[RFC PATCH v1] libcamera: pipeline: uvcvideo: Fix `ExposureTimeMode` control

[Jacopo Mondi]

Hi Barnabás

On Tue, Jan 28, 2025 at 12:14:01PM +0000, Barnabás Pőcze wrote:
> `ControlInfo(Span<const int32_t>{...})` calls the incorrect constructor
> of `ControlInfo`. The intended constructor to be called is
> `ControlInfo(Span<const ControlValue>, ...)` however that is not called
> because a span of `const int32_t` is passed. Instead, the constructor
> `ControlInfo(const ControlValue &min, const ControlValue &max, ...)`
> will be called.
>
> To fix this, simply pass a span of `ControlValue` instead.
>
> Furthermore, the mapping in `UVCCameraData::processControl()` is also not
> entirely correct because the control value is retrieved as a `bool`
> instead of - the correct type - `int32_t`. Additionally, the available
> modes are not taken into account.
>
> To fix this, stores the available modes for `V4L2_CID_EXPOSURE_AUTO`
> and select the appropriate mode based on the mapping established
> in the comment.
>
> Fixes: bad8d591f8acfa ("libcamera: uvcvideo: Register ExposureTimeMode control")
> Signed-off-by: Barnabás Pőcze <pobrn at protonmail.com>
> ---
>  src/libcamera/pipeline/uvcvideo/uvcvideo.cpp | 81 +++++++++++++-------
>  1 file changed, 53 insertions(+), 28 deletions(-)
>
> diff --git a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> index dedcac89b..7821cceb0 100644
> --- a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> +++ b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> @@ -6,6 +6,7 @@
>   */
>
>  #include <algorithm>
> +#include <bitset>
>  #include <cmath>
>  #include <fstream>
>  #include <map>
> @@ -58,6 +59,13 @@ public:
>  	Stream stream_;
>  	std::map<PixelFormat, std::vector<SizeRange>> formats_;
>
> +	std::bitset<std::max({
> +		V4L2_EXPOSURE_AUTO,
> +		V4L2_EXPOSURE_MANUAL,
> +		V4L2_EXPOSURE_APERTURE_PRIORITY,
> +		V4L2_EXPOSURE_SHUTTER_PRIORITY,
> +	}) + 1> availableExposureModes_;
> +

I presume a bitset is used for efficiency ?


>  private:
>  	bool generateId();
>
> @@ -95,8 +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;
> @@ -289,8 +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;
>
> @@ -334,10 +342,27 @@ 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);
> +		switch (value.get<int32_t>()) {
> +		case controls::ExposureTimeModeAuto:
> +			if (data->availableExposureModes_[V4L2_EXPOSURE_AUTO])
> +				controls->set(V4L2_CID_EXPOSURE_AUTO, V4L2_EXPOSURE_AUTO);
> +			else if (data->availableExposureModes_[V4L2_EXPOSURE_APERTURE_PRIORITY])
> +				controls->set(V4L2_CID_EXPOSURE_AUTO, V4L2_EXPOSURE_APERTURE_PRIORITY);
> +			else
> +				ASSERT(false);
> +			break;
> +		case controls::ExposureTimeModeManual:
> +			if (data->availableExposureModes_[V4L2_EXPOSURE_MANUAL])
> +				controls->set(V4L2_CID_EXPOSURE_AUTO, V4L2_EXPOSURE_MANUAL);
> +			else if (data->availableExposureModes_[V4L2_EXPOSURE_SHUTTER_PRIORITY])
> +				controls->set(V4L2_CID_EXPOSURE_AUTO, V4L2_EXPOSURE_SHUTTER_PRIORITY);
> +			else
> +				ASSERT(false);
> +			break;
> +		default:
> +			ASSERT(false);
> +			break;
> +		}
>  		break;
>  	}
>
> @@ -375,7 +400,7 @@ 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)
> @@ -725,25 +750,25 @@ void UVCCameraData::addControl(uint32_t cid, const ControlInfo &v4l2Info,
>  		 * ExposureTimeModeManual = { V4L2_EXPOSURE_MANUAL,
>  		 *			      V4L2_EXPOSURE_SHUTTER_PRIORITY }
>  		 */
> -		std::array<int32_t, 2> values{};
> -
> -		auto it = std::find_if(v4l2Values.begin(), v4l2Values.end(),
> -			[&](const ControlValue &val) {
> -				return (val.get<int32_t>() == V4L2_EXPOSURE_APERTURE_PRIORITY ||
> -					val.get<int32_t>() == V4L2_EXPOSURE_AUTO) ? true : false;
> -			});
> -		if (it != v4l2Values.end())
> -			values.back() = static_cast<int32_t>(controls::ExposureTimeModeAuto);
> -
> -		it = std::find_if(v4l2Values.begin(), v4l2Values.end(),
> -			[&](const ControlValue &val) {
> -				return (val.get<int32_t>() == V4L2_EXPOSURE_SHUTTER_PRIORITY ||
> -					val.get<int32_t>() == V4L2_EXPOSURE_MANUAL) ? true : false;
> -			});
> -		if (it != v4l2Values.end())
> -			values.back() = static_cast<int32_t>(controls::ExposureTimeModeManual);
> -
> -		info = ControlInfo{Span<int32_t>{values}, values[0]};
> +		for (const ControlValue &value : v4l2Values) {
> +			auto x = value.get<int32_t>();
> +			if (0 <= x && size_t(x) < availableExposureModes_.size())

Can x be negative ? It should come from enum v4l2_exposure_auto_type,
doesn't it ?

Also, isn't size_t(x) == 4, why do you need to check it against the
bitset size ?

> +				availableExposureModes_[x] = true;
> +		}
> +
> +		std::array<ControlValue, 2> values;
> +		std::size_t count = 0;
> +
> +		if (availableExposureModes_[V4L2_EXPOSURE_AUTO] || availableExposureModes_[V4L2_EXPOSURE_APERTURE_PRIORITY])
> +			values[count++] = controls::ExposureTimeModeAuto;
> +
> +		if (availableExposureModes_[V4L2_EXPOSURE_MANUAL] || availableExposureModes_[V4L2_EXPOSURE_SHUTTER_PRIORITY])
> +			values[count++] = controls::ExposureTimeModeManual;
> +
> +		if (count == 0)
> +			return;
> +
> +		info = ControlInfo{Span<const ControlValue>{ values.data(), count }, values[0]};
>  		break;
>  	}
>  	case V4L2_CID_EXPOSURE_ABSOLUTE:
> --
> 2.48.1
>
>