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 if (dmabuf->resv == (struct dma_resv *)&dmabuf[1])
80 dma_resv_fini(dmabuf->resv);
82 module_put(dmabuf->owner);
87 static int dma_buf_file_release(struct inode *inode, struct file *file)
89 struct dma_buf *dmabuf;
91 if (!is_dma_buf_file(file))
94 dmabuf = file->private_data;
96 mutex_lock(&db_list.lock);
97 list_del(&dmabuf->list_node);
98 mutex_unlock(&db_list.lock);
103 static const struct dentry_operations dma_buf_dentry_ops = {
104 .d_dname = dmabuffs_dname,
105 .d_release = dma_buf_release,
108 static struct vfsmount *dma_buf_mnt;
110 static int dma_buf_fs_init_context(struct fs_context *fc)
112 struct pseudo_fs_context *ctx;
114 ctx = init_pseudo(fc, DMA_BUF_MAGIC);
117 ctx->dops = &dma_buf_dentry_ops;
121 static struct file_system_type dma_buf_fs_type = {
123 .init_fs_context = dma_buf_fs_init_context,
124 .kill_sb = kill_anon_super,
127 static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
129 struct dma_buf *dmabuf;
131 if (!is_dma_buf_file(file))
134 dmabuf = file->private_data;
136 /* check if buffer supports mmap */
137 if (!dmabuf->ops->mmap)
140 /* check for overflowing the buffer's size */
141 if (vma->vm_pgoff + vma_pages(vma) >
142 dmabuf->size >> PAGE_SHIFT)
145 return dmabuf->ops->mmap(dmabuf, vma);
148 static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence)
150 struct dma_buf *dmabuf;
153 if (!is_dma_buf_file(file))
156 dmabuf = file->private_data;
158 /* only support discovering the end of the buffer,
159 but also allow SEEK_SET to maintain the idiomatic
160 SEEK_END(0), SEEK_CUR(0) pattern */
161 if (whence == SEEK_END)
163 else if (whence == SEEK_SET)
171 return base + offset;
175 * DOC: implicit fence polling
177 * To support cross-device and cross-driver synchronization of buffer access
178 * implicit fences (represented internally in the kernel with &struct dma_fence)
179 * can be attached to a &dma_buf. The glue for that and a few related things are
180 * provided in the &dma_resv structure.
182 * Userspace can query the state of these implicitly tracked fences using poll()
183 * and related system calls:
185 * - Checking for EPOLLIN, i.e. read access, can be use to query the state of the
186 * most recent write or exclusive fence.
188 * - Checking for EPOLLOUT, i.e. write access, can be used to query the state of
189 * all attached fences, shared and exclusive ones.
191 * Note that this only signals the completion of the respective fences, i.e. the
192 * DMA transfers are complete. Cache flushing and any other necessary
193 * preparations before CPU access can begin still need to happen.
196 static void dma_buf_poll_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
198 struct dma_buf_poll_cb_t *dcb = (struct dma_buf_poll_cb_t *)cb;
201 spin_lock_irqsave(&dcb->poll->lock, flags);
202 wake_up_locked_poll(dcb->poll, dcb->active);
204 spin_unlock_irqrestore(&dcb->poll->lock, flags);
207 static __poll_t dma_buf_poll(struct file *file, poll_table *poll)
209 struct dma_buf *dmabuf;
210 struct dma_resv *resv;
211 struct dma_resv_list *fobj;
212 struct dma_fence *fence_excl;
214 unsigned shared_count, seq;
216 dmabuf = file->private_data;
217 if (!dmabuf || !dmabuf->resv)
222 poll_wait(file, &dmabuf->poll, poll);
224 events = poll_requested_events(poll) & (EPOLLIN | EPOLLOUT);
229 seq = read_seqcount_begin(&resv->seq);
232 fobj = rcu_dereference(resv->fence);
234 shared_count = fobj->shared_count;
237 fence_excl = rcu_dereference(resv->fence_excl);
238 if (read_seqcount_retry(&resv->seq, seq)) {
243 if (fence_excl && (!(events & EPOLLOUT) || shared_count == 0)) {
244 struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_excl;
245 __poll_t pevents = EPOLLIN;
247 if (shared_count == 0)
250 spin_lock_irq(&dmabuf->poll.lock);
252 dcb->active |= pevents;
255 dcb->active = pevents;
256 spin_unlock_irq(&dmabuf->poll.lock);
258 if (events & pevents) {
259 if (!dma_fence_get_rcu(fence_excl)) {
260 /* force a recheck */
262 dma_buf_poll_cb(NULL, &dcb->cb);
263 } else if (!dma_fence_add_callback(fence_excl, &dcb->cb,
266 dma_fence_put(fence_excl);
269 * No callback queued, wake up any additional
272 dma_fence_put(fence_excl);
273 dma_buf_poll_cb(NULL, &dcb->cb);
278 if ((events & EPOLLOUT) && shared_count > 0) {
279 struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_shared;
282 /* Only queue a new callback if no event has fired yet */
283 spin_lock_irq(&dmabuf->poll.lock);
287 dcb->active = EPOLLOUT;
288 spin_unlock_irq(&dmabuf->poll.lock);
290 if (!(events & EPOLLOUT))
293 for (i = 0; i < shared_count; ++i) {
294 struct dma_fence *fence = rcu_dereference(fobj->shared[i]);
296 if (!dma_fence_get_rcu(fence)) {
298 * fence refcount dropped to zero, this means
299 * that fobj has been freed
301 * call dma_buf_poll_cb and force a recheck!
