libcamera: camera_sensor: Create abstract base class

With a camera sensor factory in place, the next step is to create an
abstract base class that all camera sensors implement, providing a
uniform API to pipeline handler. Turn all public functions of the
CameraSensor class into pure virtual functions, and move the
implementation to the CameraSensorLegacy class.

Part of the code is likely worth keeping as common helpers in a base
class. However, to follow the principle of not designing helpers with a
single user, this commit moves the whole implementation. Common helpers
will be introduced later, along with other CameraSensor subclasses.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>

5 files changed, 1110 insertions, 1036 deletions

diff --git a/Documentation/Doxyfile-internal.in b/Documentation/Doxyfile-internal.in
index cf982553..b5ad7e7f 100644
--- a/Documentation/Doxyfile-internal.in
+++ b/Documentation/Doxyfile-internal.in
@@ -25,6 +25,7 @@ EXCLUDE                = @TOP_SRCDIR@/include/libcamera/base/span.h \
                          @TOP_SRCDIR@/src/libcamera/device_enumerator_udev.cpp \
                          @TOP_SRCDIR@/src/libcamera/ipc_pipe_unixsocket.cpp \
                          @TOP_SRCDIR@/src/libcamera/pipeline/ \
+                         @TOP_SRCDIR@/src/libcamera/sensor/camera_sensor_legacy.cpp \
                          @TOP_SRCDIR@/src/libcamera/tracepoints.cpp \
                          @TOP_BUILDDIR@/include/libcamera/internal/tracepoints.h \
                          @TOP_BUILDDIR@/include/libcamera/ipa/soft_ipa_interface.h \
diff --git a/include/libcamera/internal/camera_sensor.h b/include/libcamera/internal/camera_sensor.h
index 2d6cb697..7713aea0 100644
--- a/include/libcamera/internal/camera_sensor.h
+++ b/include/libcamera/internal/camera_sensor.h
@@ -9,10 +9,10 @@
 
 #include <memory>
 #include <string>
+#include <variant>
 #include <vector>
 
 #include <libcamera/base/class.h>
-#include <libcamera/base/log.h>
 
 #include <libcamera/control_ids.h>
 #include <libcamera/controls.h>
@@ -20,8 +20,6 @@
 #include <libcamera/orientation.h>
 #include <libcamera/transform.h>
 
-#include <libcamera/ipa/core_ipa_interface.h>
-
 #include "libcamera/internal/bayer_format.h"
 #include "libcamera/internal/v4l2_subdevice.h"
 
@@ -31,105 +29,62 @@ class CameraLens;
 class MediaEntity;
 class SensorConfiguration;
 
-struct CameraSensorProperties;
-
 enum class Orientation;
 
-class CameraSensor : protected Loggable
+struct IPACameraSensorInfo;
+
+class CameraSensor
 {
 public:
-	~CameraSensor();
-
-	int init();
+	virtual ~CameraSensor();
 
-	const std::string &model() const { return model_; }
-	const std::string &id() const { return id_; }
+	virtual const std::string &model() const = 0;
+	virtual const std::string &id() const = 0;
 
-	const MediaEntity *entity() const { return entity_; }
-	V4L2Subdevice *device() { return subdev_.get(); }
+	virtual const MediaEntity *entity() const = 0;
+	virtual V4L2Subdevice *device() = 0;
 
-	CameraLens *focusLens() { return focusLens_.get(); }
+	virtual CameraLens *focusLens() = 0;
 
-	const std::vector<unsigned int> &mbusCodes() const { return mbusCodes_; }
-	std::vector<Size> sizes(unsigned int mbusCode) const;
-	Size resolution() const;
+	virtual const std::vector<unsigned int> &mbusCodes() const = 0;
+	virtual std::vector<Size> sizes(unsigned int mbusCode) const = 0;
+	virtual Size resolution() const = 0;
 
-	V4L2SubdeviceFormat getFormat(const std::vector<unsigned int> &mbusCodes,
-				      const Size &size) const;
-	int setFormat(V4L2SubdeviceFormat *format,
-		      Transform transform = Transform::Identity);
-	int tryFormat(V4L2SubdeviceFormat *format) const;
+	virtual V4L2SubdeviceFormat
+	getFormat(const std::vector<unsigned int> &mbusCodes,
+		  const Size &size) const = 0;
+	virtual int setFormat(V4L2SubdeviceFormat *format,
+			      Transform transform = Transform::Identity) = 0;
+	virtual int tryFormat(V4L2SubdeviceFormat *format) const = 0;
 
