Re: [PATCH v9 11/15] vb2: add in-fence support to QBUF

Brian Starkey
2018-05-09T10:36:46Z

Hi Ezequiel,

On Fri, May 04, 2018 at 05:06:08PM -0300, Ezequiel Garcia wrote:
>From: Gustavo Padovan <gustavo.padovan@collabora.com>
>
>Receive in-fence from userspace and add support for waiting on them
>before queueing the buffer to the driver. Buffers can't be queued to the
>driver before its fences signal. And a buffer can't be queued to the driver
>out of the order they were queued from userspace. That means that even if
>its fence signals it must wait for all other buffers, ahead of it in the queue,
>to signal first.
>
>If the fence for some buffer fails we do not queue it to the driver,
>instead we mark it as error and wait until the previous buffer is done
>to notify userspace of the error. We wait here to deliver the buffers back
>to userspace in order.
>
>v12: fixed dvb_vb2.c usage of vb2_core_qbuf.
>
>v11: - minor doc/comments fixes (Hans Verkuil)
> - reviewed the in-fence path at __fill_v4l2_buffer()
>
>v10: - rename fence to in_fence in many places
> - handle fences signalling with error better (Hans Verkuil)
>
>v9: - improve comments and docs (Hans Verkuil)
> - fix unlocking of vb->fence_cb_lock on vb2_core_qbuf (Hans Verkuil)
> - move in-fences code that was in the out-fences patch here (Alex)
>
>v8: - improve comments about fences with errors
>
>v7: - get rid of the fence array stuff for ordering and just use
> get_num_buffers_ready() (Hans)
> - fix issue of queuing the buffer twice (Hans)
> - avoid the dma_fence_wait() in core_qbuf() (Alex)
> - merge preparation commit in
>
>v6: - With fences always keep the order userspace queues the buffers.
> - Protect in_fence manipulation with a lock (Brian Starkey)
> - check if fences have the same context before adding a fence array
> - Fix last_fence ref unbalance in __set_in_fence() (Brian Starkey)
> - Clean up fence if __set_in_fence() fails (Brian Starkey)
> - treat -EINVAL from dma_fence_add_callback() (Brian Starkey)
>
>v5: - use fence_array to keep buffers ordered in vb2 core when
> needed (Brian Starkey)
> - keep backward compat on the reserved2 field (Brian Starkey)
> - protect fence callback removal with lock (Brian Starkey)
>
>v4: - Add a comment about dma_fence_add_callback() not returning a
> error (Hans)
> - Call dma_fence_put(vb->in_fence) if fence signaled (Hans)
> - select SYNC_FILE under config VIDEOBUF2_CORE (Hans)
> - Move dma_fence_is_signaled() check to __enqueue_in_driver() (Hans)
> - Remove list_for_each_entry() in __vb2_core_qbuf() (Hans)
> - Remove if (vb->state != VB2_BUF_STATE_QUEUED) from
> vb2_start_streaming() (Hans)
> - set IN_FENCE flags on __fill_v4l2_buffer (Hans)
> - Queue buffers to the driver as soon as they are ready (Hans)
> - call fill_user_buffer() after queuing the buffer (Hans)
> - add err: label to clean up fence
> - add dma_fence_wait() before calling vb2_start_streaming()
>
>v3: - document fence parameter
> - remove ternary if at vb2_qbuf() return (Mauro)
> - do not change if conditions behaviour (Mauro)
>
>v2: - fix vb2_queue_or_prepare_buf() ret check
> - remove check for VB2_MEMORY_DMABUF only (Javier)
> - check num of ready buffers to start streaming
> - when queueing, start from the first ready buffer
> - handle queue cancel
>
>Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com>
>Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
>---
> drivers/media/common/videobuf2/videobuf2-core.c | 197 ++++++++++++++++++++----
