Re: [EXT] [RFC v5 11/15] media: Documentation: Document luma-only mbus codes and CFA for cameras

Sakari Ailus
2025-02-10T14:36:05Z

Hi Mirela,

On Sun, Feb 09, 2025 at 07:48:27PM +0200, Mirela Rabulea wrote:
> Hi Sakari,
>
> On 03.02.2025 10:58, Sakari Ailus wrote:
> > Caution: This is an external email. Please take care when clicking links or opening attachments. When in doubt, report the message using the 'Report this email' button
> >
> >
> > Document the use of luma-only mbus codes for camera sensors and how the
> > V4L2_CID_COLOUR_PATTERN and V4L2_CID_COLOUR_PATTERN_FLIP controls are used
> > to convey the colour filter array pattern on UAPI.
> >
> > Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> > ---
> > .../userspace-api/media/drivers/camera-sensor.rst | 13 +++++++++++++
> > .../media/v4l/ext-ctrls-image-source.rst | 4 ++++
> > 2 files changed, 17 insertions(+)
> >
> > diff --git a/Documentation/userspace-api/media/drivers/camera-sensor.rst b/Documentation/userspace-api/media/drivers/camera-sensor.rst
> > index 5bc4c79d230c..91e5305458b9 100644
> > --- a/Documentation/userspace-api/media/drivers/camera-sensor.rst
> > +++ b/Documentation/userspace-api/media/drivers/camera-sensor.rst
> > @@ -41,6 +41,19 @@ format set on a source pad at the end of the device's internal pipeline.
> >
> > Most sensor drivers are implemented this way.
> >
> > +V4L2_CID_COLOUR_PATTERN, luma-only mbus formats, flipping and cropping
> > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > +
> > +For raw image data originating from camera sensors, :ref:`luma-only mbus codes
> > +MEDIA_BUS_FMT_Yx_1Xx (where 'x' is the bit depth) <v4l2-mbus-pixelcode-yuv8>`
> > +are used as Colour Filter Array (CFA) agnostic raw formats. The
> > +``V4L2_CID_COLOUR_PATTERN <image-source-control-colour-pattern>`` control in the
> > +same sub-device defines the native colour pattern of the device. Flipping may
> > +further affect the readout pattern as indicated by the
> > +``V4L2_CID_COLOUR_PATTERN_FLIP <image-source-control-colour-pattern-flip>``
> > +control. Further on, cropping also has an effect on the pattern if cropped
> > +amount is not divisible by the size of the pattern, horizontally and vertically.
> > +
>
> Ok, so it is clear now, the V4L2_CID_COLOUR_PATTERN stands for the "native
> colour pattern", as opposed to the "readout pattern". It is good to make the
> distinction.
>
> Maybe the V4L2_CID_COLOUR_PATTERN control description in patch #7 could also
> be made more clear with regards to native vs readout pattern?
>
> "This control determines the colour components and pixel order in the
> sensor's CFA (Colour Filter Array)..." => "This control reports the colour
> components and native pixel order in the sensor's CFA (Colour Filter
> Array)..." ?

I agree, I'll change this in v6.

--
Kind regards,

Sakari Ailus