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_add_cb(struct dma_resv *resv, bool write,
213 struct dma_buf_poll_cb_t *dcb)
215 struct dma_resv_iter cursor;
216 struct dma_fence *fence;
219 dma_resv_for_each_fence(&cursor, resv, write, fence) {
220 dma_fence_get(fence);
221 r = dma_fence_add_callback(fence, &dcb->cb, dma_buf_poll_cb);
224 dma_fence_put(fence);
230 static __poll_t dma_buf_poll(struct file *file, poll_table *poll)
232 struct dma_buf *dmabuf;
233 struct dma_resv *resv;
236 dmabuf = file->private_data;
237 if (!dmabuf || !dmabuf->resv)
242 poll_wait(file, &dmabuf->poll, poll);
244 events = poll_requested_events(poll) & (EPOLLIN | EPOLLOUT);
248 dma_resv_lock(resv, NULL);
250 if (events & EPOLLOUT) {
251 struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_out;
253 /* Check that callback isn't busy */
254 spin_lock_irq(&dmabuf->poll.lock);
258 dcb->active = EPOLLOUT;
259 spin_unlock_irq(&dmabuf->poll.lock);
261 if (events & EPOLLOUT) {
262 /* Paired with fput in dma_buf_poll_cb */
263 get_file(dmabuf->file);
265 if (!dma_buf_poll_add_cb(resv, true, dcb))
266 /* No callback queued, wake up any other waiters */
267 dma_buf_poll_cb(NULL, &dcb->cb);
273 if (events & EPOLLIN) {
274 struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_in;
276 /* Check that callback isn't busy */
277 spin_lock_irq(&dmabuf->poll.lock);
281 dcb->active = EPOLLIN;
282 spin_unlock_irq(&dmabuf->poll.lock);
284 if (events & EPOLLIN) {
285 /* Paired with fput in dma_buf_poll_cb */
286 get_file(dmabuf->file);
288 if (!dma_buf_poll_add_cb(resv, false, dcb))
289 /* No callback queued, wake up any other waiters */
290 dma_buf_poll_cb(NULL, &dcb->cb);
296 dma_resv_unlock(resv);
301 * dma_buf_set_name - Set a name to a specific dma_buf to track the usage.
302 * The name of the dma-buf buffer can only be set when the dma-buf is not
303 * attached to any devices. It could theoritically support changing the
304 * name of the dma-buf if the same piece of memory is used for multiple
305 * purpose between different devices.
307 * @dmabuf: [in] dmabuf buffer that will be renamed.
308 * @buf: [in] A piece of userspace memory that contains the name of
311 * Returns 0 on success. If the dma-buf buffer is already attached to
312 * devices, return -EBUSY.
315 static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf)
317 char *name = strndup_user(buf, DMA_BUF_NAME_LEN);
321 return PTR_ERR(name);
323 dma_resv_lock(dmabuf->resv, NULL);
324 if (!list_empty(&dmabuf->attachments)) {
329 spin_lock(&dmabuf->name_lock);
332 spin_unlock(&dmabuf->name_lock);
335 dma_resv_unlock(dmabuf->resv);
339 static long dma_buf_ioctl(struct file *file,
340 unsigned int cmd, unsigned long arg)
342 struct dma_buf *dmabuf;
343 struct dma_buf_sync sync;
344 enum dma_data_direction direction;
347 dmabuf = file->private_data;
350 case DMA_BUF_IOCTL_SYNC:
351 if (copy_from_user(&sync, (void __user *) arg, sizeof(sync)))
354 if (sync.flags & ~DMA_BUF_SYNC_VALID_FLAGS_MASK)
357 switch (sync.flags & DMA_BUF_SYNC_RW) {
358 case DMA_BUF_SYNC_READ:
359 direction = DMA_FROM_DEVICE;
361 case DMA_BUF_SYNC_WRITE:
362 direction = DMA_TO_DEVICE;
364 case DMA_BUF_SYNC_RW:
365 direction = DMA_BIDIRECTIONAL;
371 if (sync.flags & DMA_BUF_SYNC_END)
372 ret = dma_buf_end_cpu_access(dmabuf, direction);
374 ret = dma_buf_begin_cpu_access(dmabuf, direction);
378 case DMA_BUF_SET_NAME_A:
379 case DMA_BUF_SET_NAME_B:
380 return dma_buf_set_name(dmabuf, (const char __user *)arg);
387 static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file)
389 struct dma_buf *dmabuf = file->private_data;
391 seq_printf(m, "size:\t%zu\n", dmabuf->size);
392 /* Don't count the temporary reference taken inside procfs seq_show */
393 seq_printf(m, "count:\t%ld\n", file_count(dmabuf->file) - 1);
394 seq_printf(m, "exp_name:\t%s\n", dmabuf->exp_name);
395 spin_lock(&dmabuf->name_lock);
397 seq_printf(m, "name:\t%s\n", dmabuf->name);
398 spin_unlock(&dmabuf->name_lock);
401 static const struct file_operations dma_buf_fops = {
402 .release = dma_buf_file_release,
403 .mmap = dma_buf_mmap_internal,
404 .llseek = dma_buf_llseek,
405 .poll = dma_buf_poll,
406 .unlocked_ioctl = dma_buf_ioctl,
407 .compat_ioctl = compat_ptr_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 struct dma_buf object, which wraps the
487 * supplied private data and operations for struct dma_buf_ops. On either
488 * missing ops, or error in allocating struct dma_buf, will return negative
491 * For most cases the easiest way to create @exp_info is through the
492 * %DEFINE_DMA_BUF_EXPORT_INFO macro.
