[libcamera-devel] [PATCH/RFC] libcamera: camera_sensor: Accept entities exposing the ISP function

[Niklas Söderlund]

Hi Laurent,

Thanks for your work.

On 2021-02-08 03:39:03 +0200, Laurent Pinchart wrote:
> Camera sensors can include an ISP, which may be reported as a separate
> entity from the pixel array in the media graph.
> 
> Support such sensors by accepting MEDIA_ENT_F_PROC_VIDEO_ISP as a valid
> entity type. This allows using sensors that can be fully (or at least
> meaningfully) configured through the ISP's source pad only. Sensors that
> require further configuration, on the ISP sink pad and/or on the pixel
> array's source pad, will require further extension to the CameraSensor
> class.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> ---
>  src/libcamera/camera_sensor.cpp | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> This patch depends on the new MEDIA_ENT_F_PROC_VIDEO_ISP entity
> function, which will be available in v5.12-rc1. I'll update the kernel
> headers when that kernel will be released, in a few weeks from now.

Do I understand things correctly that such sensors would primarily be 
used with the simple pipeline handler? How would this work if someones 
wires up a sensor with an ISP to a pipeline with an IPA? Is the inline 
ISP close to the sensor always "passive" and controlled by user-space or 
can we create a tug-of-war between the sensor inline ISP and a pipeline 
IPA/ISP?

> 
> diff --git a/src/libcamera/camera_sensor.cpp b/src/libcamera/camera_sensor.cpp
> index 59834ffcdd94..8158a84b63db 100644
> --- a/src/libcamera/camera_sensor.cpp
> +++ b/src/libcamera/camera_sensor.cpp
> @@ -198,7 +198,12 @@ int CameraSensor::init()
>  		return -EINVAL;
>  	}
>  
> -	if (entity_->function() != MEDIA_ENT_F_CAM_SENSOR) {
> +	switch (entity_->function()) {
> +	case MEDIA_ENT_F_CAM_SENSOR:
> +	case MEDIA_ENT_F_PROC_VIDEO_ISP:
> +		break;
> +

nit: I would remove this blank line.

> +	default:
>  		LOG(CameraSensor, Error)
>  			<< "Invalid sensor function "
>  			<< utils::hex(entity_->function());
> -- 
> Regards,
> 
> Laurent Pinchart
> 
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-- 
Regards,
Niklas Söderlund