304 dma_buf_poll_cb(NULL, &dcb->cb);
307 if (!dma_fence_add_callback(fence, &dcb->cb,
309 dma_fence_put(fence);
313 dma_fence_put(fence);
316 /* No callback queued, wake up any additional waiters. */
317 if (i == shared_count)
318 dma_buf_poll_cb(NULL, &dcb->cb);
327 * dma_buf_set_name - Set a name to a specific dma_buf to track the usage.
328 * The name of the dma-buf buffer can only be set when the dma-buf is not
329 * attached to any devices. It could theoritically support changing the
330 * name of the dma-buf if the same piece of memory is used for multiple
331 * purpose between different devices.
333 * @dmabuf: [in] dmabuf buffer that will be renamed.
334 * @buf: [in] A piece of userspace memory that contains the name of
337 * Returns 0 on success. If the dma-buf buffer is already attached to
338 * devices, return -EBUSY.
341 static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf)
343 char *name = strndup_user(buf, DMA_BUF_NAME_LEN);
347 return PTR_ERR(name);
349 dma_resv_lock(dmabuf->resv, NULL);
350 if (!list_empty(&dmabuf->attachments)) {
355 spin_lock(&dmabuf->name_lock);
358 spin_unlock(&dmabuf->name_lock);
361 dma_resv_unlock(dmabuf->resv);
365 static long dma_buf_ioctl(struct file *file,
366 unsigned int cmd, unsigned long arg)
368 struct dma_buf *dmabuf;
369 struct dma_buf_sync sync;
370 enum dma_data_direction direction;
373 dmabuf = file->private_data;
376 case DMA_BUF_IOCTL_SYNC:
377 if (copy_from_user(&sync, (void __user *) arg, sizeof(sync)))
380 if (sync.flags & ~DMA_BUF_SYNC_VALID_FLAGS_MASK)
383 switch (sync.flags & DMA_BUF_SYNC_RW) {
384 case DMA_BUF_SYNC_READ:
385 direction = DMA_FROM_DEVICE;
387 case DMA_BUF_SYNC_WRITE:
388 direction = DMA_TO_DEVICE;
390 case DMA_BUF_SYNC_RW:
391 direction = DMA_BIDIRECTIONAL;
397 if (sync.flags & DMA_BUF_SYNC_END)
398 ret = dma_buf_end_cpu_access(dmabuf, direction);
400 ret = dma_buf_begin_cpu_access(dmabuf, direction);
404 case DMA_BUF_SET_NAME_A:
405 case DMA_BUF_SET_NAME_B:
406 return dma_buf_set_name(dmabuf, (const char __user *)arg);
413 static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file)
415 struct dma_buf *dmabuf = file->private_data;
417 seq_printf(m, "size:\t%zu\n", dmabuf->size);
418 /* Don't count the temporary reference taken inside procfs seq_show */
419 seq_printf(m, "count:\t%ld\n", file_count(dmabuf->file) - 1);
420 seq_printf(m, "exp_name:\t%s\n", dmabuf->exp_name);
421 spin_lock(&dmabuf->name_lock);
423 seq_printf(m, "name:\t%s\n", dmabuf->name);
424 spin_unlock(&dmabuf->name_lock);
427 static const struct file_operations dma_buf_fops = {
428 .release = dma_buf_file_release,
429 .mmap = dma_buf_mmap_internal,
430 .llseek = dma_buf_llseek,
431 .poll = dma_buf_poll,
432 .unlocked_ioctl = dma_buf_ioctl,
433 .compat_ioctl = compat_ptr_ioctl,
434 .show_fdinfo = dma_buf_show_fdinfo,
438 * is_dma_buf_file - Check if struct file* is associated with dma_buf
440 static inline int is_dma_buf_file(struct file *file)
442 return file->f_op == &dma_buf_fops;
445 static struct file *dma_buf_getfile(struct dma_buf *dmabuf, int flags)
448 struct inode *inode = alloc_anon_inode(dma_buf_mnt->mnt_sb);
451 return ERR_CAST(inode);
453 inode->i_size = dmabuf->size;
454 inode_set_bytes(inode, dmabuf->size);
456 file = alloc_file_pseudo(inode, dma_buf_mnt, "dmabuf",
457 flags, &dma_buf_fops);
460 file->f_flags = flags & (O_ACCMODE | O_NONBLOCK);
461 file->private_data = dmabuf;
462 file->f_path.dentry->d_fsdata = dmabuf;
472 * DOC: dma buf device access
474 * For device DMA access to a shared DMA buffer the usual sequence of operations
477 * 1. The exporter defines his exporter instance using
478 * DEFINE_DMA_BUF_EXPORT_INFO() and calls dma_buf_export() to wrap a private
479 * buffer object into a &dma_buf. It then exports that &dma_buf to userspace
480 * as a file descriptor by calling dma_buf_fd().
