_GPL(dma_buf_fd);
609 * dma_buf_get - returns the dma_buf structure related to an fd
610 * @fd: [in] fd associated with the dma_buf to be returned
612 * On success, returns the dma_buf structure associated with an fd; uses
613 * file's refcounting done by fget to increase refcount. returns ERR_PTR
616 struct dma_buf *dma_buf_get(int fd)
623 return ERR_PTR(-EBADF);
625 if (!is_dma_buf_file(file)) {
627 return ERR_PTR(-EINVAL);
630 return file->private_data;
632 EXPORT_SYMBOL_GPL(dma_buf_get);
635 * dma_buf_put - decreases refcount of the buffer
636 * @dmabuf: [in] buffer to reduce refcount of
638 * Uses file's refcounting done implicitly by fput().
640 * If, as a result of this call, the refcount becomes 0, the 'release' file
641 * operation related to this fd is called. It calls &dma_buf_ops.release vfunc
642 * in turn, and frees the memory allocated for dmabuf when exported.
644 void dma_buf_put(struct dma_buf *dmabuf)
646 if (WARN_ON(!dmabuf || !dmabuf->file))
651 EXPORT_SYMBOL_GPL(dma_buf_put);
654 * dma_buf_dynamic_attach - Add the device to dma_buf's attachments list; optionally,
655 * calls attach() of dma_buf_ops to allow device-specific attach functionality
656 * @dmabuf: [in] buffer to attach device to.
657 * @dev: [in] device to be attached.
658 * @importer_ops: [in] importer operations for the attachment
659 * @importer_priv: [in] importer private pointer for the attachment
661 * Returns struct dma_buf_attachment pointer for this attachment. Attachments
662 * must be cleaned up by calling dma_buf_detach().
666 * A pointer to newly created &dma_buf_attachment on success, or a negative
667 * error code wrapped into a pointer on failure.
669 * Note that this can fail if the backing storage of @dmabuf is in a place not
670 * accessible to @dev, and cannot be moved to a more suitable place. This is
671 * indicated with the error code -EBUSY.
673 struct dma_buf_attachment *
674 dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
675 const struct dma_buf_attach_ops *importer_ops,
678 struct dma_buf_attachment *attach;
681 if (WARN_ON(!dmabuf || !dev))
682 return ERR_PTR(-EINVAL);
684 if (WARN_ON(importer_ops && !importer_ops->move_notify))
685 return ERR_PTR(-EINVAL);
687 attach = kzalloc(sizeof(*attach), GFP_KERNEL);
689 return ERR_PTR(-ENOMEM);
692 attach->dmabuf = dmabuf;
694 attach->peer2peer = importer_ops->allow_peer2peer;
695 attach->importer_ops = importer_ops;
696 attach->importer_priv = importer_priv;
698 if (dmabuf->ops->attach) {
699 ret = dmabuf->ops->attach(dmabuf, attach);
703 dma_resv_lock(dmabuf->resv, NULL);
704 list_add(&attach->node, &dmabuf->attachments);
705 dma_resv_unlock(dmabuf->resv);
707 /* When either the importer or the exporter can't handle dynamic
708 * mappings we cache the mapping here to avoid issues with the
709 * reservation object lock.
711 if (dma_buf_attachment_is_dynamic(attach) !=
712 dma_buf_is_dynamic(dmabuf)) {
713 struct sg_table *sgt;
715 if (dma_buf_is_dynamic(attach->dmabuf)) {
716 dma_resv_lock(attach->dmabuf->resv, NULL);
717 ret = dma_buf_pin(attach);
722 sgt = dmabuf->ops->map_dma_buf(attach, DMA_BIDIRECTIONAL);
724 sgt = ERR_PTR(-ENOMEM);
729 if (dma_buf_is_dynamic(attach->dmabuf))
730 dma_resv_unlock(attach->dmabuf->resv);
732 attach->dir = DMA_BIDIRECTIONAL;
742 if (dma_buf_is_dynamic(attach->dmabuf))
743 dma_buf_unpin(attach);
746 if (dma_buf_is_dynamic(attach->dmabuf))
747 dma_resv_unlock(attach->dmabuf->resv);
749 dma_buf_detach(dmabuf, attach);
752 EXPORT_SYMBOL_GPL(dma_buf_dynamic_attach);
755 * dma_buf_attach - Wrapper for dma_buf_dynamic_attach
756 * @dmabuf: [in] buffer to attach device to.