> drivers/media/common/videobuf2/videobuf2-v4l2.c | 34 +++-
> drivers/media/dvb-core/dvb_vb2.c | 2 +-
> drivers/media/v4l2-core/Kconfig | 33 ++++
> include/media/videobuf2-core.h | 14 +-
> 5 files changed, 249 insertions(+), 31 deletions(-)
>
>diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
>index 6b8e083893ad..996b99497a98 100644
>--- a/drivers/media/common/videobuf2/videobuf2-core.c
>+++ b/drivers/media/common/videobuf2/videobuf2-core.c
>@@ -352,6 +352,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
> vb->index = q->num_buffers + buffer;
> vb->type = q->type;
> vb->memory = memory;
>+ spin_lock_init(&vb->fence_cb_lock);
> for (plane = 0; plane < num_planes; ++plane) {
> vb->planes[plane].length = plane_sizes[plane];
> vb->planes[plane].min_length = plane_sizes[plane];
>@@ -905,20 +906,12 @@ void *vb2_plane_cookie(struct vb2_buffer *vb, unsigned int plane_no)
> }
> EXPORT_SYMBOL_GPL(vb2_plane_cookie);
>
>-void vb2_buffer_done(struct vb2_buffer *vb, enum vb2_buffer_state state)
>+static void vb2_process_buffer_done(struct vb2_buffer *vb, enum vb2_buffer_state state)
> {
> struct vb2_queue *q = vb->vb2_queue;
> unsigned long flags;
> unsigned int plane;
>
>- if (WARN_ON(vb->state != VB2_BUF_STATE_ACTIVE))
>- return;
>-
>- if (WARN_ON(state != VB2_BUF_STATE_DONE &&
>- state != VB2_BUF_STATE_ERROR &&
>- state != VB2_BUF_STATE_QUEUED &&
>- state != VB2_BUF_STATE_REQUEUEING))
>- state = VB2_BUF_STATE_ERROR;
>
> #ifdef CONFIG_VIDEO_ADV_DEBUG
> /*
>@@ -935,6 +928,9 @@ void vb2_buffer_done(struct vb2_buffer *vb, enum vb2_buffer_state state)
> call_void_memop(vb, finish, vb->planes[plane].mem_priv);
>
> spin_lock_irqsave(&q->done_lock, flags);
>+ if (vb->state == VB2_BUF_STATE_ACTIVE)
>+ atomic_dec(&q->owned_by_drv_count);
>+
> if (state == VB2_BUF_STATE_QUEUED ||
> state == VB2_BUF_STATE_REQUEUEING) {
> vb->state = VB2_BUF_STATE_QUEUED;
>@@ -943,7 +939,7 @@ void vb2_buffer_done(struct vb2_buffer *vb, enum vb2_buffer_state state)
> list_add_tail(&vb->done_entry, &q->done_list);
> vb->state = state;
> }
>- atomic_dec(&q->owned_by_drv_count);
>+
> spin_unlock_irqrestore(&q->done_lock, flags);
>
> trace_vb2_buf_done(q, vb);
>@@ -960,6 +956,36 @@ void vb2_buffer_done(struct vb2_buffer *vb, enum vb2_buffer_state state)
> wake_up(&q->done_wq);
> break;
> }
>+
>+}
>+
>+void vb2_buffer_done(struct vb2_buffer *vb, enum vb2_buffer_state state)
>+{
>+ if (WARN_ON(vb->state != VB2_BUF_STATE_ACTIVE))
>+ return;
>+
>+ if (WARN_ON(state != VB2_BUF_STATE_DONE &&
>+ state != VB2_BUF_STATE_ERROR &&
>+ state != VB2_BUF_STATE_QUEUED &&
>+ state != VB2_BUF_STATE_REQUEUEING))
>+ state = VB2_BUF_STATE_ERROR;
>+
>+ vb2_process_buffer_done(vb, state);
>+
>+ /*
>+ * Check if there is any buffer with error in the next position of the queue,
>+ * buffers whose in-fence signaled with error are not queued to the driver
>+ * and kept on the queue until the buffer before them is done, so to not
>+ * deliver buffers back to userspace in the wrong order. Here we process
>+ * any existing buffers with errors and wake up userspace.
>+ */
>+ for (;;) {
>+ vb = list_next_entry(vb, queued_entry);
>+ if (!vb || vb->state != VB2_BUF_STATE_ERROR)
>+ break;
>+
>+ vb2_process_buffer_done(vb, VB2_BUF_STATE_ERROR);
>+ }
> }
> EXPORT_SYMBOL_GPL(vb2_buffer_done);
>
>@@ -1244,6 +1270,9 @@ static void __enqueue_in_driver(struct vb2_buffer *vb)
> {
> struct vb2_queue *q = vb->vb2_queue;
>
>+ if (vb->in_fence && !dma_fence_is_signaled(vb->in_fence))
>+ return;