482 * 2. Userspace passes this file-descriptors to all drivers it wants this buffer
483 * to share with: First the filedescriptor is converted to a &dma_buf using
484 * dma_buf_get(). Then the buffer is attached to the device using
487 * Up to this stage the exporter is still free to migrate or reallocate the
490 * 3. Once the buffer is attached to all devices userspace can initiate DMA
491 * access to the shared buffer. In the kernel this is done by calling
492 * dma_buf_map_attachment() and dma_buf_unmap_attachment().
494 * 4. Once a driver is done with a shared buffer it needs to call
495 * dma_buf_detach() (after cleaning up any mappings) and then release the
496 * reference acquired with dma_buf_get() by calling dma_buf_put().
498 * For the detailed semantics exporters are expected to implement see
503 * dma_buf_export - Creates a new dma_buf, and associates an anon file
504 * with this buffer, so it can be exported.
505 * Also connect the allocator specific data and ops to the buffer.
506 * Additionally, provide a name string for exporter; useful in debugging.
508 * @exp_info: [in] holds all the export related information provided
509 * by the exporter. see &struct dma_buf_export_info
510 * for further details.
512 * Returns, on success, a newly created struct dma_buf object, which wraps the
513 * supplied private data and operations for struct dma_buf_ops. On either
514 * missing ops, or error in allocating struct dma_buf, will return negative
517 * For most cases the easiest way to create @exp_info is through the
518 * %DEFINE_DMA_BUF_EXPORT_INFO macro.
520 struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
522 struct dma_buf *dmabuf;
523 struct dma_resv *resv = exp_info->resv;
525 size_t alloc_size = sizeof(struct dma_buf);
529 alloc_size += sizeof(struct dma_resv);
531 /* prevent &dma_buf[1] == dma_buf->resv */
534 if (WARN_ON(!exp_info->priv
536 || !exp_info->ops->map_dma_buf
537 || !exp_info->ops->unmap_dma_buf
538 || !exp_info->ops->release)) {
539 return ERR_PTR(-EINVAL);
542 if (WARN_ON(exp_info->ops->cache_sgt_mapping &&
543 (exp_info->ops->pin || exp_info->ops->unpin)))
544 return ERR_PTR(-EINVAL);
546 if (WARN_ON(!exp_info->ops->pin != !exp_info->ops->unpin))
547 return ERR_PTR(-EINVAL);
549 if (!try_module_get(exp_info->owner))
550 return ERR_PTR(-ENOENT);
552 dmabuf = kzalloc(alloc_size, GFP_KERNEL);
558 dmabuf->priv = exp_info->priv;
559 dmabuf->ops = exp_info->ops;
560 dmabuf->size = exp_info->size;
561 dmabuf->exp_name = exp_info->exp_name;
562 dmabuf->owner = exp_info->owner;
563 spin_lock_init(&dmabuf->name_lock);
564 init_waitqueue_head(&dmabuf->poll);
565 dmabuf->cb_excl.poll = dmabuf->cb_shared.poll = &dmabuf->poll;
566 dmabuf->cb_excl.active = dmabuf->cb_shared.active = 0;
569 resv = (struct dma_resv *)&dmabuf[1];
574 file = dma_buf_getfile(dmabuf, exp_info->flags);
580 file->f_mode |= FMODE_LSEEK;
583 mutex_init(&dmabuf->lock);
584 INIT_LIST_HEAD(&dmabuf->attachments);
586 mutex_lock(&db_list.lock);
587 list_add(&dmabuf->list_node, &db_list.head);
588 mutex_unlock(&db_list.lock);
595 module_put(exp_info->owner);
598 EXPORT_SYMBOL_GPL(dma_buf_export);
601 * dma_buf_fd - returns a file descriptor for the given struct dma_buf
602 * @dmabuf: [in] pointer to dma_buf for which fd is required.
603 * @flags: [in] flags to give to fd
605 * On success, returns an associated 'fd'. Else, returns error.
607 int dma_buf_fd(struct dma_buf *dmabuf, int flags)
611 if (!dmabuf || !dmabuf->file)
614 fd = get_unused_fd_flags(flags);
618 fd_install(fd, dmabuf->file);
622 EXPORT_SYMBOL_GPL(dma_buf_fd);
625 * dma_buf_get - returns the struct dma_buf related to an fd
626 * @fd: [in] fd associated with the struct dma_buf to be returned
628 * On success, returns the struct dma_buf associated with an fd; uses
629 * file's refcounting done by fget to increase refcount. returns ERR_PTR
632 struct dma_buf *dma_buf_get(int fd)
639 return ERR_PTR(-EBADF);
641 if (!is_dma_buf_file(file)) {
643 return ERR_PTR(-EINVAL);
646 return file->private_data;
648 EXPORT_SYMBOL_GPL(dma_buf_get);
651 * dma_buf_put - decreases refcount of the buffer
652 * @dmabuf: [in] buffer to reduce refcount of
654 * Uses file's refcounting done implicitly by fput().
656 * If, as a result of this call, the refcount becomes 0, the 'release' file
657 * operation related to this fd is called. It calls &dma_buf_ops.release vfunc
658 * in turn, and frees the memory allocated for dmabuf when exported.