757 * @dev: [in] device to be attached.
759 * Wrapper to call dma_buf_dynamic_attach() for drivers which still use a static
762 struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
765 return dma_buf_dynamic_attach(dmabuf, dev, NULL, NULL);
767 EXPORT_SYMBOL_GPL(dma_buf_attach);
770 * dma_buf_detach - Remove the given attachment from dmabuf's attachments list;
771 * optionally calls detach() of dma_buf_ops for device-specific detach
772 * @dmabuf: [in] buffer to detach from.
773 * @attach: [in] attachment to be detached; is free'd after this call.
775 * Clean up a device attachment obtained by calling dma_buf_attach().
777 void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
779 if (WARN_ON(!dmabuf || !attach))
783 if (dma_buf_is_dynamic(attach->dmabuf))
784 dma_resv_lock(attach->dmabuf->resv, NULL);
786 dmabuf->ops->unmap_dma_buf(attach, attach->sgt, attach->dir);
788 if (dma_buf_is_dynamic(attach->dmabuf)) {
789 dma_buf_unpin(attach);
790 dma_resv_unlock(attach->dmabuf->resv);
794 dma_resv_lock(dmabuf->resv, NULL);
795 list_del(&attach->node);
796 dma_resv_unlock(dmabuf->resv);
797 if (dmabuf->ops->detach)
798 dmabuf->ops->detach(dmabuf, attach);
802 EXPORT_SYMBOL_GPL(dma_buf_detach);
805 * dma_buf_pin - Lock down the DMA-buf
807 * @attach: [in] attachment which should be pinned
810 * 0 on success, negative error code on failure.
812 int dma_buf_pin(struct dma_buf_attachment *attach)
814 struct dma_buf *dmabuf = attach->dmabuf;
817 dma_resv_assert_held(dmabuf->resv);
819 if (dmabuf->ops->pin)
820 ret = dmabuf->ops->pin(attach);
824 EXPORT_SYMBOL_GPL(dma_buf_pin);
827 * dma_buf_unpin - Remove lock from DMA-buf
829 * @attach: [in] attachment which should be unpinned
831 void dma_buf_unpin(struct dma_buf_attachment *attach)
833 struct dma_buf *dmabuf = attach->dmabuf;
835 dma_resv_assert_held(dmabuf->resv);
837 if (dmabuf->ops->unpin)
838 dmabuf->ops->unpin(attach);
840 EXPORT_SYMBOL_GPL(dma_buf_unpin);
843 * dma_buf_map_attachment - Returns the scatterlist table of the attachment;
844 * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the
846 * @attach: [in] attachment whose scatterlist is to be returned
847 * @direction: [in] direction of DMA transfer
849 * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
850 * on error. May return -EINTR if it is interrupted by a signal.
852 * A mapping must be unmapped by using dma_buf_unmap_attachment(). Note that
853 * the underlying backing storage is pinned for as long as a mapping exists,
854 * therefore users/importers should not hold onto a mapping for undue amounts of
857 struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
858 enum dma_data_direction direction)
860 struct sg_table *sg_table;
865 if (WARN_ON(!attach || !attach->dmabuf))
866 return ERR_PTR(-EINVAL);
868 if (dma_buf_attachment_is_dynamic(attach))
869 dma_resv_assert_held(attach->dmabuf->resv);
873 * Two mappings with different directions for the same
874 * attachment are not allowed.
