Re: [PATCH 2/5] media: Documentation: it6625: document the audio controls

[Hans Verkuil]

Hi Hermes,

On 03/11/2026 07:50, Hermes Wu via B4 Relay wrote:
> From: Hermes Wu <Hermes.wu@xxxxxxxxxx>
> 
> The IT6625 driver exposes two read-only driver-specific controls,
> V4L2_CID_IT6625_AUDIO_SAMPLING_RATE and V4L2_CID_IT6625_AUDIO_PRESENT,
> which so far are described only in the uAPI header.
> 
> Add a page for the driver to the V4L2 driver-specific documentation that
> describes both controls, and list it in MAINTAINERS.
> 
> Signed-off-by: Hermes Wu <Hermes.wu@xxxxxxxxxx>
> ---
>  Documentation/userspace-api/media/drivers/index.rst  |  1 +
>  Documentation/userspace-api/media/drivers/it6625.rst | 18 ++++++++++++++++++
>  MAINTAINERS                                          |  1 +
>  3 files changed, 20 insertions(+)
> 
> diff --git a/Documentation/userspace-api/media/drivers/index.rst b/Documentation/userspace-api/media/drivers/index.rst
> index 8d2c489b8453e11b8e15ef9d9c1c0312f3da06af..57be8dd5749d7f5aa6e0e21c7e3d89d377a209d0 100644
> --- a/Documentation/userspace-api/media/drivers/index.rst
> +++ b/Documentation/userspace-api/media/drivers/index.rst
> @@ -33,6 +33,7 @@ For more details see the file COPYING in the source distribution of Linux.
>  	dcmipp
>  	dw100
>  	imx-uapi
> +	it6625
>  	mali-c55
>  	max2175
>  	npcm-video
> diff --git a/Documentation/userspace-api/media/drivers/it6625.rst b/Documentation/userspace-api/media/drivers/it6625.rst
> new file mode 100644
> index 0000000000000000000000000000000000000000..efd970e8124979abffb6f9ba3ea1e1bc193820b3
> --- /dev/null
> +++ b/Documentation/userspace-api/media/drivers/it6625.rst
> @@ -0,0 +1,18 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +ITE IT6625/IT6626 HDMI to MIPI bridge driver
> +============================================
> +
> +The IT6625 driver implements the following driver-specific controls. All of
> +them are read-only and describe the audio of the HDMI input.
> +
> +``V4L2_CID_IT6625_AUDIO_SAMPLING_RATE (integer)``
> +-------------------------------------------------
> +    The sampling rate of the HDMI audio stream, in Hz. 0 means that the rate
> +    is not available: there is no stable input signal or no audio, the bridge
> +    reported a rate code that the driver does not recognize, or reading the
> +    audio status failed.
> +
> +``V4L2_CID_IT6625_AUDIO_PRESENT (boolean)``
> +-------------------------------------------
> +    Whether the bridge currently receives HDMI audio.

Mention in the documentation that these controls are read-only.

We need to make standard controls for the audio sampling rate and presence.
They are also used by the tc358743 driver, and are in fact common for all
HDMI receiver drivers (I know of a bunch of out-of-tree drivers that use the
same controls).

So rather than creating driver-specific controls, can you add standard
controls for this? They belong to the V4L2_CID_DV_CLASS control class.

So the defines become:

V4L2_CID_DV_RX_AUDIO_SAMPLING_RATE and V4L2_CID_DV_RX_AUDIO_PRESENT.

This also means that there is no need for a separate it6625.rst.

The tc358743 driver should be extended to also support the new standard
controls. So tc358743_s_ctrl_audio_sampling_rate/_present set both the
custom and the standard control.

Sorry for this, it is a bit more work but it makes userspace easier since
there is a standard control for this instead of having driver-specific
controls.

Make sure that the patches adding support to the v4l2 core for these
two new standard controls are not mixed with the it656 changes. So
first add it to the core, then use it in this driver.

Regards,

	Hans

> diff --git a/MAINTAINERS b/MAINTAINERS
> index 760791e3635f3c306e7fed7240b948d29b45ae66..1d6de374d86d3046d993bf220195b1a75049fa8a 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -13972,6 +13972,7 @@ M:	Hermes Wu <Hermes.Wu@xxxxxxxxxx>
>  S:	Maintained
>  T:	git git://linuxtv.org/media.git
>  F:	Documentation/devicetree/bindings/media/i2c/ite,it6625.yaml
> +F:	Documentation/userspace-api/media/drivers/it6625.rst
>  F:	drivers/media/i2c/it6625.c
>  F:	include/uapi/linux/it6625.h
>  
>