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 mutex_lock(&dmabuf->lock);
50 ret = strlcpy(name, dmabuf->name, DMA_BUF_NAME_LEN);
51 mutex_unlock(&dmabuf->lock);
53 return dynamic_dname(dentry, buffer, buflen, "/%s:%s",
54 dentry->d_name.name, ret > 0 ? name : "");
57 static const struct dentry_operations dma_buf_dentry_ops = {
58 .d_dname = dmabuffs_dname,
61 static struct vfsmount *dma_buf_mnt;
63 static int dma_buf_fs_init_context(struct fs_context *fc)
65 struct pseudo_fs_context *ctx;
67 ctx = init_pseudo(fc, DMA_BUF_MAGIC);
70 ctx->dops = &dma_buf_dentry_ops;
74 static struct file_system_type dma_buf_fs_type = {
76 .init_fs_context = dma_buf_fs_init_context,
77 .kill_sb = kill_anon_super,
80 static int dma_buf_release(struct inode *inode, struct file *file)
82 struct dma_buf *dmabuf;
84 if (!is_dma_buf_file(file))
87 dmabuf = file->private_data;
89 BUG_ON(dmabuf->vmapping_counter);
92 * Any fences that a dma-buf poll can wait on should be signaled
93 * before releasing dma-buf. This is the responsibility of each
94 * driver that uses the reservation objects.
96 * If you hit this BUG() it means someone dropped their ref to the
97 * dma-buf while still having pending operation to the buffer.
99 BUG_ON(dmabuf->cb_shared.active || dmabuf->cb_excl.active);
101 dmabuf->ops->release(dmabuf);
103 mutex_lock(&db_list.lock);
104 list_del(&dmabuf->list_node);
105 mutex_unlock(&db_list.lock);
107 if (dmabuf->resv == (struct dma_resv *)&dmabuf[1])
108 dma_resv_fini(dmabuf->resv);
110 module_put(dmabuf->owner);
115 static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
117 struct dma_buf *dmabuf;
119 if (!is_dma_buf_file(file))
122 dmabuf = file->private_data;
124 /* check if buffer supports mmap */
125 if (!dmabuf->ops->mmap)
128 /* check for overflowing the buffer's size */
129 if (vma->vm_pgoff + vma_pages(vma) >
130 dmabuf->size >> PAGE_SHIFT)
133 return dmabuf->ops->mmap(dmabuf, vma);
136 static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence)
138 struct dma_buf *dmabuf;
141 if (!is_dma_buf_file(file))
144 dmabuf = file->private_data;
146 /* only support discovering the end of the buffer,
147 but also allow SEEK_SET to maintain the idiomatic
148 SEEK_END(0), SEEK_CUR(0) pattern */
149 if (whence == SEEK_END)
151 else if (whence == SEEK_SET)
159 return base + offset;
165 * To support cross-device and cross-driver synchronization of buffer access
166 * implicit fences (represented internally in the kernel with &struct fence) can
167 * be attached to a &dma_buf. The glue for that and a few related things are
168 * provided in the &dma_resv structure.
170 * Userspace can query the state of these implicitly tracked fences using poll()
171 * and related system calls:
173 * - Checking for EPOLLIN, i.e. read access, can be use to query the state of the
174 * most recent write or exclusive fence.
176 * - Checking for EPOLLOUT, i.e. write access, can be used to query the state of
177 * all attached fences, shared and exclusive ones.
179 * Note that this only signals the completion of the respective fences, i.e. the
180 * DMA transfers are complete. Cache flushing and any other necessary
181 * preparations before CPU access can begin still need to happen.