-	int applyConfiguration(const SensorConfiguration &config,
-			       Transform transform = Transform::Identity,
-			       V4L2SubdeviceFormat *sensorFormat = nullptr);
+	virtual int applyConfiguration(const SensorConfiguration &config,
+				       Transform transform = Transform::Identity,
+				       V4L2SubdeviceFormat *sensorFormat = nullptr) = 0;
 
-	const ControlList &properties() const { return properties_; }
-	int sensorInfo(IPACameraSensorInfo *info) const;
-	Transform computeTransform(Orientation *orientation) const;
-	BayerFormat::Order bayerOrder(Transform t) const;
+	virtual const ControlList &properties() const = 0;
+	virtual int sensorInfo(IPACameraSensorInfo *info) const = 0;
+	virtual Transform computeTransform(Orientation *orientation) const = 0;
+	virtual BayerFormat::Order bayerOrder(Transform t) const = 0;
 
-	const ControlInfoMap &controls() const;
-	ControlList getControls(const std::vector<uint32_t> &ids);
-	int setControls(ControlList *ctrls);
-
-	const std::vector<controls::draft::TestPatternModeEnum> &testPatternModes() const
-	{
-		return testPatternModes_;
-	}
-	int setTestPatternMode(controls::draft::TestPatternModeEnum mode);
+	virtual const ControlInfoMap &controls() const = 0;
+	virtual ControlList getControls(const std::vector<uint32_t> &ids) = 0;
+	virtual int setControls(ControlList *ctrls) = 0;
 
-protected:
-	explicit CameraSensor(const MediaEntity *entity);
-	std::string logPrefix() const override;
-
-private:
-	LIBCAMERA_DISABLE_COPY(CameraSensor)
-
-	int generateId();
-	int validateSensorDriver();
-	void initVimcDefaultProperties();
-	void initStaticProperties();
-	void initTestPatternModes();
-	int initProperties();
-	int discoverAncillaryDevices();
-	int applyTestPatternMode(controls::draft::TestPatternModeEnum mode);
-
-	const MediaEntity *entity_;
-	std::unique_ptr<V4L2Subdevice> subdev_;
-	unsigned int pad_;
-
-	const CameraSensorProperties *staticProps_;
-
-	std::string model_;
-	std::string id_;
-
-	V4L2Subdevice::Formats formats_;
-	std::vector<unsigned int> mbusCodes_;
-	std::vector<Size> sizes_;
-	std::vector<controls::draft::TestPatternModeEnum> testPatternModes_;
-	controls::draft::TestPatternModeEnum testPatternMode_;
-
-	Size pixelArraySize_;
-	Rectangle activeArea_;
-	const BayerFormat *bayerFormat_;
-	bool supportFlips_;
-	bool flipsAlterBayerOrder_;
-	Orientation mountingOrientation_;
-
-	ControlList properties_;
-
-	std::unique_ptr<CameraLens> focusLens_;
+	virtual const std::vector<controls::draft::TestPatternModeEnum> &
+	testPatternModes() const = 0;
+	virtual int setTestPatternMode(controls::draft::TestPatternModeEnum mode) = 0;
 };
 
 class CameraSensorFactoryBase
 {
 public:
-	CameraSensorFactoryBase();
+	CameraSensorFactoryBase(const char *name);
 	virtual ~CameraSensorFactoryBase() = default;
 
 	static std::unique_ptr<CameraSensor> create(MediaEntity *entity);
 
+	const std::string &name() const { return name_; }
+
 private:
 	LIBCAMERA_DISABLE_COPY_AND_MOVE(CameraSensorFactoryBase)
 
@@ -137,35 +92,30 @@ private:
 
 	static void registerFactory(CameraSensorFactoryBase *factory);
 
-	virtual bool match(const MediaEntity *entity) const = 0;
+	virtual std::variant<std::unique_ptr<CameraSensor>, int>
+	match(MediaEntity *entity) const = 0;
 
-	virtual std::unique_ptr<CameraSensor>
-	createInstance(MediaEntity *entity) const = 0;
+	std::string name_;
 };
 
 template<typename _CameraSensor>
 class CameraSensorFactory final : public CameraSensorFactoryBase
 {
 public:
-	CameraSensorFactory()
-		: CameraSensorFactoryBase()
+	CameraSensorFactory(const char *name)
+		: CameraSensorFactoryBase(name)
 	{
 	}
 
 private:
-	bool match(const MediaEntity *entity) const override
+	std::variant<std::unique_ptr<CameraSensor>, int>
+	match(MediaEntity *entity) const override
 	{
 		return _CameraSensor::match(entity);
 	}
-
-	std::unique_ptr<CameraSensor>
-	createInstance(MediaEntity *entity) const override
-	{
-		return _CameraSensor::create(entity);
-	}
 };
 
