Re: [RFC] media: Question about reserving V4L2 UAPI control IDs for out-of-tree rgb133 kernel driver

[Nicolas Dufresne]

Hi,

Le mardi 14 juillet 2026 à 15:32 +0100, Przemek Gajos a écrit :
> Hello,
> 
> I maintain the rgb133 V4L2 kernel driver, which is currently out of tree.
> 
> The driver historically uses V4L2_CID_PRIVATE_BASE (0x08000000) as the base
> for its private controls. With the modern V4L2 control framework this is now
> rejected, e.g. v4l2_ctrl_new() fails to create such controls under my 7.0-
> based kernel.

I could not find specific changes between 6.19 and 7.0 that would explain this
failure. Perhaps you could share a bit more details on what you are doing, and
how it fails ? Are you using v4l2_ctrl_new_custom() ?

> 
> I would like to ask whether the media maintainers would accept a request to
> reserve a dedicated block of custom control IDs in the V4L2 UAPI header
> (include/uapi/linux/v4l2-controls.h) for our driver?
> On initial research, I have not found any information about restricting it for
> out of tree drivers.
> 
> If this is acceptable in principle, I can prepare a patch for review.

Up-streaming is the path forward.

Nicolas

> 
> Thank you,
> Przemyslaw Gajos
> Technical Lead - Embedded
> Datapath Ltd
> przemek.gajos@xxxxxxxxxxxxxx

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