Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1422 insertions, 0 deletions

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
new file mode 100644
index 000000000..93e9bf738
--- /dev/null
+++ b/drivers/dma-buf/dma-buf.c
@@ -0,0 +1,1422 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Framework for buffer objects that can be shared across devices/subsystems.
+ *
+ * Copyright(C) 2011 Linaro Limited. All rights reserved.
+ * Author: Sumit Semwal <sumit.semwal@ti.com>
+ *
+ * Many thanks to linaro-mm-sig list, and specially
+ * Arnd Bergmann <arnd@arndb.de>, Rob Clark <rob@ti.com> and
+ * Daniel Vetter <daniel@ffwll.ch> for their support in creation and
+ * refining of this idea.
+ */
+
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/dma-buf.h>
+#include <linux/dma-fence.h>
+#include <linux/anon_inodes.h>
+#include <linux/export.h>
+#include <linux/debugfs.h>
+#include <linux/module.h>
+#include <linux/seq_file.h>
+#include <linux/poll.h>
+#include <linux/dma-resv.h>
+#include <linux/mm.h>
+#include <linux/mount.h>
+#include <linux/pseudo_fs.h>
+
+#include <uapi/linux/dma-buf.h>
+#include <uapi/linux/magic.h>
+
+static inline int is_dma_buf_file(struct file *);
+
+struct dma_buf_list {
+	struct list_head head;
+	struct mutex lock;
+};
+
+static struct dma_buf_list db_list;
+
+static char *dmabuffs_dname(struct dentry *dentry, char *buffer, int buflen)
+{
+	struct dma_buf *dmabuf;
+	char name[DMA_BUF_NAME_LEN];
+	size_t ret = 0;
+
+	dmabuf = dentry->d_fsdata;
+	spin_lock(&dmabuf->name_lock);
+	if (dmabuf->name)
+		ret = strlcpy(name, dmabuf->name, DMA_BUF_NAME_LEN);
+	spin_unlock(&dmabuf->name_lock);
+
+	return dynamic_dname(dentry, buffer, buflen, "/%s:%s",
+			     dentry->d_name.name, ret > 0 ? name : "");
+}
+
+static void dma_buf_release(struct dentry *dentry)
+{
+	struct dma_buf *dmabuf;
+
+	dmabuf = dentry->d_fsdata;
+	if (unlikely(!dmabuf))
+		return;
+
+	BUG_ON(dmabuf->vmapping_counter);
+
+	/*
+	 * Any fences that a dma-buf poll can wait on should be signaled
+	 * before releasing dma-buf. This is the responsibility of each
+	 * driver that uses the reservation objects.
+	 *
+	 * If you hit this BUG() it means someone dropped their ref to the
+	 * dma-buf while still having pending operation to the buffer.
+	 */
+	BUG_ON(dmabuf->cb_shared.active || dmabuf->cb_excl.active);
+
+	dmabuf->ops->release(dmabuf);
+
+	if (dmabuf->resv == (struct dma_resv *)&dmabuf[1])
+		dma_resv_fini(dmabuf->resv);
+
+	WARN_ON(!list_empty(&dmabuf->attachments));
+	module_put(dmabuf->owner);
+	kfree(dmabuf->name);
+	kfree(dmabuf);
+}
+
+static int dma_buf_file_release(struct inode *inode, struct file *file)
+{
+	struct dma_buf *dmabuf;
+
+	if (!is_dma_buf_file(file))
+		return -EINVAL;
+
+	dmabuf = file->private_data;
+
+	mutex_lock(&db_list.lock);
+	list_del(&dmabuf->list_node);
+	mutex_unlock(&db_list.lock);
+
+	return 0;
+}
+
+static const struct dentry_operations dma_buf_dentry_ops = {
+	.d_dname = dmabuffs_dname,
+	.d_release = dma_buf_release,
+};
+
+static struct vfsmount *dma_buf_mnt;
+
+static int dma_buf_fs_init_context(struct fs_context *fc)
+{
+	struct pseudo_fs_context *ctx;
+
+	ctx = init_pseudo(fc, DMA_BUF_MAGIC);
+	if (!ctx)
+		return -ENOMEM;
+	ctx->dops = &dma_buf_dentry_ops;
+	return 0;
+}
+
+static struct file_system_type dma_buf_fs_type = {
+	.name = "dmabuf",
+	.init_fs_context = dma_buf_fs_init_context,
+	.kill_sb = kill_anon_super,
+};
+
+static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
+{
+	struct dma_buf *dmabuf;
+
+	if (!is_dma_buf_file(file))
+		return -EINVAL;
+
+	dmabuf = file->private_data;
+
+	/* check if buffer supports mmap */
+	if (!dmabuf->ops->mmap)
+		return -EINVAL;
+
+	/* check for overflowing the buffer's size */
+	if (vma->vm_pgoff + vma_pages(vma) >
+	    dmabuf->size >> PAGE_SHIFT)
+		return -EINVAL;
+
+	return dmabuf->ops->mmap(dmabuf, vma);
+}
+
+static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence)
+{
+	struct dma_buf *dmabuf;
+	loff_t base;
+
+	if (!is_dma_buf_file(file))
+		return -EBADF;
+
+	dmabuf = file->private_data;
+
+	/* only support discovering the end of the buffer,
+	   but also allow SEEK_SET to maintain the idiomatic
+	   SEEK_END(0), SEEK_CUR(0) pattern */
+	if (whence == SEEK_END)
+		base = dmabuf->size;
+	else if (whence == SEEK_SET)
+		base = 0;
+	else
+		return -EINVAL;
+
+	if (offset != 0)
+		return -EINVAL;
+
+	return base + offset;
+}
+
+/**
+ * DOC: implicit fence polling
+ *
+ * To support cross-device and cross-driver synchronization of buffer access
+ * implicit fences (represented internally in the kernel with &struct dma_fence)
+ * can be attached to a &dma_buf. The glue for that and a few related things are
+ * provided in the &dma_resv structure.
+ *
+ * Userspace can query the state of these implicitly tracked fences using poll()
+ * and related system calls:
+ *
+ * - Checking for EPOLLIN, i.e. read access, can be use to query the state of the
+ *   most recent write or exclusive fence.
+ *
+ * - Checking for EPOLLOUT, i.e. write access, can be used to query the state of
+ *   all attached fences, shared and exclusive ones.
