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, dma_resv_usage_rw(write),
221 dma_fence_get(fence);
222 r = dma_fence_add_callback(fence, &dcb->cb, dma_buf_poll_cb);
225 dma_fence_put(fence);
231 static __poll_t dma_buf_poll(struct file *file, poll_table *poll)
233 struct dma_buf *dmabuf;
234 struct dma_resv *resv;
237 dmabuf = file->private_data;
238 if (!dmabuf || !dmabuf->resv)
243 poll_wait(file, &dmabuf->poll, poll);
245 events = poll_requested_events(poll) & (EPOLLIN | EPOLLOUT);
249 dma_resv_lock(resv, NULL);
251 if (events & EPOLLOUT) {
252 struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_out;
254 /* Check that callback isn't busy */
255 spin_lock_irq(&dmabuf->poll.lock);
259 dcb->active = EPOLLOUT;
260 spin_unlock_irq(&dmabuf->poll.lock);
262 if (events & EPOLLOUT) {
263 /* Paired with fput in dma_buf_poll_cb */
264 get_file(dmabuf->file);
266 if (!dma_buf_poll_add_cb(resv, true, dcb))
267 /* No callback queued, wake up any other waiters */
268 dma_buf_poll_cb(NULL, &dcb->cb);
274 if (events & EPOLLIN) {
275 struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_in;
277 /* Check that callback isn't busy */
278 spin_lock_irq(&dmabuf->poll.lock);
282 dcb->active = EPOLLIN;
283 spin_unlock_irq(&dmabuf->poll.lock);
285 if (events & EPOLLIN) {
286 /* Paired with fput in dma_buf_poll_cb */
287 get_file(dmabuf->file);
289 if (!dma_buf_poll_add_cb(resv, false, dcb))
290 /* No callback queued, wake up any other waiters */
291 dma_buf_poll_cb(NULL, &dcb->cb);
297 dma_resv_unlock(resv);
302 * dma_buf_set_name - Set a name to a specific dma_buf to track the usage.
303 * It could support changing the name of the dma-buf if the same
304 * piece of memory is used for multiple purpose between different devices.
306 * @dmabuf: [in] dmabuf buffer that will be renamed.
307 * @buf: [in] A piece of userspace memory that contains the name of
310 * Returns 0 on success. If the dma-buf buffer is already attached to
311 * devices, return -EBUSY.
314 static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf)
316 char *name = strndup_user(buf, DMA_BUF_NAME_LEN);
319 return PTR_ERR(name);
321 spin_lock(&dmabuf->name_lock);
324 spin_unlock(&dmabuf->name_lock);
329 static long dma_buf_ioctl(struct file *file,
330 unsigned int cmd, unsigned long arg)
332 struct dma_buf *dmabuf;
333 struct dma_buf_sync sync;
334 enum dma_data_direction direction;
337 dmabuf = file->private_data;
340 case DMA_BUF_IOCTL_SYNC:
341 if (copy_from_user(&sync, (void __user *) arg, sizeof(sync)))
344 if (sync.flags & ~DMA_BUF_SYNC_VALID_FLAGS_MASK)
347 switch (sync.flags & DMA_BUF_SYNC_RW) {
348 case DMA_BUF_SYNC_READ:
349 direction = DMA_FROM_DEVICE;
351 case DMA_BUF_SYNC_WRITE:
352 direction = DMA_TO_DEVICE;
354 case DMA_BUF_SYNC_RW:
355 direction = DMA_BIDIRECTIONAL;
361 if (sync.flags & DMA_BUF_SYNC_END)
362 ret = dma_buf_end_cpu_access(dmabuf, direction);
364 ret = dma_buf_begin_cpu_access(dmabuf, direction);
368 case DMA_BUF_SET_NAME_A:
369 case DMA_BUF_SET_NAME_B:
370 return dma_buf_set_name(dmabuf, (const char __user *)arg);
377 static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file)
379 struct dma_buf *dmabuf = file->private_data;
381 seq_printf(m, "size:\t%zu\n", dmabuf->size);
382 /* Don't count the temporary reference taken inside procfs seq_show */
383 seq_printf(m, "count:\t%ld\n", file_count(dmabuf->file) - 1);
384 seq_printf(m, "exp_name:\t%s\n", dmabuf->exp_name);
385 spin_lock(&dmabuf->name_lock);
387 seq_printf(m, "name:\t%s\n", dmabuf->name);
388 spin_unlock(&dmabuf->name_lock);
391 static const struct file_operations dma_buf_fops = {
392 .release = dma_buf_file_release,
393 .mmap = dma_buf_mmap_internal,
394 .llseek = dma_buf_llseek,
395 .poll = dma_buf_poll,
396 .unlocked_ioctl = dma_buf_ioctl,
397 .compat_ioctl = compat_ptr_ioctl,
398 .show_fdinfo = dma_buf_show_fdinfo,
402 * is_dma_buf_file - Check if struct file* is associated with dma_buf
404 static inline int is_dma_buf_file(struct file *file)
406 return file->f_op == &dma_buf_fops;
409 static struct file *dma_buf_getfile(struct dma_buf *dmabuf, int flags)
411 static atomic64_t dmabuf_inode = ATOMIC64_INIT(0);
413 struct inode *inode = alloc_anon_inode(dma_buf_mnt->mnt_sb);
416 return ERR_CAST(inode);
418 inode->i_size = dmabuf->size;
419 inode_set_bytes(inode, dmabuf->size);
422 * The ->i_ino acquired from get_next_ino() is not unique thus
423 * not suitable for using it as dentry name by dmabuf stats.