876 if (attach->dir != direction &&
877 attach->dir != DMA_BIDIRECTIONAL)
878 return ERR_PTR(-EBUSY);
883 if (dma_buf_is_dynamic(attach->dmabuf)) {
884 dma_resv_assert_held(attach->dmabuf->resv);
885 if (!IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY)) {
886 r = dma_buf_pin(attach);
892 sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
894 sg_table = ERR_PTR(-ENOMEM);
896 if (IS_ERR(sg_table) && dma_buf_is_dynamic(attach->dmabuf) &&
897 !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY))
898 dma_buf_unpin(attach);
900 if (!IS_ERR(sg_table) && attach->dmabuf->ops->cache_sgt_mapping) {
901 attach->sgt = sg_table;
902 attach->dir = direction;
907 EXPORT_SYMBOL_GPL(dma_buf_map_attachment);
910 * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might
911 * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of
913 * @attach: [in] attachment to unmap buffer from
914 * @sg_table: [in] scatterlist info of the buffer to unmap
915 * @direction: [in] direction of DMA transfer
917 * This unmaps a DMA mapping for @attached obtained by dma_buf_map_attachment().
919 void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
920 struct sg_table *sg_table,
921 enum dma_data_direction direction)
925 if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
928 if (dma_buf_attachment_is_dynamic(attach))
929 dma_resv_assert_held(attach->dmabuf->resv);
931 if (attach->sgt == sg_table)
934 if (dma_buf_is_dynamic(attach->dmabuf))
935 dma_resv_assert_held(attach->dmabuf->resv);
937 attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, direction);
939 if (dma_buf_is_dynamic(attach->dmabuf) &&
940 !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY))
941 dma_buf_unpin(attach);
943 EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment);
946 * dma_buf_move_notify - notify attachments that DMA-buf is moving
948 * @dmabuf: [in] buffer which is moving
950 * Informs all attachmenst that they need to destroy and recreated all their
953 void dma_buf_move_notify(struct dma_buf *dmabuf)
955 struct dma_buf_attachment *attach;
957 dma_resv_assert_held(dmabuf->resv);
959 list_for_each_entry(attach, &dmabuf->attachments, node)
960 if (attach->importer_ops)
961 attach->importer_ops->move_notify(attach);
963 EXPORT_SYMBOL_GPL(dma_buf_move_notify);
968 * There are mutliple reasons for supporting CPU access to a dma buffer object:
970 * - Fallback operations in the kernel, for example when a device is connected
971 * over USB and the kernel needs to shuffle the data around first before
972 * sending it away. Cache coherency is handled by braketing any transactions
973 * with calls to dma_buf_begin_cpu_access() and dma_buf_end_cpu_access()
976 * Since for most kernel internal dma-buf accesses need the entire buffer, a
977 * vmap interface is introduced. Note that on very old 32-bit architectures
978 * vmalloc space might be limited and result in vmap calls failing.
981 * void \*dma_buf_vmap(struct dma_buf \*dmabuf)
982 * void dma_buf_vunmap(struct dma_buf \*dmabuf, void \*vaddr)
984 * The vmap call can fail if there is no vmap support in the exporter, or if
985 * it runs out of vmalloc space. Fallback to kmap should be implemented. Note
986 * that the dma-buf layer keeps a reference count for all vmap access and
987 * calls down into the exporter's vmap function only when no vmapping exists,
988 * and only unmaps it once. Protection against concurrent vmap/vunmap calls is
989 * provided by taking the dma_buf->lock mutex.
991 * - For full compatibility on the importer side with existing userspace
992 * interfaces, which might already support mmap'ing buffers. This is needed in
993 * many processing pipelines (e.g. feeding a software rendered image into a
994 * hardware pipeline, thumbnail creation, snapshots, ...). Also, Android's ION
995 * framework already supported this and for DMA buffer file descriptors to
996 * replace ION buffers mmap support was needed.
998 * There is no special interfaces, userspace simply calls mmap on the dma-buf
999 * fd. But like for CPU access there's a need to braket the actual access,
1000 * which is handled by the ioctl (DMA_BUF_IOCTL_SYNC). Note that
1001 * DMA_BUF_IOCTL_SYNC can fail with -EAGAIN or -EINTR, in which case it must
1004 * Some systems might need some sort of cache coherency management e.g. when
1005 * CPU and GPU domains are being accessed through dma-buf at the same time.