+ *
+ * Note that this only signals the completion of the respective fences, i.e. the
+ * DMA transfers are complete. Cache flushing and any other necessary
+ * preparations before CPU access can begin still need to happen.
+ */
+
+static void dma_buf_poll_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
+{
+	struct dma_buf_poll_cb_t *dcb = (struct dma_buf_poll_cb_t *)cb;
+	unsigned long flags;
+
+	spin_lock_irqsave(&dcb->poll->lock, flags);
+	wake_up_locked_poll(dcb->poll, dcb->active);
+	dcb->active = 0;
+	spin_unlock_irqrestore(&dcb->poll->lock, flags);
+}
+
+static __poll_t dma_buf_poll(struct file *file, poll_table *poll)
+{
+	struct dma_buf *dmabuf;
+	struct dma_resv *resv;
+	struct dma_resv_list *fobj;
+	struct dma_fence *fence_excl;
+	__poll_t events;
+	unsigned shared_count, seq;
+
+	dmabuf = file->private_data;
+	if (!dmabuf || !dmabuf->resv)
+		return EPOLLERR;
+
+	resv = dmabuf->resv;
+
+	poll_wait(file, &dmabuf->poll, poll);
+
+	events = poll_requested_events(poll) & (EPOLLIN | EPOLLOUT);
+	if (!events)
+		return 0;
+
+retry:
+	seq = read_seqcount_begin(&resv->seq);
+	rcu_read_lock();
+
+	fobj = rcu_dereference(resv->fence);
+	if (fobj)
+		shared_count = fobj->shared_count;
+	else
+		shared_count = 0;
+	fence_excl = rcu_dereference(resv->fence_excl);
+	if (read_seqcount_retry(&resv->seq, seq)) {
+		rcu_read_unlock();
+		goto retry;
+	}
+
+	if (fence_excl && (!(events & EPOLLOUT) || shared_count == 0)) {
+		struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_excl;
+		__poll_t pevents = EPOLLIN;
+
+		if (shared_count == 0)
+			pevents |= EPOLLOUT;
+
+		spin_lock_irq(&dmabuf->poll.lock);
+		if (dcb->active) {
+			dcb->active |= pevents;
+			events &= ~pevents;
+		} else
+			dcb->active = pevents;
+		spin_unlock_irq(&dmabuf->poll.lock);
+
+		if (events & pevents) {
+			if (!dma_fence_get_rcu(fence_excl)) {
+				/* force a recheck */
+				events &= ~pevents;
+				dma_buf_poll_cb(NULL, &dcb->cb);
+			} else if (!dma_fence_add_callback(fence_excl, &dcb->cb,
+							   dma_buf_poll_cb)) {
+				events &= ~pevents;
+				dma_fence_put(fence_excl);
+			} else {
+				/*
+				 * No callback queued, wake up any additional
+				 * waiters.
+				 */
+				dma_fence_put(fence_excl);
+				dma_buf_poll_cb(NULL, &dcb->cb);
+			}
+		}
+	}
+
+	if ((events & EPOLLOUT) && shared_count > 0) {
+		struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_shared;
+		int i;
+
+		/* Only queue a new callback if no event has fired yet */
+		spin_lock_irq(&dmabuf->poll.lock);
+		if (dcb->active)
+			events &= ~EPOLLOUT;
+		else
+			dcb->active = EPOLLOUT;
+		spin_unlock_irq(&dmabuf->poll.lock);
+
+		if (!(events & EPOLLOUT))
+			goto out;
+
+		for (i = 0; i < shared_count; ++i) {
+			struct dma_fence *fence = rcu_dereference(fobj->shared[i]);
+
+			if (!dma_fence_get_rcu(fence)) {
+				/*
+				 * fence refcount dropped to zero, this means
+				 * that fobj has been freed
+				 *
+				 * call dma_buf_poll_cb and force a recheck!
+				 */
+				events &= ~EPOLLOUT;
+				dma_buf_poll_cb(NULL, &dcb->cb);
+				break;
+			}
+			if (!dma_fence_add_callback(fence, &dcb->cb,
+						    dma_buf_poll_cb)) {
+				dma_fence_put(fence);
+				events &= ~EPOLLOUT;
+				break;
+			}
+			dma_fence_put(fence);
+		}
+
+		/* No callback queued, wake up any additional waiters. */
+		if (i == shared_count)
+			dma_buf_poll_cb(NULL, &dcb->cb);
+	}
+
+out:
+	rcu_read_unlock();
+	return events;
+}
+
+/**
+ * dma_buf_set_name - Set a name to a specific dma_buf to track the usage.
+ * The name of the dma-buf buffer can only be set when the dma-buf is not
+ * attached to any devices. It could theoritically support changing the
+ * name of the dma-buf if the same piece of memory is used for multiple
+ * purpose between different devices.
+ *
+ * @dmabuf: [in]     dmabuf buffer that will be renamed.
+ * @buf:    [in]     A piece of userspace memory that contains the name of
+ *                   the dma-buf.
+ *
+ * Returns 0 on success. If the dma-buf buffer is already attached to
+ * devices, return -EBUSY.
