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 #include "dma-buf-sysfs-stats.h"
34 static inline int is_dma_buf_file(struct file *);
37 struct list_head head;
41 static struct dma_buf_list db_list;
43 static char *dmabuffs_dname(struct dentry *dentry, char *buffer, int buflen)
45 struct dma_buf *dmabuf;
46 char name[DMA_BUF_NAME_LEN];
49 dmabuf = dentry->d_fsdata;
50 spin_lock(&dmabuf->name_lock);
52 ret = strlcpy(name, dmabuf->name, DMA_BUF_NAME_LEN);
53 spin_unlock(&dmabuf->name_lock);
55 return dynamic_dname(dentry, buffer, buflen, "/%s:%s",
56 dentry->d_name.name, ret > 0 ? name : "");
59 static void dma_buf_release(struct dentry *dentry)
61 struct dma_buf *dmabuf;
63 dmabuf = dentry->d_fsdata;
64 if (unlikely(!dmabuf))
67 BUG_ON(dmabuf->vmapping_counter);
70 * If you hit this BUG() it could mean:
71 * * There's a file reference imbalance in dma_buf_poll / dma_buf_poll_cb or somewhere else
72 * * dmabuf->cb_in/out.active are non-0 despite no pending fence callback
74 BUG_ON(dmabuf->cb_in.active || dmabuf->cb_out.active);
76 dma_buf_stats_teardown(dmabuf);
77 dmabuf->ops->release(dmabuf);
79 if (dmabuf->resv == (struct dma_resv *)&dmabuf[1])
80 dma_resv_fini(dmabuf->resv);
82 WARN_ON(!list_empty(&dmabuf->attachments));
83 module_put(dmabuf->owner);
88 static int dma_buf_file_release(struct inode *inode, struct file *file)
90 struct dma_buf *dmabuf;
92 if (!is_dma_buf_file(file))
95 dmabuf = file->private_data;
97 mutex_lock(&db_list.lock);
98 list_del(&dmabuf->list_node);
99 mutex_unlock(&db_list.lock);
104 static const struct dentry_operations dma_buf_dentry_ops = {
105 .d_dname = dmabuffs_dname,
106 .d_release = dma_buf_release,
109 static struct vfsmount *dma_buf_mnt;
111 static int dma_buf_fs_init_context(struct fs_context *fc)
113 struct pseudo_fs_context *ctx;
115 ctx = init_pseudo(fc, DMA_BUF_MAGIC);
118 ctx->dops = &dma_buf_dentry_ops;
122 static struct file_system_type dma_buf_fs_type = {
124 .init_fs_context = dma_buf_fs_init_context,
125 .kill_sb = kill_anon_super,
128 static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
130 struct dma_buf *dmabuf;
132 if (!is_dma_buf_file(file))
135 dmabuf = file->private_data;
137 /* check if buffer supports mmap */
138 if (!dmabuf->ops->mmap)
141 /* check for overflowing the buffer's size */
142 if (vma->vm_pgoff + vma_pages(vma) >
143 dmabuf->size >> PAGE_SHIFT)
146 return dmabuf->ops->mmap(dmabuf, vma);
149 static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence)
151 struct dma_buf *dmabuf;
154 if (!is_dma_buf_file(file))
157 dmabuf = file->private_data;
159 /* only support discovering the end of the buffer,
160 but also allow SEEK_SET to maintain the idiomatic
161 SEEK_END(0), SEEK_CUR(0) pattern */
162 if (whence == SEEK_END)
164 else if (whence == SEEK_SET)
172 return base + offset;
176 * DOC: implicit fence polling
178 * To support cross-device and cross-driver synchronization of buffer access
179 * implicit fences (represented internally in the kernel with &struct dma_fence)
180 * can be attached to a &dma_buf. The glue for that and a few related things are
181 * provided in the &dma_resv structure.
183 * Userspace can query the state of these implicitly tracked fences using poll()
184 * and related system calls:
186 * - Checking for EPOLLIN, i.e. read access, can be use to query the state of the
187 * most recent write or exclusive fence.
189 * - Checking for EPOLLOUT, i.e. write access, can be used to query the state of
190 * all attached fences, shared and exclusive ones.
192 * Note that this only signals the completion of the respective fences, i.e. the
193 * DMA transfers are complete. Cache flushing and any other necessary
194 * preparations before CPU access can begin still need to happen.
