[v2,2/5] media: docs: Add V4L2_CAP_EDID_MEMORY

Add documentation for the new edid eeprom capability.

Signed-off-by: Erling Ljunggren <hljunggr@cisco.com>
---
 Documentation/userspace-api/media/v4l/biblio.rst      | 11 +++++++++++
 .../userspace-api/media/v4l/vidioc-querycap.rst       |  7 +++++++
 .../userspace-api/media/videodev2.h.rst.exceptions    |  1 +
 3 files changed, 19 insertions(+)

Hi Erling,

On 03/08/2022 09:58, Erling Ljunggren wrote:
> Add documentation for the new edid eeprom capability.
> 
> Signed-off-by: Erling Ljunggren <hljunggr@cisco.com>
> ---
>  Documentation/userspace-api/media/v4l/biblio.rst      | 11 +++++++++++
>  .../userspace-api/media/v4l/vidioc-querycap.rst       |  7 +++++++
>  .../userspace-api/media/videodev2.h.rst.exceptions    |  1 +
>  3 files changed, 19 insertions(+)
> 
> diff --git a/Documentation/userspace-api/media/v4l/biblio.rst b/Documentation/userspace-api/media/v4l/biblio.rst
> index 9cd18c153d19..5cbe41877a63 100644
> --- a/Documentation/userspace-api/media/v4l/biblio.rst
> +++ b/Documentation/userspace-api/media/v4l/biblio.rst
> @@ -334,6 +334,17 @@ VESA DMT
>  
>  :author:    Video Electronics Standards Association (http://www.vesa.org)
>  
> +.. _vesaeddc:
> +
> +E-DDC
> +====
> +
> +
> +:title:     VESA Enhanced Display Data Channel (E-DDC) Standard
> +:subtitle:  Version 1.3
> +
> +:author:    Video Electronics Standards Association (http://www.vesa.org)
> +
>  .. _vesaedid:
>  
>  EDID
> diff --git a/Documentation/userspace-api/media/v4l/vidioc-querycap.rst b/Documentation/userspace-api/media/v4l/vidioc-querycap.rst
> index 63e23f6f95ee..bdb530bd6816 100644
> --- a/Documentation/userspace-api/media/v4l/vidioc-querycap.rst
> +++ b/Documentation/userspace-api/media/v4l/vidioc-querycap.rst
> @@ -173,6 +173,13 @@ specification the ioctl returns an ``EINVAL`` error code.
>  	interface. A video overlay device typically stores captured images
>  	directly in the video memory of a graphics card, with hardware
>  	clipping and scaling.
> +    * - ``V4L2_CAP_EDID_MEMORY``
> +      - 0x00000008
> +      - The device is a standalone EDID memory device. This is typically an eeprom
> +        that supports the VESA Enhanced Display Data Channel Standard.
> +
> +        While an eeprom is the most common implementation, it can be something else
> +        as well, such as a microcontroller. Hence the generic name 'memory'.

I realized that this is not just needed for inputs, but also for outputs.

This is the case for an HDMI splitter that is connected to a computer via (typically)
a serial port where you can use that to get/set the EDID for the input port and
get the EDIDs for the output ports (i.e. the EDIDs from the connected displays).

It's the same concept: a standalone EDID device. However, you are not talking
directly to a memory device like an eeprom. So I think to keep things generic
this capability should be renamed to just V4L2_CAP_EDID.

The description should be updated as well since it is no longer just for inputs.

And I think we can drop the references to 'memory'. It's really about hardware
devices that store an EDID for a sink or read an EDID from a source.

Patch 5 will have to be updated as well since for an output device this cap is
associated with ENUM/S/G_OUTPUT. And for output S_EDID is not supported, of
course.

I'm working on a driver for an HDMI Splitter (CEC and EDID support), so this
would come in very handy for that.

Regards,

	Hans

>      * - ``V4L2_CAP_VBI_CAPTURE``
>        - 0x00000010
>        - The device supports the :ref:`Raw VBI Capture <raw-vbi>`
> diff --git a/Documentation/userspace-api/media/videodev2.h.rst.exceptions b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
> index 9cbb7a0c354a..12fa290828e7 100644
> --- a/Documentation/userspace-api/media/videodev2.h.rst.exceptions
> +++ b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
> @@ -185,6 +185,7 @@ replace define V4L2_CAP_META_OUTPUT device-capabilities
>  replace define V4L2_CAP_DEVICE_CAPS device-capabilities
>  replace define V4L2_CAP_TOUCH device-capabilities
>  replace define V4L2_CAP_IO_MC device-capabilities
> +replace define V4L2_CAP_EDID_MEMORY device-capabilities
>  
>  # V4L2 pix flags
>  replace define V4L2_PIX_FMT_PRIV_MAGIC :c:type:`v4l2_pix_format`