Re: [PATCH v11 21/66] media: v4l: uapi: Add a control for color pattern flipping effect

[Sakari Ailus <sakari.ailus@linux.intel.com>]

Hi Jacopo,

On Wed, Sep 03, 2025 at 01:25:30PM +0300, Sakari Ailus wrote:
> Hi Jacopo,
> 
> On Mon, Sep 01, 2025 at 04:34:56PM +0200, Jacopo Mondi wrote:
> > Hi Sakari
> > 
> > On Mon, Aug 25, 2025 at 12:50:22PM +0300, Sakari Ailus wrote:
> > > Add a bitmask control (V4L2_CID_COLOR_PATTERN_FLIP) to tell whether
> > > flipping results in a change in the sensor's color pattern, separately
> > > horizontally and vertically. The information is essential for raw formats
> > > when using generic raw mbus codes.
> > >
> > > Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> > > ---
> > >  .../userspace-api/media/v4l/ext-ctrls-image-source.rst | 10 ++++++++++
> > >  drivers/media/v4l2-core/v4l2-ctrls-defs.c              |  2 ++
> > >  include/uapi/linux/v4l2-controls.h                     |  6 ++++++
> > >  3 files changed, 18 insertions(+)
> > >
> > > diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-image-source.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-image-source.rst
> > > index 0fcd60d8c621..ef3784d1119a 100644
> > > --- a/Documentation/userspace-api/media/v4l/ext-ctrls-image-source.rst
> > > +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-image-source.rst
> > > @@ -133,3 +133,13 @@ Image Source Control IDs
> > >        - Raw Bayer, with alternating lines beginning with green, blue pixels and
> > >          red, green pixels.
> > >        - 3
> > > +
> > > +``V4L2_CID_COLOR_PATTERN_FLIP (bitmask)``
> > 
> > I still believe that having this and V4L2_CTRL_FLAG_MODIFY_LAYOUT
> > might be confusing. Should sensor driver that registers H/VFLIP still
> > mark those controls as V4L2_CTRL_FLAG_MODIFY_LAYOUT or should they
> > implement V4L2_CID_COLOR_PATTERN_FLIP, or do both ?
> > 
> > Should we deprectate V4L2_CTRL_FLAG_MODIFY_LAYOUT for flip controls ?
> > In this case I think the documentation of the flag should be updated.
> 
> Good question. I don't think the flag provides any useful information to
> the userspace in this case, it's just a matter of UAPI consistency.
> 
> How about setting set the flag to these controls in the control framework?
> I can add a patch for that.

Of course this is not workable as-is as the flag would be present on the
*FLIP controls.

This would be still worked around in the control framework, based on the
value of the flip control, but I think it'd be more practical to document
the flag does not apply to generic raw mbus codes or as you suggested, to
media bus codes at all. The patch that added it is
bf587efff165e0563cc9d2227e49eeba7eb50434 .

-- 
Regards,

Sakari Ailus