184 static void dma_buf_poll_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
186 struct dma_buf_poll_cb_t *dcb = (struct dma_buf_poll_cb_t *)cb;
189 spin_lock_irqsave(&dcb->poll->lock, flags);
190 wake_up_locked_poll(dcb->poll, dcb->active);
192 spin_unlock_irqrestore(&dcb->poll->lock, flags);
195 static __poll_t dma_buf_poll(struct file *file, poll_table *poll)
197 struct dma_buf *dmabuf;
198 struct dma_resv *resv;
199 struct dma_resv_list *fobj;
200 struct dma_fence *fence_excl;
202 unsigned shared_count;
204 dmabuf = file->private_data;
205 if (!dmabuf || !dmabuf->resv)
210 poll_wait(file, &dmabuf->poll, poll);
212 events = poll_requested_events(poll) & (EPOLLIN | EPOLLOUT);
217 dma_resv_fences(resv, &fence_excl, &fobj, &shared_count);
218 if (fence_excl && (!(events & EPOLLOUT) || shared_count == 0)) {
219 struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_excl;
220 __poll_t pevents = EPOLLIN;
222 if (shared_count == 0)
225 spin_lock_irq(&dmabuf->poll.lock);
227 dcb->active |= pevents;
230 dcb->active = pevents;
231 spin_unlock_irq(&dmabuf->poll.lock);
233 if (events & pevents) {
234 if (!dma_fence_get_rcu(fence_excl)) {
235 /* force a recheck */
237 dma_buf_poll_cb(NULL, &dcb->cb);
238 } else if (!dma_fence_add_callback(fence_excl, &dcb->cb,
241 dma_fence_put(fence_excl);
244 * No callback queued, wake up any additional
247 dma_fence_put(fence_excl);
248 dma_buf_poll_cb(NULL, &dcb->cb);
253 if ((events & EPOLLOUT) && shared_count > 0) {
254 struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_shared;
257 /* Only queue a new callback if no event has fired yet */
258 spin_lock_irq(&dmabuf->poll.lock);
262 dcb->active = EPOLLOUT;
263 spin_unlock_irq(&dmabuf->poll.lock);
265 if (!(events & EPOLLOUT))
268 for (i = 0; i < shared_count; ++i) {
269 struct dma_fence *fence = rcu_dereference(fobj->shared[i]);
271 if (!dma_fence_get_rcu(fence)) {
273 * fence refcount dropped to zero, this means
274 * that fobj has been freed
276 * call dma_buf_poll_cb and force a recheck!
279 dma_buf_poll_cb(NULL, &dcb->cb);
282 if (!dma_fence_add_callback(fence, &dcb->cb,
284 dma_fence_put(fence);
288 dma_fence_put(fence);
291 /* No callback queued, wake up any additional waiters. */
292 if (i == shared_count)
293 dma_buf_poll_cb(NULL, &dcb->cb);
302 * dma_buf_set_name - Set a name to a specific dma_buf to track the usage.
303 * The name of the dma-buf buffer can only be set when the dma-buf is not
304 * attached to any devices. It could theoritically support changing the
305 * name of the dma-buf if the same piece of memory is used for multiple
306 * purpose between different devices.
308 * @dmabuf [in] dmabuf buffer that will be renamed.
309 * @buf: [in] A piece of userspace memory that contains the name of
312 * Returns 0 on success. If the dma-buf buffer is already attached to
313 * devices, return -EBUSY.
316 static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf)
318 char *name = strndup_user(buf, DMA_BUF_NAME_LEN);
322 return PTR_ERR(name);
324 mutex_lock(&dmabuf->lock);
325 if (!list_empty(&dmabuf->attachments)) {
334 mutex_unlock(&dmabuf->lock);
338 static long dma_buf_ioctl(struct file *file,
339 unsigned int cmd, unsigned long arg)
341 struct dma_buf *dmabuf;
342 struct dma_buf_sync sync;
343 enum dma_data_direction direction;
346 dmabuf = file->private_data;
349 case DMA_BUF_IOCTL_SYNC:
350 if (copy_from_user(&sync, (void __user *) arg, sizeof(sync)))
353 if (sync.flags & ~DMA_BUF_SYNC_VALID_FLAGS_MASK)
356 switch (sync.flags & DMA_BUF_SYNC_RW) {
357 case DMA_BUF_SYNC_READ:
358 direction = DMA_FROM_DEVICE;
360 case DMA_BUF_SYNC_WRITE:
361 direction = DMA_TO_DEVICE;
363 case DMA_BUF_SYNC_RW:
364 direction = DMA_BIDIRECTIONAL;
370 if (sync.flags & DMA_BUF_SYNC_END)
371 ret = dma_buf_end_cpu_access(dmabuf, direction);
373 ret = dma_buf_begin_cpu_access(dmabuf, direction);
377 case DMA_BUF_SET_NAME:
378 return dma_buf_set_name(dmabuf, (const char __user *)arg);
385 static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file)
387 struct dma_buf *dmabuf = file->private_data;
389 seq_printf(m, "size:\t%zu\n", dmabuf->size);
390 /* Don't count the temporary reference taken inside procfs seq_show */
391 seq_printf(m, "count:\t%ld\n", file_count(dmabuf->file) - 1);
392 seq_printf(m, "exp_name:\t%s\n", dmabuf->exp_name);
393 mutex_lock(&dmabuf->lock);
395 seq_printf(m, "name:\t%s\n", dmabuf->name);