 #define REGISTER_CAMERA_SENSOR(sensor) \
-static CameraSensorFactory<sensor> global_##sensor##Factory{};
+static CameraSensorFactory<sensor> global_##sensor##Factory{ #sensor };
 
 } /* namespace libcamera */
diff --git a/src/libcamera/sensor/camera_sensor.cpp b/src/libcamera/sensor/camera_sensor.cpp
index 025c9eef..951ebd2c 100644
--- a/src/libcamera/sensor/camera_sensor.cpp
+++ b/src/libcamera/sensor/camera_sensor.cpp
@@ -7,24 +7,12 @@
 
 #include "libcamera/internal/camera_sensor.h"
 
-#include <algorithm>
-#include <cmath>
-#include <float.h>
-#include <limits.h>
-#include <map>
-#include <string.h>
+#include <memory>
+#include <vector>
 
-#include <libcamera/base/utils.h>
+#include <libcamera/base/log.h>
 
-#include <libcamera/camera.h>
-#include <libcamera/orientation.h>
-#include <libcamera/property_ids.h>
-
-#include "libcamera/internal/bayer_format.h"
-#include "libcamera/internal/camera_lens.h"
-#include "libcamera/internal/camera_sensor_properties.h"
-#include "libcamera/internal/media_device.h"
-#include "libcamera/internal/sysfs.h"
+#include "libcamera/internal/media_object.h"
 
 /**
  * \file camera_sensor.h
@@ -37,537 +25,16 @@ LOG_DEFINE_CATEGORY(CameraSensor)
 
 /**
  * \class CameraSensor
- * \brief A camera sensor based on V4L2 subdevices
+ * \brief A abstract camera sensor
  *
  * The CameraSensor class eases handling of sensors for pipeline handlers by
- * hiding the details of the V4L2 subdevice kernel API and caching sensor
- * information.
- *
- * The implementation is currently limited to sensors that expose a single V4L2
- * subdevice with a single pad. It will be extended to support more complex
- * devices as the needs arise.
- */
-
-/**
- * \brief Construct a CameraSensor
- * \param[in] entity The media entity backing the camera sensor
- *
- * Once constructed the instance must be initialized with init().
+ * hiding the details of the kernel API and caching sensor information.
  */
-CameraSensor::CameraSensor(const MediaEntity *entity)
-	: entity_(entity), pad_(UINT_MAX), staticProps_(nullptr),
-	  bayerFormat_(nullptr), supportFlips_(false),
-	  flipsAlterBayerOrder_(false), properties_(properties::properties)
-{
-}
 