1006 * To circumvent this problem there are begin/end coherency markers, that
1007 * forward directly to existing dma-buf device drivers vfunc hooks. Userspace
1008 * can make use of those markers through the DMA_BUF_IOCTL_SYNC ioctl. The
1009 * sequence would be used like following:
1012 * - for each drawing/upload cycle in CPU 1. SYNC_START ioctl, 2. read/write
1013 * to mmap area 3. SYNC_END ioctl. This can be repeated as often as you
1014 * want (with the new data being consumed by say the GPU or the scanout
1016 * - munmap once you don't need the buffer any more
1018 * For correctness and optimal performance, it is always required to use
1019 * SYNC_START and SYNC_END before and after, respectively, when accessing the
1020 * mapped address. Userspace cannot rely on coherent access, even when there
1021 * are systems where it just works without calling these ioctls.
1023 * - And as a CPU fallback in userspace processing pipelines.
1025 * Similar to the motivation for kernel cpu access it is again important that
1026 * the userspace code of a given importing subsystem can use the same
1027 * interfaces with a imported dma-buf buffer object as with a native buffer
1028 * object. This is especially important for drm where the userspace part of
1029 * contemporary OpenGL, X, and other drivers is huge, and reworking them to
1030 * use a different way to mmap a buffer rather invasive.
1032 * The assumption in the current dma-buf interfaces is that redirecting the
1033 * initial mmap is all that's needed. A survey of some of the existing
1034 * subsystems shows that no driver seems to do any nefarious thing like
1035 * syncing up with outstanding asynchronous processing on the device or
1036 * allocating special resources at fault time. So hopefully this is good
1037 * enough, since adding interfaces to intercept pagefaults and allow pte
1038 * shootdowns would increase the complexity quite a bit.
1041 * int dma_buf_mmap(struct dma_buf \*, struct vm_area_struct \*,
1044 * If the importing subsystem simply provides a special-purpose mmap call to
1045 * set up a mapping in userspace, calling do_mmap with dma_buf->file will
1046 * equally achieve that for a dma-buf object.
1049 static int __dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
1050 enum dma_data_direction direction)
1052 bool write = (direction == DMA_BIDIRECTIONAL ||
1053 direction == DMA_TO_DEVICE);
1054 struct dma_resv *resv = dmabuf->resv;
1057 /* Wait on any implicit rendering fences */
1058 ret = dma_resv_wait_timeout_rcu(resv, write, true,
1059 MAX_SCHEDULE_TIMEOUT);
1067 * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the
1068 * cpu in the kernel context. Calls begin_cpu_access to allow exporter-specific
1069 * preparations. Coherency is only guaranteed in the specified range for the
1070 * specified access direction.
1071 * @dmabuf: [in] buffer to prepare cpu access for.
1072 * @direction: [in] length of range for cpu access.
1074 * After the cpu access is complete the caller should call
1075 * dma_buf_end_cpu_access(). Only when cpu access is braketed by both calls is
1076 * it guaranteed to be coherent with other DMA access.
1078 * Can return negative error values, returns 0 on success.
1080 int dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
1081 enum dma_data_direction direction)
1085 if (WARN_ON(!dmabuf))
1088 if (dmabuf->ops->begin_cpu_access)
1089 ret = dmabuf->ops->begin_cpu_access(dmabuf, direction);
1091 /* Ensure that all fences are waited upon - but we first allow
1092 * the native handler the chance to do so more efficiently if it
1093 * chooses. A double invocation here will be reasonably cheap no-op.
1096 ret = __dma_buf_begin_cpu_access(dmabuf, direction);
1100 EXPORT_SYMBOL_GPL(dma_buf_begin_cpu_access);
1103 * dma_buf_end_cpu_access - Must be called after accessing a dma_buf from the
1104 * cpu in the kernel context. Calls end_cpu_access to allow exporter-specific
1105 * actions. Coherency is only guaranteed in the specified range for the
1106 * specified access direction.
1107 * @dmabuf: [in] buffer to complete cpu access for.
1108 * @direction: [in] length of range for cpu access.
1110 * This terminates CPU access started with dma_buf_begin_cpu_access().
1112 * Can return negative error values, returns 0 on success.