396 mutex_unlock(&dmabuf->lock);
399 static const struct file_operations dma_buf_fops = {
400 .release = dma_buf_release,
401 .mmap = dma_buf_mmap_internal,
402 .llseek = dma_buf_llseek,
403 .poll = dma_buf_poll,
404 .unlocked_ioctl = dma_buf_ioctl,
406 .compat_ioctl = dma_buf_ioctl,
408 .show_fdinfo = dma_buf_show_fdinfo,
412 * is_dma_buf_file - Check if struct file* is associated with dma_buf
414 static inline int is_dma_buf_file(struct file *file)
416 return file->f_op == &dma_buf_fops;
419 static struct file *dma_buf_getfile(struct dma_buf *dmabuf, int flags)
422 struct inode *inode = alloc_anon_inode(dma_buf_mnt->mnt_sb);
425 return ERR_CAST(inode);
427 inode->i_size = dmabuf->size;
428 inode_set_bytes(inode, dmabuf->size);
430 file = alloc_file_pseudo(inode, dma_buf_mnt, "dmabuf",
431 flags, &dma_buf_fops);
434 file->f_flags = flags & (O_ACCMODE | O_NONBLOCK);
435 file->private_data = dmabuf;
436 file->f_path.dentry->d_fsdata = dmabuf;
446 * DOC: dma buf device access
448 * For device DMA access to a shared DMA buffer the usual sequence of operations
451 * 1. The exporter defines his exporter instance using
452 * DEFINE_DMA_BUF_EXPORT_INFO() and calls dma_buf_export() to wrap a private
453 * buffer object into a &dma_buf. It then exports that &dma_buf to userspace
454 * as a file descriptor by calling dma_buf_fd().
456 * 2. Userspace passes this file-descriptors to all drivers it wants this buffer
457 * to share with: First the filedescriptor is converted to a &dma_buf using
458 * dma_buf_get(). Then the buffer is attached to the device using
461 * Up to this stage the exporter is still free to migrate or reallocate the
464 * 3. Once the buffer is attached to all devices userspace can initiate DMA
465 * access to the shared buffer. In the kernel this is done by calling
466 * dma_buf_map_attachment() and dma_buf_unmap_attachment().
468 * 4. Once a driver is done with a shared buffer it needs to call
469 * dma_buf_detach() (after cleaning up any mappings) and then release the
470 * reference acquired with dma_buf_get by calling dma_buf_put().
472 * For the detailed semantics exporters are expected to implement see
477 * dma_buf_export - Creates a new dma_buf, and associates an anon file
478 * with this buffer, so it can be exported.
479 * Also connect the allocator specific data and ops to the buffer.
480 * Additionally, provide a name string for exporter; useful in debugging.
482 * @exp_info: [in] holds all the export related information provided
483 * by the exporter. see &struct dma_buf_export_info
484 * for further details.
486 * Returns, on success, a newly created dma_buf object, which wraps the
487 * supplied private data and operations for dma_buf_ops. On either missing
488 * ops, or error in allocating struct dma_buf, will return negative error.
490 * For most cases the easiest way to create @exp_info is through the
491 * %DEFINE_DMA_BUF_EXPORT_INFO macro.
493 struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
495 struct dma_buf *dmabuf;
496 struct dma_resv *resv = exp_info->resv;
498 size_t alloc_size = sizeof(struct dma_buf);
502 alloc_size += sizeof(struct dma_resv);
504 /* prevent &dma_buf[1] == dma_buf->resv */
507 if (WARN_ON(!exp_info->priv
509 || !exp_info->ops->map_dma_buf
510 || !exp_info->ops->unmap_dma_buf
511 || !exp_info->ops->release)) {
512 return ERR_PTR(-EINVAL);
515 if (!try_module_get(exp_info->owner))
516 return ERR_PTR(-ENOENT);
518 dmabuf = kzalloc(alloc_size, GFP_KERNEL);
524 dmabuf->priv = exp_info->priv;
525 dmabuf->ops = exp_info->ops;
526 dmabuf->size = exp_info->size;
527 dmabuf->exp_name = exp_info->exp_name;
528 dmabuf->owner = exp_info->owner;
529 init_waitqueue_head(&dmabuf->poll);
530 dmabuf->cb_excl.poll = dmabuf->cb_shared.poll = &dmabuf->poll;
531 dmabuf->cb_excl.active = dmabuf->cb_shared.active = 0;
534 resv = (struct dma_resv *)&dmabuf[1];
539 file = dma_buf_getfile(dmabuf, exp_info->flags);
545 file->f_mode |= FMODE_LSEEK;
548 mutex_init(&dmabuf->lock);
549 INIT_LIST_HEAD(&dmabuf->attachments);
551 mutex_lock(&db_list.lock);
552 list_add(&dmabuf->list_node, &db_list.head);
553 mutex_unlock(&db_list.lock);
560 module_put(exp_info->owner);
563 EXPORT_SYMBOL_GPL(dma_buf_export);
566 * dma_buf_fd - returns a file descriptor for the given dma_buf
567 * @dmabuf: [in] pointer to dma_buf for which fd is required.