494 struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
496 struct dma_buf *dmabuf;
497 struct dma_resv *resv = exp_info->resv;
499 size_t alloc_size = sizeof(struct dma_buf);
503 alloc_size += sizeof(struct dma_resv);
505 /* prevent &dma_buf[1] == dma_buf->resv */
508 if (WARN_ON(!exp_info->priv
510 || !exp_info->ops->map_dma_buf
511 || !exp_info->ops->unmap_dma_buf
512 || !exp_info->ops->release)) {
513 return ERR_PTR(-EINVAL);
516 if (WARN_ON(exp_info->ops->cache_sgt_mapping &&
517 (exp_info->ops->pin || exp_info->ops->unpin)))
518 return ERR_PTR(-EINVAL);
520 if (WARN_ON(!exp_info->ops->pin != !exp_info->ops->unpin))
521 return ERR_PTR(-EINVAL);
523 if (!try_module_get(exp_info->owner))
524 return ERR_PTR(-ENOENT);
526 dmabuf = kzalloc(alloc_size, GFP_KERNEL);
532 dmabuf->priv = exp_info->priv;
533 dmabuf->ops = exp_info->ops;
534 dmabuf->size = exp_info->size;
535 dmabuf->exp_name = exp_info->exp_name;
536 dmabuf->owner = exp_info->owner;
537 spin_lock_init(&dmabuf->name_lock);
538 init_waitqueue_head(&dmabuf->poll);
539 dmabuf->cb_in.poll = dmabuf->cb_out.poll = &dmabuf->poll;
540 dmabuf->cb_in.active = dmabuf->cb_out.active = 0;
543 resv = (struct dma_resv *)&dmabuf[1];
548 file = dma_buf_getfile(dmabuf, exp_info->flags);
554 file->f_mode |= FMODE_LSEEK;
557 ret = dma_buf_stats_setup(dmabuf);
561 mutex_init(&dmabuf->lock);
562 INIT_LIST_HEAD(&dmabuf->attachments);
564 mutex_lock(&db_list.lock);
565 list_add(&dmabuf->list_node, &db_list.head);
566 mutex_unlock(&db_list.lock);
572 * Set file->f_path.dentry->d_fsdata to NULL so that when
573 * dma_buf_release() gets invoked by dentry_ops, it exits
574 * early before calling the release() dma_buf op.
576 file->f_path.dentry->d_fsdata = NULL;
581 module_put(exp_info->owner);
584 EXPORT_SYMBOL_NS_GPL(dma_buf_export, DMA_BUF);
587 * dma_buf_fd - returns a file descriptor for the given struct dma_buf
588 * @dmabuf: [in] pointer to dma_buf for which fd is required.
589 * @flags: [in] flags to give to fd
591 * On success, returns an associated 'fd'. Else, returns error.
593 int dma_buf_fd(struct dma_buf *dmabuf, int flags)
597 if (!dmabuf || !dmabuf->file)
600 fd = get_unused_fd_flags(flags);
604 fd_install(fd, dmabuf->file);
608 EXPORT_SYMBOL_NS_GPL(dma_buf_fd, DMA_BUF);
611 * dma_buf_get - returns the struct dma_buf related to an fd
612 * @fd: [in] fd associated with the struct dma_buf to be returned
614 * On success, returns the struct dma_buf associated with an fd; uses
615 * file's refcounting done by fget to increase refcount. returns ERR_PTR
618 struct dma_buf *dma_buf_get(int fd)
625 return ERR_PTR(-EBADF);
627 if (!is_dma_buf_file(file)) {
629 return ERR_PTR(-EINVAL);
632 return file->private_data;
634 EXPORT_SYMBOL_NS_GPL(dma_buf_get, DMA_BUF);
637 * dma_buf_put - decreases refcount of the buffer
638 * @dmabuf: [in] buffer to reduce refcount of
640 * Uses file's refcounting done implicitly by fput().