660 void dma_buf_put(struct dma_buf *dmabuf)
662 if (WARN_ON(!dmabuf || !dmabuf->file))
667 EXPORT_SYMBOL_GPL(dma_buf_put);
669 static void mangle_sg_table(struct sg_table *sg_table)
671 #ifdef CONFIG_DMABUF_DEBUG
673 struct scatterlist *sg;
675 /* To catch abuse of the underlying struct page by importers mix
676 * up the bits, but take care to preserve the low SG_ bits to
677 * not corrupt the sgt. The mixing is undone in __unmap_dma_buf
678 * before passing the sgt back to the exporter. */
679 for_each_sgtable_sg(sg_table, sg, i)
680 sg->page_link ^= ~0xffUL;
684 static struct sg_table * __map_dma_buf(struct dma_buf_attachment *attach,
685 enum dma_data_direction direction)
687 struct sg_table *sg_table;
689 sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
691 if (!IS_ERR_OR_NULL(sg_table))
692 mangle_sg_table(sg_table);
698 * dma_buf_dynamic_attach - Add the device to dma_buf's attachments list
699 * @dmabuf: [in] buffer to attach device to.
700 * @dev: [in] device to be attached.
701 * @importer_ops: [in] importer operations for the attachment
702 * @importer_priv: [in] importer private pointer for the attachment
704 * Returns struct dma_buf_attachment pointer for this attachment. Attachments
705 * must be cleaned up by calling dma_buf_detach().
707 * Optionally this calls &dma_buf_ops.attach to allow device-specific attach
712 * A pointer to newly created &dma_buf_attachment on success, or a negative
713 * error code wrapped into a pointer on failure.
715 * Note that this can fail if the backing storage of @dmabuf is in a place not
716 * accessible to @dev, and cannot be moved to a more suitable place. This is
717 * indicated with the error code -EBUSY.
719 struct dma_buf_attachment *
720 dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
721 const struct dma_buf_attach_ops *importer_ops,
724 struct dma_buf_attachment *attach;
727 if (WARN_ON(!dmabuf || !dev))
728 return ERR_PTR(-EINVAL);
730 if (WARN_ON(importer_ops && !importer_ops->move_notify))
731 return ERR_PTR(-EINVAL);
733 attach = kzalloc(sizeof(*attach), GFP_KERNEL);
735 return ERR_PTR(-ENOMEM);
738 attach->dmabuf = dmabuf;
740 attach->peer2peer = importer_ops->allow_peer2peer;
741 attach->importer_ops = importer_ops;
742 attach->importer_priv = importer_priv;
744 if (dmabuf->ops->attach) {
745 ret = dmabuf->ops->attach(dmabuf, attach);
749 dma_resv_lock(dmabuf->resv, NULL);
750 list_add(&attach->node, &dmabuf->attachments);
751 dma_resv_unlock(dmabuf->resv);
753 /* When either the importer or the exporter can't handle dynamic
754 * mappings we cache the mapping here to avoid issues with the
755 * reservation object lock.
757 if (dma_buf_attachment_is_dynamic(attach) !=
758 dma_buf_is_dynamic(dmabuf)) {
759 struct sg_table *sgt;
761 if (dma_buf_is_dynamic(attach->dmabuf)) {
762 dma_resv_lock(attach->dmabuf->resv, NULL);
763 ret = dma_buf_pin(attach);
768 sgt = __map_dma_buf(attach, DMA_BIDIRECTIONAL);
770 sgt = ERR_PTR(-ENOMEM);
775 if (dma_buf_is_dynamic(attach->dmabuf))
776 dma_resv_unlock(attach->dmabuf->resv);
778 attach->dir = DMA_BIDIRECTIONAL;
788 if (dma_buf_is_dynamic(attach->dmabuf))
789 dma_buf_unpin(attach);
792 if (dma_buf_is_dynamic(attach->dmabuf))
793 dma_resv_unlock(attach->dmabuf->resv);
795 dma_buf_detach(dmabuf, attach);
798 EXPORT_SYMBOL_GPL(dma_buf_dynamic_attach);
801 * dma_buf_attach - Wrapper for dma_buf_dynamic_attach
802 * @dmabuf: [in] buffer to attach device to.
803 * @dev: [in] device to be attached.
805 * Wrapper to call dma_buf_dynamic_attach() for drivers which still use a static
808 struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
811 return dma_buf_dynamic_attach(dmabuf, dev, NULL, NULL);
813 EXPORT_SYMBOL_GPL(dma_buf_attach);
815 static void __unmap_dma_buf(struct dma_buf_attachment *attach,
816 struct sg_table *sg_table,
817 enum dma_data_direction direction)
819 /* uses XOR, hence this unmangles */
820 mangle_sg_table(sg_table);
822 attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, direction);
826 * dma_buf_detach - Remove the given attachment from dmabuf's attachments list
827 * @dmabuf: [in] buffer to detach from.
828 * @attach: [in] attachment to be detached; is free'd after this call.
830 * Clean up a device attachment obtained by calling dma_buf_attach().
832 * Optionally this calls &dma_buf_ops.detach for device-specific detach.