+ *
+ */
+static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf)
+{
+	char *name = strndup_user(buf, DMA_BUF_NAME_LEN);
+	long ret = 0;
+
+	if (IS_ERR(name))
+		return PTR_ERR(name);
+
+	dma_resv_lock(dmabuf->resv, NULL);
+	if (!list_empty(&dmabuf->attachments)) {
+		ret = -EBUSY;
+		kfree(name);
+		goto out_unlock;
+	}
+	spin_lock(&dmabuf->name_lock);
+	kfree(dmabuf->name);
+	dmabuf->name = name;
+	spin_unlock(&dmabuf->name_lock);
+
+out_unlock:
+	dma_resv_unlock(dmabuf->resv);
+	return ret;
+}
+
+static long dma_buf_ioctl(struct file *file,
+			  unsigned int cmd, unsigned long arg)
+{
+	struct dma_buf *dmabuf;
+	struct dma_buf_sync sync;
+	enum dma_data_direction direction;
+	int ret;
+
+	dmabuf = file->private_data;
+
+	switch (cmd) {
+	case DMA_BUF_IOCTL_SYNC:
+		if (copy_from_user(&sync, (void __user *) arg, sizeof(sync)))
+			return -EFAULT;
+
+		if (sync.flags & ~DMA_BUF_SYNC_VALID_FLAGS_MASK)
+			return -EINVAL;
+
+		switch (sync.flags & DMA_BUF_SYNC_RW) {
+		case DMA_BUF_SYNC_READ:
+			direction = DMA_FROM_DEVICE;
+			break;
+		case DMA_BUF_SYNC_WRITE:
+			direction = DMA_TO_DEVICE;
+			break;
+		case DMA_BUF_SYNC_RW:
+			direction = DMA_BIDIRECTIONAL;
+			break;
+		default:
+			return -EINVAL;
+		}
+
+		if (sync.flags & DMA_BUF_SYNC_END)
+			ret = dma_buf_end_cpu_access(dmabuf, direction);
+		else
+			ret = dma_buf_begin_cpu_access(dmabuf, direction);
+
+		return ret;
+
+	case DMA_BUF_SET_NAME_A:
+	case DMA_BUF_SET_NAME_B:
+		return dma_buf_set_name(dmabuf, (const char __user *)arg);
+
+	default:
+		return -ENOTTY;
+	}
+}
+
+static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file)
+{
+	struct dma_buf *dmabuf = file->private_data;
+
+	seq_printf(m, "size:\t%zu\n", dmabuf->size);
+	/* Don't count the temporary reference taken inside procfs seq_show */
+	seq_printf(m, "count:\t%ld\n", file_count(dmabuf->file) - 1);
+	seq_printf(m, "exp_name:\t%s\n", dmabuf->exp_name);
+	spin_lock(&dmabuf->name_lock);
+	if (dmabuf->name)
+		seq_printf(m, "name:\t%s\n", dmabuf->name);
+	spin_unlock(&dmabuf->name_lock);
+}
+
+static const struct file_operations dma_buf_fops = {
+	.release	= dma_buf_file_release,
+	.mmap		= dma_buf_mmap_internal,
+	.llseek		= dma_buf_llseek,
+	.poll		= dma_buf_poll,
+	.unlocked_ioctl	= dma_buf_ioctl,
+	.compat_ioctl	= compat_ptr_ioctl,
+	.show_fdinfo	= dma_buf_show_fdinfo,
+};
+
+/*
+ * is_dma_buf_file - Check if struct file* is associated with dma_buf
+ */
+static inline int is_dma_buf_file(struct file *file)
+{
+	return file->f_op == &dma_buf_fops;
+}
+
+static struct file *dma_buf_getfile(struct dma_buf *dmabuf, int flags)
+{
+	struct file *file;
+	struct inode *inode = alloc_anon_inode(dma_buf_mnt->mnt_sb);
+
+	if (IS_ERR(inode))
+		return ERR_CAST(inode);
+
+	inode->i_size = dmabuf->size;
+	inode_set_bytes(inode, dmabuf->size);
+
+	file = alloc_file_pseudo(inode, dma_buf_mnt, "dmabuf",
+				 flags, &dma_buf_fops);
+	if (IS_ERR(file))
+		goto err_alloc_file;
+	file->f_flags = flags & (O_ACCMODE | O_NONBLOCK);
+	file->private_data = dmabuf;
+	file->f_path.dentry->d_fsdata = dmabuf;
+
+	return file;
+
+err_alloc_file:
+	iput(inode);
+	return file;
+}
+
+/**
+ * DOC: dma buf device access
+ *
+ * For device DMA access to a shared DMA buffer the usual sequence of operations
+ * is fairly simple:
+ *
+ * 1. The exporter defines his exporter instance using
+ *    DEFINE_DMA_BUF_EXPORT_INFO() and calls dma_buf_export() to wrap a private
+ *    buffer object into a &dma_buf. It then exports that &dma_buf to userspace
+ *    as a file descriptor by calling dma_buf_fd().
+ *
+ * 2. Userspace passes this file-descriptors to all drivers it wants this buffer
+ *    to share with: First the filedescriptor is converted to a &dma_buf using
+ *    dma_buf_get(). Then the buffer is attached to the device using
+ *    dma_buf_attach().
+ *
+ *    Up to this stage the exporter is still free to migrate or reallocate the
+ *    backing storage.
+ *
+ * 3. Once the buffer is attached to all devices userspace can initiate DMA
+ *    access to the shared buffer. In the kernel this is done by calling
+ *    dma_buf_map_attachment() and dma_buf_unmap_attachment().
+ *
+ * 4. Once a driver is done with a shared buffer it needs to call
+ *    dma_buf_detach() (after cleaning up any mappings) and then release the
+ *    reference acquired with dma_buf_get by calling dma_buf_put().
+ *
+ * For the detailed semantics exporters are expected to implement see
+ * &dma_buf_ops.
+ */
+
+/**
+ * dma_buf_export - Creates a new dma_buf, and associates an anon file
+ * with this buffer, so it can be exported.
+ * Also connect the allocator specific data and ops to the buffer.
+ * Additionally, provide a name string for exporter; useful in debugging.
+ *
+ * @exp_info:	[in]	holds all the export related information provided
+ *			by the exporter. see &struct dma_buf_export_info
+ *			for further details.
+ *
+ * Returns, on success, a newly created dma_buf object, which wraps the
+ * supplied private data and operations for dma_buf_ops. On either missing
+ * ops, or error in allocating struct dma_buf, will return negative error.
+ *
+ * For most cases the easiest way to create @exp_info is through the
+ * %DEFINE_DMA_BUF_EXPORT_INFO macro.
