[PATCH v2 2/2] libcamera: pipeline: uvcvideo: Fix `ExposureTimeMode` control setting

[Kieran Bingham]

Quoting Barnabás Pőcze (2025-02-17 18:53:39)
> The mapping in `UVCCameraData::processControl()` is not entirely correct
> because the control value is retrieved as a `bool` instead of `int32_t`.
> Additionally, the available modes are not taken into account.
> 
> To fix this, retrieve the control with the proper type - `int32_t` -,
> and use the available modes stored in `UVCCameraData` to determine
> which value to use for the V4L2 control.
> 
> Fixes: bad8d591f8acfa ("libcamera: uvcvideo: Register ExposureTimeMode control")
> Signed-off-by: Barnabás Pőcze <pobrn at protonmail.com>
> ---
>  src/libcamera/pipeline/uvcvideo/uvcvideo.cpp | 38 +++++++++++++++-----
>  1 file changed, 29 insertions(+), 9 deletions(-)
> 
> diff --git a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> index 1f604b91e..adab6aa18 100644
> --- a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> +++ b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> @@ -103,8 +103,8 @@ public:
>         bool match(DeviceEnumerator *enumerator) override;
>  
>  private:
> -       int processControl(ControlList *controls, unsigned int id,
> -                          const ControlValue &value);
> +       int processControl(UVCCameraData *data, ControlList *controls,
> +                          unsigned int id, const ControlValue &value);
>         int processControls(UVCCameraData *data, Request *request);
>  
>         bool acquireDevice(Camera *camera) override;
> @@ -297,8 +297,8 @@ void PipelineHandlerUVC::stopDevice(Camera *camera)
>         data->video_->releaseBuffers();
>  }
>  
> -int PipelineHandlerUVC::processControl(ControlList *controls, unsigned int id,
> -                                      const ControlValue &value)
> +int PipelineHandlerUVC::processControl(UVCCameraData *data, ControlList *controls,
> +                                      unsigned int id, const ControlValue &value)
>  {
>         uint32_t cid;
>  
> @@ -342,10 +342,30 @@ int PipelineHandlerUVC::processControl(ControlList *controls, unsigned int id,
>         }
>  
>         case V4L2_CID_EXPOSURE_AUTO: {
> -               int32_t ivalue = value.get<bool>()
> -                              ? V4L2_EXPOSURE_APERTURE_PRIORITY
> -                              : V4L2_EXPOSURE_MANUAL;
> -               controls->set(V4L2_CID_EXPOSURE_AUTO, ivalue);
> +               v4l2_exposure_auto_type exposureMode = {};
> +
> +               switch (value.get<int32_t>()) {
> +               case controls::ExposureTimeModeAuto:
> +                       if (data->availableExposureModes_[V4L2_EXPOSURE_AUTO])
> +                               exposureMode = V4L2_EXPOSURE_AUTO;
> +                       else if (data->availableExposureModes_[V4L2_EXPOSURE_APERTURE_PRIORITY])
> +                               exposureMode = V4L2_EXPOSURE_APERTURE_PRIORITY;
> +                       else

Is this really an impossible to reach code path ? Or can a rogue
application 'decide' to try to set an unsupported mode just to see what
would happen ?

> +                               ASSERT(false);
> +                       break;
> +               case controls::ExposureTimeModeManual:
> +                       if (data->availableExposureModes_[V4L2_EXPOSURE_MANUAL])
> +                               exposureMode = V4L2_EXPOSURE_MANUAL;
> +                       else if (data->availableExposureModes_[V4L2_EXPOSURE_SHUTTER_PRIORITY])
> +                               exposureMode = V4L2_EXPOSURE_SHUTTER_PRIORITY;
> +                       else
> +                               ASSERT(false);
> +                       break;
> +               default:
> +                       return -EINVAL;
> +               }
> +
> +               controls->set(V4L2_CID_EXPOSURE_AUTO, exposureMode);
>                 break;
>         }
>  
> @@ -383,7 +403,7 @@ int PipelineHandlerUVC::processControls(UVCCameraData *data, Request *request)
>         ControlList controls(data->video_->controls());
>  
>         for (const auto &[id, value] : request->controls())
> -               processControl(&controls, id, value);
> +               processControl(data, &controls, id, value);
>  
>         for (const auto &ctrl : controls)
>                 LOG(UVC, Debug)
> -- 
> 2.48.1
> 
>