834 void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
836 if (WARN_ON(!dmabuf || !attach))
840 if (dma_buf_is_dynamic(attach->dmabuf))
841 dma_resv_lock(attach->dmabuf->resv, NULL);
843 __unmap_dma_buf(attach, attach->sgt, attach->dir);
845 if (dma_buf_is_dynamic(attach->dmabuf)) {
846 dma_buf_unpin(attach);
847 dma_resv_unlock(attach->dmabuf->resv);
851 dma_resv_lock(dmabuf->resv, NULL);
852 list_del(&attach->node);
853 dma_resv_unlock(dmabuf->resv);
854 if (dmabuf->ops->detach)
855 dmabuf->ops->detach(dmabuf, attach);
859 EXPORT_SYMBOL_GPL(dma_buf_detach);
862 * dma_buf_pin - Lock down the DMA-buf
863 * @attach: [in] attachment which should be pinned
865 * Only dynamic importers (who set up @attach with dma_buf_dynamic_attach()) may
866 * call this, and only for limited use cases like scanout and not for temporary
867 * pin operations. It is not permitted to allow userspace to pin arbitrary
868 * amounts of buffers through this interface.
870 * Buffers must be unpinned by calling dma_buf_unpin().
873 * 0 on success, negative error code on failure.
875 int dma_buf_pin(struct dma_buf_attachment *attach)
877 struct dma_buf *dmabuf = attach->dmabuf;
880 WARN_ON(!dma_buf_attachment_is_dynamic(attach));
882 dma_resv_assert_held(dmabuf->resv);
884 if (dmabuf->ops->pin)
885 ret = dmabuf->ops->pin(attach);
889 EXPORT_SYMBOL_GPL(dma_buf_pin);
892 * dma_buf_unpin - Unpin a DMA-buf
893 * @attach: [in] attachment which should be unpinned
895 * This unpins a buffer pinned by dma_buf_pin() and allows the exporter to move
896 * any mapping of @attach again and inform the importer through
897 * &dma_buf_attach_ops.move_notify.
899 void dma_buf_unpin(struct dma_buf_attachment *attach)
901 struct dma_buf *dmabuf = attach->dmabuf;
903 WARN_ON(!dma_buf_attachment_is_dynamic(attach));
905 dma_resv_assert_held(dmabuf->resv);
907 if (dmabuf->ops->unpin)
908 dmabuf->ops->unpin(attach);
910 EXPORT_SYMBOL_GPL(dma_buf_unpin);
913 * dma_buf_map_attachment - Returns the scatterlist table of the attachment;
914 * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the
916 * @attach: [in] attachment whose scatterlist is to be returned
917 * @direction: [in] direction of DMA transfer
919 * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
920 * on error. May return -EINTR if it is interrupted by a signal.
922 * On success, the DMA addresses and lengths in the returned scatterlist are
925 * A mapping must be unmapped by using dma_buf_unmap_attachment(). Note that
926 * the underlying backing storage is pinned for as long as a mapping exists,
927 * therefore users/importers should not hold onto a mapping for undue amounts of
930 struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
931 enum dma_data_direction direction)
933 struct sg_table *sg_table;
938 if (WARN_ON(!attach || !attach->dmabuf))
939 return ERR_PTR(-EINVAL);
941 if (dma_buf_attachment_is_dynamic(attach))
942 dma_resv_assert_held(attach->dmabuf->resv);
946 * Two mappings with different directions for the same
947 * attachment are not allowed.
949 if (attach->dir != direction &&
950 attach->dir != DMA_BIDIRECTIONAL)
951 return ERR_PTR(-EBUSY);
956 if (dma_buf_is_dynamic(attach->dmabuf)) {
957 dma_resv_assert_held(attach->dmabuf->resv);
958 if (!IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY)) {
959 r = dma_buf_pin(attach);
965 sg_table = __map_dma_buf(attach, direction);
967 sg_table = ERR_PTR(-ENOMEM);
969 if (IS_ERR(sg_table) && dma_buf_is_dynamic(attach->dmabuf) &&
970 !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY))
971 dma_buf_unpin(attach);
973 if (!IS_ERR(sg_table) && attach->dmabuf->ops->cache_sgt_mapping) {
974 attach->sgt = sg_table;
975 attach->dir = direction;
978 #ifdef CONFIG_DMA_API_DEBUG
979 if (!IS_ERR(sg_table)) {
980 struct scatterlist *sg;
985 for_each_sgtable_dma_sg(sg_table, sg, i) {
986 addr = sg_dma_address(sg);
987 len = sg_dma_len(sg);
988 if (!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(len)) {
989 pr_debug("%s: addr %llx or len %x is not page aligned!\n",
990 __func__, addr, len);
994 #endif /* CONFIG_DMA_API_DEBUG */
998 EXPORT_SYMBOL_GPL(dma_buf_map_attachment);
1001 * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might
1002 * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of
1004 * @attach: [in] attachment to unmap buffer from
1005 * @sg_table: [in] scatterlist info of the buffer to unmap
1006 * @direction: [in] direction of DMA transfer
1008 * This unmaps a DMA mapping for @attached obtained by dma_buf_map_attachment().