568 * @flags: [in] flags to give to fd
570 * On success, returns an associated 'fd'. Else, returns error.
572 int dma_buf_fd(struct dma_buf *dmabuf, int flags)
576 if (!dmabuf || !dmabuf->file)
579 fd = get_unused_fd_flags(flags);
583 fd_install(fd, dmabuf->file);
587 EXPORT_SYMBOL_GPL(dma_buf_fd);
590 * dma_buf_get - returns the dma_buf structure related to an fd
591 * @fd: [in] fd associated with the dma_buf to be returned
593 * On success, returns the dma_buf structure associated with an fd; uses
594 * file's refcounting done by fget to increase refcount. returns ERR_PTR
597 struct dma_buf *dma_buf_get(int fd)
604 return ERR_PTR(-EBADF);
606 if (!is_dma_buf_file(file)) {
608 return ERR_PTR(-EINVAL);
611 return file->private_data;
613 EXPORT_SYMBOL_GPL(dma_buf_get);
616 * dma_buf_put - decreases refcount of the buffer
617 * @dmabuf: [in] buffer to reduce refcount of
619 * Uses file's refcounting done implicitly by fput().
621 * If, as a result of this call, the refcount becomes 0, the 'release' file
622 * operation related to this fd is called. It calls &dma_buf_ops.release vfunc
623 * in turn, and frees the memory allocated for dmabuf when exported.
625 void dma_buf_put(struct dma_buf *dmabuf)
627 if (WARN_ON(!dmabuf || !dmabuf->file))
632 EXPORT_SYMBOL_GPL(dma_buf_put);
635 * dma_buf_attach - Add the device to dma_buf's attachments list; optionally,
636 * calls attach() of dma_buf_ops to allow device-specific attach functionality
637 * @dmabuf: [in] buffer to attach device to.
638 * @dev: [in] device to be attached.
640 * Returns struct dma_buf_attachment pointer for this attachment. Attachments
641 * must be cleaned up by calling dma_buf_detach().
645 * A pointer to newly created &dma_buf_attachment on success, or a negative
646 * error code wrapped into a pointer on failure.
648 * Note that this can fail if the backing storage of @dmabuf is in a place not
649 * accessible to @dev, and cannot be moved to a more suitable place. This is
650 * indicated with the error code -EBUSY.
652 struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
655 struct dma_buf_attachment *attach;
658 if (WARN_ON(!dmabuf || !dev))
659 return ERR_PTR(-EINVAL);
661 attach = kzalloc(sizeof(*attach), GFP_KERNEL);
663 return ERR_PTR(-ENOMEM);
666 attach->dmabuf = dmabuf;
668 mutex_lock(&dmabuf->lock);
670 if (dmabuf->ops->attach) {
671 ret = dmabuf->ops->attach(dmabuf, attach);
675 list_add(&attach->node, &dmabuf->attachments);
677 mutex_unlock(&dmabuf->lock);
683 mutex_unlock(&dmabuf->lock);
686 EXPORT_SYMBOL_GPL(dma_buf_attach);
689 * dma_buf_detach - Remove the given attachment from dmabuf's attachments list;
690 * optionally calls detach() of dma_buf_ops for device-specific detach
691 * @dmabuf: [in] buffer to detach from.
692 * @attach: [in] attachment to be detached; is free'd after this call.
694 * Clean up a device attachment obtained by calling dma_buf_attach().
696 void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
698 if (WARN_ON(!dmabuf || !attach))
702 dmabuf->ops->unmap_dma_buf(attach, attach->sgt, attach->dir);
704 mutex_lock(&dmabuf->lock);
705 list_del(&attach->node);
706 if (dmabuf->ops->detach)
707 dmabuf->ops->detach(dmabuf, attach);
709 mutex_unlock(&dmabuf->lock);
712 EXPORT_SYMBOL_GPL(dma_buf_detach);
715 * dma_buf_map_attachment - Returns the scatterlist table of the attachment;
716 * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the
718 * @attach: [in] attachment whose scatterlist is to be returned
719 * @direction: [in] direction of DMA transfer
721 * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
722 * on error. May return -EINTR if it is interrupted by a signal.
