Re: [PATCH v3 5/6] media: qcom: iris: vdec: update find_format to handle 8bit and 10bit formats

[Neil Armstrong]

On 5/20/26 17:30, Vikash Garodia wrote:
> On 5/18/2026 1:06 PM, Neil Armstrong wrote:
> > On 5/13/26 21:27, Vikash Garodia wrote:
> > > On 5/11/2026 2:50 PM, Neil Armstrong wrote:
> > > > The 10bit pixel format can be only used when the decoder identifies the
> > > > stream as decoding into 10bit pixel format buffers, so update the
> > > > find_format helper to filter the formats and only allow the proper
> > > > formats when setting or trying a capture format.
> > > >
> > > > Signed-off-by: Neil Armstrong <neil.armstrong@xxxxxxxxxx>
> > > > ---
> > > >   drivers/media/platform/qcom/iris/iris_platform_common.h |  1 +
> > > >   drivers/media/platform/qcom/iris/iris_vdec.c            | 10 ++++++ ++++
> > > >   2 files changed, 11 insertions(+)
> > > >
> > > > diff --git a/drivers/media/platform/qcom/iris/iris_platform_common.h b/drivers/media/platform/qcom/iris/iris_platform_common.h
> > > > index 5a489917580e..cd3509da4b75 100644
> > > > --- a/drivers/media/platform/qcom/iris/iris_platform_common.h
> > > > +++ b/drivers/media/platform/qcom/iris/iris_platform_common.h
> > > > @@ -18,6 +18,7 @@ struct iris_inst;
> > > >   #define REGISTER_BIT_DEPTH(luma, chroma)    ((luma) << 16 | (chroma))
> > > >   #define BIT_DEPTH_8                REGISTER_BIT_DEPTH(8, 8)
> > > > +#define BIT_DEPTH_10                REGISTER_BIT_DEPTH(10, 10)
> > > >   #define CODED_FRAMES_PROGRESSIVE        0x0
> > > >   #define DEFAULT_MAX_HOST_BUF_COUNT        64
> > > >   #define DEFAULT_MAX_HOST_BURST_BUF_COUNT    256
> > > > diff --git a/drivers/media/platform/qcom/iris/iris_vdec.c b/drivers/ media/platform/qcom/iris/iris_vdec.c
> > > > index eea69f937147..f4d9951ed04c 100644
> > > > --- a/drivers/media/platform/qcom/iris/iris_vdec.c
> > > > +++ b/drivers/media/platform/qcom/iris/iris_vdec.c
> > > > @@ -99,6 +99,16 @@ find_format(struct iris_inst *inst, u32 pixfmt, u32 type)
> > > >       if (i == size || fmt[i].type != type)
> > > >           return NULL;
> > > > +    if (type == V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE) {
> > > > +        if (iris_fmt_is_8bit(fmt[i].pixfmt) &&
> > > > +            inst->fw_caps[BIT_DEPTH].value == BIT_DEPTH_10)
> > > > +            return NULL;
> > > > +
> > > > +        if (iris_fmt_is_10bit(fmt[i].pixfmt) &&
> > > > +            inst->fw_caps[BIT_DEPTH].value != BIT_DEPTH_10)
> > > > +            return NULL;
> > > > +    }
> > >
> > > similar logic would be now needed while enumerating fmt.
> > >
> > > VIDIOC_ENUM_FMT will now enumerate all capture formats (NV12, QC08C, QC10C..) regardless of the stream's bit depth, while VIDIOC_S_FMT will reject the wrong-depth formats.
> > >
> > > userspace will see formats via ENUM_FMT that it cannot successfully set with S_FMT.
> >
> > So initially I did that, but I reverted since it broke decoding with gstreamer when trying
> > to use QC10C since it requires negociating the src/sink before sending the fist buffer
> > and then get the source format change to switch to 10bit.
>
> Does that mean that src is still producing the data in Q10c, while sink is configured to NV12 (8bit) ?

No, it's early src/sink negociation capabilities with the special DRM DMABUF format to handle the QC10c, way before playback starts and starts the v4l2 dance.

> > I checked and none of the other v4l2 drivers supporting 10bit does that, so it seems right
> > to allow enumerating all possibly supported formats and only accept the session supported
> > one with S_FMT.
>
> I was reading the documentation on this aspects, and it says to keep all the supported ones, instead of changing runtime and limit it to 10bit ones, in this case.

Hmm, so my change is correct ?

> +ing Nico and Hans incase they would like to comment on this.
>
> > > > +
> > > >       return &fmt[i];
> > > >   }
> > >
> > > Regards,
> > > Vikash