197 static void dma_buf_poll_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
199 struct dma_buf_poll_cb_t *dcb = (struct dma_buf_poll_cb_t *)cb;
200 struct dma_buf *dmabuf = container_of(dcb->poll, struct dma_buf, poll);
203 spin_lock_irqsave(&dcb->poll->lock, flags);
204 wake_up_locked_poll(dcb->poll, dcb->active);
206 spin_unlock_irqrestore(&dcb->poll->lock, flags);
207 dma_fence_put(fence);
208 /* Paired with get_file in dma_buf_poll */
212 static bool dma_buf_poll_shared(struct dma_resv *resv,
213 struct dma_buf_poll_cb_t *dcb)
215 struct dma_resv_list *fobj = dma_resv_shared_list(resv);
216 struct dma_fence *fence;
222 for (i = 0; i < fobj->shared_count; ++i) {
223 fence = rcu_dereference_protected(fobj->shared[i],
224 dma_resv_held(resv));
225 dma_fence_get(fence);
226 r = dma_fence_add_callback(fence, &dcb->cb, dma_buf_poll_cb);
229 dma_fence_put(fence);
235 static bool dma_buf_poll_excl(struct dma_resv *resv,
236 struct dma_buf_poll_cb_t *dcb)
238 struct dma_fence *fence = dma_resv_excl_fence(resv);
244 dma_fence_get(fence);
245 r = dma_fence_add_callback(fence, &dcb->cb, dma_buf_poll_cb);
248 dma_fence_put(fence);
253 static __poll_t dma_buf_poll(struct file *file, poll_table *poll)
255 struct dma_buf *dmabuf;
256 struct dma_resv *resv;
259 dmabuf = file->private_data;
260 if (!dmabuf || !dmabuf->resv)
265 poll_wait(file, &dmabuf->poll, poll);
267 events = poll_requested_events(poll) & (EPOLLIN | EPOLLOUT);
271 dma_resv_lock(resv, NULL);
273 if (events & EPOLLOUT) {
274 struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_out;
276 /* Check that callback isn't busy */
277 spin_lock_irq(&dmabuf->poll.lock);
281 dcb->active = EPOLLOUT;
282 spin_unlock_irq(&dmabuf->poll.lock);
284 if (events & EPOLLOUT) {
285 /* Paired with fput in dma_buf_poll_cb */
286 get_file(dmabuf->file);
288 if (!dma_buf_poll_shared(resv, dcb) &&
289 !dma_buf_poll_excl(resv, dcb))
291 /* No callback queued, wake up any other waiters */
292 dma_buf_poll_cb(NULL, &dcb->cb);
298 if (events & EPOLLIN) {
299 struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_in;
301 /* Check that callback isn't busy */
302 spin_lock_irq(&dmabuf->poll.lock);
306 dcb->active = EPOLLIN;
307 spin_unlock_irq(&dmabuf->poll.lock);
309 if (events & EPOLLIN) {
310 /* Paired with fput in dma_buf_poll_cb */
311 get_file(dmabuf->file);
313 if (!dma_buf_poll_excl(resv, dcb))
314 /* No callback queued, wake up any other waiters */
315 dma_buf_poll_cb(NULL, &dcb->cb);
321 dma_resv_unlock(resv);
326 * dma_buf_set_name - Set a name to a specific dma_buf to track the usage.
327 * The name of the dma-buf buffer can only be set when the dma-buf is not
328 * attached to any devices. It could theoritically support changing the
329 * name of the dma-buf if the same piece of memory is used for multiple
330 * purpose between different devices.
332 * @dmabuf: [in] dmabuf buffer that will be renamed.
333 * @buf: [in] A piece of userspace memory that contains the name of
336 * Returns 0 on success. If the dma-buf buffer is already attached to
337 * devices, return -EBUSY.
340 static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf)
342 char *name = strndup_user(buf, DMA_BUF_NAME_LEN);
346 return PTR_ERR(name);
348 dma_resv_lock(dmabuf->resv, NULL);
349 if (!list_empty(&dmabuf->attachments)) {
354 spin_lock(&dmabuf->name_lock);
357 spin_unlock(&dmabuf->name_lock);
360 dma_resv_unlock(dmabuf->resv);
364 static long dma_buf_ioctl(struct file *file,
365 unsigned int cmd, unsigned long arg)
367 struct dma_buf *dmabuf;
368 struct dma_buf_sync sync;
369 enum dma_data_direction direction;
372 dmabuf = file->private_data;
375 case DMA_BUF_IOCTL_SYNC:
376 if (copy_from_user(&sync, (void __user *) arg, sizeof(sync)))
379 if (sync.flags & ~DMA_BUF_SYNC_VALID_FLAGS_MASK)
382 switch (sync.flags & DMA_BUF_SYNC_RW) {
383 case DMA_BUF_SYNC_READ:
384 direction = DMA_FROM_DEVICE;
386 case DMA_BUF_SYNC_WRITE:
387 direction = DMA_TO_DEVICE;
389 case DMA_BUF_SYNC_RW:
390 direction = DMA_BIDIRECTIONAL;
396 if (sync.flags & DMA_BUF_SYNC_END)
397 ret = dma_buf_end_cpu_access(dmabuf, direction);
399 ret = dma_buf_begin_cpu_access(dmabuf, direction);
403 case DMA_BUF_SET_NAME_A:
404 case DMA_BUF_SET_NAME_B:
405 return dma_buf_set_name(dmabuf, (const char __user *)arg);
412 static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file)
414 struct dma_buf *dmabuf = file->private_data;
416 seq_printf(m, "size:\t%zu\n", dmabuf->size);
417 /* Don't count the temporary reference taken inside procfs seq_show */
418 seq_printf(m, "count:\t%ld\n", file_count(dmabuf->file) - 1);
419 seq_printf(m, "exp_name:\t%s\n", dmabuf->exp_name);
420 spin_lock(&dmabuf->name_lock);
422 seq_printf(m, "name:\t%s\n", dmabuf->name);
423 spin_unlock(&dmabuf->name_lock);
426 static const struct file_operations dma_buf_fops = {
427 .release = dma_buf_file_release,
428 .mmap = dma_buf_mmap_internal,
429 .llseek = dma_buf_llseek,
430 .poll = dma_buf_poll,
431 .unlocked_ioctl = dma_buf_ioctl,
432 .compat_ioctl = compat_ptr_ioctl,
433 .show_fdinfo = dma_buf_show_fdinfo,
437 * is_dma_buf_file - Check if struct file* is associated with dma_buf
439 static inline int is_dma_buf_file(struct file *file)
441 return file->f_op == &dma_buf_fops;
444 static struct file *dma_buf_getfile(struct dma_buf *dmabuf, int flags)
446 static atomic64_t dmabuf_inode = ATOMIC64_INIT(0);
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);
457 * The ->i_ino acquired from get_next_ino() is not unique thus
458 * not suitable for using it as dentry name by dmabuf stats.