424 * Override ->i_ino with the unique and dmabuffs specific
427 inode->i_ino = atomic64_add_return(1, &dmabuf_inode);
428 file = alloc_file_pseudo(inode, dma_buf_mnt, "dmabuf",
429 flags, &dma_buf_fops);
432 file->f_flags = flags & (O_ACCMODE | O_NONBLOCK);
433 file->private_data = dmabuf;
434 file->f_path.dentry->d_fsdata = dmabuf;
444 * DOC: dma buf device access
446 * For device DMA access to a shared DMA buffer the usual sequence of operations
449 * 1. The exporter defines his exporter instance using
450 * DEFINE_DMA_BUF_EXPORT_INFO() and calls dma_buf_export() to wrap a private
451 * buffer object into a &dma_buf. It then exports that &dma_buf to userspace
452 * as a file descriptor by calling dma_buf_fd().
454 * 2. Userspace passes this file-descriptors to all drivers it wants this buffer
455 * to share with: First the file descriptor is converted to a &dma_buf using
456 * dma_buf_get(). Then the buffer is attached to the device using
459 * Up to this stage the exporter is still free to migrate or reallocate the
462 * 3. Once the buffer is attached to all devices userspace can initiate DMA
463 * access to the shared buffer. In the kernel this is done by calling
464 * dma_buf_map_attachment() and dma_buf_unmap_attachment().
466 * 4. Once a driver is done with a shared buffer it needs to call
467 * dma_buf_detach() (after cleaning up any mappings) and then release the
468 * reference acquired with dma_buf_get() by calling dma_buf_put().
470 * For the detailed semantics exporters are expected to implement see
475 * dma_buf_export - Creates a new dma_buf, and associates an anon file
476 * with this buffer, so it can be exported.
477 * Also connect the allocator specific data and ops to the buffer.
478 * Additionally, provide a name string for exporter; useful in debugging.
480 * @exp_info: [in] holds all the export related information provided
481 * by the exporter. see &struct dma_buf_export_info
482 * for further details.
484 * Returns, on success, a newly created struct dma_buf object, which wraps the
485 * supplied private data and operations for struct dma_buf_ops. On either
486 * missing ops, or error in allocating struct dma_buf, will return negative
489 * For most cases the easiest way to create @exp_info is through the
490 * %DEFINE_DMA_BUF_EXPORT_INFO macro.
492 struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
494 struct dma_buf *dmabuf;
495 struct dma_resv *resv = exp_info->resv;
497 size_t alloc_size = sizeof(struct dma_buf);
501 alloc_size += sizeof(struct dma_resv);
503 /* prevent &dma_buf[1] == dma_buf->resv */
506 if (WARN_ON(!exp_info->priv
508 || !exp_info->ops->map_dma_buf
509 || !exp_info->ops->unmap_dma_buf
510 || !exp_info->ops->release)) {
511 return ERR_PTR(-EINVAL);
514 if (WARN_ON(exp_info->ops->cache_sgt_mapping &&
515 (exp_info->ops->pin || exp_info->ops->unpin)))
516 return ERR_PTR(-EINVAL);
518 if (WARN_ON(!exp_info->ops->pin != !exp_info->ops->unpin))
519 return ERR_PTR(-EINVAL);
521 if (!try_module_get(exp_info->owner))
522 return ERR_PTR(-ENOENT);
524 dmabuf = kzalloc(alloc_size, GFP_KERNEL);
530 dmabuf->priv = exp_info->priv;
531 dmabuf->ops = exp_info->ops;
532 dmabuf->size = exp_info->size;
533 dmabuf->exp_name = exp_info->exp_name;
534 dmabuf->owner = exp_info->owner;
535 spin_lock_init(&dmabuf->name_lock);
536 init_waitqueue_head(&dmabuf->poll);
537 dmabuf->cb_in.poll = dmabuf->cb_out.poll = &dmabuf->poll;
538 dmabuf->cb_in.active = dmabuf->cb_out.active = 0;
541 resv = (struct dma_resv *)&dmabuf[1];
546 file = dma_buf_getfile(dmabuf, exp_info->flags);
552 file->f_mode |= FMODE_LSEEK;
555 mutex_init(&dmabuf->lock);
556 INIT_LIST_HEAD(&dmabuf->attachments);
558 mutex_lock(&db_list.lock);
559 list_add(&dmabuf->list_node, &db_list.head);
560 mutex_unlock(&db_list.lock);
562 ret = dma_buf_stats_setup(dmabuf);
570 * Set file->f_path.dentry->d_fsdata to NULL so that when
571 * dma_buf_release() gets invoked by dentry_ops, it exits
572 * early before calling the release() dma_buf op.