642 * If, as a result of this call, the refcount becomes 0, the 'release' file
643 * operation related to this fd is called. It calls &dma_buf_ops.release vfunc
644 * in turn, and frees the memory allocated for dmabuf when exported.
646 void dma_buf_put(struct dma_buf *dmabuf)
648 if (WARN_ON(!dmabuf || !dmabuf->file))
653 EXPORT_SYMBOL_NS_GPL(dma_buf_put, DMA_BUF);
655 static void mangle_sg_table(struct sg_table *sg_table)
657 #ifdef CONFIG_DMABUF_DEBUG
659 struct scatterlist *sg;
661 /* To catch abuse of the underlying struct page by importers mix
662 * up the bits, but take care to preserve the low SG_ bits to
663 * not corrupt the sgt. The mixing is undone in __unmap_dma_buf
664 * before passing the sgt back to the exporter. */
665 for_each_sgtable_sg(sg_table, sg, i)
666 sg->page_link ^= ~0xffUL;
670 static struct sg_table * __map_dma_buf(struct dma_buf_attachment *attach,
671 enum dma_data_direction direction)
673 struct sg_table *sg_table;
675 sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
677 if (!IS_ERR_OR_NULL(sg_table))
678 mangle_sg_table(sg_table);
684 * dma_buf_dynamic_attach - Add the device to dma_buf's attachments list
685 * @dmabuf: [in] buffer to attach device to.
686 * @dev: [in] device to be attached.
687 * @importer_ops: [in] importer operations for the attachment
688 * @importer_priv: [in] importer private pointer for the attachment
690 * Returns struct dma_buf_attachment pointer for this attachment. Attachments
691 * must be cleaned up by calling dma_buf_detach().
693 * Optionally this calls &dma_buf_ops.attach to allow device-specific attach
698 * A pointer to newly created &dma_buf_attachment on success, or a negative
699 * error code wrapped into a pointer on failure.
701 * Note that this can fail if the backing storage of @dmabuf is in a place not
702 * accessible to @dev, and cannot be moved to a more suitable place. This is
703 * indicated with the error code -EBUSY.
705 struct dma_buf_attachment *
706 dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
707 const struct dma_buf_attach_ops *importer_ops,
710 struct dma_buf_attachment *attach;
713 if (WARN_ON(!dmabuf || !dev))
714 return ERR_PTR(-EINVAL);
716 if (WARN_ON(importer_ops && !importer_ops->move_notify))
717 return ERR_PTR(-EINVAL);
719 attach = kzalloc(sizeof(*attach), GFP_KERNEL);
721 return ERR_PTR(-ENOMEM);
724 attach->dmabuf = dmabuf;
726 attach->peer2peer = importer_ops->allow_peer2peer;
727 attach->importer_ops = importer_ops;
728 attach->importer_priv = importer_priv;
730 if (dmabuf->ops->attach) {
731 ret = dmabuf->ops->attach(dmabuf, attach);
735 dma_resv_lock(dmabuf->resv, NULL);
736 list_add(&attach->node, &dmabuf->attachments);
737 dma_resv_unlock(dmabuf->resv);
739 /* When either the importer or the exporter can't handle dynamic
740 * mappings we cache the mapping here to avoid issues with the
741 * reservation object lock.
743 if (dma_buf_attachment_is_dynamic(attach) !=
744 dma_buf_is_dynamic(dmabuf)) {
745 struct sg_table *sgt;
747 if (dma_buf_is_dynamic(attach->dmabuf)) {
748 dma_resv_lock(attach->dmabuf->resv, NULL);
749 ret = dmabuf->ops->pin(attach);
754 sgt = __map_dma_buf(attach, DMA_BIDIRECTIONAL);
756 sgt = ERR_PTR(-ENOMEM);
761 if (dma_buf_is_dynamic(attach->dmabuf))
762 dma_resv_unlock(attach->dmabuf->resv);
764 attach->dir = DMA_BIDIRECTIONAL;
774 if (dma_buf_is_dynamic(attach->dmabuf))
775 dmabuf->ops->unpin(attach);
778 if (dma_buf_is_dynamic(attach->dmabuf))
779 dma_resv_unlock(attach->dmabuf->resv);
781 dma_buf_detach(dmabuf, attach);
784 EXPORT_SYMBOL_NS_GPL(dma_buf_dynamic_attach, DMA_BUF);
787 * dma_buf_attach - Wrapper for dma_buf_dynamic_attach
788 * @dmabuf: [in] buffer to attach device to.
