Hi I'd like to propose some new V4L2 controls as defined in the attached patches. The controls are: V4L2_CID_NOTIFY_GAIN_RED V4L2_CID_NOTIFY_GAIN_GREENR V4L2_CID_NOTIFY_GAIN_BLUE V4L2_CID_NOTIFY_GAIN_GREENB The purpose of these controls is to be able to notify a raw sensor what colour gains will be applied by subsequent processing (such as by an ISP). Equivalently we can think of them as telling the sensor what the white point is. Note that the sensor is told these gains but does not apply them - which the choice of name is trying to convey. Some sensors need to know these numbers for the processing that they perform. Here I'm thinking in particular of so-called "quad Bayer" (also sometimes "tetracell") sensors that have a special read-out mode that converts the non-standard Bayer pattern into a standard one, also at full resolution. Sensors of this type are becoming quite common on cell phones where, for example, a 48MP sensor may be able to deliver multiple exposures at 12MP (for HDR processing perhaps) but they may also have a mode as described above where they can generate a standard Bayer output at 48MP. This processing works better - we might expect less colour aliasing? - when the sensor knows what values correspond to "white". One question in my mind is whether it's worth having a control for each green channel. The sensor I'm currently looking at only wants a single green gain, but perhaps it's one of those instances where it would be annoying to put in a single gain and discover, sometime later, a sensor that wants both. Opinions on the matter always appreciated! Thanks very much and best regards David David Plowman (2): media: v4l2-ctrls: Add V4L2_CID_NOTIFY_GAIN_XXX controls media: v4l2-ctrls: Document V4L2_CID_NOTIFY_GAIN_XXX controls .../media/v4l/ext-ctrls-image-source.rst | 28 +++++++++++++++++++ drivers/media/v4l2-core/v4l2-ctrls.c | 4 +++ include/uapi/linux/v4l2-controls.h | 4 +++ 3 files changed, 36 insertions(+) -- 2.17.1