1010 void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
1011 struct sg_table *sg_table,
1012 enum dma_data_direction direction)
1016 if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
1019 if (dma_buf_attachment_is_dynamic(attach))
1020 dma_resv_assert_held(attach->dmabuf->resv);
1022 if (attach->sgt == sg_table)
1025 if (dma_buf_is_dynamic(attach->dmabuf))
1026 dma_resv_assert_held(attach->dmabuf->resv);
1028 __unmap_dma_buf(attach, sg_table, direction);
1030 if (dma_buf_is_dynamic(attach->dmabuf) &&
1031 !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY))
1032 dma_buf_unpin(attach);
1034 EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment);
1037 * dma_buf_move_notify - notify attachments that DMA-buf is moving
1039 * @dmabuf: [in] buffer which is moving
1041 * Informs all attachmenst that they need to destroy and recreated all their
1044 void dma_buf_move_notify(struct dma_buf *dmabuf)
1046 struct dma_buf_attachment *attach;
1048 dma_resv_assert_held(dmabuf->resv);
1050 list_for_each_entry(attach, &dmabuf->attachments, node)
1051 if (attach->importer_ops)
1052 attach->importer_ops->move_notify(attach);
1054 EXPORT_SYMBOL_GPL(dma_buf_move_notify);
1059 * There are mutliple reasons for supporting CPU access to a dma buffer object:
1061 * - Fallback operations in the kernel, for example when a device is connected
1062 * over USB and the kernel needs to shuffle the data around first before
1063 * sending it away. Cache coherency is handled by braketing any transactions
1064 * with calls to dma_buf_begin_cpu_access() and dma_buf_end_cpu_access()
1067 * Since for most kernel internal dma-buf accesses need the entire buffer, a
1068 * vmap interface is introduced. Note that on very old 32-bit architectures
1069 * vmalloc space might be limited and result in vmap calls failing.
1073 * void \*dma_buf_vmap(struct dma_buf \*dmabuf)
1074 * void dma_buf_vunmap(struct dma_buf \*dmabuf, void \*vaddr)
1076 * The vmap call can fail if there is no vmap support in the exporter, or if
1077 * it runs out of vmalloc space. Note that the dma-buf layer keeps a reference
1078 * count for all vmap access and calls down into the exporter's vmap function
1079 * only when no vmapping exists, and only unmaps it once. Protection against
1080 * concurrent vmap/vunmap calls is provided by taking the &dma_buf.lock mutex.
1082 * - For full compatibility on the importer side with existing userspace
1083 * interfaces, which might already support mmap'ing buffers. This is needed in
1084 * many processing pipelines (e.g. feeding a software rendered image into a
1085 * hardware pipeline, thumbnail creation, snapshots, ...). Also, Android's ION
1086 * framework already supported this and for DMA buffer file descriptors to
1087 * replace ION buffers mmap support was needed.
1089 * There is no special interfaces, userspace simply calls mmap on the dma-buf
1090 * fd. But like for CPU access there's a need to braket the actual access,
1091 * which is handled by the ioctl (DMA_BUF_IOCTL_SYNC). Note that
1092 * DMA_BUF_IOCTL_SYNC can fail with -EAGAIN or -EINTR, in which case it must
1095 * Some systems might need some sort of cache coherency management e.g. when
1096 * CPU and GPU domains are being accessed through dma-buf at the same time.
1097 * To circumvent this problem there are begin/end coherency markers, that
1098 * forward directly to existing dma-buf device drivers vfunc hooks. Userspace
1099 * can make use of those markers through the DMA_BUF_IOCTL_SYNC ioctl. The
1100 * sequence would be used like following:
1103 * - for each drawing/upload cycle in CPU 1. SYNC_START ioctl, 2. read/write
1104 * to mmap area 3. SYNC_END ioctl. This can be repeated as often as you
1105 * want (with the new data being consumed by say the GPU or the scanout
1107 * - munmap once you don't need the buffer any more
1109 * For correctness and optimal performance, it is always required to use
1110 * SYNC_START and SYNC_END before and after, respectively, when accessing the
1111 * mapped address. Userspace cannot rely on coherent access, even when there
1112 * are systems where it just works without calling these ioctls.
1114 * - And as a CPU fallback in userspace processing pipelines.
1116 * Similar to the motivation for kernel cpu access it is again important that
1117 * the userspace code of a given importing subsystem can use the same
1118 * interfaces with a imported dma-buf buffer object as with a native buffer
1119 * object. This is especially important for drm where the userspace part of
1120 * contemporary OpenGL, X, and other drivers is huge, and reworking them to
1121 * use a different way to mmap a buffer rather invasive.
1123 * The assumption in the current dma-buf interfaces is that redirecting the
1124 * initial mmap is all that's needed. A survey of some of the existing
1125 * subsystems shows that no driver seems to do any nefarious thing like
1126 * syncing up with outstanding asynchronous processing on the device or
1127 * allocating special resources at fault time. So hopefully this is good
1128 * enough, since adding interfaces to intercept pagefaults and allow pte
1129 * shootdowns would increase the complexity quite a bit.
1133 * int dma_buf_mmap(struct dma_buf \*, struct vm_area_struct \*,
1136 * If the importing subsystem simply provides a special-purpose mmap call to
1137 * set up a mapping in userspace, calling do_mmap with &dma_buf.file will
1138 * equally achieve that for a dma-buf object.
1141 static int __dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
1142 enum dma_data_direction direction)
1144 bool write = (direction == DMA_BIDIRECTIONAL ||
1145 direction == DMA_TO_DEVICE);
1146 struct dma_resv *resv = dmabuf->resv;
1149 /* Wait on any implicit rendering fences */
1150 ret = dma_resv_wait_timeout_rcu(resv, write, true,
1151 MAX_SCHEDULE_TIMEOUT);
1159 * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the
1160 * cpu in the kernel context. Calls begin_cpu_access to allow exporter-specific
1161 * preparations. Coherency is only guaranteed in the specified range for the
1162 * specified access direction.