Seems like this is not needed now. Either __enqueue_in_driver() is
called when there's no in_fence; or it's called from the fence_cb in
which case we're guaranteed to already be signaled.

Might be worth a loud error if these conditions are ever true - but
the silent return is a leftover from old patches I think.

>+
> vb->state = VB2_BUF_STATE_ACTIVE;
> atomic_inc(&q->owned_by_drv_count);
>
>@@ -1295,6 +1324,24 @@ static int __buf_prepare(struct vb2_buffer *vb, const void *pb)
> return 0;
> }
>
>+static int __get_num_ready_buffers(struct vb2_queue *q)
>+{
>+ struct vb2_buffer *vb;
>+ int ready_count = 0;
>+ unsigned long flags;
>+
>+ /* count num of buffers ready in front of the queued_list */
>+ list_for_each_entry(vb, &q->queued_list, queued_entry) {
>+ spin_lock_irqsave(&vb->fence_cb_lock, flags);
>+ if (vb->in_fence && !dma_fence_is_signaled(vb->in_fence))
>+ break;
>+ ready_count++;
>+ spin_unlock_irqrestore(&vb->fence_cb_lock, flags);
>+ }
>+
>+ return ready_count;
>+}
>+
> int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb)
> {
> struct vb2_buffer *vb;
>@@ -1383,9 +1430,43 @@ static int vb2_start_streaming(struct vb2_queue *q)
> return ret;
> }
>
>-int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb)
>+static void vb2_qbuf_fence_cb(struct dma_fence *f, struct dma_fence_cb *cb)
>+{
>+ struct vb2_buffer *vb = container_of(cb, struct vb2_buffer, fence_cb);
>+ struct vb2_queue *q = vb->vb2_queue;
>+ unsigned long flags;
>+
>+ spin_lock_irqsave(&vb->fence_cb_lock, flags);
>+ /*
>+ * If the fence signals with an error we mark the buffer as such
>+ * and avoid using it by setting it to VB2_BUF_STATE_ERROR and
>+ * not queueing it to the driver. However we can't notify the error
>+ * to userspace right now because, at the time this callback run, QBUF
>+ * has returned already.
>+ * So we delay that to DQBUF time. See comments in vb2_buffer_done()
>+ * as well.
>+ */
>+ if (vb->in_fence->error)
>+ vb->state = VB2_BUF_STATE_ERROR;
>+
>+ dma_fence_put(vb->in_fence);
>+ vb->in_fence = NULL;
>+
>+ if (vb->state == VB2_BUF_STATE_ERROR) {
>+ spin_unlock_irqrestore(&vb->fence_cb_lock, flags);
>+ return;
>+ }
>+
>+ if (q->start_streaming_called)
>+ __enqueue_in_driver(vb);
>+ spin_unlock_irqrestore(&vb->fence_cb_lock, flags);
>+}
>+
>+int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb,
>+ struct dma_fence *in_fence)
> {
> struct vb2_buffer *vb;
>+ unsigned long flags;
> int ret;
>
> vb = q->bufs[index];
>@@ -1394,16 +1475,18 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb)
> case VB2_BUF_STATE_DEQUEUED:
> ret = __buf_prepare(vb, pb);
> if (ret)
>- return ret;
>+ goto err;
> break;
> case VB2_BUF_STATE_PREPARED:
> break;
> case VB2_BUF_STATE_PREPARING:
> dprintk(1, "buffer still being prepared\n");
>- return -EINVAL;
>+ ret = -EINVAL;
>+ goto err;
> default:
> dprintk(1, "invalid buffer state %d\n", vb->state);
>- return -EINVAL;
>+ ret = -EINVAL;
>+ goto err;
> }
>
> /*
>@@ -1414,6 +1497,7 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb)
> q->queued_count++;
> q->waiting_for_buffers = false;
> vb->state = VB2_BUF_STATE_QUEUED;
>+ vb->in_fence = in_fence;
>
> if (pb)
> call_void_bufop(q, copy_timestamp, vb, pb);
>@@ -1421,15 +1505,40 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb)
> trace_vb2_qbuf(q, vb);
>
> /*
>- * If already streaming, give the buffer to driver for processing.
>- * If not, the buffer will be given to driver on next streamon.
>+ * For explicit synchronization: If the fence didn't signal
>+ * yet we setup a callback to queue the buffer once the fence
>+ * signals and then return successfully. But if the fence
>+ * already signaled we lose the reference we held and queue the
>+ * buffer to the driver.
> */
>- if (q->start_streaming_called)
>- __enqueue_in_driver(vb);
>+ spin_lock_irqsave(&vb->fence_cb_lock, flags);
>+ if (vb->in_fence) {
>+ ret = dma_fence_add_callback(vb->in_fence, &vb->fence_cb,
>+ vb2_qbuf_fence_cb);
>+ /* is the fence signaled? */
>+ if (ret == -ENOENT) {
>+ dma_fence_put(vb->in_fence);
>+ vb->in_fence = NULL;
>+ } else if (ret) {
>+ goto unlock;
>+ }
>+ }
>
>- /* Fill buffer information for the userspace */
>- if (pb)
>- call_void_bufop(q, fill_user_buffer, vb, pb);
>+ /*
>+ * If already streaming and there is no fence to wait on
>+ * give the buffer to driver for processing.
>+ */
>+ if (q->start_streaming_called) {
>+ struct vb2_buffer *b;
>+
>+ list_for_each_entry(b, &q->queued_list, queued_entry) {
>+ if (b->state != VB2_BUF_STATE_QUEUED)
>+ continue;
>+ if (b->in_fence)
>+ break;
>+ __enqueue_in_driver(b);
>+ }
>+ }
>
> /*
> * If streamon has been called, and we haven't yet called
>@@ -1438,14 +1547,36 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb)
> * then we can finally call start_streaming().
> */
> if (q->streaming && !q->start_streaming_called &&
>- q->queued_count >= q->min_buffers_needed) {
>+ __get_num_ready_buffers(q) >= q->min_buffers_needed) {
> ret = vb2_start_streaming(q);