459 * Override ->i_ino with the unique and dmabuffs specific
462 inode->i_ino = atomic64_add_return(1, &dmabuf_inode);
463 file = alloc_file_pseudo(inode, dma_buf_mnt, "dmabuf",
464 flags, &dma_buf_fops);
467 file->f_flags = flags & (O_ACCMODE | O_NONBLOCK);
468 file->private_data = dmabuf;
469 file->f_path.dentry->d_fsdata = dmabuf;
479 * DOC: dma buf device access
481 * For device DMA access to a shared DMA buffer the usual sequence of operations
484 * 1. The exporter defines his exporter instance using
485 * DEFINE_DMA_BUF_EXPORT_INFO() and calls dma_buf_export() to wrap a private
486 * buffer object into a &dma_buf. It then exports that &dma_buf to userspace
487 * as a file descriptor by calling dma_buf_fd().
489 * 2. Userspace passes this file-descriptors to all drivers it wants this buffer
490 * to share with: First the filedescriptor is converted to a &dma_buf using
491 * dma_buf_get(). Then the buffer is attached to the device using
494 * Up to this stage the exporter is still free to migrate or reallocate the
497 * 3. Once the buffer is attached to all devices userspace can initiate DMA
498 * access to the shared buffer. In the kernel this is done by calling
499 * dma_buf_map_attachment() and dma_buf_unmap_attachment().
501 * 4. Once a driver is done with a shared buffer it needs to call
502 * dma_buf_detach() (after cleaning up any mappings) and then release the
503 * reference acquired with dma_buf_get() by calling dma_buf_put().
505 * For the detailed semantics exporters are expected to implement see
510 * dma_buf_export - Creates a new dma_buf, and associates an anon file
511 * with this buffer, so it can be exported.
512 * Also connect the allocator specific data and ops to the buffer.
513 * Additionally, provide a name string for exporter; useful in debugging.
515 * @exp_info: [in] holds all the export related information provided
516 * by the exporter. see &struct dma_buf_export_info
517 * for further details.
519 * Returns, on success, a newly created struct dma_buf object, which wraps the
520 * supplied private data and operations for struct dma_buf_ops. On either
521 * missing ops, or error in allocating struct dma_buf, will return negative
524 * For most cases the easiest way to create @exp_info is through the
525 * %DEFINE_DMA_BUF_EXPORT_INFO macro.
527 struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
529 struct dma_buf *dmabuf;
530 struct dma_resv *resv = exp_info->resv;
532 size_t alloc_size = sizeof(struct dma_buf);
536 alloc_size += sizeof(struct dma_resv);
538 /* prevent &dma_buf[1] == dma_buf->resv */
541 if (WARN_ON(!exp_info->priv
543 || !exp_info->ops->map_dma_buf
544 || !exp_info->ops->unmap_dma_buf
545 || !exp_info->ops->release)) {
546 return ERR_PTR(-EINVAL);
549 if (WARN_ON(exp_info->ops->cache_sgt_mapping &&
550 (exp_info->ops->pin || exp_info->ops->unpin)))
551 return ERR_PTR(-EINVAL);
553 if (WARN_ON(!exp_info->ops->pin != !exp_info->ops->unpin))
554 return ERR_PTR(-EINVAL);
556 if (!try_module_get(exp_info->owner))
557 return ERR_PTR(-ENOENT);
559 dmabuf = kzalloc(alloc_size, GFP_KERNEL);
565 dmabuf->priv = exp_info->priv;
566 dmabuf->ops = exp_info->ops;
567 dmabuf->size = exp_info->size;
568 dmabuf->exp_name = exp_info->exp_name;
569 dmabuf->owner = exp_info->owner;
570 spin_lock_init(&dmabuf->name_lock);
571 init_waitqueue_head(&dmabuf->poll);
572 dmabuf->cb_in.poll = dmabuf->cb_out.poll = &dmabuf->poll;
573 dmabuf->cb_in.active = dmabuf->cb_out.active = 0;
576 resv = (struct dma_resv *)&dmabuf[1];
581 file = dma_buf_getfile(dmabuf, exp_info->flags);
587 file->f_mode |= FMODE_LSEEK;
590 mutex_init(&dmabuf->lock);
591 INIT_LIST_HEAD(&dmabuf->attachments);
593 mutex_lock(&db_list.lock);
594 list_add(&dmabuf->list_node, &db_list.head);
595 mutex_unlock(&db_list.lock);
597 ret = dma_buf_stats_setup(dmabuf);
605 * Set file->f_path.dentry->d_fsdata to NULL so that when
606 * dma_buf_release() gets invoked by dentry_ops, it exits
607 * early before calling the release() dma_buf op.
609 file->f_path.dentry->d_fsdata = NULL;
614 module_put(exp_info->owner);
617 EXPORT_SYMBOL_GPL(dma_buf_export);
620 * dma_buf_fd - returns a file descriptor for the given struct dma_buf
621 * @dmabuf: [in] pointer to dma_buf for which fd is required.
622 * @flags: [in] flags to give to fd
624 * On success, returns an associated 'fd'. Else, returns error.
