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

Hans Verkuil
2018-05-09T10:53:02Z

On 05/09/18 12:36, Brian Starkey wrote:
> 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).

Good point, I think you are right about that.

This same sequence should be present in the fence_cb path. Question: can
fence_cb be called from interrupt context? If so, then that needs to start a
workqueue or something since vb2_start_streaming cannot run in interrupt
context. And in addition that workqueue needs to take and release q->lock.
We should discuss locking on irc, there are some subtleties there.

This would be a good test to add to v4l2-compliance, BTW.

>
>> 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.

I'm not sure about this either. This also ties in with the Request API
series which has a similar issue. I think setting this to -1 when unused
is better.

Regards,

Hans

>
> 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
>>