724 * A mapping must be unmapped by using dma_buf_unmap_attachment(). Note that
725 * the underlying backing storage is pinned for as long as a mapping exists,
726 * therefore users/importers should not hold onto a mapping for undue amounts of
729 struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
730 enum dma_data_direction direction)
732 struct sg_table *sg_table;
736 if (WARN_ON(!attach || !attach->dmabuf))
737 return ERR_PTR(-EINVAL);
741 * Two mappings with different directions for the same
742 * attachment are not allowed.
744 if (attach->dir != direction &&
745 attach->dir != DMA_BIDIRECTIONAL)
746 return ERR_PTR(-EBUSY);
751 sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
753 sg_table = ERR_PTR(-ENOMEM);
755 if (!IS_ERR(sg_table) && attach->dmabuf->ops->cache_sgt_mapping) {
756 attach->sgt = sg_table;
757 attach->dir = direction;
762 EXPORT_SYMBOL_GPL(dma_buf_map_attachment);
765 * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might
766 * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of
768 * @attach: [in] attachment to unmap buffer from
769 * @sg_table: [in] scatterlist info of the buffer to unmap
770 * @direction: [in] direction of DMA transfer
772 * This unmaps a DMA mapping for @attached obtained by dma_buf_map_attachment().
774 void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
775 struct sg_table *sg_table,
776 enum dma_data_direction direction)
780 if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
783 if (attach->sgt == sg_table)
786 attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, direction);
788 EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment);
793 * There are mutliple reasons for supporting CPU access to a dma buffer object:
795 * - Fallback operations in the kernel, for example when a device is connected
796 * over USB and the kernel needs to shuffle the data around first before
797 * sending it away. Cache coherency is handled by braketing any transactions
798 * with calls to dma_buf_begin_cpu_access() and dma_buf_end_cpu_access()
801 * To support dma_buf objects residing in highmem cpu access is page-based
802 * using an api similar to kmap. Accessing a dma_buf is done in aligned chunks
803 * of PAGE_SIZE size. Before accessing a chunk it needs to be mapped, which
804 * returns a pointer in kernel virtual address space. Afterwards the chunk
805 * needs to be unmapped again. There is no limit on how often a given chunk
806 * can be mapped and unmapped, i.e. the importer does not need to call
807 * begin_cpu_access again before mapping the same chunk again.
810 * void \*dma_buf_kmap(struct dma_buf \*, unsigned long);
811 * void dma_buf_kunmap(struct dma_buf \*, unsigned long, void \*);
813 * Implementing the functions is optional for exporters and for importers all
814 * the restrictions of using kmap apply.
816 * dma_buf kmap calls outside of the range specified in begin_cpu_access are
817 * undefined. If the range is not PAGE_SIZE aligned, kmap needs to succeed on
818 * the partial chunks at the beginning and end but may return stale or bogus
819 * data outside of the range (in these partial chunks).
821 * For some cases the overhead of kmap can be too high, a vmap interface
822 * is introduced. This interface should be used very carefully, as vmalloc
823 * space is a limited resources on many architectures.
826 * void \*dma_buf_vmap(struct dma_buf \*dmabuf)
827 * void dma_buf_vunmap(struct dma_buf \*dmabuf, void \*vaddr)
829 * The vmap call can fail if there is no vmap support in the exporter, or if
830 * it runs out of vmalloc space. Fallback to kmap should be implemented. Note
831 * that the dma-buf layer keeps a reference count for all vmap access and
832 * calls down into the exporter's vmap function only when no vmapping exists,
833 * and only unmaps it once. Protection against concurrent vmap/vunmap calls is
834 * provided by taking the dma_buf->lock mutex.
836 * - For full compatibility on the importer side with existing userspace
837 * interfaces, which might already support mmap'ing buffers. This is needed in
838 * many processing pipelines (e.g. feeding a software rendered image into a
839 * hardware pipeline, thumbnail creation, snapshots, ...). Also, Android's ION
840 * framework already supported this and for DMA buffer file descriptors to
841 * replace ION buffers mmap support was needed.
843 * There is no special interfaces, userspace simply calls mmap on the dma-buf
844 * fd. But like for CPU access there's a need to braket the actual access,
845 * which is handled by the ioctl (DMA_BUF_IOCTL_SYNC). Note that
846 * DMA_BUF_IOCTL_SYNC can fail with -EAGAIN or -EINTR, in which case it must
849 * Some systems might need some sort of cache coherency management e.g. when
850 * CPU and GPU domains are being accessed through dma-buf at the same time.
