Re: [PATCH for 5.4] media: hantro: Fix s_fmt for dynamic resolution changes

[Ezequiel Garcia <ezequiel@collabora.com>]

On Wed, 2019-09-04 at 12:13 +0200, Philipp Zabel wrote:
> Hi Ezequiel,
> 
> On Tue, 2019-09-03 at 14:12 -0300, Ezequiel Garcia wrote:
> > Commit 953aaa1492c53 ("media: rockchip/vpu: Prepare things to support decoders")
> > changed the conditions under S_FMT was allowed for OUTPUT
> > CAPTURE buffers.
> > 
> > However, and according to the mem-to-mem stateless decoder specification,
> > in order to support dynamic resolution changes, S_FMT should be allowed
> > even if OUTPUT buffers have been allocated.
> > 
> > Relax decoder S_FMT restrictions on OUTPUT buffers, allowing a resolution
> > modification, provided the pixel format stays the same.
> > 
> > Tested on RK3288 platforms using ChromiumOS Video Decode/Encode Accelerator Unittests.
> > 
> > Fixes: 953aaa1492c53 ("media: rockchip/vpu: Prepare things to support decoders")
> > Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
> > ---
> >  drivers/staging/media/hantro/hantro_v4l2.c | 22 ++++++++++++++++------
> >  1 file changed, 16 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/staging/media/hantro/hantro_v4l2.c b/drivers/staging/media/hantro/hantro_v4l2.c
> > index 3dae52abb96c..d48b548842cf 100644
> > --- a/drivers/staging/media/hantro/hantro_v4l2.c
> > +++ b/drivers/staging/media/hantro/hantro_v4l2.c
> > @@ -367,19 +367,22 @@ vidioc_s_fmt_out_mplane(struct file *file, void *priv, struct v4l2_format *f)
> >  {
> >  	struct v4l2_pix_format_mplane *pix_mp = &f->fmt.pix_mp;
> >  	struct hantro_ctx *ctx = fh_to_ctx(priv);
> > +	struct vb2_queue *vq = v4l2_m2m_get_vq(ctx->fh.m2m_ctx, f->type);
> >  	const struct hantro_fmt *formats;
> >  	unsigned int num_fmts;
> > -	struct vb2_queue *vq;
> >  	int ret;
> >  
> > -	/* Change not allowed if queue is busy. */
> > -	vq = v4l2_m2m_get_vq(ctx->fh.m2m_ctx, f->type);
> > -	if (vb2_is_busy(vq))
> > -		return -EBUSY;
> > -
> >  	if (!hantro_is_encoder_ctx(ctx)) {
> >  		struct vb2_queue *peer_vq;
> >  
> > +		/*
> > +		 * In other to support dynamic resolution change,
> > +		 * the decoder admits a resolution change, as long
> > +		 * as the pixelformat remains. Can't be done if streaming.
> > +		 */
> > +		if (vb2_is_streaming(vq) || (vb2_is_busy(vq) &&
> > +		    pix_mp->pixelformat != ctx->src_fmt.pixelformat))
> 
> Before using contents of the v4l2_format f for comparison, we should run
> vidioc_try_fmt_out_mplane over it.

Right, good catch.

>  Also, besides pixelformat, sizeimage
> shouldn't change either, at least if this is a VB2_MMAP queue.
> 

This is the OUTPUT queue, so I don't see why the sizeimage
of the coded buffers should stay the same. Maybe I'm missing
something? 

> > +			return -EBUSY;
> >  		/*
> >  		 * Since format change on the OUTPUT queue will reset
> >  		 * the CAPTURE queue, we can't allow doing so
> > @@ -389,6 +392,13 @@ vidioc_s_fmt_out_mplane(struct file *file, void *priv, struct v4l2_format *f)
> >  					  V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE);
> >  		if (vb2_is_busy(peer_vq))
> >  			return -EBUSY;
> > +	} else {
> > +		/*
> > +		 * The encoder doesn't admit a format change if
> > +		 * there are OUTPUT buffers allocated.
> > +		 */
> > +		if (vb2_is_busy(vq))
> > +			return -EBUSY;
> >  	}
> >  
> >  	ret = vidioc_try_fmt_out_mplane(file, priv, f);
> 
> I think this needs to be moved up.
> 

Right.

Thanks,
Ezequiel