Re: [PATCH 2/3] media: Documentation: v4l: LINK_FREQ can be an INTEGER64 control

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On 20/02/2024 14:03, Sakari Ailus wrote:
> When a device passes through the video data while still having its own
> receiver and transmitter, it can use the same frequency as the upstream
> link does. The Intel MEI CSI device is an example of this. An integer menu
> control isn't useful in conveying the actual frequency to the receiver in
> this case.
> 
> Document that the LINK_FREQ control may also be a 64-bit integer control.
> 
> Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> ---
>  .../userspace-api/media/v4l/ext-ctrls-image-process.rst         | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst
> index b1c2ab2854af..7a3ccb100e1d 100644
> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst
> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst
> @@ -22,7 +22,7 @@ Image Process Control IDs
>  
>  .. _v4l2-cid-link-freq:
>  
> -``V4L2_CID_LINK_FREQ (integer menu)``
> +``V4L2_CID_LINK_FREQ (integer menu or 64-bit integer)``
>      The frequency of the data bus (e.g. parallel or CSI-2).

I really think a new control should be created for this.

As I understand it, V4L2_CID_LINK_FREQ gives a set of supported frequencies,
and the application has to pick one (I think?). Is it supposed to be a
read-only control? Some driver seem to set the READ_ONLY flag, and some do not.
The documentation isn't helpful in that respect.

In the case of the Intel MEI CSI and similar devices a new control would be
better, I think. Do I understand it correctly that for these devices it would
always be a read-only control? I.e. it just reports the frequency, but applications
cannot change it?

Regards,

	Hans

>  
>  .. _v4l2-cid-pixel-rate:





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