574 file->f_path.dentry->d_fsdata = NULL;
579 module_put(exp_info->owner);
582 EXPORT_SYMBOL_NS_GPL(dma_buf_export, DMA_BUF);
585 * dma_buf_fd - returns a file descriptor for the given struct dma_buf
586 * @dmabuf: [in] pointer to dma_buf for which fd is required.
587 * @flags: [in] flags to give to fd
589 * On success, returns an associated 'fd'. Else, returns error.
591 int dma_buf_fd(struct dma_buf *dmabuf, int flags)
595 if (!dmabuf || !dmabuf->file)
598 fd = get_unused_fd_flags(flags);
602 fd_install(fd, dmabuf->file);
606 EXPORT_SYMBOL_NS_GPL(dma_buf_fd, DMA_BUF);
609 * dma_buf_get - returns the struct dma_buf related to an fd
610 * @fd: [in] fd associated with the struct dma_buf to be returned
612 * On success, returns the struct dma_buf associated with an fd; uses
613 * file's refcounting done by fget to increase refcount. returns ERR_PTR
616 struct dma_buf *dma_buf_get(int fd)
623 return ERR_PTR(-EBADF);
625 if (!is_dma_buf_file(file)) {
627 return ERR_PTR(-EINVAL);
630 return file->private_data;
632 EXPORT_SYMBOL_NS_GPL(dma_buf_get, DMA_BUF);
635 * dma_buf_put - decreases refcount of the buffer
636 * @dmabuf: [in] buffer to reduce refcount of
638 * Uses file's refcounting done implicitly by fput().
640 * If, as a result of this call, the refcount becomes 0, the 'release' file
641 * operation related to this fd is called. It calls &dma_buf_ops.release vfunc
642 * in turn, and frees the memory allocated for dmabuf when exported.
644 void dma_buf_put(struct dma_buf *dmabuf)
646 if (WARN_ON(!dmabuf || !dmabuf->file))
651 EXPORT_SYMBOL_NS_GPL(dma_buf_put, DMA_BUF);
653 static void mangle_sg_table(struct sg_table *sg_table)
655 #ifdef CONFIG_DMABUF_DEBUG
657 struct scatterlist *sg;
659 /* To catch abuse of the underlying struct page by importers mix
660 * up the bits, but take care to preserve the low SG_ bits to
661 * not corrupt the sgt. The mixing is undone in __unmap_dma_buf
662 * before passing the sgt back to the exporter. */
663 for_each_sgtable_sg(sg_table, sg, i)
664 sg->page_link ^= ~0xffUL;
668 static struct sg_table * __map_dma_buf(struct dma_buf_attachment *attach,
669 enum dma_data_direction direction)
671 struct sg_table *sg_table;
674 sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
675 if (IS_ERR_OR_NULL(sg_table))
678 if (!dma_buf_attachment_is_dynamic(attach)) {
679 ret = dma_resv_wait_timeout(attach->dmabuf->resv,
680 DMA_RESV_USAGE_KERNEL, true,
681 MAX_SCHEDULE_TIMEOUT);
683 attach->dmabuf->ops->unmap_dma_buf(attach, sg_table,
689 mangle_sg_table(sg_table);
694 * dma_buf_dynamic_attach - Add the device to dma_buf's attachments list
695 * @dmabuf: [in] buffer to attach device to.
696 * @dev: [in] device to be attached.
697 * @importer_ops: [in] importer operations for the attachment
698 * @importer_priv: [in] importer private pointer for the attachment
700 * Returns struct dma_buf_attachment pointer for this attachment. Attachments
701 * must be cleaned up by calling dma_buf_detach().
703 * Optionally this calls &dma_buf_ops.attach to allow device-specific attach
708 * A pointer to newly created &dma_buf_attachment on success, or a negative
709 * error code wrapped into a pointer on failure.
711 * Note that this can fail if the backing storage of @dmabuf is in a place not
712 * accessible to @dev, and cannot be moved to a more suitable place. This is
713 * indicated with the error code -EBUSY.
