linux-kernel - Re: [PATCH v1 3/9] media: verisilicon: Save bit depth for AV1 decoder

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Message-ID: <CAAEAJfDoX_aSTg1TO8F21iSriYeTXtRbHPo8wxx5br2v6eCt7Q@mail.gmail.com>
Date:   Mon, 19 Dec 2022 18:29:20 -0300
From:   Ezequiel Garcia <ezequiel@...guardiasur.com.ar>
To:     Nicolas Dufresne <nicolas@...fresne.ca>
Cc:     Benjamin Gaignard <benjamin.gaignard@...labora.com>,
        p.zabel@...gutronix.de, mchehab@...nel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, heiko@...ech.de,
        daniel.almeida@...labora.com, nicolas.dufresne@...labora.co.uk,
        linux-media@...r.kernel.org, linux-rockchip@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, kernel@...labora.com
Subject: Re: [PATCH v1 3/9] media: verisilicon: Save bit depth for AV1 decoder

Bonjour Nicolas,

On Mon, Dec 19, 2022 at 5:37 PM Nicolas Dufresne <nicolas@...fresne.ca> wrote:
>
> Le lundi 19 décembre 2022 à 16:56 +0100, Benjamin Gaignard a écrit :
> > Store bit depth information from AV1 sequence control.
> >
> > Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...labora.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 *ctrl)
> >       return 0;
> >  }
> >
> > +static int hantro_av1_s_ctrl(struct v4l2_ctrl *ctrl)
> > +{
> > +     struct hantro_ctx *ctx;
> > +
> > +     ctx = container_of(ctrl->handler,
> > +                        struct hantro_ctx, ctrl_handler);
> > +
> > +     switch (ctrl->id) {
> > +     case V4L2_CID_STATELESS_AV1_SEQUENCE:
> > +             ctx->bit_depth = ctrl->p_new.p_av1_sequence->bit_depth;
>
> That seems a little be weak, what happens if you change the bit_depth with a
> non-request s_ctrl while its decoding ? To be this deserve a little bit of
> protection, a something that validate and copy it at the start of the decoding.
>

Oh, nice catch. We need to return EBUSY, see
https://www.kernel.org/doc/html/v5.0/media/uapi/v4l/buffer.html#interactions-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-and-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 = {
> >       .try_ctrl = hantro_try_ctrl,
> >  };
> > @@ -336,6 +355,12 @@ static const struct v4l2_ctrl_ops hantro_vp9_ctrl_ops = {
> >       .s_ctrl = hantro_vp9_s_ctrl,
> >  };
> >
> > +static const struct v4l2_ctrl_ops hantro_av1_ctrl_ops = {
> > +     .try_ctrl = hantro_try_ctrl,
> > +     .s_ctrl = 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[] = {
> >               .codec = HANTRO_AV1_DECODER,
> >               .cfg = {
> >                       .id = V4L2_CID_STATELESS_AV1_SEQUENCE,
> > +                     .ops = &hantro_av1_ctrl_ops,
> >               },
> >       }, {
> >               .codec = HANTRO_AV1_DECODER,
>