+ */
+struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
+{
+	struct dma_buf *dmabuf;
+	struct dma_resv *resv = exp_info->resv;
+	struct file *file;
+	size_t alloc_size = sizeof(struct dma_buf);
+	int ret;
+
+	if (!exp_info->resv)
+		alloc_size += sizeof(struct dma_resv);
+	else
+		/* prevent &dma_buf[1] == dma_buf->resv */
+		alloc_size += 1;
+
+	if (WARN_ON(!exp_info->priv
+			  || !exp_info->ops
+			  || !exp_info->ops->map_dma_buf
+			  || !exp_info->ops->unmap_dma_buf
+			  || !exp_info->ops->release)) {
+		return ERR_PTR(-EINVAL);
+	}
+
+	if (WARN_ON(exp_info->ops->cache_sgt_mapping &&
+		    (exp_info->ops->pin || exp_info->ops->unpin)))
+		return ERR_PTR(-EINVAL);
+
+	if (WARN_ON(!exp_info->ops->pin != !exp_info->ops->unpin))
+		return ERR_PTR(-EINVAL);
+
+	if (!try_module_get(exp_info->owner))
+		return ERR_PTR(-ENOENT);
+
+	dmabuf = kzalloc(alloc_size, GFP_KERNEL);
+	if (!dmabuf) {
+		ret = -ENOMEM;
+		goto err_module;
+	}
+
+	dmabuf->priv = exp_info->priv;
+	dmabuf->ops = exp_info->ops;
+	dmabuf->size = exp_info->size;
+	dmabuf->exp_name = exp_info->exp_name;
+	dmabuf->owner = exp_info->owner;
+	spin_lock_init(&dmabuf->name_lock);
+	init_waitqueue_head(&dmabuf->poll);
+	dmabuf->cb_excl.poll = dmabuf->cb_shared.poll = &dmabuf->poll;
+	dmabuf->cb_excl.active = dmabuf->cb_shared.active = 0;
+
+	if (!resv) {
+		resv = (struct dma_resv *)&dmabuf[1];
+		dma_resv_init(resv);
+	}
+	dmabuf->resv = resv;
+
+	file = dma_buf_getfile(dmabuf, exp_info->flags);
+	if (IS_ERR(file)) {
+		ret = PTR_ERR(file);
+		goto err_dmabuf;
+	}
+
+	file->f_mode |= FMODE_LSEEK;
+	dmabuf->file = file;
+
+	mutex_init(&dmabuf->lock);
+	INIT_LIST_HEAD(&dmabuf->attachments);
+
+	mutex_lock(&db_list.lock);
+	list_add(&dmabuf->list_node, &db_list.head);
+	mutex_unlock(&db_list.lock);
+
+	return dmabuf;
+
+err_dmabuf:
+	kfree(dmabuf);
+err_module:
+	module_put(exp_info->owner);
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(dma_buf_export);
+
+/**
+ * dma_buf_fd - returns a file descriptor for the given dma_buf
+ * @dmabuf:	[in]	pointer to dma_buf for which fd is required.
+ * @flags:      [in]    flags to give to fd
+ *
+ * On success, returns an associated 'fd'. Else, returns error.
+ */
+int dma_buf_fd(struct dma_buf *dmabuf, int flags)
+{
+	int fd;
+
+	if (!dmabuf || !dmabuf->file)
+		return -EINVAL;
+
+	fd = get_unused_fd_flags(flags);
+	if (fd < 0)
+		return fd;
+
+	fd_install(fd, dmabuf->file);
+
+	return fd;
+}
+EXPORT_SYMBOL_GPL(dma_buf_fd);
+
+/**
+ * dma_buf_get - returns the dma_buf structure related to an fd
+ * @fd:	[in]	fd associated with the dma_buf to be returned
+ *
+ * On success, returns the dma_buf structure associated with an fd; uses
+ * file's refcounting done by fget to increase refcount. returns ERR_PTR
+ * otherwise.
+ */
+struct dma_buf *dma_buf_get(int fd)
+{
+	struct file *file;
+
+	file = fget(fd);
+
+	if (!file)
+		return ERR_PTR(-EBADF);
+
+	if (!is_dma_buf_file(file)) {
+		fput(file);
+		return ERR_PTR(-EINVAL);
+	}
+
+	return file->private_data;
+}
+EXPORT_SYMBOL_GPL(dma_buf_get);
+
+/**
+ * dma_buf_put - decreases refcount of the buffer
+ * @dmabuf:	[in]	buffer to reduce refcount of
+ *
+ * Uses file's refcounting done implicitly by fput().
+ *
+ * If, as a result of this call, the refcount becomes 0, the 'release' file
+ * operation related to this fd is called. It calls &dma_buf_ops.release vfunc
+ * in turn, and frees the memory allocated for dmabuf when exported.
+ */
+void dma_buf_put(struct dma_buf *dmabuf)
+{
+	if (WARN_ON(!dmabuf || !dmabuf->file))
+		return;
+
+	fput(dmabuf->file);
+}
+EXPORT_SYMBOL_GPL(dma_buf_put);
+
+/**
+ * dma_buf_dynamic_attach - Add the device to dma_buf's attachments list; optionally,
+ * calls attach() of dma_buf_ops to allow device-specific attach functionality
+ * @dmabuf:		[in]	buffer to attach device to.
+ * @dev:		[in]	device to be attached.
+ * @importer_ops:	[in]	importer operations for the attachment
+ * @importer_priv:	[in]	importer private pointer for the attachment
+ *
+ * Returns struct dma_buf_attachment pointer for this attachment. Attachments
+ * must be cleaned up by calling dma_buf_detach().
+ *
+ * Returns:
+ *
+ * A pointer to newly created &dma_buf_attachment on success, or a negative
+ * error code wrapped into a pointer on failure.
+ *
+ * Note that this can fail if the backing storage of @dmabuf is in a place not
+ * accessible to @dev, and cannot be moved to a more suitable place. This is
+ * indicated with the error code -EBUSY.
+ */
+struct dma_buf_attachment *
+dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
+		       const struct dma_buf_attach_ops *importer_ops,
+		       void *importer_priv)
+{
+	struct dma_buf_attachment *attach;
+	int ret;
+
+	if (WARN_ON(!dmabuf || !dev))
+		return ERR_PTR(-EINVAL);
+
+	if (WARN_ON(importer_ops && !importer_ops->move_notify))
+		return ERR_PTR(-EINVAL);
+
+	attach = kzalloc(sizeof(*attach), GFP_KERNEL);
+	if (!attach)
+		return ERR_PTR(-ENOMEM);
+
+	attach->dev = dev;
+	attach->dmabuf = dmabuf;
+	if (importer_ops)
+		attach->peer2peer = importer_ops->allow_peer2peer;
+	attach->importer_ops = importer_ops;
+	attach->importer_priv = importer_priv;
+
+	if (dmabuf->ops->attach) {
+		ret = dmabuf->ops->attach(dmabuf, attach);
+		if (ret)
+			goto err_attach;
+	}
+	dma_resv_lock(dmabuf->resv, NULL);
+	list_add(&attach->node, &dmabuf->attachments);
+	dma_resv_unlock(dmabuf->resv);
+
+	/* When either the importer or the exporter can't handle dynamic
+	 * mappings we cache the mapping here to avoid issues with the
+	 * reservation object lock.