851 * To circumvent this problem there are begin/end coherency markers, that
852 * forward directly to existing dma-buf device drivers vfunc hooks. Userspace
853 * can make use of those markers through the DMA_BUF_IOCTL_SYNC ioctl. The
854 * sequence would be used like following:
857 * - for each drawing/upload cycle in CPU 1. SYNC_START ioctl, 2. read/write
858 * to mmap area 3. SYNC_END ioctl. This can be repeated as often as you
859 * want (with the new data being consumed by say the GPU or the scanout
861 * - munmap once you don't need the buffer any more
863 * For correctness and optimal performance, it is always required to use
864 * SYNC_START and SYNC_END before and after, respectively, when accessing the
865 * mapped address. Userspace cannot rely on coherent access, even when there
866 * are systems where it just works without calling these ioctls.
868 * - And as a CPU fallback in userspace processing pipelines.
870 * Similar to the motivation for kernel cpu access it is again important that
871 * the userspace code of a given importing subsystem can use the same
872 * interfaces with a imported dma-buf buffer object as with a native buffer
873 * object. This is especially important for drm where the userspace part of
874 * contemporary OpenGL, X, and other drivers is huge, and reworking them to
875 * use a different way to mmap a buffer rather invasive.
877 * The assumption in the current dma-buf interfaces is that redirecting the
878 * initial mmap is all that's needed. A survey of some of the existing
879 * subsystems shows that no driver seems to do any nefarious thing like
880 * syncing up with outstanding asynchronous processing on the device or
881 * allocating special resources at fault time. So hopefully this is good
882 * enough, since adding interfaces to intercept pagefaults and allow pte
883 * shootdowns would increase the complexity quite a bit.
886 * int dma_buf_mmap(struct dma_buf \*, struct vm_area_struct \*,
889 * If the importing subsystem simply provides a special-purpose mmap call to
890 * set up a mapping in userspace, calling do_mmap with dma_buf->file will
891 * equally achieve that for a dma-buf object.
894 static int __dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
895 enum dma_data_direction direction)
897 bool write = (direction == DMA_BIDIRECTIONAL ||
898 direction == DMA_TO_DEVICE);
899 struct dma_resv *resv = dmabuf->resv;
902 /* Wait on any implicit rendering fences */
903 ret = dma_resv_wait_timeout_rcu(resv, write, true,
904 MAX_SCHEDULE_TIMEOUT);
912 * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the
913 * cpu in the kernel context. Calls begin_cpu_access to allow exporter-specific
914 * preparations. Coherency is only guaranteed in the specified range for the
915 * specified access direction.
916 * @dmabuf: [in] buffer to prepare cpu access for.
917 * @direction: [in] length of range for cpu access.
919 * After the cpu access is complete the caller should call
920 * dma_buf_end_cpu_access(). Only when cpu access is braketed by both calls is
921 * it guaranteed to be coherent with other DMA access.
923 * Can return negative error values, returns 0 on success.
925 int dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
926 enum dma_data_direction direction)
930 if (WARN_ON(!dmabuf))
933 if (dmabuf->ops->begin_cpu_access)
934 ret = dmabuf->ops->begin_cpu_access(dmabuf, direction);
936 /* Ensure that all fences are waited upon - but we first allow
937 * the native handler the chance to do so more efficiently if it
938 * chooses. A double invocation here will be reasonably cheap no-op.
941 ret = __dma_buf_begin_cpu_access(dmabuf, direction);
945 EXPORT_SYMBOL_GPL(dma_buf_begin_cpu_access);
948 * dma_buf_end_cpu_access - Must be called after accessing a dma_buf from the
949 * cpu in the kernel context. Calls end_cpu_access to allow exporter-specific
950 * actions. Coherency is only guaranteed in the specified range for the
951 * specified access direction.
952 * @dmabuf: [in] buffer to complete cpu access for.
953 * @direction: [in] length of range for cpu access.
955 * This terminates CPU access started with dma_buf_begin_cpu_access().
957 * Can return negative error values, returns 0 on success.
959 int dma_buf_end_cpu_access(struct dma_buf *dmabuf,
960 enum dma_data_direction direction)
966 if (dmabuf->ops->end_cpu_access)
967 ret = dmabuf->ops->end_cpu_access(dmabuf, direction);
971 EXPORT_SYMBOL_GPL(dma_buf_end_cpu_access);
974 * dma_buf_kmap - Map a page of the buffer object into kernel address space. The
975 * same restrictions as for kmap and friends apply.