715 struct dma_buf_attachment *
716 dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
717 const struct dma_buf_attach_ops *importer_ops,
720 struct dma_buf_attachment *attach;
723 if (WARN_ON(!dmabuf || !dev))
724 return ERR_PTR(-EINVAL);
726 if (WARN_ON(importer_ops && !importer_ops->move_notify))
727 return ERR_PTR(-EINVAL);
729 attach = kzalloc(sizeof(*attach), GFP_KERNEL);
731 return ERR_PTR(-ENOMEM);
734 attach->dmabuf = dmabuf;
736 attach->peer2peer = importer_ops->allow_peer2peer;
737 attach->importer_ops = importer_ops;
738 attach->importer_priv = importer_priv;
740 if (dmabuf->ops->attach) {
741 ret = dmabuf->ops->attach(dmabuf, attach);
745 dma_resv_lock(dmabuf->resv, NULL);
746 list_add(&attach->node, &dmabuf->attachments);
747 dma_resv_unlock(dmabuf->resv);
749 /* When either the importer or the exporter can't handle dynamic
750 * mappings we cache the mapping here to avoid issues with the
751 * reservation object lock.
753 if (dma_buf_attachment_is_dynamic(attach) !=
754 dma_buf_is_dynamic(dmabuf)) {
755 struct sg_table *sgt;
757 if (dma_buf_is_dynamic(attach->dmabuf)) {
758 dma_resv_lock(attach->dmabuf->resv, NULL);
759 ret = dmabuf->ops->pin(attach);
764 sgt = __map_dma_buf(attach, DMA_BIDIRECTIONAL);
766 sgt = ERR_PTR(-ENOMEM);
771 if (dma_buf_is_dynamic(attach->dmabuf))
772 dma_resv_unlock(attach->dmabuf->resv);
774 attach->dir = DMA_BIDIRECTIONAL;
784 if (dma_buf_is_dynamic(attach->dmabuf))
785 dmabuf->ops->unpin(attach);
788 if (dma_buf_is_dynamic(attach->dmabuf))
789 dma_resv_unlock(attach->dmabuf->resv);
791 dma_buf_detach(dmabuf, attach);
794 EXPORT_SYMBOL_NS_GPL(dma_buf_dynamic_attach, DMA_BUF);
797 * dma_buf_attach - Wrapper for dma_buf_dynamic_attach
798 * @dmabuf: [in] buffer to attach device to.
799 * @dev: [in] device to be attached.
801 * Wrapper to call dma_buf_dynamic_attach() for drivers which still use a static
804 struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
807 return dma_buf_dynamic_attach(dmabuf, dev, NULL, NULL);
809 EXPORT_SYMBOL_NS_GPL(dma_buf_attach, DMA_BUF);
811 static void __unmap_dma_buf(struct dma_buf_attachment *attach,
812 struct sg_table *sg_table,
813 enum dma_data_direction direction)
815 /* uses XOR, hence this unmangles */
816 mangle_sg_table(sg_table);
818 attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, direction);
822 * dma_buf_detach - Remove the given attachment from dmabuf's attachments list
823 * @dmabuf: [in] buffer to detach from.
824 * @attach: [in] attachment to be detached; is free'd after this call.
826 * Clean up a device attachment obtained by calling dma_buf_attach().
828 * Optionally this calls &dma_buf_ops.detach for device-specific detach.
830 void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
832 if (WARN_ON(!dmabuf || !attach))
836 if (dma_buf_is_dynamic(attach->dmabuf))
837 dma_resv_lock(attach->dmabuf->resv, NULL);
839 __unmap_dma_buf(attach, attach->sgt, attach->dir);
841 if (dma_buf_is_dynamic(attach->dmabuf)) {
842 dmabuf->ops->unpin(attach);
843 dma_resv_unlock(attach->dmabuf->resv);
847 dma_resv_lock(dmabuf->resv, NULL);
848 list_del(&attach->node);
849 dma_resv_unlock(dmabuf->resv);
850 if (dmabuf->ops->detach)
851 dmabuf->ops->detach(dmabuf, attach);
855 EXPORT_SYMBOL_NS_GPL(dma_buf_detach, DMA_BUF);
858 * dma_buf_pin - Lock down the DMA-buf
859 * @attach: [in] attachment which should be pinned
861 * Only dynamic importers (who set up @attach with dma_buf_dynamic_attach()) may
862 * call this, and only for limited use cases like scanout and not for temporary
863 * pin operations. It is not permitted to allow userspace to pin arbitrary
864 * amounts of buffers through this interface.
866 * Buffers must be unpinned by calling dma_buf_unpin().
869 * 0 on success, negative error code on failure.
871 int dma_buf_pin(struct dma_buf_attachment *attach)
873 struct dma_buf *dmabuf = attach->dmabuf;
876 WARN_ON(!dma_buf_attachment_is_dynamic(attach));
878 dma_resv_assert_held(dmabuf->resv);
880 if (dmabuf->ops->pin)
881 ret = dmabuf->ops->pin(attach);
885 EXPORT_SYMBOL_NS_GPL(dma_buf_pin, DMA_BUF);
888 * dma_buf_unpin - Unpin a DMA-buf
889 * @attach: [in] attachment which should be unpinned
891 * This unpins a buffer pinned by dma_buf_pin() and allows the exporter to move
892 * any mapping of @attach again and inform the importer through
893 * &dma_buf_attach_ops.move_notify.