789 * @dev: [in] device to be attached.
791 * Wrapper to call dma_buf_dynamic_attach() for drivers which still use a static
794 struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
797 return dma_buf_dynamic_attach(dmabuf, dev, NULL, NULL);
799 EXPORT_SYMBOL_NS_GPL(dma_buf_attach, DMA_BUF);
801 static void __unmap_dma_buf(struct dma_buf_attachment *attach,
802 struct sg_table *sg_table,
803 enum dma_data_direction direction)
805 /* uses XOR, hence this unmangles */
806 mangle_sg_table(sg_table);
808 attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, direction);
812 * dma_buf_detach - Remove the given attachment from dmabuf's attachments list
813 * @dmabuf: [in] buffer to detach from.
814 * @attach: [in] attachment to be detached; is free'd after this call.
816 * Clean up a device attachment obtained by calling dma_buf_attach().
818 * Optionally this calls &dma_buf_ops.detach for device-specific detach.
820 void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
822 if (WARN_ON(!dmabuf || !attach))
826 if (dma_buf_is_dynamic(attach->dmabuf))
827 dma_resv_lock(attach->dmabuf->resv, NULL);
829 __unmap_dma_buf(attach, attach->sgt, attach->dir);
831 if (dma_buf_is_dynamic(attach->dmabuf)) {
832 dmabuf->ops->unpin(attach);
833 dma_resv_unlock(attach->dmabuf->resv);
837 dma_resv_lock(dmabuf->resv, NULL);
838 list_del(&attach->node);
839 dma_resv_unlock(dmabuf->resv);
840 if (dmabuf->ops->detach)
841 dmabuf->ops->detach(dmabuf, attach);
845 EXPORT_SYMBOL_NS_GPL(dma_buf_detach, DMA_BUF);
848 * dma_buf_pin - Lock down the DMA-buf
849 * @attach: [in] attachment which should be pinned
851 * Only dynamic importers (who set up @attach with dma_buf_dynamic_attach()) may
852 * call this, and only for limited use cases like scanout and not for temporary
853 * pin operations. It is not permitted to allow userspace to pin arbitrary
854 * amounts of buffers through this interface.
856 * Buffers must be unpinned by calling dma_buf_unpin().
859 * 0 on success, negative error code on failure.
861 int dma_buf_pin(struct dma_buf_attachment *attach)
863 struct dma_buf *dmabuf = attach->dmabuf;
866 WARN_ON(!dma_buf_attachment_is_dynamic(attach));
868 dma_resv_assert_held(dmabuf->resv);
870 if (dmabuf->ops->pin)
871 ret = dmabuf->ops->pin(attach);
875 EXPORT_SYMBOL_NS_GPL(dma_buf_pin, DMA_BUF);
878 * dma_buf_unpin - Unpin a DMA-buf
879 * @attach: [in] attachment which should be unpinned
881 * This unpins a buffer pinned by dma_buf_pin() and allows the exporter to move
882 * any mapping of @attach again and inform the importer through
883 * &dma_buf_attach_ops.move_notify.
885 void dma_buf_unpin(struct dma_buf_attachment *attach)
887 struct dma_buf *dmabuf = attach->dmabuf;
889 WARN_ON(!dma_buf_attachment_is_dynamic(attach));
891 dma_resv_assert_held(dmabuf->resv);
893 if (dmabuf->ops->unpin)
894 dmabuf->ops->unpin(attach);
896 EXPORT_SYMBOL_NS_GPL(dma_buf_unpin, DMA_BUF);
899 * dma_buf_map_attachment - Returns the scatterlist table of the attachment;
900 * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the
902 * @attach: [in] attachment whose scatterlist is to be returned
903 * @direction: [in] direction of DMA transfer
905 * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
906 * on error. May return -EINTR if it is interrupted by a signal.
908 * On success, the DMA addresses and lengths in the returned scatterlist are
911 * A mapping must be unmapped by using dma_buf_unmap_attachment(). Note that
912 * the underlying backing storage is pinned for as long as a mapping exists,
913 * therefore users/importers should not hold onto a mapping for undue amounts of
916 * Important: Dynamic importers must wait for the exclusive fence of the struct
917 * dma_resv attached to the DMA-BUF first.
919 struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
920 enum dma_data_direction direction)
922 struct sg_table *sg_table;
927 if (WARN_ON(!attach || !attach->dmabuf))
928 return ERR_PTR(-EINVAL);
930 if (dma_buf_attachment_is_dynamic(attach))
931 dma_resv_assert_held(attach->dmabuf->resv);
935 * Two mappings with different directions for the same
936 * attachment are not allowed.