1114 int dma_buf_end_cpu_access(struct dma_buf *dmabuf,
1115 enum dma_data_direction direction)
1121 if (dmabuf->ops->end_cpu_access)
1122 ret = dmabuf->ops->end_cpu_access(dmabuf, direction);
1126 EXPORT_SYMBOL_GPL(dma_buf_end_cpu_access);
1130 * dma_buf_mmap - Setup up a userspace mmap with the given vma
1131 * @dmabuf: [in] buffer that should back the vma
1132 * @vma: [in] vma for the mmap
1133 * @pgoff: [in] offset in pages where this mmap should start within the
1136 * This function adjusts the passed in vma so that it points at the file of the
1137 * dma_buf operation. It also adjusts the starting pgoff and does bounds
1138 * checking on the size of the vma. Then it calls the exporters mmap function to
1139 * set up the mapping.
1141 * Can return negative error values, returns 0 on success.
1143 int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
1144 unsigned long pgoff)
1146 struct file *oldfile;
1149 if (WARN_ON(!dmabuf || !vma))
1152 /* check if buffer supports mmap */
1153 if (!dmabuf->ops->mmap)
1156 /* check for offset overflow */
1157 if (pgoff + vma_pages(vma) < pgoff)
1160 /* check for overflowing the buffer's size */
1161 if (pgoff + vma_pages(vma) >
1162 dmabuf->size >> PAGE_SHIFT)
1165 /* readjust the vma */
1166 get_file(dmabuf->file);
1167 oldfile = vma->vm_file;
1168 vma->vm_file = dmabuf->file;
1169 vma->vm_pgoff = pgoff;
1171 ret = dmabuf->ops->mmap(dmabuf, vma);
1173 /* restore old parameters on failure */
1174 vma->vm_file = oldfile;
1183 EXPORT_SYMBOL_GPL(dma_buf_mmap);
1186 * dma_buf_vmap - Create virtual mapping for the buffer object into kernel
1187 * address space. Same restrictions as for vmap and friends apply.
1188 * @dmabuf: [in] buffer to vmap
1190 * This call may fail due to lack of virtual mapping address space.
1191 * These calls are optional in drivers. The intended use for them
1192 * is for mapping objects linear in kernel space for high use objects.
1193 * Please attempt to use kmap/kunmap before thinking about these interfaces.
1195 * Returns NULL on error.
1197 void *dma_buf_vmap(struct dma_buf *dmabuf)
1201 if (WARN_ON(!dmabuf))
1204 if (!dmabuf->ops->vmap)
1207 mutex_lock(&dmabuf->lock);
1208 if (dmabuf->vmapping_counter) {
1209 dmabuf->vmapping_counter++;
1210 BUG_ON(!dmabuf->vmap_ptr);
1211 ptr = dmabuf->vmap_ptr;
1215 BUG_ON(dmabuf->vmap_ptr);
1217 ptr = dmabuf->ops->vmap(dmabuf);
1218 if (WARN_ON_ONCE(IS_ERR(ptr)))
1223 dmabuf->vmap_ptr = ptr;
1224 dmabuf->vmapping_counter = 1;
1227 mutex_unlock(&dmabuf->lock);
1230 EXPORT_SYMBOL_GPL(dma_buf_vmap);
1233 * dma_buf_vunmap - Unmap a vmap obtained by dma_buf_vmap.