895 void dma_buf_unpin(struct dma_buf_attachment *attach)
897 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->unpin)
904 dmabuf->ops->unpin(attach);
906 EXPORT_SYMBOL_NS_GPL(dma_buf_unpin, DMA_BUF);
909 * dma_buf_map_attachment - Returns the scatterlist table of the attachment;
910 * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the
912 * @attach: [in] attachment whose scatterlist is to be returned
913 * @direction: [in] direction of DMA transfer
915 * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
916 * on error. May return -EINTR if it is interrupted by a signal.
918 * On success, the DMA addresses and lengths in the returned scatterlist are
921 * A mapping must be unmapped by using dma_buf_unmap_attachment(). Note that
922 * the underlying backing storage is pinned for as long as a mapping exists,
923 * therefore users/importers should not hold onto a mapping for undue amounts of
926 * Important: Dynamic importers must wait for the exclusive fence of the struct
927 * dma_resv attached to the DMA-BUF first.
929 struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
930 enum dma_data_direction direction)
932 struct sg_table *sg_table;
937 if (WARN_ON(!attach || !attach->dmabuf))
938 return ERR_PTR(-EINVAL);
940 if (dma_buf_attachment_is_dynamic(attach))
941 dma_resv_assert_held(attach->dmabuf->resv);
945 * Two mappings with different directions for the same
946 * attachment are not allowed.
948 if (attach->dir != direction &&
949 attach->dir != DMA_BIDIRECTIONAL)
950 return ERR_PTR(-EBUSY);
955 if (dma_buf_is_dynamic(attach->dmabuf)) {
956 dma_resv_assert_held(attach->dmabuf->resv);
957 if (!IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY)) {
958 r = attach->dmabuf->ops->pin(attach);
964 sg_table = __map_dma_buf(attach, direction);
966 sg_table = ERR_PTR(-ENOMEM);
968 if (IS_ERR(sg_table) && dma_buf_is_dynamic(attach->dmabuf) &&
969 !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY))
970 attach->dmabuf->ops->unpin(attach);
972 if (!IS_ERR(sg_table) && attach->dmabuf->ops->cache_sgt_mapping) {
973 attach->sgt = sg_table;
974 attach->dir = direction;
977 #ifdef CONFIG_DMA_API_DEBUG
978 if (!IS_ERR(sg_table)) {
979 struct scatterlist *sg;
984 for_each_sgtable_dma_sg(sg_table, sg, i) {
985 addr = sg_dma_address(sg);
986 len = sg_dma_len(sg);
987 if (!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(len)) {
988 pr_debug("%s: addr %llx or len %x is not page aligned!\n",
989 __func__, addr, len);
993 #endif /* CONFIG_DMA_API_DEBUG */
996 EXPORT_SYMBOL_NS_GPL(dma_buf_map_attachment, DMA_BUF);
999 * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might
1000 * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of
1002 * @attach: [in] attachment to unmap buffer from
1003 * @sg_table: [in] scatterlist info of the buffer to unmap
1004 * @direction: [in] direction of DMA transfer
1006 * This unmaps a DMA mapping for @attached obtained by dma_buf_map_attachment().
1008 void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
1009 struct sg_table *sg_table,
1010 enum dma_data_direction direction)
1014 if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
1017 if (dma_buf_attachment_is_dynamic(attach))
1018 dma_resv_assert_held(attach->dmabuf->resv);
1020 if (attach->sgt == sg_table)
1023 if (dma_buf_is_dynamic(attach->dmabuf))
1024 dma_resv_assert_held(attach->dmabuf->resv);
1026 __unmap_dma_buf(attach, sg_table, direction);
1028 if (dma_buf_is_dynamic(attach->dmabuf) &&
1029 !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY))
1030 dma_buf_unpin(attach);
1032 EXPORT_SYMBOL_NS_GPL(dma_buf_unmap_attachment, DMA_BUF);
1035 * dma_buf_move_notify - notify attachments that DMA-buf is moving
1037 * @dmabuf: [in] buffer which is moving
1039 * Informs all attachmenst that they need to destroy and recreated all their
1042 void dma_buf_move_notify(struct dma_buf *dmabuf)
1044 struct dma_buf_attachment *attach;
1046 dma_resv_assert_held(dmabuf->resv);
1048 list_for_each_entry(attach, &dmabuf->attachments, node)
1049 if (attach->importer_ops)
1050 attach->importer_ops->move_notify(attach);
1052 EXPORT_SYMBOL_NS_GPL(dma_buf_move_notify, DMA_BUF);
1057 * There are mutliple reasons for supporting CPU access to a dma buffer object:
1059 * - Fallback operations in the kernel, for example when a device is connected
1060 * over USB and the kernel needs to shuffle the data around first before
1061 * sending it away. Cache coherency is handled by braketing any transactions
1062 * with calls to dma_buf_begin_cpu_access() and dma_buf_end_cpu_access()
1065 * Since for most kernel internal dma-buf accesses need the entire buffer, a
1066 * vmap interface is introduced. Note that on very old 32-bit architectures
1067 * vmalloc space might be limited and result in vmap calls failing.
