Re: [PATCH 02/12] [media] vb2: split out queueing from vb_core_qbuf()

[Gustavo Padovan]

2017-07-06 Hans Verkuil :

> On 06/16/17 09:39, Gustavo Padovan wrote:
> > From: Gustavo Padovan 
> > 
> > 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 
> > ---
> >  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

Re: [PATCH 02/12] [media] vb2: split out queueing from vb_core_qbuf()

[Hans Verkuil]

On 06/16/17 09:39, Gustavo Padovan wrote:
> From: Gustavo Padovan 
> 
> 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 
> ---
>  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.

>  
> - /*
> -  * 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;
> + return __vb2_core_qbuf(vb, q);
>  }
>  EXPORT_SYMBOL_GPL(vb2_core_qbuf);
>  
> 

Regards,

Hans

Re: [PATCH 02/12] [media] vb2: split out queueing from vb_core_qbuf()

[Mauro Carvalho Chehab]

Em Fri, 16 Jun 2017 16:39:05 +0900
Gustavo Padovan  escreveu:

> From: Gustavo Padovan 
> 
> 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.

Looks good to me.


Acked-by: Mauro Carvalho Chehab 

> 
> Signed-off-by: Gustavo Padovan 
> ---
>  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);
>  
> - /*
> -  * 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;
> + return __vb2_core_qbuf(vb, q);
>  }
>  EXPORT_SYMBOL_GPL(vb2_core_qbuf);
>  


-- 
Thanks,
Mauro