938 if (attach->dir != direction &&
939 attach->dir != DMA_BIDIRECTIONAL)
940 return ERR_PTR(-EBUSY);
945 if (dma_buf_is_dynamic(attach->dmabuf)) {
946 dma_resv_assert_held(attach->dmabuf->resv);
947 if (!IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY)) {
948 r = attach->dmabuf->ops->pin(attach);
954 sg_table = __map_dma_buf(attach, direction);
956 sg_table = ERR_PTR(-ENOMEM);
958 if (IS_ERR(sg_table) && dma_buf_is_dynamic(attach->dmabuf) &&
959 !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY))
960 attach->dmabuf->ops->unpin(attach);
962 if (!IS_ERR(sg_table) && attach->dmabuf->ops->cache_sgt_mapping) {
963 attach->sgt = sg_table;
964 attach->dir = direction;
967 #ifdef CONFIG_DMA_API_DEBUG
968 if (!IS_ERR(sg_table)) {
969 struct scatterlist *sg;
974 for_each_sgtable_dma_sg(sg_table, sg, i) {
975 addr = sg_dma_address(sg);
976 len = sg_dma_len(sg);
977 if (!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(len)) {
978 pr_debug("%s: addr %llx or len %x is not page aligned!\n",
979 __func__, addr, len);
983 #endif /* CONFIG_DMA_API_DEBUG */
986 EXPORT_SYMBOL_NS_GPL(dma_buf_map_attachment, DMA_BUF);
989 * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might
990 * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of
992 * @attach: [in] attachment to unmap buffer from
993 * @sg_table: [in] scatterlist info of the buffer to unmap
994 * @direction: [in] direction of DMA transfer
996 * This unmaps a DMA mapping for @attached obtained by dma_buf_map_attachment().
998 void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
999 struct sg_table *sg_table,
1000 enum dma_data_direction direction)
1004 if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
1007 if (dma_buf_attachment_is_dynamic(attach))
1008 dma_resv_assert_held(attach->dmabuf->resv);
1010 if (attach->sgt == sg_table)
1013 if (dma_buf_is_dynamic(attach->dmabuf))
1014 dma_resv_assert_held(attach->dmabuf->resv);
1016 __unmap_dma_buf(attach, sg_table, direction);
1018 if (dma_buf_is_dynamic(attach->dmabuf) &&
1019 !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY))
1020 dma_buf_unpin(attach);
1022 EXPORT_SYMBOL_NS_GPL(dma_buf_unmap_attachment, DMA_BUF);
1025 * dma_buf_move_notify - notify attachments that DMA-buf is moving
1027 * @dmabuf: [in] buffer which is moving
1029 * Informs all attachmenst that they need to destroy and recreated all their
1032 void dma_buf_move_notify(struct dma_buf *dmabuf)
1034 struct dma_buf_attachment *attach;
1036 dma_resv_assert_held(dmabuf->resv);
1038 list_for_each_entry(attach, &dmabuf->attachments, node)
1039 if (attach->importer_ops)
1040 attach->importer_ops->move_notify(attach);
1042 EXPORT_SYMBOL_NS_GPL(dma_buf_move_notify, DMA_BUF);
1047 * There are mutliple reasons for supporting CPU access to a dma buffer object:
1049 * - Fallback operations in the kernel, for example when a device is connected
1050 * over USB and the kernel needs to shuffle the data around first before
1051 * sending it away. Cache coherency is handled by braketing any transactions
1052 * with calls to dma_buf_begin_cpu_access() and dma_buf_end_cpu_access()
1055 * Since for most kernel internal dma-buf accesses need the entire buffer, a
1056 * vmap interface is introduced. Note that on very old 32-bit architectures
1057 * vmalloc space might be limited and result in vmap calls failing.
1061 * void \*dma_buf_vmap(struct dma_buf \*dmabuf)
1062 * void dma_buf_vunmap(struct dma_buf \*dmabuf, void \*vaddr)
1064 * The vmap call can fail if there is no vmap support in the exporter, or if
1065 * it runs out of vmalloc space. Note that the dma-buf layer keeps a reference
1066 * count for all vmap access and calls down into the exporter's vmap function
1067 * only when no vmapping exists, and only unmaps it once. Protection against
1068 * concurrent vmap/vunmap calls is provided by taking the &dma_buf.lock mutex.