+	 */
+	if (dma_buf_attachment_is_dynamic(attach) !=
+	    dma_buf_is_dynamic(dmabuf)) {
+		struct sg_table *sgt;
+
+		if (dma_buf_is_dynamic(attach->dmabuf)) {
+			dma_resv_lock(attach->dmabuf->resv, NULL);
+			ret = dma_buf_pin(attach);
+			if (ret)
+				goto err_unlock;
+		}
+
+		sgt = dmabuf->ops->map_dma_buf(attach, DMA_BIDIRECTIONAL);
+		if (!sgt)
+			sgt = ERR_PTR(-ENOMEM);
+		if (IS_ERR(sgt)) {
+			ret = PTR_ERR(sgt);
+			goto err_unpin;
+		}
+		if (dma_buf_is_dynamic(attach->dmabuf))
+			dma_resv_unlock(attach->dmabuf->resv);
+		attach->sgt = sgt;
+		attach->dir = DMA_BIDIRECTIONAL;
+	}
+
+	return attach;
+
+err_attach:
+	kfree(attach);
+	return ERR_PTR(ret);
+
+err_unpin:
+	if (dma_buf_is_dynamic(attach->dmabuf))
+		dma_buf_unpin(attach);
+
+err_unlock:
+	if (dma_buf_is_dynamic(attach->dmabuf))
+		dma_resv_unlock(attach->dmabuf->resv);
+
+	dma_buf_detach(dmabuf, attach);
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(dma_buf_dynamic_attach);
+
+/**
+ * dma_buf_attach - Wrapper for dma_buf_dynamic_attach
+ * @dmabuf:	[in]	buffer to attach device to.
+ * @dev:	[in]	device to be attached.
+ *
+ * Wrapper to call dma_buf_dynamic_attach() for drivers which still use a static
+ * mapping.
+ */
+struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
+					  struct device *dev)
+{
+	return dma_buf_dynamic_attach(dmabuf, dev, NULL, NULL);
+}
+EXPORT_SYMBOL_GPL(dma_buf_attach);
+
+/**
+ * dma_buf_detach - Remove the given attachment from dmabuf's attachments list;
+ * optionally calls detach() of dma_buf_ops for device-specific detach
+ * @dmabuf:	[in]	buffer to detach from.
+ * @attach:	[in]	attachment to be detached; is free'd after this call.
+ *
+ * Clean up a device attachment obtained by calling dma_buf_attach().
+ */
+void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
+{
+	if (WARN_ON(!dmabuf || !attach))
+		return;
+
+	if (attach->sgt) {
+		if (dma_buf_is_dynamic(attach->dmabuf))
+			dma_resv_lock(attach->dmabuf->resv, NULL);
+
+		dmabuf->ops->unmap_dma_buf(attach, attach->sgt, attach->dir);
+
+		if (dma_buf_is_dynamic(attach->dmabuf)) {
+			dma_buf_unpin(attach);
+			dma_resv_unlock(attach->dmabuf->resv);
+		}
+	}
+
+	dma_resv_lock(dmabuf->resv, NULL);
+	list_del(&attach->node);
+	dma_resv_unlock(dmabuf->resv);
+	if (dmabuf->ops->detach)
+		dmabuf->ops->detach(dmabuf, attach);
+
+	kfree(attach);
+}
+EXPORT_SYMBOL_GPL(dma_buf_detach);
+
+/**
+ * dma_buf_pin - Lock down the DMA-buf
+ *
+ * @attach:	[in]	attachment which should be pinned
+ *
+ * Returns:
+ * 0 on success, negative error code on failure.
+ */
+int dma_buf_pin(struct dma_buf_attachment *attach)
+{
+	struct dma_buf *dmabuf = attach->dmabuf;
+	int ret = 0;
+
+	dma_resv_assert_held(dmabuf->resv);
+
+	if (dmabuf->ops->pin)
+		ret = dmabuf->ops->pin(attach);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(dma_buf_pin);
+
+/**
+ * dma_buf_unpin - Remove lock from DMA-buf
+ *
+ * @attach:	[in]	attachment which should be unpinned
+ */
+void dma_buf_unpin(struct dma_buf_attachment *attach)
+{
+	struct dma_buf *dmabuf = attach->dmabuf;
+
+	dma_resv_assert_held(dmabuf->resv);
+
+	if (dmabuf->ops->unpin)
+		dmabuf->ops->unpin(attach);
+}
+EXPORT_SYMBOL_GPL(dma_buf_unpin);
+
+/**
+ * dma_buf_map_attachment - Returns the scatterlist table of the attachment;
+ * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the
+ * dma_buf_ops.
+ * @attach:	[in]	attachment whose scatterlist is to be returned
+ * @direction:	[in]	direction of DMA transfer
+ *
+ * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
+ * on error. May return -EINTR if it is interrupted by a signal.
+ *
+ * A mapping must be unmapped by using dma_buf_unmap_attachment(). Note that
+ * the underlying backing storage is pinned for as long as a mapping exists,
+ * therefore users/importers should not hold onto a mapping for undue amounts of
+ * time.
+ */
+struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
+					enum dma_data_direction direction)
+{
+	struct sg_table *sg_table;
+	int r;
+
+	might_sleep();
+
+	if (WARN_ON(!attach || !attach->dmabuf))
+		return ERR_PTR(-EINVAL);
+
+	if (dma_buf_attachment_is_dynamic(attach))
+		dma_resv_assert_held(attach->dmabuf->resv);
+
+	if (attach->sgt) {
+		/*
+		 * Two mappings with different directions for the same
+		 * attachment are not allowed.
+		 */
+		if (attach->dir != direction &&
+		    attach->dir != DMA_BIDIRECTIONAL)
+			return ERR_PTR(-EBUSY);
+
+		return attach->sgt;
+	}
+
+	if (dma_buf_is_dynamic(attach->dmabuf)) {
+		dma_resv_assert_held(attach->dmabuf->resv);
+		if (!IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY)) {
+			r = dma_buf_pin(attach);
+			if (r)
+				return ERR_PTR(r);
+		}
+	}
+
+	sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
+	if (!sg_table)
+		sg_table = ERR_PTR(-ENOMEM);
+
+	if (IS_ERR(sg_table) && dma_buf_is_dynamic(attach->dmabuf) &&
+	     !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY))
+		dma_buf_unpin(attach);
+
+	if (!IS_ERR(sg_table) && attach->dmabuf->ops->cache_sgt_mapping) {
+		attach->sgt = sg_table;
+		attach->dir = direction;
+	}
+
+	return sg_table;
+}
+EXPORT_SYMBOL_GPL(dma_buf_map_attachment);
+
+/**
+ * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might
+ * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of
+ * dma_buf_ops.
