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

[Maxime Ripard]

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?

Maxime
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