1070 * - For full compatibility on the importer side with existing userspace
1071 * interfaces, which might already support mmap'ing buffers. This is needed in
1072 * many processing pipelines (e.g. feeding a software rendered image into a
1073 * hardware pipeline, thumbnail creation, snapshots, ...). Also, Android's ION
1074 * framework already supported this and for DMA buffer file descriptors to
1075 * replace ION buffers mmap support was needed.
1077 * There is no special interfaces, userspace simply calls mmap on the dma-buf
1078 * fd. But like for CPU access there's a need to braket the actual access,
1079 * which is handled by the ioctl (DMA_BUF_IOCTL_SYNC). Note that
1080 * DMA_BUF_IOCTL_SYNC can fail with -EAGAIN or -EINTR, in which case it must
1083 * Some systems might need some sort of cache coherency management e.g. when
1084 * CPU and GPU domains are being accessed through dma-buf at the same time.
1085 * To circumvent this problem there are begin/end coherency markers, that
1086 * forward directly to existing dma-buf device drivers vfunc hooks. Userspace
1087 * can make use of those markers through the DMA_BUF_IOCTL_SYNC ioctl. The
1088 * sequence would be used like following:
1091 * - for each drawing/upload cycle in CPU 1. SYNC_START ioctl, 2. read/write
1092 * to mmap area 3. SYNC_END ioctl. This can be repeated as often as you
1093 * want (with the new data being consumed by say the GPU or the scanout
1095 * - munmap once you don't need the buffer any more
1097 * For correctness and optimal performance, it is always required to use
1098 * SYNC_START and SYNC_END before and after, respectively, when accessing the
1099 * mapped address. Userspace cannot rely on coherent access, even when there
1100 * are systems where it just works without calling these ioctls.
1102 * - And as a CPU fallback in userspace processing pipelines.
1104 * Similar to the motivation for kernel cpu access it is again important that
1105 * the userspace code of a given importing subsystem can use the same
1106 * interfaces with a imported dma-buf buffer object as with a native buffer
1107 * object. This is especially important for drm where the userspace part of
1108 * contemporary OpenGL, X, and other drivers is huge, and reworking them to
1109 * use a different way to mmap a buffer rather invasive.
1111 * The assumption in the current dma-buf interfaces is that redirecting the
1112 * initial mmap is all that's needed. A survey of some of the existing
1113 * subsystems shows that no driver seems to do any nefarious thing like
1114 * syncing up with outstanding asynchronous processing on the device or
1115 * allocating special resources at fault time. So hopefully this is good
1116 * enough, since adding interfaces to intercept pagefaults and allow pte
1117 * shootdowns would increase the complexity quite a bit.
1121 * int dma_buf_mmap(struct dma_buf \*, struct vm_area_struct \*,
1124 * If the importing subsystem simply provides a special-purpose mmap call to
1125 * set up a mapping in userspace, calling do_mmap with &dma_buf.file will
1126 * equally achieve that for a dma-buf object.
1129 static int __dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
1130 enum dma_data_direction direction)
1132 bool write = (direction == DMA_BIDIRECTIONAL ||
1133 direction == DMA_TO_DEVICE);
1134 struct dma_resv *resv = dmabuf->resv;
1137 /* Wait on any implicit rendering fences */
1138 ret = dma_resv_wait_timeout(resv, write, true, MAX_SCHEDULE_TIMEOUT);
1146 * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the
1147 * cpu in the kernel context. Calls begin_cpu_access to allow exporter-specific
1148 * preparations. Coherency is only guaranteed in the specified range for the
1149 * specified access direction.
1150 * @dmabuf: [in] buffer to prepare cpu access for.
1151 * @direction: [in] length of range for cpu access.
1153 * After the cpu access is complete the caller should call
1154 * dma_buf_end_cpu_access(). Only when cpu access is braketed by both calls is
1155 * it guaranteed to be coherent with other DMA access.
1157 * This function will also wait for any DMA transactions tracked through
1158 * implicit synchronization in &dma_buf.resv. For DMA transactions with explicit
1159 * synchronization this function will only ensure cache coherency, callers must
1160 * ensure synchronization with such DMA transactions on their own.
1162 * Can return negative error values, returns 0 on success.
1164 int dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
1165 enum dma_data_direction direction)
1169 if (WARN_ON(!dmabuf))
1172 might_lock(&dmabuf->resv->lock.base);
1174 if (dmabuf->ops->begin_cpu_access)
1175 ret = dmabuf->ops->begin_cpu_access(dmabuf, direction);
1177 /* Ensure that all fences are waited upon - but we first allow
1178 * the native handler the chance to do so more efficiently if it
1179 * chooses. A double invocation here will be reasonably cheap no-op.
