path: root/drivers/dma-buf/dma-buf.c

/*
 * 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.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#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/reservation.h>
#include <linux/mm.h>

#include <uapi/linux/dma-buf.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 int dma_buf_release(struct inode *inode, struct file *file)
{
	struct dma_buf *dmabuf;

	if (!is_dma_buf_file(file))
		return -EINVAL;

	dmabuf = file->private_data;

	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);

	mutex_lock(&db_list.lock);
	list_del(&dmabuf->list_node);
	mutex_unlock(&db_list.lock);

	if (dmabuf->resv == (struct reservation_object *)&dmabuf[1])
		reservation_object_fini(dmabuf->resv);

	module_put(dmabuf->owner);
	kfree(dmabuf);
	return 0;
}

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 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: fence polling
 *
 * To support cross-device and cross-driver synchronization of buffer access
 * implicit fences (represented internally in the kernel with &struct fence) can
 * be attached to a &dma_buf. The glue for that and a few related things are
 * provided in the &reservation_object 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 reservation_object *resv;
	struct reservation_object_list *fobj;
	struct dma_fence *fence_excl;
	__poll_t events;
	unsigned shared_count, seq;

	dmabuf = file->private_data;
	if (!dmabuf || !dmabuf->resv)