1071 * void \*dma_buf_vmap(struct dma_buf \*dmabuf, struct iosys_map \*map)
1072 * void dma_buf_vunmap(struct dma_buf \*dmabuf, struct iosys_map \*map)
1074 * The vmap call can fail if there is no vmap support in the exporter, or if
1075 * it runs out of vmalloc space. Note that the dma-buf layer keeps a reference
1076 * count for all vmap access and calls down into the exporter's vmap function
1077 * only when no vmapping exists, and only unmaps it once. Protection against
1078 * concurrent vmap/vunmap calls is provided by taking the &dma_buf.lock mutex.
1080 * - For full compatibility on the importer side with existing userspace
1081 * interfaces, which might already support mmap'ing buffers. This is needed in
1082 * many processing pipelines (e.g. feeding a software rendered image into a
1083 * hardware pipeline, thumbnail creation, snapshots, ...). Also, Android's ION
1084 * framework already supported this and for DMA buffer file descriptors to
1085 * replace ION buffers mmap support was needed.
1087 * There is no special interfaces, userspace simply calls mmap on the dma-buf
1088 * fd. But like for CPU access there's a need to braket the actual access,
1089 * which is handled by the ioctl (DMA_BUF_IOCTL_SYNC). Note that
1090 * DMA_BUF_IOCTL_SYNC can fail with -EAGAIN or -EINTR, in which case it must
1093 * Some systems might need some sort of cache coherency management e.g. when
1094 * CPU and GPU domains are being accessed through dma-buf at the same time.
1095 * To circumvent this problem there are begin/end coherency markers, that
1096 * forward directly to existing dma-buf device drivers vfunc hooks. Userspace
1097 * can make use of those markers through the DMA_BUF_IOCTL_SYNC ioctl. The
1098 * sequence would be used like following:
1101 * - for each drawing/upload cycle in CPU 1. SYNC_START ioctl, 2. read/write
1102 * to mmap area 3. SYNC_END ioctl. This can be repeated as often as you
1103 * want (with the new data being consumed by say the GPU or the scanout
1105 * - munmap once you don't need the buffer any more
1107 * For correctness and optimal performance, it is always required to use
1108 * SYNC_START and SYNC_END before and after, respectively, when accessing the
1109 * mapped address. Userspace cannot rely on coherent access, even when there
1110 * are systems where it just works without calling these ioctls.
1112 * - And as a CPU fallback in userspace processing pipelines.
1114 * Similar to the motivation for kernel cpu access it is again important that
1115 * the userspace code of a given importing subsystem can use the same
1116 * interfaces with a imported dma-buf buffer object as with a native buffer
1117 * object. This is especially important for drm where the userspace part of
1118 * contemporary OpenGL, X, and other drivers is huge, and reworking them to
1119 * use a different way to mmap a buffer rather invasive.
1121 * The assumption in the current dma-buf interfaces is that redirecting the
1122 * initial mmap is all that's needed. A survey of some of the existing
1123 * subsystems shows that no driver seems to do any nefarious thing like
1124 * syncing up with outstanding asynchronous processing on the device or
1125 * allocating special resources at fault time. So hopefully this is good
1126 * enough, since adding interfaces to intercept pagefaults and allow pte
1127 * shootdowns would increase the complexity quite a bit.
1131 * int dma_buf_mmap(struct dma_buf \*, struct vm_area_struct \*,
1134 * If the importing subsystem simply provides a special-purpose mmap call to
1135 * set up a mapping in userspace, calling do_mmap with &dma_buf.file will
1136 * equally achieve that for a dma-buf object.
1139 static int __dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
1140 enum dma_data_direction direction)
1142 bool write = (direction == DMA_BIDIRECTIONAL ||
1143 direction == DMA_TO_DEVICE);
1144 struct dma_resv *resv = dmabuf->resv;
1147 /* Wait on any implicit rendering fences */
1148 ret = dma_resv_wait_timeout(resv, dma_resv_usage_rw(write),
1149 true, MAX_SCHEDULE_TIMEOUT);
1157 * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the
1158 * cpu in the kernel context. Calls begin_cpu_access to allow exporter-specific
1159 * preparations. Coherency is only guaranteed in the specified range for the
1160 * specified access direction.
1161 * @dmabuf: [in] buffer to prepare cpu access for.
1162 * @direction: [in] length of range for cpu access.