1163 * @dmabuf: [in] buffer to prepare cpu access for.
1164 * @direction: [in] length of range for cpu access.
1166 * After the cpu access is complete the caller should call
1167 * dma_buf_end_cpu_access(). Only when cpu access is braketed by both calls is
1168 * it guaranteed to be coherent with other DMA access.
1170 * This function will also wait for any DMA transactions tracked through
1171 * implicit synchronization in &dma_buf.resv. For DMA transactions with explicit
1172 * synchronization this function will only ensure cache coherency, callers must
1173 * ensure synchronization with such DMA transactions on their own.
1175 * Can return negative error values, returns 0 on success.
1177 int dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
1178 enum dma_data_direction direction)
1182 if (WARN_ON(!dmabuf))
1185 might_lock(&dmabuf->resv->lock.base);
1187 if (dmabuf->ops->begin_cpu_access)
1188 ret = dmabuf->ops->begin_cpu_access(dmabuf, direction);
1190 /* Ensure that all fences are waited upon - but we first allow
1191 * the native handler the chance to do so more efficiently if it
1192 * chooses. A double invocation here will be reasonably cheap no-op.
1195 ret = __dma_buf_begin_cpu_access(dmabuf, direction);
1199 EXPORT_SYMBOL_GPL(dma_buf_begin_cpu_access);
1202 * dma_buf_end_cpu_access - Must be called after accessing a dma_buf from the
1203 * cpu in the kernel context. Calls end_cpu_access to allow exporter-specific
1204 * actions. Coherency is only guaranteed in the specified range for the
1205 * specified access direction.
1206 * @dmabuf: [in] buffer to complete cpu access for.
1207 * @direction: [in] length of range for cpu access.
1209 * This terminates CPU access started with dma_buf_begin_cpu_access().
1211 * Can return negative error values, returns 0 on success.
1213 int dma_buf_end_cpu_access(struct dma_buf *dmabuf,
1214 enum dma_data_direction direction)
1220 might_lock(&dmabuf->resv->lock.base);
1222 if (dmabuf->ops->end_cpu_access)
1223 ret = dmabuf->ops->end_cpu_access(dmabuf, direction);
1227 EXPORT_SYMBOL_GPL(dma_buf_end_cpu_access);
1231 * dma_buf_mmap - Setup up a userspace mmap with the given vma
1232 * @dmabuf: [in] buffer that should back the vma
1233 * @vma: [in] vma for the mmap
1234 * @pgoff: [in] offset in pages where this mmap should start within the
1237 * This function adjusts the passed in vma so that it points at the file of the
1238 * dma_buf operation. It also adjusts the starting pgoff and does bounds
1239 * checking on the size of the vma. Then it calls the exporters mmap function to
1240 * set up the mapping.
1242 * Can return negative error values, returns 0 on success.
1244 int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
1245 unsigned long pgoff)
1247 if (WARN_ON(!dmabuf || !vma))
1250 /* check if buffer supports mmap */
1251 if (!dmabuf->ops->mmap)
1254 /* check for offset overflow */
1255 if (pgoff + vma_pages(vma) < pgoff)
1258 /* check for overflowing the buffer's size */
1259 if (pgoff + vma_pages(vma) >
1260 dmabuf->size >> PAGE_SHIFT)
1263 /* readjust the vma */
1264 vma_set_file(vma, dmabuf->file);
1265 vma->vm_pgoff = pgoff;
1267 return dmabuf->ops->mmap(dmabuf, vma);
1269 EXPORT_SYMBOL_GPL(dma_buf_mmap);
1272 * dma_buf_vmap - Create virtual mapping for the buffer object into kernel
1273 * address space. Same restrictions as for vmap and friends apply.
1274 * @dmabuf: [in] buffer to vmap
1275 * @map: [out] returns the vmap pointer
1277 * This call may fail due to lack of virtual mapping address space.
1278 * These calls are optional in drivers. The intended use for them
1279 * is for mapping objects linear in kernel space for high use objects.
1281 * To ensure coherency users must call dma_buf_begin_cpu_access() and
1282 * dma_buf_end_cpu_access() around any cpu access performed through this
1285 * Returns 0 on success, or a negative errno code otherwise.
1287 int dma_buf_vmap(struct dma_buf *dmabuf, struct dma_buf_map *map)
1289 struct dma_buf_map ptr;
1292 dma_buf_map_clear(map);
1294 if (WARN_ON(!dmabuf))
1297 if (!dmabuf->ops->vmap)
1300 mutex_lock(&dmabuf->lock);
1301 if (dmabuf->vmapping_counter) {
1302 dmabuf->vmapping_counter++;
1303 BUG_ON(dma_buf_map_is_null(&dmabuf->vmap_ptr));
1304 *map = dmabuf->vmap_ptr;
1308 BUG_ON(dma_buf_map_is_set(&dmabuf->vmap_ptr));
1310 ret = dmabuf->ops->vmap(dmabuf, &ptr);
1311 if (WARN_ON_ONCE(ret))
1314 dmabuf->vmap_ptr = ptr;
1315 dmabuf->vmapping_counter = 1;
1317 *map = dmabuf->vmap_ptr;
1320 mutex_unlock(&dmabuf->lock);
1323 EXPORT_SYMBOL_GPL(dma_buf_vmap);
1326 * dma_buf_vunmap - Unmap a vmap obtained by dma_buf_vmap.
