libcamera: camera_sensor: Validate driver support

The CameraSensor class requires the sensor driver to report
information through V4L2 controls and through the V4L2 selection API,
and uses that information to register Camera properties and to
construct CameraSensorInfo class instances to provide them to the IPA.

Currently, validation of the kernel support happens each time a
feature is requested, with slighly similar debug/error messages
output to the user in case a feature is not supported.

Rationalize this by validating the sensor driver requirements in a
single function

Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>

2 files changed, 85 insertions, 0 deletions

diff --git a/include/libcamera/internal/camera_sensor.h b/include/libcamera/internal/camera_sensor.h
index f80d8361..aee10aa6 100644
--- a/include/libcamera/internal/camera_sensor.h
+++ b/include/libcamera/internal/camera_sensor.h
@@ -69,6 +69,7 @@ protected:
 
 private:
 	int generateId();
+	int validateSensorDriver();
 	int initProperties();
 
 	const MediaEntity *entity_;
diff --git a/src/libcamera/camera_sensor.cpp b/src/libcamera/camera_sensor.cpp
index e786821d..048fcd6a 100644
--- a/src/libcamera/camera_sensor.cpp
+++ b/src/libcamera/camera_sensor.cpp
@@ -207,6 +207,10 @@ int CameraSensor::init()
 	 */
 	resolution_ = sizes_.back();
 
+	ret = validateSensorDriver();
+	if (ret)
+		return ret;
+
 	ret = initProperties();
 	if (ret)
 		return ret;
@@ -214,6 +218,86 @@ int CameraSensor::init()
 	return 0;
 }
 
+int CameraSensor::validateSensorDriver()
+{
+	/*
+	 * Make sure the sensor driver supports the mandatory controls
+	 * required by the CameraSensor class.
+	 * - V4L2_CID_PIXEL_RATE is used to calculate the sensor timings
+	 * - V4L2_CID_HBLANK is used to calculate the line length
+	 */
+	const std::vector<uint32_t> mandatoryControls{
+		V4L2_CID_PIXEL_RATE,
+		V4L2_CID_HBLANK,
+	};
+
+	ControlList ctrls = subdev_->getControls(mandatoryControls);
+	if (ctrls.empty()) {
+		LOG(CameraSensor, Error)
+			<< "Mandatory V4L2 controls not available";
+		LOG(CameraSensor, Error)
+			<< "The sensor kernel driver needs to be fixed";
+		LOG(CameraSensor, Error)
+			<< "See Documentation/sensor_driver_requirements.rst in the libcamera sources for more information";
+		return -EINVAL;
+	}
+
+	/*
+	 * Optional controls are used to register optional sensor properties. If
+	 * not present, some values will be defaulted.
+	 */
+	const std::vector<uint32_t> optionalControls{
+		V4L2_CID_CAMERA_ORIENTATION,
+		V4L2_CID_CAMERA_SENSOR_ROTATION,
+	};
+
+	ctrls = subdev_->getControls(optionalControls);
+	if (ctrls.empty())
+		LOG(CameraSensor, Debug) << "Optional V4L2 controls not supported";
+
+	/*
+	 * Make sure the required selection targets are supported.
+	 *
+	 * Failures in reading any of the targets are not deemed to be fatal,
+	 * but some properties and features, like constructing a
+	 * CameraSensorInfo for the IPA module, won't be supported.
+	 *
+	 * \todo Make support for selection targets mandatory as soon as all
+	 * test platforms have been updated.
+	 */
+	int err = 0;
+	Rectangle rect;
+	int ret = subdev_->getSelection(pad_, V4L2_SEL_TGT_CROP_BOUNDS, &rect);
+	if (ret) {
+		LOG(CameraSensor, Warning)
+			<< "Failed to retrieve the readable pixel array size";
+		err = -EINVAL;
+	}
+
+	ret = subdev_->getSelection(pad_, V4L2_SEL_TGT_CROP_DEFAULT, &rect);
+	if (ret) {
+		LOG(CameraSensor, Warning)
+			<< "Failed to retrieve the active pixel array size";
+		err = -EINVAL;
+	}
+
+	ret = subdev_->getSelection(pad_, V4L2_SEL_TGT_CROP, &rect);
+	if (ret) {
+		LOG(CameraSensor, Warning)
+			<< "Failed to retrieve the sensor crop rectangle";
+		err = -EINVAL;
+	}
+
+	if (err) {
+		LOG(CameraSensor, Warning)
+			<< "The sensor kernel driver needs to be fixed";
+		LOG(CameraSensor, Warning)
+			<< "See Documentation/sensor_driver_requirements.rst in the libcamera sources for more information";
+	}
+
+	return 0;
+}
+
 int CameraSensor::initProperties()
 {
 	/*