626 int dma_buf_fd(struct dma_buf *dmabuf, int flags)
630 if (!dmabuf || !dmabuf->file)
633 fd = get_unused_fd_flags(flags);
637 fd_install(fd, dmabuf->file);
641 EXPORT_SYMBOL_GPL(dma_buf_fd);
644 * dma_buf_get - returns the struct dma_buf related to an fd
645 * @fd: [in] fd associated with the struct dma_buf to be returned
647 * On success, returns the struct dma_buf associated with an fd; uses
648 * file's refcounting done by fget to increase refcount. returns ERR_PTR
651 struct dma_buf *dma_buf_get(int fd)
658 return ERR_PTR(-EBADF);
660 if (!is_dma_buf_file(file)) {
662 return ERR_PTR(-EINVAL);
665 return file->private_data;
667 EXPORT_SYMBOL_GPL(dma_buf_get);
670 * dma_buf_put - decreases refcount of the buffer
671 * @dmabuf: [in] buffer to reduce refcount of
673 * Uses file's refcounting done implicitly by fput().
675 * If, as a result of this call, the refcount becomes 0, the 'release' file
676 * operation related to this fd is called. It calls &dma_buf_ops.release vfunc
677 * in turn, and frees the memory allocated for dmabuf when exported.
679 void dma_buf_put(struct dma_buf *dmabuf)
681 if (WARN_ON(!dmabuf || !dmabuf->file))
686 EXPORT_SYMBOL_GPL(dma_buf_put);
688 static void mangle_sg_table(struct sg_table *sg_table)
690 #ifdef CONFIG_DMABUF_DEBUG
692 struct scatterlist *sg;
694 /* To catch abuse of the underlying struct page by importers mix
695 * up the bits, but take care to preserve the low SG_ bits to
696 * not corrupt the sgt. The mixing is undone in __unmap_dma_buf
697 * before passing the sgt back to the exporter. */
698 for_each_sgtable_sg(sg_table, sg, i)
699 sg->page_link ^= ~0xffUL;
703 static struct sg_table * __map_dma_buf(struct dma_buf_attachment *attach,
704 enum dma_data_direction direction)
706 struct sg_table *sg_table;
708 sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
710 if (!IS_ERR_OR_NULL(sg_table))
711 mangle_sg_table(sg_table);
717 * dma_buf_dynamic_attach - Add the device to dma_buf's attachments list
718 * @dmabuf: [in] buffer to attach device to.
719 * @dev: [in] device to be attached.
720 * @importer_ops: [in] importer operations for the attachment
721 * @importer_priv: [in] importer private pointer for the attachment
723 * Returns struct dma_buf_attachment pointer for this attachment. Attachments
724 * must be cleaned up by calling dma_buf_detach().
726 * Optionally this calls &dma_buf_ops.attach to allow device-specific attach
731 * A pointer to newly created &dma_buf_attachment on success, or a negative
732 * error code wrapped into a pointer on failure.
734 * Note that this can fail if the backing storage of @dmabuf is in a place not
735 * accessible to @dev, and cannot be moved to a more suitable place. This is
736 * indicated with the error code -EBUSY.
738 struct dma_buf_attachment *
739 dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
740 const struct dma_buf_attach_ops *importer_ops,
743 struct dma_buf_attachment *attach;
746 if (WARN_ON(!dmabuf || !dev))
747 return ERR_PTR(-EINVAL);
749 if (WARN_ON(importer_ops && !importer_ops->move_notify))
750 return ERR_PTR(-EINVAL);
752 attach = kzalloc(sizeof(*attach), GFP_KERNEL);
754 return ERR_PTR(-ENOMEM);
757 attach->dmabuf = dmabuf;
759 attach->peer2peer = importer_ops->allow_peer2peer;
760 attach->importer_ops = importer_ops;
761 attach->importer_priv = importer_priv;
763 if (dmabuf->ops->attach) {
764 ret = dmabuf->ops->attach(dmabuf, attach);
768 dma_resv_lock(dmabuf->resv, NULL);
769 list_add(&attach->node, &dmabuf->attachments);
770 dma_resv_unlock(dmabuf->resv);
772 /* When either the importer or the exporter can't handle dynamic
773 * mappings we cache the mapping here to avoid issues with the
774 * reservation object lock.
776 if (dma_buf_attachment_is_dynamic(attach) !=
777 dma_buf_is_dynamic(dmabuf)) {
778 struct sg_table *sgt;
780 if (dma_buf_is_dynamic(attach->dmabuf)) {
781 dma_resv_lock(attach->dmabuf->resv, NULL);
782 ret = dmabuf->ops->pin(attach);
787 sgt = __map_dma_buf(attach, DMA_BIDIRECTIONAL);
789 sgt = ERR_PTR(-ENOMEM);
794 if (dma_buf_is_dynamic(attach->dmabuf))
795 dma_resv_unlock(attach->dmabuf->resv);
797 attach->dir = DMA_BIDIRECTIONAL;
807 if (dma_buf_is_dynamic(attach->dmabuf))
808 dmabuf->ops->unpin(attach);
811 if (dma_buf_is_dynamic(attach->dmabuf))
812 dma_resv_unlock(attach->dmabuf->resv);
814 dma_buf_detach(dmabuf, attach);
817 EXPORT_SYMBOL_GPL(dma_buf_dynamic_attach);
820 * dma_buf_attach - Wrapper for dma_buf_dynamic_attach
821 * @dmabuf: [in] buffer to attach device to.
822 * @dev: [in] device to be attached.
824 * Wrapper to call dma_buf_dynamic_attach() for drivers which still use a static
827 struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
830 return dma_buf_dynamic_attach(dmabuf, dev, NULL, NULL);
832 EXPORT_SYMBOL_GPL(dma_buf_attach);
834 static void __unmap_dma_buf(struct dma_buf_attachment *attach,
835 struct sg_table *sg_table,
836 enum dma_data_direction direction)
838 /* uses XOR, hence this unmangles */
839 mangle_sg_table(sg_table);
841 attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, direction);
845 * dma_buf_detach - Remove the given attachment from dmabuf's attachments list
846 * @dmabuf: [in] buffer to detach from.