1234 * @dmabuf: [in] buffer to vunmap
1235 * @vaddr: [in] vmap to vunmap
1237 void dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr)
1239 if (WARN_ON(!dmabuf))
1242 BUG_ON(!dmabuf->vmap_ptr);
1243 BUG_ON(dmabuf->vmapping_counter == 0);
1244 BUG_ON(dmabuf->vmap_ptr != vaddr);
1246 mutex_lock(&dmabuf->lock);
1247 if (--dmabuf->vmapping_counter == 0) {
1248 if (dmabuf->ops->vunmap)
1249 dmabuf->ops->vunmap(dmabuf, vaddr);
1250 dmabuf->vmap_ptr = NULL;
1252 mutex_unlock(&dmabuf->lock);
1254 EXPORT_SYMBOL_GPL(dma_buf_vunmap);
1256 #ifdef CONFIG_DEBUG_FS
1257 static int dma_buf_debug_show(struct seq_file *s, void *unused)
1260 struct dma_buf *buf_obj;
1261 struct dma_buf_attachment *attach_obj;
1262 struct dma_resv *robj;
1263 struct dma_resv_list *fobj;
1264 struct dma_fence *fence;
1266 int count = 0, attach_count, shared_count, i;
1269 ret = mutex_lock_interruptible(&db_list.lock);
1274 seq_puts(s, "\nDma-buf Objects:\n");
1275 seq_printf(s, "%-8s\t%-8s\t%-8s\t%-8s\texp_name\t%-8s\n",
1276 "size", "flags", "mode", "count", "ino");
1278 list_for_each_entry(buf_obj, &db_list.head, list_node) {
1280 ret = dma_resv_lock_interruptible(buf_obj->resv, NULL);
1284 seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\t%08lu\t%s\n",
1286 buf_obj->file->f_flags, buf_obj->file->f_mode,
1287 file_count(buf_obj->file),
1289 file_inode(buf_obj->file)->i_ino,
1290 buf_obj->name ?: "");
1292 robj = buf_obj->resv;
1294 seq = read_seqcount_begin(&robj->seq);
1296 fobj = rcu_dereference(robj->fence);
1297 shared_count = fobj ? fobj->shared_count : 0;
1298 fence = rcu_dereference(robj->fence_excl);
1299 if (!read_seqcount_retry(&robj->seq, seq))
1305 seq_printf(s, "\tExclusive fence: %s %s %ssignalled\n",
1306 fence->ops->get_driver_name(fence),
1307 fence->ops->get_timeline_name(fence),
1308 dma_fence_is_signaled(fence) ? "" : "un");
1309 for (i = 0; i < shared_count; i++) {
1310 fence = rcu_dereference(fobj->shared[i]);
1311 if (!dma_fence_get_rcu(fence))
1313 seq_printf(s, "\tShared fence: %s %s %ssignalled\n",
1314 fence->ops->get_driver_name(fence),
1315 fence->ops->get_timeline_name(fence),
1316 dma_fence_is_signaled(fence) ? "" : "un");
1317 dma_fence_put(fence);
1321 seq_puts(s, "\tAttached Devices:\n");
1324 list_for_each_entry(attach_obj, &buf_obj->attachments, node) {
1325 seq_printf(s, "\t%s\n", dev_name(attach_obj->dev));
1328 dma_resv_unlock(buf_obj->resv);
1330 seq_printf(s, "Total %d devices attached\n\n",
1334 size += buf_obj->size;
1337 seq_printf(s, "\nTotal %d objects, %zu bytes\n", count, size);
1339 mutex_unlock(&db_list.lock);
1343 mutex_unlock(&db_list.lock);
1347 DEFINE_SHOW_ATTRIBUTE(dma_buf_debug);
1349 static struct dentry *dma_buf_debugfs_dir;
1351 static int dma_buf_init_debugfs(void)
1356 d = debugfs_create_dir("dma_buf", NULL);
1360 dma_buf_debugfs_dir = d;
1362 d = debugfs_create_file("bufinfo", S_IRUGO, dma_buf_debugfs_dir,
1363 NULL, &dma_buf_debug_fops);
1365 pr_debug("dma_buf: debugfs: failed to create node bufinfo\n");
1366 debugfs_remove_recursive(dma_buf_debugfs_dir);
1367 dma_buf_debugfs_dir = NULL;
1374 static void dma_buf_uninit_debugfs(void)
1376 debugfs_remove_recursive(dma_buf_debugfs_dir);
1379 static inline int dma_buf_init_debugfs(void)
1383 static inline void dma_buf_uninit_debugfs(void)
1388 static int __init dma_buf_init(void)
1390 dma_buf_mnt = kern_mount(&dma_buf_fs_type);
1391 if (IS_ERR(dma_buf_mnt))
1392 return PTR_ERR(dma_buf_mnt);
1394 mutex_init(&db_list.lock);
1395 INIT_LIST_HEAD(&db_list.head);
1396 dma_buf_init_debugfs();
1399 subsys_initcall(dma_buf_init);
1401 static void __exit dma_buf_deinit(void)
1403 dma_buf_uninit_debugfs();
1404 kern_unmount(dma_buf_mnt);
1406 __exitcall(dma_buf_deinit);