+ * @attach:	[in]	attachment to unmap buffer from
+ * @sg_table:	[in]	scatterlist info of the buffer to unmap
+ * @direction:  [in]    direction of DMA transfer
+ *
+ * This unmaps a DMA mapping for @attached obtained by dma_buf_map_attachment().
+ */
+void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
+				struct sg_table *sg_table,
+				enum dma_data_direction direction)
+{
+	might_sleep();
+
+	if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
+		return;
+
+	if (dma_buf_attachment_is_dynamic(attach))
+		dma_resv_assert_held(attach->dmabuf->resv);
+
+	if (attach->sgt == sg_table)
+		return;
+
+	if (dma_buf_is_dynamic(attach->dmabuf))
+		dma_resv_assert_held(attach->dmabuf->resv);
+
+	attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, direction);
+
+	if (dma_buf_is_dynamic(attach->dmabuf) &&
+	    !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY))
+		dma_buf_unpin(attach);
+}
+EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment);
+
+/**
+ * dma_buf_move_notify - notify attachments that DMA-buf is moving
+ *
+ * @dmabuf:	[in]	buffer which is moving
+ *
+ * Informs all attachmenst that they need to destroy and recreated all their
+ * mappings.
+ */
+void dma_buf_move_notify(struct dma_buf *dmabuf)
+{
+	struct dma_buf_attachment *attach;
+
+	dma_resv_assert_held(dmabuf->resv);
+
+	list_for_each_entry(attach, &dmabuf->attachments, node)
+		if (attach->importer_ops)
+			attach->importer_ops->move_notify(attach);
+}
+EXPORT_SYMBOL_GPL(dma_buf_move_notify);
+
+/**
+ * DOC: cpu access
+ *
+ * There are mutliple reasons for supporting CPU access to a dma buffer object:
+ *
+ * - Fallback operations in the kernel, for example when a device is connected
+ *   over USB and the kernel needs to shuffle the data around first before
+ *   sending it away. Cache coherency is handled by braketing any transactions
+ *   with calls to dma_buf_begin_cpu_access() and dma_buf_end_cpu_access()
+ *   access.
+ *
+ *   Since for most kernel internal dma-buf accesses need the entire buffer, a
+ *   vmap interface is introduced. Note that on very old 32-bit architectures
+ *   vmalloc space might be limited and result in vmap calls failing.
+ *
+ *   Interfaces::
+ *      void \*dma_buf_vmap(struct dma_buf \*dmabuf)
+ *      void dma_buf_vunmap(struct dma_buf \*dmabuf, void \*vaddr)
+ *
+ *   The vmap call can fail if there is no vmap support in the exporter, or if
+ *   it runs out of vmalloc space. Fallback to kmap should be implemented. Note
+ *   that the dma-buf layer keeps a reference count for all vmap access and
+ *   calls down into the exporter's vmap function only when no vmapping exists,
+ *   and only unmaps it once. Protection against concurrent vmap/vunmap calls is
+ *   provided by taking the dma_buf->lock mutex.
+ *
+ * - For full compatibility on the importer side with existing userspace
+ *   interfaces, which might already support mmap'ing buffers. This is needed in
+ *   many processing pipelines (e.g. feeding a software rendered image into a
+ *   hardware pipeline, thumbnail creation, snapshots, ...). Also, Android's ION
+ *   framework already supported this and for DMA buffer file descriptors to
+ *   replace ION buffers mmap support was needed.
+ *
+ *   There is no special interfaces, userspace simply calls mmap on the dma-buf
+ *   fd. But like for CPU access there's a need to braket the actual access,
+ *   which is handled by the ioctl (DMA_BUF_IOCTL_SYNC). Note that
+ *   DMA_BUF_IOCTL_SYNC can fail with -EAGAIN or -EINTR, in which case it must
+ *   be restarted.
+ *
+ *   Some systems might need some sort of cache coherency management e.g. when
+ *   CPU and GPU domains are being accessed through dma-buf at the same time.
+ *   To circumvent this problem there are begin/end coherency markers, that
+ *   forward directly to existing dma-buf device drivers vfunc hooks. Userspace
+ *   can make use of those markers through the DMA_BUF_IOCTL_SYNC ioctl. The
+ *   sequence would be used like following:
+ *
+ *     - mmap dma-buf fd
+ *     - for each drawing/upload cycle in CPU 1. SYNC_START ioctl, 2. read/write
+ *       to mmap area 3. SYNC_END ioctl. This can be repeated as often as you
+ *       want (with the new data being consumed by say the GPU or the scanout
+ *       device)
+ *     - munmap once you don't need the buffer any more
+ *
+ *    For correctness and optimal performance, it is always required to use
+ *    SYNC_START and SYNC_END before and after, respectively, when accessing the
+ *    mapped address. Userspace cannot rely on coherent access, even when there
+ *    are systems where it just works without calling these ioctls.
+ *
+ * - And as a CPU fallback in userspace processing pipelines.
+ *
+ *   Similar to the motivation for kernel cpu access it is again important that
+ *   the userspace code of a given importing subsystem can use the same
+ *   interfaces with a imported dma-buf buffer object as with a native buffer
+ *   object. This is especially important for drm where the userspace part of
+ *   contemporary OpenGL, X, and other drivers is huge, and reworking them to
+ *   use a different way to mmap a buffer rather invasive.
+ *
+ *   The assumption in the current dma-buf interfaces is that redirecting the
+ *   initial mmap is all that's needed. A survey of some of the existing
+ *   subsystems shows that no driver seems to do any nefarious thing like
+ *   syncing up with outstanding asynchronous processing on the device or
+ *   allocating special resources at fault time. So hopefully this is good
+ *   enough, since adding interfaces to intercept pagefaults and allow pte
+ *   shootdowns would increase the complexity quite a bit.
