[PATCH v3 4/4] libcamera: pipeline: uvcvideo: Fix `ExposureTime` control handling

[Jacopo Mondi]

On Fri, Mar 21, 2025 at 03:33:59PM +0100, Barnabás Pőcze wrote:
> Hi
>
> 2025. 03. 21. 15:17 keltezéssel, Jacopo Mondi írta:
> > Hi Barnabás
> >
> > On Fri, Mar 14, 2025 at 06:42:48PM +0100, Barnabás Pőcze wrote:
> > > The documentation of `ExposureTime` states that its value is ignored if
> > > `ExposureTimeMode` is not manual. This is currently not handled, and if
> > > `ExposureTimeMode` is automatic and `ExposureTime` is set, then the
> > > controls will be rejected, as expected.
> > >
> > > Only try to set `V4L2_CID_EXPOSURE_ABSOLUTE` if the current exposure mode
> > > is manual. To be able to handle requests that set both `ExposureTime{,Mode}`,
> > > process `ExposureTimeMode` first directly in `processControls()`, and store
> > > this new mode in a temporary location. Then have `processControl()` act on
> > > this temporary state, and only persist the temporary state if `setControls()`
> > > on the video device succeeds.
> > >
> > > Bug: https://bugs.libcamera.org/show_bug.cgi?id=242
> > > Signed-off-by: Barnabás Pőcze <barnabas.pocze at ideasonboard.com>
> > > ---
> > >   src/libcamera/pipeline/uvcvideo/uvcvideo.cpp | 52 ++++++++++++--------
> > >   1 file changed, 31 insertions(+), 21 deletions(-)
> > >
> > > diff --git a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > > index 7d882ebe1..22d286e49 100644
> > > --- a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > > +++ b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > > @@ -108,7 +108,7 @@ public:
> > >   	bool match(DeviceEnumerator *enumerator) override;
> > >
> > >   private:
> > > -	int processControl(const UVCCameraData *data, ControlList *controls,
> > > +	int processControl(const UVCCameraData::State &state, ControlList *controls,
> > >   			   unsigned int id, const ControlValue &value);
> > >   	int processControls(UVCCameraData *data, Request *request);
> > >
> > > @@ -333,7 +333,7 @@ void PipelineHandlerUVC::stopDevice(Camera *camera)
> > >   	data->state_.reset();
> > >   }
> > >
> > > -int PipelineHandlerUVC::processControl(const UVCCameraData *data, ControlList *controls,
> > > +int PipelineHandlerUVC::processControl(const UVCCameraData::State &state, ControlList *controls,
> > >   				       unsigned int id, const ControlValue &value)
> > >   {
> > >   	uint32_t cid;
> > > @@ -378,26 +378,13 @@ int PipelineHandlerUVC::processControl(const UVCCameraData *data, ControlList *c
> > >   	}
> > >
> > >   	case V4L2_CID_EXPOSURE_AUTO: {
> > > -		std::optional<v4l2_exposure_auto_type> mode;
> > > -
> > > -		switch (value.get<int32_t>()) {
> > > -		case controls::ExposureTimeModeAuto:
> > > -			mode = data->autoExposureMode_;
> > > -			break;
> > > -		case controls::ExposureTimeModeManual:
> > > -			mode = data->manualExposureMode_;
> > > -			break;
> > > -		}
> > > -
> > > -		if (!mode)
> > > -			return -EINVAL;
> > > -
> > > -		controls->set(V4L2_CID_EXPOSURE_AUTO, static_cast<int32_t>(*mode));
> > > +		/* Handled directly in `processControls()`. */
> > >   		break;
> > >   	}
> > >
> > >   	case V4L2_CID_EXPOSURE_ABSOLUTE:
> > > -		controls->set(cid, value.get<int32_t>() / 100);
> > > +		if (state.exp == controls::ExposureTimeModeManual)
> > > +			controls->set(cid, value.get<int32_t>() / 100);
> > >   		break;
> > >
> > >   	case V4L2_CID_CONTRAST:
> > > @@ -428,9 +415,30 @@ int PipelineHandlerUVC::processControl(const UVCCameraData *data, ControlList *c
> > >   int PipelineHandlerUVC::processControls(UVCCameraData *data, Request *request)
> > >   {
> > >   	ControlList controls(data->video_->controls());
> > > +	const auto &reqControls = request->controls();
> > > +	auto newState = data->state_;
> > > +
> > > +	if (const auto exp = reqControls.get(controls::ExposureTimeMode)) {
> > > +		std::optional<v4l2_exposure_auto_type> mode;
> > >
> > > -	for (const auto &[id, value] : request->controls())
> > > -		processControl(data, &controls, id, value);
> > > +		switch (*exp) {
> > > +		case controls::ExposureTimeModeAuto:
> > > +			mode = data->autoExposureMode_;
> > > +			break;
> > > +		case controls::ExposureTimeModeManual:
> > > +			mode = data->manualExposureMode_;
> > > +			break;
> > > +		}
> > > +
> > > +		if (!mode)
> > > +			return -EINVAL;
> > > +
> > > +		controls.set(V4L2_CID_EXPOSURE_AUTO, static_cast<int32_t>(*mode));
> > > +		newState.exp = static_cast<controls::ExposureTimeModeEnum>(*exp);
> >
> > Can't you just update data->state before calling processControl to
> > avoid passing newState to that function ?
>
> If the controls cannot be set, then I think the state should not be changed, this
> is why it operates on a copy, which is only persisted after `setControls()` succeeds.

Which control ? Even if ABSOLUTE cannot be set (because we're in AUTO)
if the mode is changed, it should anyway be

Ah you mean to protect against a failure in

	int ret = data->video_->setControls(&controls);

?

Then yes, maybe keep the state update after this makes sense

Reviewed-by: Jacopo Mondi <jacopo.mondi at ideasonboard.com>

Thanks
  j


>
>
> Regards,
> Barnabás Pőcze
>
> >
> > > +	}
> > > +
> > > +	for (const auto &[id, value] : reqControls)
> > > +		processControl(newState, &controls, id, value);
> > >
> > >   	for (const auto &ctrl : controls)
> > >   		LOG(UVC, Debug)
> > > @@ -443,7 +451,9 @@ int PipelineHandlerUVC::processControls(UVCCameraData *data, Request *request)
> > >   		return ret < 0 ? ret : -EINVAL;
> > >   	}
> > >
> > > -	return ret;
> > > +	data->state_ = newState;
> > > +
> > > +	return 0;
> > >   }
> > >
> > >   int PipelineHandlerUVC::queueRequestDevice(Camera *camera, Request *request)
> > > --
> > > 2.48.1
> > >
>