[libcamera-devel] [PATCH v3 2/5] libcamera: uvcvideo: Update exposure/gain ctrls set with new units

[Laurent Pinchart]

Hi Naush,

Thank you for the patch.

On Fri, Apr 03, 2020 at 03:53:02PM +0100, Naushir Patuck wrote:
> The ExposureTime control now uses units of 1 micro-second, and UVC
> uses units of 100 micro-seconds. Correctly map the values before
> setting V4L2_CID_EXPOSURE_ABSOLUTE on the V4L2 device.
> 
> The AnalogueGain control now uses floats to allow fractional gain
> values. Since UVC has no explicit gain units, map the default gain value
> to 1.0 and linearly map to the requested value.
> 
> Signed-off-by: Naushir Patuck <naush at raspberrypi.com>

Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

> ---
>  src/libcamera/pipeline/uvcvideo/uvcvideo.cpp | 17 +++++++++++++++--
>  1 file changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> index d7df95e4..9d589f69 100644
> --- a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> +++ b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> @@ -253,9 +253,22 @@ int PipelineHandlerUVC::processControls(UVCCameraData *data, Request *request)
>  			controls.set(V4L2_CID_SATURATION, value);
>  		} else if (id == controls::ExposureTime) {
>  			controls.set(V4L2_CID_EXPOSURE_AUTO, static_cast<int32_t>(1));
> -			controls.set(V4L2_CID_EXPOSURE_ABSOLUTE, value);
> +			/*
> +			 * controls::ExposureTime is in units of 1 us, and UVC
> +			 * expects V4L2_CID_EXPOSURE_ABSOLUTE in units of 100 us.
> +			 */
> +			controls.set(V4L2_CID_EXPOSURE_ABSOLUTE,
> +				     value.get<int32_t>() / 100);
>  		} else if (id == controls::AnalogueGain) {
> -			controls.set(V4L2_CID_GAIN, value);
> +			/*
> +			 * controls::AnalogueGain is specified as an absolute
> +			 * multiplier for all RGB samples. Map this multiplier
> +			 * in a linear way such that 1.0 -> default gain
> +			 * of the V4L2_CID_GAIN control on the uvcvideo device.
> +			 */
> +			const ControlInfo &gainInfo = controls.infoMap()->at(V4L2_CID_GAIN);
> +			int32_t gain = value.get<float>() * gainInfo.def().get<int32_t>();
> +			controls.set(V4L2_CID_GAIN, gain);
>  		}
>  	}
>  

-- 
Regards,

Laurent Pinchart