libcamera: camera_sensor: Restrict sensor info to raw sensors

YUV sensors don't provide the necessary information to fill
CameraSensorInfo, as they include an ISP and provide a higher-level API
that doesn't always expose low-level information. The CameraSensor class
makes low-level V4L2 controls mandatory for all sensors, which prevents
usage of YUV sensors with the simple pipeline handler.

Make CameraSensor::sensorInfo() available for raw sensors only. This
won't introduce any regression in pipeline handlers that currently use
the sensorInfo() function as they all operate with raw sensors, and
won't be a limitation for the simple pipeline handler as well as it
doesn't use sensor info. If part of the sensor info (such as the active
pixel array size for instance) becomes useful to expose for YUV sensors
in the future, the sensorInfo() function can be extended to report that
information only and skip data that is only available for raw sensors.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>

2 files changed, 37 insertions, 26 deletions

diff --git a/Documentation/sensor_driver_requirements.rst b/Documentation/sensor_driver_requirements.rst
index 590797f0..17841ddd 100644
--- a/Documentation/sensor_driver_requirements.rst
+++ b/Documentation/sensor_driver_requirements.rst
@@ -22,7 +22,7 @@ Mandatory Requirements
 
 The sensor driver is assumed to be fully compliant with the V4L2 specification.
 
-The sensor driver shall support the following V4L2 controls:
+For RAW sensors, the sensor driver shall support the following V4L2 controls:
 
 * `V4L2_CID_EXPOSURE`_
 * `V4L2_CID_HBLANK`_
diff --git a/src/libcamera/camera_sensor.cpp b/src/libcamera/camera_sensor.cpp
index 563e531e..9d5d4f99 100644
--- a/src/libcamera/camera_sensor.cpp
+++ b/src/libcamera/camera_sensor.cpp
@@ -277,28 +277,6 @@ int CameraSensor::init()
 int CameraSensor::validateSensorDriver()
 {
 	/*
-	 * Make sure the sensor driver supports the mandatory controls
-	 * required by the CameraSensor class.
-	 */
-	const std::vector<uint32_t> mandatoryControls{
-		V4L2_CID_EXPOSURE,
-		V4L2_CID_HBLANK,
-		V4L2_CID_PIXEL_RATE,
-		V4L2_CID_VBLANK,
-	};
-
-	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.
 	 */
@@ -307,7 +285,7 @@ int CameraSensor::validateSensorDriver()
 		V4L2_CID_CAMERA_SENSOR_ROTATION,
 	};
 
-	ctrls = subdev_->getControls(optionalControls);
+	ControlList ctrls = subdev_->getControls(optionalControls);
 	if (ctrls.empty())
 		LOG(CameraSensor, Debug) << "Optional V4L2 controls not supported";
 
@@ -357,6 +335,31 @@ int CameraSensor::validateSensorDriver()
 			<< "See Documentation/sensor_driver_requirements.rst in the libcamera sources for more information";
 	}
 
+	if (!bayerFormat_)
+		return 0;
+
+	/*
+	 * For raw sensors, make sure the sensor driver supports the controls
+	 * required by the CameraSensor class.
+	 */
+	const std::vector<uint32_t> mandatoryControls{
+		V4L2_CID_EXPOSURE,
+		V4L2_CID_HBLANK,
+		V4L2_CID_PIXEL_RATE,
+		V4L2_CID_VBLANK,
+	};
+
+	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;
+	}
+
 	return 0;
 }
 
@@ -693,13 +696,21 @@ int CameraSensor::setControls(ControlList *ctrls)
  * \brief Assemble and return the camera sensor info
  * \param[out] info The camera sensor info
  *
- * The CameraSensorInfo content is assembled by inspecting the currently
- * applied sensor configuration and the sensor static properties.
+ * This function fills \a info with information that describes the camera sensor
+ * and its current configuration. The information combines static data (such as
+ * the the sensor model or active pixel array size) and data specific to the
+ * current sensor configuration (such as the line length and pixel rate).
+ *
+ * Sensor information is only available for raw sensors. When called for a YUV
+ * sensor, this function returns -EINVAL.
  *
  * \return 0 on success, a negative error code otherwise
  */
 int CameraSensor::sensorInfo(CameraSensorInfo *info) const
 {
+	if (!bayerFormat_)
+		return -EINVAL;
+
 	info->model = model();
 
 	/*