2017-07-06 Hans Verkuil <hverkuil@xxxxxxxxx>:
> On 06/16/17 09:39, Gustavo Padovan wrote:
> > From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxx>
> >
> > In order to support explicit synchronization we need to divide
> > vb2_core_qbuf() in two parts, one to be executed before the fence
> > signals and another one to do the actual queueing of the buffer.
> >
> > Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxx>
> > ---
> > drivers/media/v4l2-core/videobuf2-core.c | 51 ++++++++++++++++++--------------
> > 1 file changed, 29 insertions(+), 22 deletions(-)
> >
> > diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
> > index 3107e21..ea83126 100644
> > --- a/drivers/media/v4l2-core/videobuf2-core.c
> > +++ b/drivers/media/v4l2-core/videobuf2-core.c
> > @@ -1367,6 +1367,34 @@ static int vb2_start_streaming(struct vb2_queue *q)
> > return ret;
> > }
> >
> > +static int __vb2_core_qbuf(struct vb2_buffer *vb, struct vb2_queue *q)
> > +{
> > + int ret;
> > +
> > + /*
> > + * If already streaming, give the buffer to driver for processing.
> > + * If not, the buffer will be given to driver on next streamon.
> > + */
> > + if (q->start_streaming_called)
> > + __enqueue_in_driver(vb);
> > +
> > + /*
> > + * If streamon has been called, and we haven't yet called
> > + * start_streaming() since not enough buffers were queued, and
> > + * we now have reached the minimum number of queued buffers,
> > + * then we can finally call start_streaming().
> > + */
> > + if (q->streaming && !q->start_streaming_called &&
> > + q->queued_count >= q->min_buffers_needed) {
> > + ret = vb2_start_streaming(q);
> > + if (ret)
> > + return ret;
> > + }
> > +
> > + dprintk(1, "qbuf of buffer %d succeeded\n", vb->index);
> > + return 0;
> > +}
> > +
> > int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb)
> > {
> > struct vb2_buffer *vb;
> > @@ -1404,32 +1432,11 @@ 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.
> > - */
> > - if (q->start_streaming_called)
> > - __enqueue_in_driver(vb);
> > -
> > /* Fill buffer information for the userspace */
> > if (pb)
> > call_void_bufop(q, fill_user_buffer, vb, pb);
>
> This should be called *after* the __vb2_core_qbuf call. That call changes
> vb->state which is used by buffer to fill in v4l2_buffer. So the order
> should be swapped here to ensure we return the latest state of the buffer.
I didn't pay attention to that detail. The reason why I put it here is
that later when in-fences are introduced we will only call
__vb2_core_qbuf() after the fence signals and that may happen after we
returned to userspace. I'll look into possible ways to solve this
problem.
Gustavo