1182 ret = __dma_buf_begin_cpu_access(dmabuf, direction);
1186 EXPORT_SYMBOL_NS_GPL(dma_buf_begin_cpu_access, DMA_BUF);
1189 * dma_buf_end_cpu_access - Must be called after accessing a dma_buf from the
1190 * cpu in the kernel context. Calls end_cpu_access to allow exporter-specific
1191 * actions. Coherency is only guaranteed in the specified range for the
1192 * specified access direction.
1193 * @dmabuf: [in] buffer to complete cpu access for.
1194 * @direction: [in] length of range for cpu access.
1196 * This terminates CPU access started with dma_buf_begin_cpu_access().
1198 * Can return negative error values, returns 0 on success.
1200 int dma_buf_end_cpu_access(struct dma_buf *dmabuf,
1201 enum dma_data_direction direction)
1207 might_lock(&dmabuf->resv->lock.base);
1209 if (dmabuf->ops->end_cpu_access)
1210 ret = dmabuf->ops->end_cpu_access(dmabuf, direction);
1214 EXPORT_SYMBOL_NS_GPL(dma_buf_end_cpu_access, DMA_BUF);
1218 * dma_buf_mmap - Setup up a userspace mmap with the given vma
1219 * @dmabuf: [in] buffer that should back the vma
1220 * @vma: [in] vma for the mmap
1221 * @pgoff: [in] offset in pages where this mmap should start within the
1224 * This function adjusts the passed in vma so that it points at the file of the
1225 * dma_buf operation. It also adjusts the starting pgoff and does bounds
1226 * checking on the size of the vma. Then it calls the exporters mmap function to
1227 * set up the mapping.
1229 * Can return negative error values, returns 0 on success.
1231 int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
1232 unsigned long pgoff)
1234 if (WARN_ON(!dmabuf || !vma))
1237 /* check if buffer supports mmap */
1238 if (!dmabuf->ops->mmap)
1241 /* check for offset overflow */
1242 if (pgoff + vma_pages(vma) < pgoff)
1245 /* check for overflowing the buffer's size */
1246 if (pgoff + vma_pages(vma) >
1247 dmabuf->size >> PAGE_SHIFT)
1250 /* readjust the vma */
1251 vma_set_file(vma, dmabuf->file);
1252 vma->vm_pgoff = pgoff;
1254 return dmabuf->ops->mmap(dmabuf, vma);
1256 EXPORT_SYMBOL_NS_GPL(dma_buf_mmap, DMA_BUF);
1259 * dma_buf_vmap - Create virtual mapping for the buffer object into kernel
1260 * address space. Same restrictions as for vmap and friends apply.
1261 * @dmabuf: [in] buffer to vmap
1262 * @map: [out] returns the vmap pointer
1264 * This call may fail due to lack of virtual mapping address space.
1265 * These calls are optional in drivers. The intended use for them
1266 * is for mapping objects linear in kernel space for high use objects.
1268 * To ensure coherency users must call dma_buf_begin_cpu_access() and
1269 * dma_buf_end_cpu_access() around any cpu access performed through this
1272 * Returns 0 on success, or a negative errno code otherwise.
1274 int dma_buf_vmap(struct dma_buf *dmabuf, struct dma_buf_map *map)
1276 struct dma_buf_map ptr;
1279 dma_buf_map_clear(map);
1281 if (WARN_ON(!dmabuf))
1284 if (!dmabuf->ops->vmap)
1287 mutex_lock(&dmabuf->lock);
1288 if (dmabuf->vmapping_counter) {
1289 dmabuf->vmapping_counter++;
1290 BUG_ON(dma_buf_map_is_null(&dmabuf->vmap_ptr));
1291 *map = dmabuf->vmap_ptr;
1295 BUG_ON(dma_buf_map_is_set(&dmabuf->vmap_ptr));
1297 ret = dmabuf->ops->vmap(dmabuf, &ptr);
1298 if (WARN_ON_ONCE(ret))
1301 dmabuf->vmap_ptr = ptr;
1302 dmabuf->vmapping_counter = 1;
1304 *map = dmabuf->vmap_ptr;
1307 mutex_unlock(&dmabuf->lock);
1310 EXPORT_SYMBOL_NS_GPL(dma_buf_vmap, DMA_BUF);
1313 * dma_buf_vunmap - Unmap a vmap obtained by dma_buf_vmap.