 /**
  * \brief Destroy a CameraSensor
  */
-CameraSensor::~CameraSensor()
-{
-}
-
-/**
- * \brief Initialize the camera sensor instance
- *
- * This function performs the initialisation steps of the CameraSensor that may
- * fail. It shall be called once and only once after constructing the instance.
- *
- * \return 0 on success or a negative error code otherwise
- */
-int CameraSensor::init()
-{
-	for (const MediaPad *pad : entity_->pads()) {
-		if (pad->flags() & MEDIA_PAD_FL_SOURCE) {
-			pad_ = pad->index();
-			break;
-		}
-	}
-
-	if (pad_ == UINT_MAX) {
-		LOG(CameraSensor, Error)
-			<< "Sensors with more than one pad are not supported";
-		return -EINVAL;
-	}
-
-	switch (entity_->function()) {
-	case MEDIA_ENT_F_CAM_SENSOR:
-	case MEDIA_ENT_F_PROC_VIDEO_ISP:
-		break;
-
-	default:
-		LOG(CameraSensor, Error)
-			<< "Invalid sensor function "
-			<< utils::hex(entity_->function());
-		return -EINVAL;
-	}
-
-	/* Create and open the subdev. */
-	subdev_ = std::make_unique<V4L2Subdevice>(entity_);
-	int ret = subdev_->open();
-	if (ret < 0)
-		return ret;
-
-	/*
-	 * Clear any flips to be sure we get the "native" Bayer order. This is
-	 * harmless for sensors where the flips don't affect the Bayer order.
-	 */
-	ControlList ctrls(subdev_->controls());
-	if (subdev_->controls().find(V4L2_CID_HFLIP) != subdev_->controls().end())
-		ctrls.set(V4L2_CID_HFLIP, 0);
-	if (subdev_->controls().find(V4L2_CID_VFLIP) != subdev_->controls().end())
-		ctrls.set(V4L2_CID_VFLIP, 0);
-	subdev_->setControls(&ctrls);
-
-	/* Enumerate, sort and cache media bus codes and sizes. */
-	formats_ = subdev_->formats(pad_);
-	if (formats_.empty()) {
-		LOG(CameraSensor, Error) << "No image format found";
-		return -EINVAL;
-	}
-
-	mbusCodes_ = utils::map_keys(formats_);
-	std::sort(mbusCodes_.begin(), mbusCodes_.end());
-
-	for (const auto &format : formats_) {
-		const std::vector<SizeRange> &ranges = format.second;
-		std::transform(ranges.begin(), ranges.end(), std::back_inserter(sizes_),
-			       [](const SizeRange &range) { return range.max; });
-	}
-
-	std::sort(sizes_.begin(), sizes_.end());
-
-	/* Remove duplicates. */
-	auto last = std::unique(sizes_.begin(), sizes_.end());
-	sizes_.erase(last, sizes_.end());
-
-	/*
-	 * VIMC is a bit special, as it does not yet support all the mandatory
-	 * requirements regular sensors have to respect.
-	 *
-	 * Do not validate the driver if it's VIMC and initialize the sensor
-	 * properties with static information.
-	 *
-	 * \todo Remove the special case once the VIMC driver has been
-	 * updated in all test platforms.
-	 */
-	if (entity_->device()->driver() == "vimc") {
-		initVimcDefaultProperties();
-
-		ret = initProperties();
-		if (ret)
-			return ret;
-
-		return discoverAncillaryDevices();
-	}
-
-	/* Get the color filter array pattern (only for RAW sensors). */
-	for (unsigned int mbusCode : mbusCodes_) {
-		const BayerFormat &bayerFormat = BayerFormat::fromMbusCode(mbusCode);
-		if (bayerFormat.isValid()) {
-			bayerFormat_ = &bayerFormat;
-			break;
-		}
-	}
-
-	ret = validateSensorDriver();
-	if (ret)
-		return ret;
-
-	ret = initProperties();
-	if (ret)
-		return ret;
-
-	ret = discoverAncillaryDevices();
-	if (ret)
-		return ret;
-
-	/*
-	 * Set HBLANK to the minimum to start with a well-defined line length,
-	 * allowing IPA modules that do not modify HBLANK to use the sensor
-	 * minimum line length in their calculations.
-	 */
-	const struct v4l2_query_ext_ctrl *hblankInfo = subdev_->controlInfo(V4L2_CID_HBLANK);
-	if (hblankInfo && !(hblankInfo->flags & V4L2_CTRL_FLAG_READ_ONLY)) {
-		ControlList ctrl(subdev_->controls());
-
-		ctrl.set(V4L2_CID_HBLANK, static_cast<int32_t>(hblankInfo->minimum));
-		ret = subdev_->setControls(&ctrl);
-		if (ret)
-			return ret;
-	}
-
-	return applyTestPatternMode(controls::draft::TestPatternModeEnum::TestPatternModeOff);
-}
-
-int CameraSensor::generateId()
-{
-	const std::string devPath = subdev_->devicePath();
-
-	/* Try to get ID from firmware description. */
-	id_ = sysfs::firmwareNodePath(devPath);
-	if (!id_.empty())
-		return 0;
-
-	/*
-	 * Virtual sensors not described in firmware
-	 *
-	 * Verify it's a platform device and construct ID from the device path
-	 * and model of sensor.
-	 */
-	if (devPath.find("/sys/devices/platform/", 0) == 0) {