847 * @attach: [in] attachment to be detached; is free'd after this call.
849 * Clean up a device attachment obtained by calling dma_buf_attach().
851 * Optionally this calls &dma_buf_ops.detach for device-specific detach.
853 void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
855 if (WARN_ON(!dmabuf || !attach))
859 if (dma_buf_is_dynamic(attach->dmabuf))
860 dma_resv_lock(attach->dmabuf->resv, NULL);
862 __unmap_dma_buf(attach, attach->sgt, attach->dir);
864 if (dma_buf_is_dynamic(attach->dmabuf)) {
865 dmabuf->ops->unpin(attach);
866 dma_resv_unlock(attach->dmabuf->resv);
870 dma_resv_lock(dmabuf->resv, NULL);
871 list_del(&attach->node);
872 dma_resv_unlock(dmabuf->resv);
873 if (dmabuf->ops->detach)
874 dmabuf->ops->detach(dmabuf, attach);
878 EXPORT_SYMBOL_GPL(dma_buf_detach);
881 * dma_buf_pin - Lock down the DMA-buf
882 * @attach: [in] attachment which should be pinned
884 * Only dynamic importers (who set up @attach with dma_buf_dynamic_attach()) may
885 * call this, and only for limited use cases like scanout and not for temporary
886 * pin operations. It is not permitted to allow userspace to pin arbitrary
887 * amounts of buffers through this interface.
889 * Buffers must be unpinned by calling dma_buf_unpin().
892 * 0 on success, negative error code on failure.
894 int dma_buf_pin(struct dma_buf_attachment *attach)
896 struct dma_buf *dmabuf = attach->dmabuf;
899 WARN_ON(!dma_buf_attachment_is_dynamic(attach));
901 dma_resv_assert_held(dmabuf->resv);
903 if (dmabuf->ops->pin)
904 ret = dmabuf->ops->pin(attach);
908 EXPORT_SYMBOL_GPL(dma_buf_pin);
911 * dma_buf_unpin - Unpin a DMA-buf
912 * @attach: [in] attachment which should be unpinned
914 * This unpins a buffer pinned by dma_buf_pin() and allows the exporter to move
915 * any mapping of @attach again and inform the importer through
916 * &dma_buf_attach_ops.move_notify.
918 void dma_buf_unpin(struct dma_buf_attachment *attach)
920 struct dma_buf *dmabuf = attach->dmabuf;
922 WARN_ON(!dma_buf_attachment_is_dynamic(attach));
924 dma_resv_assert_held(dmabuf->resv);
926 if (dmabuf->ops->unpin)
927 dmabuf->ops->unpin(attach);
929 EXPORT_SYMBOL_GPL(dma_buf_unpin);
932 * dma_buf_map_attachment - Returns the scatterlist table of the attachment;
933 * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the
935 * @attach: [in] attachment whose scatterlist is to be returned
936 * @direction: [in] direction of DMA transfer
938 * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
939 * on error. May return -EINTR if it is interrupted by a signal.
941 * On success, the DMA addresses and lengths in the returned scatterlist are
944 * A mapping must be unmapped by using dma_buf_unmap_attachment(). Note that
945 * the underlying backing storage is pinned for as long as a mapping exists,
946 * therefore users/importers should not hold onto a mapping for undue amounts of
949 * Important: Dynamic importers must wait for the exclusive fence of the struct
950 * dma_resv attached to the DMA-BUF first.
952 struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
953 enum dma_data_direction direction)
955 struct sg_table *sg_table;
960 if (WARN_ON(!attach || !attach->dmabuf))
961 return ERR_PTR(-EINVAL);
963 if (dma_buf_attachment_is_dynamic(attach))
964 dma_resv_assert_held(attach->dmabuf->resv);
968 * Two mappings with different directions for the same
969 * attachment are not allowed.
971 if (attach->dir != direction &&
972 attach->dir != DMA_BIDIRECTIONAL)
973 return ERR_PTR(-EBUSY);
978 if (dma_buf_is_dynamic(attach->dmabuf)) {
979 dma_resv_assert_held(attach->dmabuf->resv);
980 if (!IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY)) {
981 r = attach->dmabuf->ops->pin(attach);
987 sg_table = __map_dma_buf(attach, direction);
989 sg_table = ERR_PTR(-ENOMEM);
991 if (IS_ERR(sg_table) && dma_buf_is_dynamic(attach->dmabuf) &&
992 !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY))
993 attach->dmabuf->ops->unpin(attach);
995 if (!IS_ERR(sg_table) && attach->dmabuf->ops->cache_sgt_mapping) {
996 attach->sgt = sg_table;
997 attach->dir = direction;
1000 #ifdef CONFIG_DMA_API_DEBUG
1001 if (!IS_ERR(sg_table)) {
1002 struct scatterlist *sg;
1007 for_each_sgtable_dma_sg(sg_table, sg, i) {
1008 addr = sg_dma_address(sg);
1009 len = sg_dma_len(sg);
1010 if (!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(len)) {
1011 pr_debug("%s: addr %llx or len %x is not page aligned!\n",
1012 __func__, addr, len);
1016 #endif /* CONFIG_DMA_API_DEBUG */
1019 EXPORT_SYMBOL_GPL(dma_buf_map_attachment);
1022 * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might
1023 * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of
1025 * @attach: [in] attachment to unmap buffer from
1026 * @sg_table: [in] scatterlist info of the buffer to unmap
1027 * @direction: [in] direction of DMA transfer
1029 * This unmaps a DMA mapping for @attached obtained by dma_buf_map_attachment().