1327 * @dmabuf: [in] buffer to vunmap
1328 * @map: [in] vmap pointer to vunmap
1330 void dma_buf_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map)
1332 if (WARN_ON(!dmabuf))
1335 BUG_ON(dma_buf_map_is_null(&dmabuf->vmap_ptr));
1336 BUG_ON(dmabuf->vmapping_counter == 0);
1337 BUG_ON(!dma_buf_map_is_equal(&dmabuf->vmap_ptr, map));
1339 mutex_lock(&dmabuf->lock);
1340 if (--dmabuf->vmapping_counter == 0) {
1341 if (dmabuf->ops->vunmap)
1342 dmabuf->ops->vunmap(dmabuf, map);
1343 dma_buf_map_clear(&dmabuf->vmap_ptr);
1345 mutex_unlock(&dmabuf->lock);
1347 EXPORT_SYMBOL_GPL(dma_buf_vunmap);
1349 #ifdef CONFIG_DEBUG_FS
1350 static int dma_buf_debug_show(struct seq_file *s, void *unused)
1353 struct dma_buf *buf_obj;
1354 struct dma_buf_attachment *attach_obj;
1355 struct dma_resv *robj;
1356 struct dma_resv_list *fobj;
1357 struct dma_fence *fence;
1359 int count = 0, attach_count, shared_count, i;
1362 ret = mutex_lock_interruptible(&db_list.lock);
1367 seq_puts(s, "\nDma-buf Objects:\n");
1368 seq_printf(s, "%-8s\t%-8s\t%-8s\t%-8s\texp_name\t%-8s\n",
1369 "size", "flags", "mode", "count", "ino");
1371 list_for_each_entry(buf_obj, &db_list.head, list_node) {
1373 ret = dma_resv_lock_interruptible(buf_obj->resv, NULL);
1377 seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\t%08lu\t%s\n",
1379 buf_obj->file->f_flags, buf_obj->file->f_mode,
1380 file_count(buf_obj->file),
1382 file_inode(buf_obj->file)->i_ino,
1383 buf_obj->name ?: "");
1385 robj = buf_obj->resv;
1387 seq = read_seqcount_begin(&robj->seq);
1389 fobj = rcu_dereference(robj->fence);
1390 shared_count = fobj ? fobj->shared_count : 0;
1391 fence = rcu_dereference(robj->fence_excl);
1392 if (!read_seqcount_retry(&robj->seq, seq))
1398 seq_printf(s, "\tExclusive fence: %s %s %ssignalled\n",
1399 fence->ops->get_driver_name(fence),
1400 fence->ops->get_timeline_name(fence),
1401 dma_fence_is_signaled(fence) ? "" : "un");
1402 for (i = 0; i < shared_count; i++) {
1403 fence = rcu_dereference(fobj->shared[i]);
1404 if (!dma_fence_get_rcu(fence))
1406 seq_printf(s, "\tShared fence: %s %s %ssignalled\n",
1407 fence->ops->get_driver_name(fence),
1408 fence->ops->get_timeline_name(fence),
1409 dma_fence_is_signaled(fence) ? "" : "un");
1410 dma_fence_put(fence);
1414 seq_puts(s, "\tAttached Devices:\n");
1417 list_for_each_entry(attach_obj, &buf_obj->attachments, node) {
1418 seq_printf(s, "\t%s\n", dev_name(attach_obj->dev));
1421 dma_resv_unlock(buf_obj->resv);
1423 seq_printf(s, "Total %d devices attached\n\n",
1427 size += buf_obj->size;
1430 seq_printf(s, "\nTotal %d objects, %zu bytes\n", count, size);
1432 mutex_unlock(&db_list.lock);
1436 mutex_unlock(&db_list.lock);
1440 DEFINE_SHOW_ATTRIBUTE(dma_buf_debug);
1442 static struct dentry *dma_buf_debugfs_dir;
1444 static int dma_buf_init_debugfs(void)
1449 d = debugfs_create_dir("dma_buf", NULL);
1453 dma_buf_debugfs_dir = d;
1455 d = debugfs_create_file("bufinfo", S_IRUGO, dma_buf_debugfs_dir,
1456 NULL, &dma_buf_debug_fops);
1458 pr_debug("dma_buf: debugfs: failed to create node bufinfo\n");
1459 debugfs_remove_recursive(dma_buf_debugfs_dir);
1460 dma_buf_debugfs_dir = NULL;
1467 static void dma_buf_uninit_debugfs(void)
1469 debugfs_remove_recursive(dma_buf_debugfs_dir);
1472 static inline int dma_buf_init_debugfs(void)
1476 static inline void dma_buf_uninit_debugfs(void)
1481 static int __init dma_buf_init(void)
1483 dma_buf_mnt = kern_mount(&dma_buf_fs_type);
1484 if (IS_ERR(dma_buf_mnt))
1485 return PTR_ERR(dma_buf_mnt);
1487 mutex_init(&db_list.lock);
1488 INIT_LIST_HEAD(&db_list.head);
1489 dma_buf_init_debugfs();
1492 subsys_initcall(dma_buf_init);
1494 static void __exit dma_buf_deinit(void)
1496 dma_buf_uninit_debugfs();
1497 kern_unmount(dma_buf_mnt);
1499 __exitcall(dma_buf_deinit);