linux-kernel - Re: [PATCH v2 10/11] media: cedrus: Adjust buffer size based on control values

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Message-ID: <1908973.PYKUYFuaPT@jernej-laptop>
Date:   Fri, 04 Nov 2022 19:10:52 +0100
From:   Jernej Škrabec <jernej.skrabec@...il.com>
To:     mripard@...nel.org, paul.kocialkowski@...tlin.com,
        Hans Verkuil <hverkuil-cisco@...all.nl>
Cc:     mchehab@...nel.org, gregkh@...uxfoundation.org, wens@...e.org,
        samuel@...lland.org, linux-media@...r.kernel.org,
        linux-staging@...ts.linux.dev,
        linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 10/11] media: cedrus: Adjust buffer size based on control values

Dne petek, 04. november 2022 ob 16:27:29 CET je Hans Verkuil napisal(a):
> Hi Jernej,
> 
> On 02/11/2022 19:08, Jernej Skrabec wrote:
> > In some cases decoding engine needs extra space in capture buffers. This
> > is the case for decoding 10-bit HEVC frames into 8-bit capture format.
> > This commit only adds infrastructure for such cases.
> > 
> > Signed-off-by: Jernej Skrabec <jernej.skrabec@...il.com>
> > ---
> > 
> >  drivers/staging/media/sunxi/cedrus/cedrus.c       | 14 ++++++++++++++
> >  drivers/staging/media/sunxi/cedrus/cedrus.h       |  2 ++
> >  drivers/staging/media/sunxi/cedrus/cedrus_video.c |  4 ++++
> >  3 files changed, 20 insertions(+)
> > 
> > diff --git a/drivers/staging/media/sunxi/cedrus/cedrus.c
> > b/drivers/staging/media/sunxi/cedrus/cedrus.c index
> > 6a2c08928613..c36999e47591 100644
> > --- a/drivers/staging/media/sunxi/cedrus/cedrus.c
> > +++ b/drivers/staging/media/sunxi/cedrus/cedrus.c
> > @@ -68,8 +68,22 @@ static int cedrus_try_ctrl(struct v4l2_ctrl *ctrl)
> > 
> >  	return 0;
> >  
> >  }
> > 
> > +static int cedrus_s_ctrl(struct v4l2_ctrl *ctrl)
> > +{
> > +	struct cedrus_ctx *ctx = container_of(ctrl->handler,
> > +					      struct 
cedrus_ctx, hdl);
> > +	struct vb2_queue *vq = v4l2_m2m_get_vq(ctx->fh.m2m_ctx,
> > +					       
V4L2_BUF_TYPE_VIDEO_CAPTURE);
> > +
> > +	if (!vb2_is_busy(vq) && !vb2_is_streaming(vq))
> 
> You can drop the !vb2_is_streaming part. If you are streaming, then
> it will also be 'busy'.
> 
> > +		cedrus_reset_cap_format(ctx);
> 
> This is weird. I would expect that this is only called for specific
> controls, since presumably not all will change the sizeimage value. It
> looks like it applies only to V4L2_CID_STATELESS_HEVC_SPS, so I see no
> reason why you would call cedrus_reset_cap_format() for other controls as
> well.

It's more general approach. It's harmless for other cases, still within specs. 
Anyway, I can make it more specific.

> 
> And what happens if someone makes such a change *while streaming*?
> Shouldn't cedrus_try_ctrl detect that and fail with -EBUSY in that case?

SPS can also be changed during streaming, so we can't outright deny setting it 
during streaming. Also, if it changes from 10 to 8, that also works, since 
capture buffers are still big enough. Only change from 8 to 10 during streaming 
won't work and that check can be added.

> 
> Regardless, this is unexpected behavior, so some explanatory comments
> would be useful.
> 
> I'm also not sure whether it isn't better to add cedrus_s_ctrl in the next
> patch, I think it would be more understandable when seen with an actual
> control.

I guess I can move logic to cedrus_try_ctrl(), where some of this logic 
already exists and it would be just a little bit expanded and more selective.

Best regards,
Jernej

> 
> Regards,
> 
> 	Hans
> 
> > +
> > +	return 0;
> > +}
> > +
> > 
> >  static const struct v4l2_ctrl_ops cedrus_ctrl_ops = {
> >  
> >  	.try_ctrl = cedrus_try_ctrl,
> > 
> > +	.s_ctrl = cedrus_s_ctrl,
> > 
> >  };
> >  
> >  static const struct cedrus_control cedrus_controls[] = {
> > 
> > diff --git a/drivers/staging/media/sunxi/cedrus/cedrus.h
> > b/drivers/staging/media/sunxi/cedrus/cedrus.h index
> > 5904294f3108..774fe8048ce3 100644
> > --- a/drivers/staging/media/sunxi/cedrus/cedrus.h
> > +++ b/drivers/staging/media/sunxi/cedrus/cedrus.h
> > @@ -162,6 +162,8 @@ struct cedrus_dec_ops {
> > 
> >  	int (*start)(struct cedrus_ctx *ctx);
> >  	void (*stop)(struct cedrus_ctx *ctx);
> >  	void (*trigger)(struct cedrus_ctx *ctx);
> > 
> > +	unsigned int (*extra_cap_size)(struct cedrus_ctx *ctx,
> > +				       struct v4l2_pix_format 
*pix_fmt);
> > 
> >  };
> >  
> >  struct cedrus_variant {
> > 
> > diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_video.c
> > b/drivers/staging/media/sunxi/cedrus/cedrus_video.c index
> > dec5d3ae4871..dc67940f1ade 100644
> > --- a/drivers/staging/media/sunxi/cedrus/cedrus_video.c
> > +++ b/drivers/staging/media/sunxi/cedrus/cedrus_video.c
> > @@ -250,6 +250,10 @@ static int cedrus_try_fmt_vid_cap_p(struct cedrus_ctx
> > *ctx,> 
> >  	pix_fmt->height = ctx->src_fmt.height;
> >  	cedrus_prepare_format(pix_fmt);
> > 
> > +	if (ctx->current_codec->extra_cap_size)
> > +		pix_fmt->sizeimage +=
> > +			ctx->current_codec->extra_cap_size(ctx, 
pix_fmt);
> > +
> > 
> >  	return 0;
> >  
> >  }