1031 void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
1032 struct sg_table *sg_table,
1033 enum dma_data_direction direction)
1037 if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
1040 if (dma_buf_attachment_is_dynamic(attach))
1041 dma_resv_assert_held(attach->dmabuf->resv);
1043 if (attach->sgt == sg_table)
1046 if (dma_buf_is_dynamic(attach->dmabuf))
1047 dma_resv_assert_held(attach->dmabuf->resv);
1049 __unmap_dma_buf(attach, sg_table, direction);
1051 if (dma_buf_is_dynamic(attach->dmabuf) &&
1052 !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY))
1053 dma_buf_unpin(attach);
1055 EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment);
1058 * dma_buf_move_notify - notify attachments that DMA-buf is moving
1060 * @dmabuf: [in] buffer which is moving
1062 * Informs all attachmenst that they need to destroy and recreated all their
1065 void dma_buf_move_notify(struct dma_buf *dmabuf)
1067 struct dma_buf_attachment *attach;
1069 dma_resv_assert_held(dmabuf->resv);
1071 list_for_each_entry(attach, &dmabuf->attachments, node)
1072 if (attach->importer_ops)
1073 attach->importer_ops->move_notify(attach);
1075 EXPORT_SYMBOL_GPL(dma_buf_move_notify);
1080 * There are mutliple reasons for supporting CPU access to a dma buffer object:
1082 * - Fallback operations in the kernel, for example when a device is connected
1083 * over USB and the kernel needs to shuffle the data around first before
1084 * sending it away. Cache coherency is handled by braketing any transactions
1085 * with calls to dma_buf_begin_cpu_access() and dma_buf_end_cpu_access()
1088 * Since for most kernel internal dma-buf accesses need the entire buffer, a
1089 * vmap interface is introduced. Note that on very old 32-bit architectures
1090 * vmalloc space might be limited and result in vmap calls failing.
1094 * void \*dma_buf_vmap(struct dma_buf \*dmabuf)
1095 * void dma_buf_vunmap(struct dma_buf \*dmabuf, void \*vaddr)
1097 * The vmap call can fail if there is no vmap support in the exporter, or if
1098 * it runs out of vmalloc space. Note that the dma-buf layer keeps a reference
1099 * count for all vmap access and calls down into the exporter's vmap function
1100 * only when no vmapping exists, and only unmaps it once. Protection against
1101 * concurrent vmap/vunmap calls is provided by taking the &dma_buf.lock mutex.
1103 * - For full compatibility on the importer side with existing userspace
1104 * interfaces, which might already support mmap'ing buffers. This is needed in
1105 * many processing pipelines (e.g. feeding a software rendered image into a
1106 * hardware pipeline, thumbnail creation, snapshots, ...). Also, Android's ION
1107 * framework already supported this and for DMA buffer file descriptors to
1108 * replace ION buffers mmap support was needed.
1110 * There is no special interfaces, userspace simply calls mmap on the dma-buf
1111 * fd. But like for CPU access there's a need to braket the actual access,
1112 * which is handled by the ioctl (DMA_BUF_IOCTL_SYNC). Note that
1113 * DMA_BUF_IOCTL_SYNC can fail with -EAGAIN or -EINTR, in which case it must
1116 * Some systems might need some sort of cache coherency management e.g. when
1117 * CPU and GPU domains are being accessed through dma-buf at the same time.
1118 * To circumvent this problem there are begin/end coherency markers, that
1119 * forward directly to existing dma-buf device drivers vfunc hooks. Userspace
1120 * can make use of those markers through the DMA_BUF_IOCTL_SYNC ioctl. The
1121 * sequence would be used like following:
1124 * - for each drawing/upload cycle in CPU 1. SYNC_START ioctl, 2. read/write
1125 * to mmap area 3. SYNC_END ioctl. This can be repeated as often as you
1126 * want (with the new data being consumed by say the GPU or the scanout
1128 * - munmap once you don't need the buffer any more
1130 * For correctness and optimal performance, it is always required to use
1131 * SYNC_START and SYNC_END before and after, respectively, when accessing the
1132 * mapped address. Userspace cannot rely on coherent access, even when there
1133 * are systems where it just works without calling these ioctls.
1135 * - And as a CPU fallback in userspace processing pipelines.
1137 * Similar to the motivation for kernel cpu access it is again important that
1138 * the userspace code of a given importing subsystem can use the same
1139 * interfaces with a imported dma-buf buffer object as with a native buffer
1140 * object. This is especially important for drm where the userspace part of
1141 * contemporary OpenGL, X, and other drivers is huge, and reworking them to
1142 * use a different way to mmap a buffer rather invasive.
1144 * The assumption in the current dma-buf interfaces is that redirecting the
1145 * initial mmap is all that's needed. A survey of some of the existing
1146 * subsystems shows that no driver seems to do any nefarious thing like
1147 * syncing up with outstanding asynchronous processing on the device or
1148 * allocating special resources at fault time. So hopefully this is good
1149 * enough, since adding interfaces to intercept pagefaults and allow pte
1150 * shootdowns would increase the complexity quite a bit.
1154 * int dma_buf_mmap(struct dma_buf \*, struct vm_area_struct \*,
1157 * If the importing subsystem simply provides a special-purpose mmap call to
1158 * set up a mapping in userspace, calling do_mmap with &dma_buf.file will
1159 * equally achieve that for a dma-buf object.
