Document the suggested way to exposure controls for exposure and gain for camera sensor drivers. Signed-off-by: Jacopo Mondi <jacopo.mondi@xxxxxxxxxxxxxxxx> --- .../driver-api/media/camera-sensor.rst | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/Documentation/driver-api/media/camera-sensor.rst b/Documentation/driver-api/media/camera-sensor.rst index ee4a7fe5f72a..dfe8f35aecea 100644 --- a/Documentation/driver-api/media/camera-sensor.rst +++ b/Documentation/driver-api/media/camera-sensor.rst @@ -189,3 +189,22 @@ the ``V4L2_CID_VFLIP`` and ``V4L2_CID_HFLIP`` controls with the a flip can potentially change the output buffer content layout. Flips should also be taken into account when enumerating and handling media bus formats on the camera sensor source pads. + +Exposure and Gain Control +------------------------- + +Camera sensor drivers that allows applications to control the image exposure +and gain should do so by exposing dedicated controls to applications. + +Exposure time is controlled by registering the ``V4L2_CID_EXPOSURE`` control. +The control definition does not specify a unit to allow maximum flexibility +for multiple device types, but when used for camera sensor driver it should be +expressed in unit of lines whenever possible. + +Camera sensor driver should try whenever possible to distinguish between the +analogue and digital gain control functions. Analogue gain is a multiplier +factor applied to all color channels on the pixel array before they get +converted in the digital domain. It should be be made controllable by +registering the ``V4L2_CID_ANALOGUE_GAIN`` control, expressed as a device +specific gain code. Digital gain control is optional and should be exposed to +applications by registering ``V4L2_CID_DIGITAL_GAIN``. Camera sensor drivers are -- 2.40.1