If (q->streaming && !q->start_streaming_called), and all buffers have
in_fences which aren't signalled yet, then who calls
vb2_start_streaming()?

It seems like the fence path will always jump over here, and I don't
see a call to vb2_start_streaming() in the fence_cb path. (Sorry if I
missed something).

> if (ret)
>- return ret;
>+ goto unlock;
> }
>
>+ spin_unlock_irqrestore(&vb->fence_cb_lock, flags);
>+
>+ /* Fill buffer information for the userspace */
>+ if (pb)
>+ call_void_bufop(q, fill_user_buffer, vb, pb);
>+
> dprintk(2, "qbuf of buffer %d succeeded\n", vb->index);
> return 0;
>+
>+unlock:
>+ spin_unlock_irqrestore(&vb->fence_cb_lock, flags);
>+
>+err:
>+ /* Fill buffer information for the userspace */
>+ if (pb)
>+ call_void_bufop(q, fill_user_buffer, vb, pb);
>+
>+ if (vb->in_fence) {
>+ dma_fence_put(vb->in_fence);
>+ vb->in_fence = NULL;
>+ }
>+
>+ return ret;
>+
> }
> EXPORT_SYMBOL_GPL(vb2_core_qbuf);
>
>@@ -1656,6 +1787,8 @@ EXPORT_SYMBOL_GPL(vb2_core_dqbuf);
> static void __vb2_queue_cancel(struct vb2_queue *q)
> {
> unsigned int i;
>+ struct vb2_buffer *vb;
>+ unsigned long flags;
>
> /*
> * Tell driver to stop all transactions and release all queued
>@@ -1686,6 +1819,16 @@ static void __vb2_queue_cancel(struct vb2_queue *q)
> q->queued_count = 0;
> q->error = 0;
>
>+ list_for_each_entry(vb, &q->queued_list, queued_entry) {
>+ spin_lock_irqsave(&vb->fence_cb_lock, flags);
>+ if (vb->in_fence) {
>+ dma_fence_remove_callback(vb->in_fence, &vb->fence_cb);
>+ dma_fence_put(vb->in_fence);
>+ vb->in_fence = NULL;
>+ }
>+ spin_unlock_irqrestore(&vb->fence_cb_lock, flags);
>+ }
>+
> /*
> * Remove all buffers from videobuf's list...
> */
>@@ -1756,7 +1899,7 @@ int vb2_core_streamon(struct vb2_queue *q, unsigned int type)
> * Tell driver to start streaming provided sufficient buffers
> * are available.
> */
>- if (q->queued_count >= q->min_buffers_needed) {
>+ if (__get_num_ready_buffers(q) >= q->min_buffers_needed) {
> ret = v4l_vb2q_enable_media_source(q);
> if (ret)
> return ret;
>@@ -2278,7 +2421,7 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
> * Queue all buffers.
> */
> for (i = 0; i < q->num_buffers; i++) {
>- ret = vb2_core_qbuf(q, i, NULL);
>+ ret = vb2_core_qbuf(q, i, NULL, NULL);
> if (ret)
> goto err_reqbufs;
> fileio->bufs[i].queued = 1;
>@@ -2457,7 +2600,7 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
>
> if (copy_timestamp)
> b->timestamp = ktime_get_ns();
>- ret = vb2_core_qbuf(q, index, NULL);
>+ ret = vb2_core_qbuf(q, index, NULL, NULL);
> dprintk(5, "vb2_dbuf result: %d\n", ret);
> if (ret)
> return ret;
>@@ -2560,7 +2703,7 @@ static int vb2_thread(void *data)
> if (copy_timestamp)
> vb->timestamp = ktime_get_ns();
> if (!threadio->stop)
>- ret = vb2_core_qbuf(q, vb->index, NULL);
>+ ret = vb2_core_qbuf(q, vb->index, NULL, NULL);
> call_void_qop(q, wait_prepare, q);
> if (ret || threadio->stop)
> break;
>diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>index b1c0fa2b0b88..74d7062e5285 100644
>--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
>+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>@@ -23,6 +23,7 @@
> #include <linux/sched.h>
> #include <linux/freezer.h>
> #include <linux/kthread.h>
>+#include <linux/sync_file.h>
>
> #include <media/v4l2-dev.h>
> #include <media/v4l2-fh.h>
>@@ -178,6 +179,17 @@ static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct v4l2_buffer *b,
> return -EINVAL;
> }
>
>+ if ((b->fence_fd != 0 && b->fence_fd != -1) &&
>+ !(b->flags & V4L2_BUF_FLAG_IN_FENCE)) {
>+ dprintk(1, "%s: fence_fd set without IN_FENCE flag\n", opname);
>+ return -EINVAL;
>+ }
>+
>+ if (b->fence_fd < 0 && (b->flags & V4L2_BUF_FLAG_IN_FENCE)) {
>+ dprintk(1, "%s: IN_FENCE flag set but no fence_fd\n", opname);
>+ return -EINVAL;
>+ }
>+
> return __verify_planes_array(q->bufs[b->index], b);
> }
>
>@@ -203,9 +215,14 @@ static void __fill_v4l2_buffer(struct vb2_buffer *vb, void *pb)
> b->timestamp = ns_to_timeval(vb->timestamp);
> b->timecode = vbuf->timecode;
> b->sequence = vbuf->sequence;
>- b->fence_fd = 0;
> b->reserved = 0;
>
>+ b->fence_fd = 0;