1164 * After the cpu access is complete the caller should call
1165 * dma_buf_end_cpu_access(). Only when cpu access is braketed by both calls is
1166 * it guaranteed to be coherent with other DMA access.
1168 * This function will also wait for any DMA transactions tracked through
1169 * implicit synchronization in &dma_buf.resv. For DMA transactions with explicit
1170 * synchronization this function will only ensure cache coherency, callers must
1171 * ensure synchronization with such DMA transactions on their own.
1173 * Can return negative error values, returns 0 on success.
1175 int dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
1176 enum dma_data_direction direction)
1180 if (WARN_ON(!dmabuf))
1183 might_lock(&dmabuf->resv->lock.base);
1185 if (dmabuf->ops->begin_cpu_access)
1186 ret = dmabuf->ops->begin_cpu_access(dmabuf, direction);
1188 /* Ensure that all fences are waited upon - but we first allow
1189 * the native handler the chance to do so more efficiently if it
1190 * chooses. A double invocation here will be reasonably cheap no-op.
1193 ret = __dma_buf_begin_cpu_access(dmabuf, direction);
1197 EXPORT_SYMBOL_NS_GPL(dma_buf_begin_cpu_access, DMA_BUF);
1200 * dma_buf_end_cpu_access - Must be called after accessing a dma_buf from the
1201 * cpu in the kernel context. Calls end_cpu_access to allow exporter-specific
1202 * actions. Coherency is only guaranteed in the specified range for the
1203 * specified access direction.
1204 * @dmabuf: [in] buffer to complete cpu access for.
1205 * @direction: [in] length of range for cpu access.
1207 * This terminates CPU access started with dma_buf_begin_cpu_access().
1209 * Can return negative error values, returns 0 on success.
1211 int dma_buf_end_cpu_access(struct dma_buf *dmabuf,
1212 enum dma_data_direction direction)
1218 might_lock(&dmabuf->resv->lock.base);
1220 if (dmabuf->ops->end_cpu_access)
1221 ret = dmabuf->ops->end_cpu_access(dmabuf, direction);
1225 EXPORT_SYMBOL_NS_GPL(dma_buf_end_cpu_access, DMA_BUF);
1229 * dma_buf_mmap - Setup up a userspace mmap with the given vma
1230 * @dmabuf: [in] buffer that should back the vma
1231 * @vma: [in] vma for the mmap
1232 * @pgoff: [in] offset in pages where this mmap should start within the
1235 * This function adjusts the passed in vma so that it points at the file of the
1236 * dma_buf operation. It also adjusts the starting pgoff and does bounds
1237 * checking on the size of the vma. Then it calls the exporters mmap function to
1238 * set up the mapping.
1240 * Can return negative error values, returns 0 on success.
1242 int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
1243 unsigned long pgoff)
1245 if (WARN_ON(!dmabuf || !vma))
1248 /* check if buffer supports mmap */
1249 if (!dmabuf->ops->mmap)
1252 /* check for offset overflow */
1253 if (pgoff + vma_pages(vma) < pgoff)
1256 /* check for overflowing the buffer's size */
1257 if (pgoff + vma_pages(vma) >
1258 dmabuf->size >> PAGE_SHIFT)
1261 /* readjust the vma */
1262 vma_set_file(vma, dmabuf->file);
1263 vma->vm_pgoff = pgoff;
1265 return dmabuf->ops->mmap(dmabuf, vma);
1267 EXPORT_SYMBOL_NS_GPL(dma_buf_mmap, DMA_BUF);
1270 * dma_buf_vmap - Create virtual mapping for the buffer object into kernel
1271 * address space. Same restrictions as for vmap and friends apply.
1272 * @dmabuf: [in] buffer to vmap
1273 * @map: [out] returns the vmap pointer
1275 * This call may fail due to lack of virtual mapping address space.
1276 * These calls are optional in drivers. The intended use for them
1277 * is for mapping objects linear in kernel space for high use objects.
1279 * To ensure coherency users must call dma_buf_begin_cpu_access() and
1280 * dma_buf_end_cpu_access() around any cpu access performed through this
1283 * Returns 0 on success, or a negative errno code otherwise.
1285 int dma_buf_vmap(struct dma_buf *dmabuf, struct iosys_map *map)
1287 struct iosys_map ptr;
1290 iosys_map_clear(map);
1292 if (WARN_ON(!dmabuf))
1295 if (!dmabuf->ops->vmap)
1298 mutex_lock(&dmabuf->lock);
1299 if (dmabuf->vmapping_counter) {
1300 dmabuf->vmapping_counter++;
1301 BUG_ON(iosys_map_is_null(&dmabuf->vmap_ptr));
1302 *map = dmabuf->vmap_ptr;
1306 BUG_ON(iosys_map_is_set(&dmabuf->vmap_ptr));
1308 ret = dmabuf->ops->vmap(dmabuf, &ptr);
1309 if (WARN_ON_ONCE(ret))
1312 dmabuf->vmap_ptr = ptr;
1313 dmabuf->vmapping_counter = 1;
1315 *map = dmabuf->vmap_ptr;
1318 mutex_unlock(&dmabuf->lock);
1321 EXPORT_SYMBOL_NS_GPL(dma_buf_vmap, DMA_BUF);
1324 * dma_buf_vunmap - Unmap a vmap obtained by dma_buf_vmap.