976 * @dmabuf: [in] buffer to map page from.
977 * @page_num: [in] page in PAGE_SIZE units to map.
979 * This call must always succeed, any necessary preparations that might fail
980 * need to be done in begin_cpu_access.
982 void *dma_buf_kmap(struct dma_buf *dmabuf, unsigned long page_num)
986 if (!dmabuf->ops->map)
988 return dmabuf->ops->map(dmabuf, page_num);
990 EXPORT_SYMBOL_GPL(dma_buf_kmap);
993 * dma_buf_kunmap - Unmap a page obtained by dma_buf_kmap.
994 * @dmabuf: [in] buffer to unmap page from.
995 * @page_num: [in] page in PAGE_SIZE units to unmap.
996 * @vaddr: [in] kernel space pointer obtained from dma_buf_kmap.
998 * This call must always succeed.
1000 void dma_buf_kunmap(struct dma_buf *dmabuf, unsigned long page_num,
1005 if (dmabuf->ops->unmap)
1006 dmabuf->ops->unmap(dmabuf, page_num, vaddr);
1008 EXPORT_SYMBOL_GPL(dma_buf_kunmap);
1012 * dma_buf_mmap - Setup up a userspace mmap with the given vma
1013 * @dmabuf: [in] buffer that should back the vma
1014 * @vma: [in] vma for the mmap
1015 * @pgoff: [in] offset in pages where this mmap should start within the
1018 * This function adjusts the passed in vma so that it points at the file of the
1019 * dma_buf operation. It also adjusts the starting pgoff and does bounds
1020 * checking on the size of the vma. Then it calls the exporters mmap function to
1021 * set up the mapping.
1023 * Can return negative error values, returns 0 on success.
1025 int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
1026 unsigned long pgoff)
1028 struct file *oldfile;
1031 if (WARN_ON(!dmabuf || !vma))
1034 /* check if buffer supports mmap */
1035 if (!dmabuf->ops->mmap)
1038 /* check for offset overflow */
1039 if (pgoff + vma_pages(vma) < pgoff)
1042 /* check for overflowing the buffer's size */
1043 if (pgoff + vma_pages(vma) >
1044 dmabuf->size >> PAGE_SHIFT)
1047 /* readjust the vma */
1048 get_file(dmabuf->file);
1049 oldfile = vma->vm_file;
1050 vma->vm_file = dmabuf->file;
1051 vma->vm_pgoff = pgoff;
1053 ret = dmabuf->ops->mmap(dmabuf, vma);
1055 /* restore old parameters on failure */
1056 vma->vm_file = oldfile;
1065 EXPORT_SYMBOL_GPL(dma_buf_mmap);
1068 * dma_buf_vmap - Create virtual mapping for the buffer object into kernel
1069 * address space. Same restrictions as for vmap and friends apply.
1070 * @dmabuf: [in] buffer to vmap
1072 * This call may fail due to lack of virtual mapping address space.
1073 * These calls are optional in drivers. The intended use for them
1074 * is for mapping objects linear in kernel space for high use objects.
1075 * Please attempt to use kmap/kunmap before thinking about these interfaces.
1077 * Returns NULL on error.
1079 void *dma_buf_vmap(struct dma_buf *dmabuf)
1083 if (WARN_ON(!dmabuf))
1086 if (!dmabuf->ops->vmap)
1089 mutex_lock(&dmabuf->lock);
1090 if (dmabuf->vmapping_counter) {
1091 dmabuf->vmapping_counter++;
1092 BUG_ON(!dmabuf->vmap_ptr);
1093 ptr = dmabuf->vmap_ptr;
1097 BUG_ON(dmabuf->vmap_ptr);
1099 ptr = dmabuf->ops->vmap(dmabuf);
1100 if (WARN_ON_ONCE(IS_ERR(ptr)))
1105 dmabuf->vmap_ptr = ptr;
1106 dmabuf->vmapping_counter = 1;
1109 mutex_unlock(&dmabuf->lock);
1112 EXPORT_SYMBOL_GPL(dma_buf_vmap);
1115 * dma_buf_vunmap - Unmap a vmap obtained by dma_buf_vmap.