+ *
+ *   Interface::
+ *      int dma_buf_mmap(struct dma_buf \*, struct vm_area_struct \*,
+ *		       unsigned long);
+ *
+ *   If the importing subsystem simply provides a special-purpose mmap call to
+ *   set up a mapping in userspace, calling do_mmap with dma_buf->file will
+ *   equally achieve that for a dma-buf object.
+ */
+
+static int __dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
+				      enum dma_data_direction direction)
+{
+	bool write = (direction == DMA_BIDIRECTIONAL ||
+		      direction == DMA_TO_DEVICE);
+	struct dma_resv *resv = dmabuf->resv;
+	long ret;
+
+	/* Wait on any implicit rendering fences */
+	ret = dma_resv_wait_timeout_rcu(resv, write, true,
+						  MAX_SCHEDULE_TIMEOUT);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
+/**
+ * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the
+ * cpu in the kernel context. Calls begin_cpu_access to allow exporter-specific
+ * preparations. Coherency is only guaranteed in the specified range for the
+ * specified access direction.
+ * @dmabuf:	[in]	buffer to prepare cpu access for.
+ * @direction:	[in]	length of range for cpu access.
+ *
+ * After the cpu access is complete the caller should call
+ * dma_buf_end_cpu_access(). Only when cpu access is braketed by both calls is
+ * it guaranteed to be coherent with other DMA access.
+ *
+ * Can return negative error values, returns 0 on success.
+ */
+int dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
+			     enum dma_data_direction direction)
+{
+	int ret = 0;
+
+	if (WARN_ON(!dmabuf))
+		return -EINVAL;
+
+	if (dmabuf->ops->begin_cpu_access)
+		ret = dmabuf->ops->begin_cpu_access(dmabuf, direction);
+
+	/* Ensure that all fences are waited upon - but we first allow
+	 * the native handler the chance to do so more efficiently if it
+	 * chooses. A double invocation here will be reasonably cheap no-op.
+	 */
+	if (ret == 0)
+		ret = __dma_buf_begin_cpu_access(dmabuf, direction);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(dma_buf_begin_cpu_access);
+
+/**
+ * dma_buf_end_cpu_access - Must be called after accessing a dma_buf from the
+ * cpu in the kernel context. Calls end_cpu_access to allow exporter-specific
+ * actions. Coherency is only guaranteed in the specified range for the
+ * specified access direction.
+ * @dmabuf:	[in]	buffer to complete cpu access for.
+ * @direction:	[in]	length of range for cpu access.
+ *
+ * This terminates CPU access started with dma_buf_begin_cpu_access().
+ *
+ * Can return negative error values, returns 0 on success.
+ */
+int dma_buf_end_cpu_access(struct dma_buf *dmabuf,
+			   enum dma_data_direction direction)
+{
+	int ret = 0;
+
+	WARN_ON(!dmabuf);
+
+	if (dmabuf->ops->end_cpu_access)
+		ret = dmabuf->ops->end_cpu_access(dmabuf, direction);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(dma_buf_end_cpu_access);
+
+
+/**
+ * dma_buf_mmap - Setup up a userspace mmap with the given vma
+ * @dmabuf:	[in]	buffer that should back the vma
+ * @vma:	[in]	vma for the mmap
+ * @pgoff:	[in]	offset in pages where this mmap should start within the
+ *			dma-buf buffer.
+ *
+ * This function adjusts the passed in vma so that it points at the file of the
+ * dma_buf operation. It also adjusts the starting pgoff and does bounds
+ * checking on the size of the vma. Then it calls the exporters mmap function to
+ * set up the mapping.
+ *
+ * Can return negative error values, returns 0 on success.
+ */
+int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
+		 unsigned long pgoff)
+{
+	struct file *oldfile;
+	int ret;
+
+	if (WARN_ON(!dmabuf || !vma))
+		return -EINVAL;
+
+	/* check if buffer supports mmap */
+	if (!dmabuf->ops->mmap)
+		return -EINVAL;
+
+	/* check for offset overflow */
+	if (pgoff + vma_pages(vma) < pgoff)
+		return -EOVERFLOW;
+
+	/* check for overflowing the buffer's size */
+	if (pgoff + vma_pages(vma) >
+	    dmabuf->size >> PAGE_SHIFT)
+		return -EINVAL;
+
+	/* readjust the vma */
+	get_file(dmabuf->file);
+	oldfile = vma->vm_file;
+	vma->vm_file = dmabuf->file;
+	vma->vm_pgoff = pgoff;
+
+	ret = dmabuf->ops->mmap(dmabuf, vma);
+	if (ret) {
+		/* restore old parameters on failure */
+		vma->vm_file = oldfile;
+		fput(dmabuf->file);
+	} else {
+		if (oldfile)
+			fput(oldfile);
+	}
+	return ret;
+
+}
+EXPORT_SYMBOL_GPL(dma_buf_mmap);
+
+/**
+ * dma_buf_vmap - Create virtual mapping for the buffer object into kernel
+ * address space. Same restrictions as for vmap and friends apply.
+ * @dmabuf:	[in]	buffer to vmap
+ *
+ * This call may fail due to lack of virtual mapping address space.
+ * These calls are optional in drivers. The intended use for them
+ * is for mapping objects linear in kernel space for high use objects.
+ * Please attempt to use kmap/kunmap before thinking about these interfaces.
+ *
+ * Returns NULL on error.
+ */
+void *dma_buf_vmap(struct dma_buf *dmabuf)
+{
+	void *ptr;
+
+	if (WARN_ON(!dmabuf))
+		return NULL;
+
+	if (!dmabuf->ops->vmap)
+		return NULL;
+
+	mutex_lock(&dmabuf->lock);
+	if (dmabuf->vmapping_counter) {
+		dmabuf->vmapping_counter++;
+		BUG_ON(!dmabuf->vmap_ptr);
+		ptr = dmabuf->vmap_ptr;
+		goto out_unlock;
+	}
+
+	BUG_ON(dmabuf->vmap_ptr);
+
+	ptr = dmabuf->ops->vmap(dmabuf);
+	if (WARN_ON_ONCE(IS_ERR(ptr)))
+		ptr = NULL;
+	if (!ptr)
+		goto out_unlock;
+
+	dmabuf->vmap_ptr = ptr;
+	dmabuf->vmapping_counter = 1;
+
+out_unlock:
+	mutex_unlock(&dmabuf->lock);
+	return ptr;
+}
+EXPORT_SYMBOL_GPL(dma_buf_vmap);
+
+/**
+ * dma_buf_vunmap - Unmap a vmap obtained by dma_buf_vmap.
