linux-kernel - Re: [PATCH] venus: vdec: fix decoded data size

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Date:   Wed, 18 Jul 2018 09:26:49 -0400
From:   Nicolas Dufresne <nicolas@...fresne.ca>
To:     Stanimir Varbanov <stanimir.varbanov@...aro.org>,
        Vikash Garodia <vgarodia@...eaurora.org>
Cc:     linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, acourbot@...omium.org
Subject: Re: [PATCH] venus: vdec: fix decoded data size

Le mercredi 18 juillet 2018 à 14:31 +0300, Stanimir Varbanov a écrit :
> Hi Vikash,
> 
> On 07/02/2018 10:44 AM, Vikash Garodia wrote:
> > Exisiting code returns the max of the decoded
> > size and buffer size. It turns out that buffer
> > size is always greater due to hardware alignment
> > requirement. As a result, payload size given to
> > client is incorrect. This change ensures that
> > the bytesused is assigned to actual payload size.
> > 
> > Change-Id: Ie6f3429c0cb23f682544748d181fa4fa63ca2e28
> > Signed-off-by: Vikash Garodia <vgarodia@...eaurora.org>
> > ---
> >  drivers/media/platform/qcom/venus/vdec.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/media/platform/qcom/venus/vdec.c
> > b/drivers/media/platform/qcom/venus/vdec.c
> > index d079aeb..ada1d2f 100644
> > --- a/drivers/media/platform/qcom/venus/vdec.c
> > +++ b/drivers/media/platform/qcom/venus/vdec.c
> > @@ -890,7 +890,7 @@ static void vdec_buf_done(struct venus_inst
> > *inst, unsigned int buf_type,
> >  
> >  		vb = &vbuf->vb2_buf;
> >  		vb->planes[0].bytesused =
> > -			max_t(unsigned int, opb_sz, bytesused);
> > +			min_t(unsigned int, opb_sz, bytesused);
> 
> Most probably my intension was to avoid bytesused == 0, but that is
> allowed from v4l2 driver -> userspace direction

It remains bad practice since it was used by decoders to indicate the
last buffer. Some userspace (some GStreamer versions) will stop working
if you start returning 0.

> 
> Could you drop min/max_t macros at all and use bytesused directly
> i.e.
> 
> vb2_set_plane_payload(vb, 0, bytesused)

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