1314 * @dmabuf: [in] buffer to vunmap
1315 * @map: [in] vmap pointer to vunmap
1317 void dma_buf_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map)
1319 if (WARN_ON(!dmabuf))
1322 BUG_ON(dma_buf_map_is_null(&dmabuf->vmap_ptr));
1323 BUG_ON(dmabuf->vmapping_counter == 0);
1324 BUG_ON(!dma_buf_map_is_equal(&dmabuf->vmap_ptr, map));
1326 mutex_lock(&dmabuf->lock);
1327 if (--dmabuf->vmapping_counter == 0) {
1328 if (dmabuf->ops->vunmap)
1329 dmabuf->ops->vunmap(dmabuf, map);
1330 dma_buf_map_clear(&dmabuf->vmap_ptr);
1332 mutex_unlock(&dmabuf->lock);
1334 EXPORT_SYMBOL_NS_GPL(dma_buf_vunmap, DMA_BUF);
1336 #ifdef CONFIG_DEBUG_FS
1337 static int dma_buf_debug_show(struct seq_file *s, void *unused)
1339 struct dma_buf *buf_obj;
1340 struct dma_buf_attachment *attach_obj;
1341 struct dma_resv_iter cursor;
1342 struct dma_fence *fence;
1343 int count = 0, attach_count;
1347 ret = mutex_lock_interruptible(&db_list.lock);
1352 seq_puts(s, "\nDma-buf Objects:\n");
1353 seq_printf(s, "%-8s\t%-8s\t%-8s\t%-8s\texp_name\t%-8s\n",
1354 "size", "flags", "mode", "count", "ino");
1356 list_for_each_entry(buf_obj, &db_list.head, list_node) {
1358 ret = dma_resv_lock_interruptible(buf_obj->resv, NULL);
1363 spin_lock(&buf_obj->name_lock);
1364 seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\t%08lu\t%s\n",
1366 buf_obj->file->f_flags, buf_obj->file->f_mode,
1367 file_count(buf_obj->file),
1369 file_inode(buf_obj->file)->i_ino,
1370 buf_obj->name ?: "");
1371 spin_unlock(&buf_obj->name_lock);
1373 dma_resv_for_each_fence(&cursor, buf_obj->resv, true, fence) {
1374 seq_printf(s, "\t%s fence: %s %s %ssignalled\n",
1375 dma_resv_iter_is_exclusive(&cursor) ?
1376 "Exclusive" : "Shared",
1377 fence->ops->get_driver_name(fence),
1378 fence->ops->get_timeline_name(fence),
1379 dma_fence_is_signaled(fence) ? "" : "un");
1382 seq_puts(s, "\tAttached Devices:\n");
1385 list_for_each_entry(attach_obj, &buf_obj->attachments, node) {
1386 seq_printf(s, "\t%s\n", dev_name(attach_obj->dev));
1389 dma_resv_unlock(buf_obj->resv);
1391 seq_printf(s, "Total %d devices attached\n\n",
1395 size += buf_obj->size;
1398 seq_printf(s, "\nTotal %d objects, %zu bytes\n", count, size);
1400 mutex_unlock(&db_list.lock);
1404 mutex_unlock(&db_list.lock);
1408 DEFINE_SHOW_ATTRIBUTE(dma_buf_debug);
1410 static struct dentry *dma_buf_debugfs_dir;
1412 static int dma_buf_init_debugfs(void)
1417 d = debugfs_create_dir("dma_buf", NULL);
1421 dma_buf_debugfs_dir = d;
1423 d = debugfs_create_file("bufinfo", S_IRUGO, dma_buf_debugfs_dir,
1424 NULL, &dma_buf_debug_fops);
1426 pr_debug("dma_buf: debugfs: failed to create node bufinfo\n");
1427 debugfs_remove_recursive(dma_buf_debugfs_dir);
1428 dma_buf_debugfs_dir = NULL;
1435 static void dma_buf_uninit_debugfs(void)
1437 debugfs_remove_recursive(dma_buf_debugfs_dir);
1440 static inline int dma_buf_init_debugfs(void)
1444 static inline void dma_buf_uninit_debugfs(void)
1449 static int __init dma_buf_init(void)
1453 ret = dma_buf_init_sysfs_statistics();
1457 dma_buf_mnt = kern_mount(&dma_buf_fs_type);
1458 if (IS_ERR(dma_buf_mnt))
1459 return PTR_ERR(dma_buf_mnt);
1461 mutex_init(&db_list.lock);
1462 INIT_LIST_HEAD(&db_list.head);
1463 dma_buf_init_debugfs();
1466 subsys_initcall(dma_buf_init);
1468 static void __exit dma_buf_deinit(void)
1470 dma_buf_uninit_debugfs();
1471 kern_unmount(dma_buf_mnt);
1472 dma_buf_uninit_sysfs_statistics();
1474 __exitcall(dma_buf_deinit);