I didn't understand why we're returning 0 instead of -1. Actually the
doc in patch 10 seems to say it will be -1 or 0 depending on whether
we set one of the fence flags? I'm not sure:

For all other ioctls V4L2 sets this field to -1 if
``V4L2_BUF_FLAG_IN_FENCE`` and/or ``V4L2_BUF_FLAG_OUT_FENCE`` are set,
otherwise this field is set to 0 for backward compatibility.

Cheers,
-Brian

>+ if (vb->in_fence)
>+ b->flags |= V4L2_BUF_FLAG_IN_FENCE;
>+ else
>+ b->flags &= ~V4L2_BUF_FLAG_IN_FENCE;
>+
> if (q->is_multiplanar) {
> /*
> * Fill in plane-related data if userspace provided an array
>@@ -562,6 +579,7 @@ EXPORT_SYMBOL_GPL(vb2_create_bufs);
>
> int vb2_qbuf(struct vb2_queue *q, struct v4l2_buffer *b)
> {
>+ struct dma_fence *in_fence = NULL;
> int ret;
>
> if (vb2_fileio_is_active(q)) {
>@@ -570,7 +588,19 @@ int vb2_qbuf(struct vb2_queue *q, struct v4l2_buffer *b)
> }
>
> ret = vb2_queue_or_prepare_buf(q, b, "qbuf");
>- return ret ? ret : vb2_core_qbuf(q, b->index, b);
>+ if (ret)
>+ return ret;
>+
>+ if (b->flags & V4L2_BUF_FLAG_IN_FENCE) {
>+ in_fence = sync_file_get_fence(b->fence_fd);
>+ if (!in_fence) {
>+ dprintk(1, "failed to get in-fence from fd %d\n",
>+ b->fence_fd);
>+ return -EINVAL;
>+ }
>+ }
>+
>+ return vb2_core_qbuf(q, b->index, b, in_fence);
> }
> EXPORT_SYMBOL_GPL(vb2_qbuf);
>
>diff --git a/drivers/media/dvb-core/dvb_vb2.c b/drivers/media/dvb-core/dvb_vb2.c
>index b811adf88afa..7da53f10db1a 100644
>--- a/drivers/media/dvb-core/dvb_vb2.c
>+++ b/drivers/media/dvb-core/dvb_vb2.c
>@@ -385,7 +385,7 @@ int dvb_vb2_qbuf(struct dvb_vb2_ctx *ctx, struct dmx_buffer *b)
> {
> int ret;
>
>- ret = vb2_core_qbuf(&ctx->vb_q, b->index, b);
>+ ret = vb2_core_qbuf(&ctx->vb_q, b->index, b, NULL);
> if (ret) {
> dprintk(1, "[%s] index=%d errno=%d\n", ctx->name,
> b->index, ret);
>diff --git a/drivers/media/v4l2-core/Kconfig b/drivers/media/v4l2-core/Kconfig
>index 8e37e7c5e0f7..79dfb5dfd1fc 100644
>--- a/drivers/media/v4l2-core/Kconfig
>+++ b/drivers/media/v4l2-core/Kconfig
>@@ -80,3 +80,36 @@ config VIDEOBUF_DMA_CONTIG
> config VIDEOBUF_DVB
> tristate
> select VIDEOBUF_GEN
>+
>+# Used by drivers that need Videobuf2 modules
>+config VIDEOBUF2_CORE
>+ select DMA_SHARED_BUFFER
>+ select SYNC_FILE
>+ tristate
>+
>+config VIDEOBUF2_MEMOPS
>+ tristate
>+ select FRAME_VECTOR
>+
>+config VIDEOBUF2_DMA_CONTIG
