[libcamera-devel] [PATCH 2/3] libcamera: controls: Specify manual gain units and change exposure units

[Kieran Bingham]

Hi Naush,

On 17/02/2020 14:26, Naushir Patuck wrote:
> Use micro-seconds for ManualExposure. This is changed from milli-
> seconds. The latter would not allow very low exposure times.
> 
> Use double for ManualGain to allow fractional gain adjustments.
> 
> Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
> ---
>  src/libcamera/control_ids.yaml | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/src/libcamera/control_ids.yaml b/src/libcamera/control_ids.yaml
> index 4befec7..33062d6 100644
> --- a/src/libcamera/control_ids.yaml
> +++ b/src/libcamera/control_ids.yaml
> @@ -44,10 +44,10 @@ controls:
>  
>    - ManualExposure:
>        type: int32_t
> -      description: Specify a fixed exposure time in milli-seconds
> +      description: Specify a fixed exposure time in micro-seconds

At the moment, the only user of this control
(PipelineHandlerUVC::processControls()) sets this directly on the V4L2
control.

As we don't yet have anything much actually testing this, it's fairly
arbitrary - so I'm certainly not against changing the units.

But we may need to consider how to map this directly at the platform.

That said - that's a job for the pipeline handlers ...


But perhaps we need to divide the value by 1000 in the current code at
pipeline/uvcvideo.cpp to maintain consistency.
			


>    - ManualGain:
> -      type: int32_t
> -      description: Specify a fixed gain parameter
> +      type: double
> +      description: Specify a fixed gain parameter.


Same comment applies here that if this is changed, the usage in
pipeline/uvcvideo.cpp needs to be updated at the same time, so I think
we'll need to split this patch out to change the units and fix the
(current) implementation for each of the controls one control at a time.

But Otherwise, I agree on the unit changes.

-- 
Regards
--
Kieran