1162 static int __dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
1163 enum dma_data_direction direction)
1165 bool write = (direction == DMA_BIDIRECTIONAL ||
1166 direction == DMA_TO_DEVICE);
1167 struct dma_resv *resv = dmabuf->resv;
1170 /* Wait on any implicit rendering fences */
1171 ret = dma_resv_wait_timeout(resv, write, true, MAX_SCHEDULE_TIMEOUT);
1179 * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the
1180 * cpu in the kernel context. Calls begin_cpu_access to allow exporter-specific
1181 * preparations. Coherency is only guaranteed in the specified range for the
1182 * specified access direction.
1183 * @dmabuf: [in] buffer to prepare cpu access for.
1184 * @direction: [in] length of range for cpu access.
1186 * After the cpu access is complete the caller should call
1187 * dma_buf_end_cpu_access(). Only when cpu access is braketed by both calls is
1188 * it guaranteed to be coherent with other DMA access.
1190 * This function will also wait for any DMA transactions tracked through
1191 * implicit synchronization in &dma_buf.resv. For DMA transactions with explicit
1192 * synchronization this function will only ensure cache coherency, callers must
1193 * ensure synchronization with such DMA transactions on their own.
1195 * Can return negative error values, returns 0 on success.
1197 int dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
1198 enum dma_data_direction direction)
1202 if (WARN_ON(!dmabuf))
1205 might_lock(&dmabuf->resv->lock.base);
1207 if (dmabuf->ops->begin_cpu_access)
1208 ret = dmabuf->ops->begin_cpu_access(dmabuf, direction);
1210 /* Ensure that all fences are waited upon - but we first allow
1211 * the native handler the chance to do so more efficiently if it
1212 * chooses. A double invocation here will be reasonably cheap no-op.
1215 ret = __dma_buf_begin_cpu_access(dmabuf, direction);
1219 EXPORT_SYMBOL_GPL(dma_buf_begin_cpu_access);
1222 * dma_buf_end_cpu_access - Must be called after accessing a dma_buf from the
1223 * cpu in the kernel context. Calls end_cpu_access to allow exporter-specific
1224 * actions. Coherency is only guaranteed in the specified range for the
1225 * specified access direction.
1226 * @dmabuf: [in] buffer to complete cpu access for.
1227 * @direction: [in] length of range for cpu access.
1229 * This terminates CPU access started with dma_buf_begin_cpu_access().
1231 * Can return negative error values, returns 0 on success.
1233 int dma_buf_end_cpu_access(struct dma_buf *dmabuf,
1234 enum dma_data_direction direction)
1240 might_lock(&dmabuf->resv->lock.base);
1242 if (dmabuf->ops->end_cpu_access)
1243 ret = dmabuf->ops->end_cpu_access(dmabuf, direction);
1247 EXPORT_SYMBOL_GPL(dma_buf_end_cpu_access);
1251 * dma_buf_mmap - Setup up a userspace mmap with the given vma
1252 * @dmabuf: [in] buffer that should back the vma
1253 * @vma: [in] vma for the mmap
1254 * @pgoff: [in] offset in pages where this mmap should start within the
1257 * This function adjusts the passed in vma so that it points at the file of the
1258 * dma_buf operation. It also adjusts the starting pgoff and does bounds
1259 * checking on the size of the vma. Then it calls the exporters mmap function to
1260 * set up the mapping.
1262 * Can return negative error values, returns 0 on success.
1264 int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
1265 unsigned long pgoff)
1267 if (WARN_ON(!dmabuf || !vma))
1270 /* check if buffer supports mmap */
1271 if (!dmabuf->ops->mmap)
1274 /* check for offset overflow */
1275 if (pgoff + vma_pages(vma) < pgoff)
1278 /* check for overflowing the buffer's size */
1279 if (pgoff + vma_pages(vma) >
1280 dmabuf->size >> PAGE_SHIFT)
1283 /* readjust the vma */
1284 vma_set_file(vma, dmabuf->file);
1285 vma->vm_pgoff = pgoff;
1287 return dmabuf->ops->mmap(dmabuf, vma);
1289 EXPORT_SYMBOL_GPL(dma_buf_mmap);
1292 * dma_buf_vmap - Create virtual mapping for the buffer object into kernel
1293 * address space. Same restrictions as for vmap and friends apply.
1294 * @dmabuf: [in] buffer to vmap
1295 * @map: [out] returns the vmap pointer
1297 * This call may fail due to lack of virtual mapping address space.
1298 * These calls are optional in drivers. The intended use for them
1299 * is for mapping objects linear in kernel space for high use objects.
1301 * To ensure coherency users must call dma_buf_begin_cpu_access() and
1302 * dma_buf_end_cpu_access() around any cpu access performed through this
1305 * Returns 0 on success, or a negative errno code otherwise.
1307 int dma_buf_vmap(struct dma_buf *dmabuf, struct dma_buf_map *map)
1309 struct dma_buf_map ptr;
1312 dma_buf_map_clear(map);
1314 if (WARN_ON(!dmabuf))
1317 if (!dmabuf->ops->vmap)
1320 mutex_lock(&dmabuf->lock);
1321 if (dmabuf->vmapping_counter) {
1322 dmabuf->vmapping_counter++;
1323 BUG_ON(dma_buf_map_is_null(&dmabuf->vmap_ptr));
1324 *map = dmabuf->vmap_ptr;
1328 BUG_ON(dma_buf_map_is_set(&dmabuf->vmap_ptr));
1330 ret = dmabuf->ops->vmap(dmabuf, &ptr);
1331 if (WARN_ON_ONCE(ret))
1334 dmabuf->vmap_ptr = ptr;
1335 dmabuf->vmapping_counter = 1;
1337 *map = dmabuf->vmap_ptr;
1340 mutex_unlock(&dmabuf->lock);
1343 EXPORT_SYMBOL_GPL(dma_buf_vmap);
1346 * dma_buf_vunmap - Unmap a vmap obtained by dma_buf_vmap.