+ * @dmabuf:	[in]	buffer to vunmap
+ * @vaddr:	[in]	vmap to vunmap
+ */
+void dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr)
+{
+	if (WARN_ON(!dmabuf))
+		return;
+
+	BUG_ON(!dmabuf->vmap_ptr);
+	BUG_ON(dmabuf->vmapping_counter == 0);
+	BUG_ON(dmabuf->vmap_ptr != vaddr);
+
+	mutex_lock(&dmabuf->lock);
+	if (--dmabuf->vmapping_counter == 0) {
+		if (dmabuf->ops->vunmap)
+			dmabuf->ops->vunmap(dmabuf, vaddr);
+		dmabuf->vmap_ptr = NULL;
+	}
+	mutex_unlock(&dmabuf->lock);
+}
+EXPORT_SYMBOL_GPL(dma_buf_vunmap);
+
+#ifdef CONFIG_DEBUG_FS
+static int dma_buf_debug_show(struct seq_file *s, void *unused)
+{
+	int ret;
+	struct dma_buf *buf_obj;
+	struct dma_buf_attachment *attach_obj;
+	struct dma_resv *robj;
+	struct dma_resv_list *fobj;
+	struct dma_fence *fence;
+	unsigned seq;
+	int count = 0, attach_count, shared_count, i;
+	size_t size = 0;
+
+	ret = mutex_lock_interruptible(&db_list.lock);
+
+	if (ret)
+		return ret;
+
+	seq_puts(s, "\nDma-buf Objects:\n");
+	seq_printf(s, "%-8s\t%-8s\t%-8s\t%-8s\texp_name\t%-8s\n",
+		   "size", "flags", "mode", "count", "ino");
+
+	list_for_each_entry(buf_obj, &db_list.head, list_node) {
+
+		ret = dma_resv_lock_interruptible(buf_obj->resv, NULL);
+		if (ret)
+			goto error_unlock;
+
+		seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\t%08lu\t%s\n",
+				buf_obj->size,
+				buf_obj->file->f_flags, buf_obj->file->f_mode,
+				file_count(buf_obj->file),
+				buf_obj->exp_name,
+				file_inode(buf_obj->file)->i_ino,
+				buf_obj->name ?: "");
+
+		robj = buf_obj->resv;
+		while (true) {
+			seq = read_seqcount_begin(&robj->seq);
+			rcu_read_lock();
+			fobj = rcu_dereference(robj->fence);
+			shared_count = fobj ? fobj->shared_count : 0;
+			fence = rcu_dereference(robj->fence_excl);
+			if (!read_seqcount_retry(&robj->seq, seq))
+				break;
+			rcu_read_unlock();
+		}
+
+		if (fence)
+			seq_printf(s, "\tExclusive fence: %s %s %ssignalled\n",
+				   fence->ops->get_driver_name(fence),
+				   fence->ops->get_timeline_name(fence),
+				   dma_fence_is_signaled(fence) ? "" : "un");
+		for (i = 0; i < shared_count; i++) {
+			fence = rcu_dereference(fobj->shared[i]);
+			if (!dma_fence_get_rcu(fence))
+				continue;
+			seq_printf(s, "\tShared fence: %s %s %ssignalled\n",
+				   fence->ops->get_driver_name(fence),
+				   fence->ops->get_timeline_name(fence),
+				   dma_fence_is_signaled(fence) ? "" : "un");
+			dma_fence_put(fence);
+		}
+		rcu_read_unlock();
+
+		seq_puts(s, "\tAttached Devices:\n");
+		attach_count = 0;
+
+		list_for_each_entry(attach_obj, &buf_obj->attachments, node) {
+			seq_printf(s, "\t%s\n", dev_name(attach_obj->dev));
+			attach_count++;
+		}
+		dma_resv_unlock(buf_obj->resv);
+
+		seq_printf(s, "Total %d devices attached\n\n",
+				attach_count);
+
+		count++;
+		size += buf_obj->size;
+	}
+
+	seq_printf(s, "\nTotal %d objects, %zu bytes\n", count, size);
+
+	mutex_unlock(&db_list.lock);
+	return 0;
+
+error_unlock:
+	mutex_unlock(&db_list.lock);
+	return ret;
+}
+
+DEFINE_SHOW_ATTRIBUTE(dma_buf_debug);
+
+static struct dentry *dma_buf_debugfs_dir;
+
+static int dma_buf_init_debugfs(void)
+{
+	struct dentry *d;
+	int err = 0;
+
+	d = debugfs_create_dir("dma_buf", NULL);
+	if (IS_ERR(d))
+		return PTR_ERR(d);
+
+	dma_buf_debugfs_dir = d;
+
+	d = debugfs_create_file("bufinfo", S_IRUGO, dma_buf_debugfs_dir,
+				NULL, &dma_buf_debug_fops);
+	if (IS_ERR(d)) {
+		pr_debug("dma_buf: debugfs: failed to create node bufinfo\n");
+		debugfs_remove_recursive(dma_buf_debugfs_dir);
+		dma_buf_debugfs_dir = NULL;
+		err = PTR_ERR(d);
+	}
+
+	return err;
+}
+
+static void dma_buf_uninit_debugfs(void)
+{
+	debugfs_remove_recursive(dma_buf_debugfs_dir);
+}
+#else
+static inline int dma_buf_init_debugfs(void)
+{
+	return 0;
+}
+static inline void dma_buf_uninit_debugfs(void)
+{
+}
+#endif
+
+static int __init dma_buf_init(void)
+{
+	dma_buf_mnt = kern_mount(&dma_buf_fs_type);
+	if (IS_ERR(dma_buf_mnt))
+		return PTR_ERR(dma_buf_mnt);
+
+	mutex_init(&db_list.lock);
+	INIT_LIST_HEAD(&db_list.head);
+	dma_buf_init_debugfs();
+	return 0;
+}
+subsys_initcall(dma_buf_init);
+
+static void __exit dma_buf_deinit(void)
+{
+	dma_buf_uninit_debugfs();
+	kern_unmount(dma_buf_mnt);
+}
+__exitcall(dma_buf_deinit);