>+ tristate
>+ depends on HAS_DMA
>+ select VIDEOBUF2_CORE
>+ select VIDEOBUF2_MEMOPS
>+ select DMA_SHARED_BUFFER
>+
>+config VIDEOBUF2_VMALLOC
>+ tristate
>+ select VIDEOBUF2_CORE
>+ select VIDEOBUF2_MEMOPS
>+ select DMA_SHARED_BUFFER
>+
>+config VIDEOBUF2_DMA_SG
>+ tristate
>+ depends on HAS_DMA
>+ select VIDEOBUF2_CORE
>+ select VIDEOBUF2_MEMOPS
>+
>+config VIDEOBUF2_DVB
>+ tristate
>+ select VIDEOBUF2_CORE
>diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
>index 364e4cb41b10..28ce8f66882e 100644
>--- a/include/media/videobuf2-core.h
>+++ b/include/media/videobuf2-core.h
>@@ -17,6 +17,7 @@
> #include <linux/poll.h>
> #include <linux/dma-buf.h>
> #include <linux/bitops.h>
>+#include <linux/dma-fence.h>
>
> #define VB2_MAX_FRAME (32)
> #define VB2_MAX_PLANES (8)
>@@ -255,12 +256,21 @@ struct vb2_buffer {
> * done_entry: entry on the list that stores all buffers ready
> * to be dequeued to userspace
> * vb2_plane: per-plane information; do not change
>+ * in_fence: fence received from vb2 client to wait on before
>+ * using the buffer (queueing to the driver)
>+ * fence_cb: fence callback information
>+ * fence_cb_lock: protect callback signal/remove
> */
> enum vb2_buffer_state state;
>
> struct vb2_plane planes[VB2_MAX_PLANES];
> struct list_head queued_entry;
> struct list_head done_entry;
>+
>+ struct dma_fence *in_fence;
>+ struct dma_fence_cb fence_cb;
>+ spinlock_t fence_cb_lock;
>+
> #ifdef CONFIG_VIDEO_ADV_DEBUG
> /*
> * Counters for how often these buffer-related ops are
>@@ -773,6 +783,7 @@ int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb);
> * @index: id number of the buffer
> * @pb: buffer structure passed from userspace to
> * v4l2_ioctl_ops->vidioc_qbuf handler in driver
>+ * @in_fence: in-fence to wait on before queueing the buffer
> *
> * Videobuf2 core helper to implement VIDIOC_QBUF() operation. It is called
> * internally by VB2 by an API-specific handler, like ``videobuf2-v4l2.h``.
>@@ -787,7 +798,8 @@ int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb);
> *
> * Return: returns zero on success; an error code otherwise.
> */
>-int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb);
>+int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb,
>+ struct dma_fence *in_fence);
>
> /**
> * vb2_core_dqbuf() - Dequeue a buffer to the userspace
>--
>2.16.3
>