Re: [PATCH v7 00/10] drm: add DRM HDMI Codec framework

Dmitry Baryshkov
2024-12-18T05:24:39Z

On Tue, 17 Dec 2024 at 19:21, Maxime Ripard <mripard@kernel.org> wrote:
>
> Hi,
>
> On Tue, Dec 17, 2024 at 02:40:22AM +0200, Dmitry Baryshkov wrote:
> > While porting lt9611 DSI-to-HDMI bridge driver to use HDMI Connector
> > framework, I stumbled upon an issue while handling the Audio InfoFrames.
> > The HDMI codec callbacks weren't receiving the drm_atomic_state, so
> > there was no simple way to get the drm_connector that stayed at the end
> > of the bridge chain. At the same point the drm_hdmi_connector functions
> > expected to get drm_connector instance.
> >
> > While looking for a way to solve the issue, I stumbled upon several
> > deficiencies in existing hdmi_codec_ops implementations. Only few of the
> > implementations were able to handle codec's 'plugged' callback. One
> > third of the drivers didn't implement the get_eld() callback.
> >
> > Most of the issues can be solved if drm_connector handles
> > hdmi-audio-codec on its own, delegating functionality to the actual
> > implementation, be it a driver that implements drm_connector or
> > drm_bridge.
> >
> > Implement such high-level framework, adding proper support for Audio
> > InfoFrame generation to the LT9611 driver.
> >
> > Several design decisions to be kept in mind:
> >
> > - drm_connector_hdmi_codec is kept as simple as possible. It implements
> > generic functionality (ELD, hotplug, registration).
> >
> > - drm_hdmi_connector sets up HDMI codec device if the connector
> > is setup correspondingly (either I2S or S/PDIF is marked as
> > supported).
> >
> > - drm_bridge_connector provides a way to link HDMI audio codec
> > funcionality in the drm_bridge with the drm_connector_hdmi_codec
> > framework.
> >
> > - It might be worth reverting the no_i2s_capture / no_spdif_capture
> > bits. Only TDA889x driver sets them, while it's safe to assume that
> > most of HDMI / DP devices do not support ARC / capture. I think the
> > drivers should opt-in capture support rather than having to opt-out of
> > it.
>
> Sorry if this isn't clear to me and I'm quite late to the party, but did
> you test this on vc4 with both a pi3 and pi4, or was it just compile
> tested?

LT9611 is actually tested, VC4 is only compile-tested. Should I put an RFT tag?

--
With best wishes
Dmitry