1116 * @dmabuf: [in] buffer to vunmap
1117 * @vaddr: [in] vmap to vunmap
1119 void dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr)
1121 if (WARN_ON(!dmabuf))
1124 BUG_ON(!dmabuf->vmap_ptr);
1125 BUG_ON(dmabuf->vmapping_counter == 0);
1126 BUG_ON(dmabuf->vmap_ptr != vaddr);
1128 mutex_lock(&dmabuf->lock);
1129 if (--dmabuf->vmapping_counter == 0) {
1130 if (dmabuf->ops->vunmap)
1131 dmabuf->ops->vunmap(dmabuf, vaddr);
1132 dmabuf->vmap_ptr = NULL;
1134 mutex_unlock(&dmabuf->lock);
1136 EXPORT_SYMBOL_GPL(dma_buf_vunmap);
1138 #ifdef CONFIG_DEBUG_FS
1139 static int dma_buf_debug_show(struct seq_file *s, void *unused)
1142 struct dma_buf *buf_obj;
1143 struct dma_buf_attachment *attach_obj;
1144 struct dma_resv *robj;
1145 struct dma_resv_list *fobj;
1146 struct dma_fence *fence;
1147 int count = 0, attach_count, shared_count, i;
1150 ret = mutex_lock_interruptible(&db_list.lock);
1155 seq_puts(s, "\nDma-buf Objects:\n");
1156 seq_printf(s, "%-8s\t%-8s\t%-8s\t%-8s\texp_name\t%-8s\n",
1157 "size", "flags", "mode", "count", "ino");
1159 list_for_each_entry(buf_obj, &db_list.head, list_node) {
1160 ret = mutex_lock_interruptible(&buf_obj->lock);
1164 "\tERROR locking buffer object: skipping\n");
1168 seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\t%08lu\t%s\n",
1170 buf_obj->file->f_flags, buf_obj->file->f_mode,
1171 file_count(buf_obj->file),
1173 file_inode(buf_obj->file)->i_ino,
1174 buf_obj->name ?: "");
1176 robj = buf_obj->resv;
1178 dma_resv_fences(robj, &fence, &fobj, &shared_count);
1182 seq_printf(s, "\tExclusive fence: %s %s %ssignalled\n",
1183 fence->ops->get_driver_name(fence),
1184 fence->ops->get_timeline_name(fence),
1185 dma_fence_is_signaled(fence) ? "" : "un");
1186 for (i = 0; i < shared_count; i++) {
1187 fence = rcu_dereference(fobj->shared[i]);
1188 if (!dma_fence_get_rcu(fence))
1190 seq_printf(s, "\tShared fence: %s %s %ssignalled\n",
1191 fence->ops->get_driver_name(fence),
1192 fence->ops->get_timeline_name(fence),
1193 dma_fence_is_signaled(fence) ? "" : "un");
1194 dma_fence_put(fence);
1198 seq_puts(s, "\tAttached Devices:\n");
1201 list_for_each_entry(attach_obj, &buf_obj->attachments, node) {
1202 seq_printf(s, "\t%s\n", dev_name(attach_obj->dev));
1206 seq_printf(s, "Total %d devices attached\n\n",
1210 size += buf_obj->size;
1211 mutex_unlock(&buf_obj->lock);
1214 seq_printf(s, "\nTotal %d objects, %zu bytes\n", count, size);
1216 mutex_unlock(&db_list.lock);
1220 DEFINE_SHOW_ATTRIBUTE(dma_buf_debug);
1222 static struct dentry *dma_buf_debugfs_dir;
1224 static int dma_buf_init_debugfs(void)
1229 d = debugfs_create_dir("dma_buf", NULL);
1233 dma_buf_debugfs_dir = d;
1235 d = debugfs_create_file("bufinfo", S_IRUGO, dma_buf_debugfs_dir,
1236 NULL, &dma_buf_debug_fops);
1238 pr_debug("dma_buf: debugfs: failed to create node bufinfo\n");
1239 debugfs_remove_recursive(dma_buf_debugfs_dir);
1240 dma_buf_debugfs_dir = NULL;
1247 static void dma_buf_uninit_debugfs(void)
1249 debugfs_remove_recursive(dma_buf_debugfs_dir);
1252 static inline int dma_buf_init_debugfs(void)
1256 static inline void dma_buf_uninit_debugfs(void)
1261 static int __init dma_buf_init(void)
1263 dma_buf_mnt = kern_mount(&dma_buf_fs_type);
1264 if (IS_ERR(dma_buf_mnt))
1265 return PTR_ERR(dma_buf_mnt);
1267 mutex_init(&db_list.lock);
1268 INIT_LIST_HEAD(&db_list.head);
1269 dma_buf_init_debugfs();
1272 subsys_initcall(dma_buf_init);
1274 static void __exit dma_buf_deinit(void)
1276 dma_buf_uninit_debugfs();
1277 kern_unmount(dma_buf_mnt);
1279 __exitcall(dma_buf_deinit);