1325 * @dmabuf: [in] buffer to vunmap
1326 * @map: [in] vmap pointer to vunmap
1328 void dma_buf_vunmap(struct dma_buf *dmabuf, struct iosys_map *map)
1330 if (WARN_ON(!dmabuf))
1333 BUG_ON(iosys_map_is_null(&dmabuf->vmap_ptr));
1334 BUG_ON(dmabuf->vmapping_counter == 0);
1335 BUG_ON(!iosys_map_is_equal(&dmabuf->vmap_ptr, map));
1337 mutex_lock(&dmabuf->lock);
1338 if (--dmabuf->vmapping_counter == 0) {
1339 if (dmabuf->ops->vunmap)
1340 dmabuf->ops->vunmap(dmabuf, map);
1341 iosys_map_clear(&dmabuf->vmap_ptr);
1343 mutex_unlock(&dmabuf->lock);
1345 EXPORT_SYMBOL_NS_GPL(dma_buf_vunmap, DMA_BUF);
1347 #ifdef CONFIG_DEBUG_FS
1348 static int dma_buf_debug_show(struct seq_file *s, void *unused)
1350 struct dma_buf *buf_obj;
1351 struct dma_buf_attachment *attach_obj;
1352 int count = 0, attach_count;
1356 ret = mutex_lock_interruptible(&db_list.lock);
1361 seq_puts(s, "\nDma-buf Objects:\n");
1362 seq_printf(s, "%-8s\t%-8s\t%-8s\t%-8s\texp_name\t%-8s\n",
1363 "size", "flags", "mode", "count", "ino");
1365 list_for_each_entry(buf_obj, &db_list.head, list_node) {
1367 ret = dma_resv_lock_interruptible(buf_obj->resv, NULL);
1372 spin_lock(&buf_obj->name_lock);
1373 seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\t%08lu\t%s\n",
1375 buf_obj->file->f_flags, buf_obj->file->f_mode,
1376 file_count(buf_obj->file),
1378 file_inode(buf_obj->file)->i_ino,
1379 buf_obj->name ?: "");
1380 spin_unlock(&buf_obj->name_lock);
1382 dma_resv_describe(buf_obj->resv, s);
1384 seq_puts(s, "\tAttached Devices:\n");
1387 list_for_each_entry(attach_obj, &buf_obj->attachments, node) {
1388 seq_printf(s, "\t%s\n", dev_name(attach_obj->dev));
1391 dma_resv_unlock(buf_obj->resv);
1393 seq_printf(s, "Total %d devices attached\n\n",
1397 size += buf_obj->size;
1400 seq_printf(s, "\nTotal %d objects, %zu bytes\n", count, size);
1402 mutex_unlock(&db_list.lock);
1406 mutex_unlock(&db_list.lock);
1410 DEFINE_SHOW_ATTRIBUTE(dma_buf_debug);
1412 static struct dentry *dma_buf_debugfs_dir;
1414 static int dma_buf_init_debugfs(void)
1419 d = debugfs_create_dir("dma_buf", NULL);
1423 dma_buf_debugfs_dir = d;
1425 d = debugfs_create_file("bufinfo", S_IRUGO, dma_buf_debugfs_dir,
1426 NULL, &dma_buf_debug_fops);
1428 pr_debug("dma_buf: debugfs: failed to create node bufinfo\n");
1429 debugfs_remove_recursive(dma_buf_debugfs_dir);
1430 dma_buf_debugfs_dir = NULL;
1437 static void dma_buf_uninit_debugfs(void)
1439 debugfs_remove_recursive(dma_buf_debugfs_dir);
1442 static inline int dma_buf_init_debugfs(void)
1446 static inline void dma_buf_uninit_debugfs(void)
1451 static int __init dma_buf_init(void)
1455 ret = dma_buf_init_sysfs_statistics();
1459 dma_buf_mnt = kern_mount(&dma_buf_fs_type);
1460 if (IS_ERR(dma_buf_mnt))
1461 return PTR_ERR(dma_buf_mnt);
1463 mutex_init(&db_list.lock);
1464 INIT_LIST_HEAD(&db_list.head);
1465 dma_buf_init_debugfs();
1468 subsys_initcall(dma_buf_init);
1470 static void __exit dma_buf_deinit(void)
1472 dma_buf_uninit_debugfs();
1473 kern_unmount(dma_buf_mnt);
1474 dma_buf_uninit_sysfs_statistics();
1476 __exitcall(dma_buf_deinit);