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References: <20221219155616.848690-1-benjamin.gaignard@collabora.com>
 <20221219155616.848690-4-benjamin.gaignard@collabora.com> <07747babe7f83a496f9cd82849c6c2386550ac28.camel@ndufresne.ca>
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From:   Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Date:   Mon, 19 Dec 2022 18:29:20 -0300
Message-ID: <CAAEAJfDoX_aSTg1TO8F21iSriYeTXtRbHPo8wxx5br2v6eCt7Q@mail.gmail.com>
Subject: Re: [PATCH v1 3/9] media: verisilicon: Save bit depth for AV1 decoder
To:     Nicolas Dufresne <nicolas@ndufresne.ca>
Cc:     Benjamin Gaignard <benjamin.gaignard@collabora.com>,
        p.zabel@pengutronix.de, mchehab@kernel.org, robh+dt@kernel.org,
        krzysztof.kozlowski+dt@linaro.org, heiko@sntech.de,
        daniel.almeida@collabora.com, nicolas.dufresne@collabora.co.uk,
        linux-media@vger.kernel.org, linux-rockchip@lists.infradead.org,
        devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, kernel@collabora.com
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Bonjour Nicolas,

On Mon, Dec 19, 2022 at 5:37 PM Nicolas Dufresne <nicolas@ndufresne.ca> wro=
te:
>
> Le lundi 19 d=C3=A9cembre 2022 =C3=A0 16:56 +0100, Benjamin Gaignard a =
=C3=A9crit :
> > Store bit depth information from AV1 sequence control.
> >
> > Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
> > ---
> >  .../media/platform/verisilicon/hantro_drv.c   | 26 +++++++++++++++++++
> >  1 file changed, 26 insertions(+)
> >
> > diff --git a/drivers/media/platform/verisilicon/hantro_drv.c b/drivers/=
media/platform/verisilicon/hantro_drv.c
> > index 4500e1fc0f2c..8e93710dcfed 100644
> > --- a/drivers/media/platform/verisilicon/hantro_drv.c
> > +++ b/drivers/media/platform/verisilicon/hantro_drv.c
> > @@ -324,6 +324,25 @@ static int hantro_vp9_s_ctrl(struct v4l2_ctrl *ctr=
l)
> >       return 0;
> >  }
> >
> > +static int hantro_av1_s_ctrl(struct v4l2_ctrl *ctrl)
> > +{
> > +     struct hantro_ctx *ctx;
> > +
> > +     ctx =3D container_of(ctrl->handler,
> > +                        struct hantro_ctx, ctrl_handler);
> > +
> > +     switch (ctrl->id) {
> > +     case V4L2_CID_STATELESS_AV1_SEQUENCE:
> > +             ctx->bit_depth =3D ctrl->p_new.p_av1_sequence->bit_depth;
>
> That seems a little be weak, what happens if you change the bit_depth wit=
h a
> non-request s_ctrl while its decoding ? To be this deserve a little bit o=
f
> protection, a something that validate and copy it at the start of the dec=
oding.
>

Oh, nice catch. We need to return EBUSY, see
https://www.kernel.org/doc/html/v5.0/media/uapi/v4l/buffer.html#interaction=
s-between-formats-controls-and-buffers.

There's already an API in the V4L2 control framework for drivers to use,
see v4l2_ctrl_grab in
https://www.kernel.org/doc/html/v5.0/media/kapi/v4l2-controls.html#active-a=
nd-grabbed-controls.

> p.s. I know, VP9 seems similar, though arguably that was copied from jpeg=
, for
> which it seems totally save to change the quality at run-time.
>

No, wasn't copied from JPEG :-) I just didn't realize this was an
issue, but it is
given the bit_depth affects the buffers so you are correct, it needs
to be fixed for VP9 too.

Thanks!
Ezequiel

> > +             break;
> > +     default:
> > +             return -EINVAL;
> > +     }
> > +
> > +     return 0;
> > +}
> > +
> > +
> >  static const struct v4l2_ctrl_ops hantro_ctrl_ops =3D {
> >       .try_ctrl =3D hantro_try_ctrl,
> >  };
> > @@ -336,6 +355,12 @@ static const struct v4l2_ctrl_ops hantro_vp9_ctrl_=
ops =3D {
> >       .s_ctrl =3D hantro_vp9_s_ctrl,
> >  };
> >
> > +static const struct v4l2_ctrl_ops hantro_av1_ctrl_ops =3D {
> > +     .try_ctrl =3D hantro_try_ctrl,
> > +     .s_ctrl =3D hantro_av1_s_ctrl,
> > +};
> > +
> > +
> >  #define HANTRO_JPEG_ACTIVE_MARKERS   (V4L2_JPEG_ACTIVE_MARKER_APP0 | \
> >                                        V4L2_JPEG_ACTIVE_MARKER_COM | \
> >                                        V4L2_JPEG_ACTIVE_MARKER_DQT | \
> > @@ -513,6 +538,7 @@ static const struct hantro_ctrl controls[] =3D {
> >               .codec =3D HANTRO_AV1_DECODER,
> >               .cfg =3D {
> >                       .id =3D V4L2_CID_STATELESS_AV1_SEQUENCE,
> > +                     .ops =3D &hantro_av1_ctrl_ops,
> >               },
> >       }, {
> >               .codec =3D HANTRO_AV1_DECODER,
>