1347 * @dmabuf: [in] buffer to vunmap
1348 * @map: [in] vmap pointer to vunmap
1350 void dma_buf_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map)
1352 if (WARN_ON(!dmabuf))
1355 BUG_ON(dma_buf_map_is_null(&dmabuf->vmap_ptr));
1356 BUG_ON(dmabuf->vmapping_counter == 0);
1357 BUG_ON(!dma_buf_map_is_equal(&dmabuf->vmap_ptr, map));
1359 mutex_lock(&dmabuf->lock);
1360 if (--dmabuf->vmapping_counter == 0) {
1361 if (dmabuf->ops->vunmap)
1362 dmabuf->ops->vunmap(dmabuf, map);
1363 dma_buf_map_clear(&dmabuf->vmap_ptr);
1365 mutex_unlock(&dmabuf->lock);
1367 EXPORT_SYMBOL_GPL(dma_buf_vunmap);
1369 #ifdef CONFIG_DEBUG_FS
1370 static int dma_buf_debug_show(struct seq_file *s, void *unused)
1372 struct dma_buf *buf_obj;
1373 struct dma_buf_attachment *attach_obj;
1374 struct dma_resv *robj;
1375 struct dma_resv_list *fobj;
1376 struct dma_fence *fence;
1377 int count = 0, attach_count, shared_count, i;
1381 ret = mutex_lock_interruptible(&db_list.lock);
1386 seq_puts(s, "\nDma-buf Objects:\n");
1387 seq_printf(s, "%-8s\t%-8s\t%-8s\t%-8s\texp_name\t%-8s\n",
1388 "size", "flags", "mode", "count", "ino");
1390 list_for_each_entry(buf_obj, &db_list.head, list_node) {
1392 ret = dma_resv_lock_interruptible(buf_obj->resv, NULL);
1396 seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\t%08lu\t%s\n",
1398 buf_obj->file->f_flags, buf_obj->file->f_mode,
1399 file_count(buf_obj->file),
1401 file_inode(buf_obj->file)->i_ino,
1402 buf_obj->name ?: "");
1404 robj = buf_obj->resv;
1405 fence = dma_resv_excl_fence(robj);
1407 seq_printf(s, "\tExclusive fence: %s %s %ssignalled\n",
1408 fence->ops->get_driver_name(fence),
1409 fence->ops->get_timeline_name(fence),
1410 dma_fence_is_signaled(fence) ? "" : "un");
1412 fobj = rcu_dereference_protected(robj->fence,
1413 dma_resv_held(robj));
1414 shared_count = fobj ? fobj->shared_count : 0;
1415 for (i = 0; i < shared_count; i++) {
1416 fence = rcu_dereference_protected(fobj->shared[i],
1417 dma_resv_held(robj));
1418 seq_printf(s, "\tShared fence: %s %s %ssignalled\n",
1419 fence->ops->get_driver_name(fence),
1420 fence->ops->get_timeline_name(fence),
1421 dma_fence_is_signaled(fence) ? "" : "un");
1424 seq_puts(s, "\tAttached Devices:\n");
1427 list_for_each_entry(attach_obj, &buf_obj->attachments, node) {
1428 seq_printf(s, "\t%s\n", dev_name(attach_obj->dev));
1431 dma_resv_unlock(buf_obj->resv);
1433 seq_printf(s, "Total %d devices attached\n\n",
1437 size += buf_obj->size;
1440 seq_printf(s, "\nTotal %d objects, %zu bytes\n", count, size);
1442 mutex_unlock(&db_list.lock);
1446 mutex_unlock(&db_list.lock);
1450 DEFINE_SHOW_ATTRIBUTE(dma_buf_debug);
1452 static struct dentry *dma_buf_debugfs_dir;
1454 static int dma_buf_init_debugfs(void)
1459 d = debugfs_create_dir("dma_buf", NULL);
1463 dma_buf_debugfs_dir = d;
1465 d = debugfs_create_file("bufinfo", S_IRUGO, dma_buf_debugfs_dir,
1466 NULL, &dma_buf_debug_fops);
1468 pr_debug("dma_buf: debugfs: failed to create node bufinfo\n");
1469 debugfs_remove_recursive(dma_buf_debugfs_dir);
1470 dma_buf_debugfs_dir = NULL;
1477 static void dma_buf_uninit_debugfs(void)
1479 debugfs_remove_recursive(dma_buf_debugfs_dir);
1482 static inline int dma_buf_init_debugfs(void)
1486 static inline void dma_buf_uninit_debugfs(void)
1491 static int __init dma_buf_init(void)
1495 ret = dma_buf_init_sysfs_statistics();
1499 dma_buf_mnt = kern_mount(&dma_buf_fs_type);
1500 if (IS_ERR(dma_buf_mnt))
1501 return PTR_ERR(dma_buf_mnt);
1503 mutex_init(&db_list.lock);
1504 INIT_LIST_HEAD(&db_list.head);
1505 dma_buf_init_debugfs();
1508 subsys_initcall(dma_buf_init);
1510 static void __exit dma_buf_deinit(void)
1512 dma_buf_uninit_debugfs();
1513 kern_unmount(dma_buf_mnt);
1514 dma_buf_uninit_sysfs_statistics();
1516 __exitcall(dma_buf_deinit);