-		id_ = devPath.substr(strlen("/sys/devices/")) + " " + model();
-		return 0;
-	}
-
-	LOG(CameraSensor, Error) << "Can't generate sensor ID";
-	return -EINVAL;
-}
-
-int CameraSensor::validateSensorDriver()
-{
-	int err = 0;
-
-	/*
-	 * Optional controls are used to register optional sensor properties. If
-	 * not present, some values will be defaulted.
-	 */
-	static constexpr uint32_t optionalControls[] = {
-		V4L2_CID_CAMERA_SENSOR_ROTATION,
-	};
-
-	const ControlIdMap &controls = subdev_->controls().idmap();
-	for (uint32_t ctrl : optionalControls) {
-		if (!controls.count(ctrl))
-			LOG(CameraSensor, Debug)
-				<< "Optional V4L2 control " << utils::hex(ctrl)
-				<< " not supported";
-	}
-
-	/*
-	 * Recommended controls are similar to optional controls, but will
-	 * become mandatory in the near future. Be loud if they're missing.
-	 */
-	static constexpr uint32_t recommendedControls[] = {
-		V4L2_CID_CAMERA_ORIENTATION,
-	};
-
-	for (uint32_t ctrl : recommendedControls) {
-		if (!controls.count(ctrl)) {
-			LOG(CameraSensor, Warning)
-				<< "Recommended V4L2 control " << utils::hex(ctrl)
-				<< " not supported";
-			err = -EINVAL;
-		}
-	}
-
-	/*
-	 * Verify if sensor supports horizontal/vertical flips
-	 *
-	 * \todo Handle horizontal and vertical flips independently.
-	 */
-	const struct v4l2_query_ext_ctrl *hflipInfo = subdev_->controlInfo(V4L2_CID_HFLIP);
-	const struct v4l2_query_ext_ctrl *vflipInfo = subdev_->controlInfo(V4L2_CID_VFLIP);
-	if (hflipInfo && !(hflipInfo->flags & V4L2_CTRL_FLAG_READ_ONLY) &&
-	    vflipInfo && !(vflipInfo->flags & V4L2_CTRL_FLAG_READ_ONLY)) {
-		supportFlips_ = true;
-
-		if (hflipInfo->flags & V4L2_CTRL_FLAG_MODIFY_LAYOUT ||
-		    vflipInfo->flags & V4L2_CTRL_FLAG_MODIFY_LAYOUT)
-			flipsAlterBayerOrder_ = true;
-	}
-
-	if (!supportFlips_)
-		LOG(CameraSensor, Debug)
-			<< "Camera sensor does not support horizontal/vertical flip";
-
-	/*
-	 * 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
-	 * IPACameraSensorInfo for the IPA module, won't be supported.
-	 *
-	 * \todo Make support for selection targets mandatory as soon as all
-	 * test platforms have been updated.
-	 */
-	Rectangle rect;
-	int ret = subdev_->getSelection(pad_, V4L2_SEL_TGT_CROP_BOUNDS, &rect);
-	if (ret) {
-		/*
-		 * Default the pixel array size to the largest size supported
-		 * by the sensor. The sizes_ vector is sorted in ascending
-		 * order, the largest size is thus the last element.
-		 */
-		pixelArraySize_ = sizes_.back();
-
-		LOG(CameraSensor, Warning)
-			<< "The PixelArraySize property has been defaulted to "
-			<< pixelArraySize_;
-		err = -EINVAL;
-	} else {
-		pixelArraySize_ = rect.size();
-	}
-
-	ret = subdev_->getSelection(pad_, V4L2_SEL_TGT_CROP_DEFAULT, &activeArea_);
-	if (ret) {
-		activeArea_ = Rectangle(pixelArraySize_);
-		LOG(CameraSensor, Warning)
-			<< "The PixelArrayActiveAreas property has been defaulted to "
-			<< activeArea_;
-		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";
-	}
-
-	if (!bayerFormat_)
-		return 0;
-
-	/*
-	 * For raw sensors, make sure the sensor driver supports the controls
-	 * required by the CameraSensor class.
-	 */
-	static constexpr uint32_t mandatoryControls[] = {
-		V4L2_CID_ANALOGUE_GAIN,
-		V4L2_CID_EXPOSURE,
-		V4L2_CID_HBLANK,
-		V4L2_CID_PIXEL_RATE,
-		V4L2_CID_VBLANK,
-	};
-
-	err = 0;
-	for (uint32_t ctrl : mandatoryControls) {
-		if (!controls.count(ctrl)) {
-			LOG(CameraSensor, Error)
-				<< "Mandatory V4L2 control " << utils::hex(ctrl)
-				<< " not available";
-			err = -EINVAL;
-		}
-	}
-
-	if (err) {
-		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 err;
-	}
-
-	return 0;
-}
-
-/*
- * \brief Initialize properties that cannot be intialized by the
- * regular initProperties() function for VIMC
- */
-void CameraSensor::initVimcDefaultProperties()
-{
-	/* Use the largest supported size. */
-	pixelArraySize_ = sizes_.back();
-	activeArea_ = Rectangle(pixelArraySize_);
-}
-
-void CameraSensor::initStaticProperties()
-{
-	staticProps_ = CameraSensorProperties::get(model_);
-	if (!staticProps_)
-		return;
-
-	/* Register the properties retrieved from the sensor database. */
-	properties_.set(properties::UnitCellSize, staticProps_->unitCellSize);
-
-	initTestPatternModes();
-}
-
-void CameraSensor::initTestPatternModes()
-{
-	const auto &v4l2TestPattern = controls().find(V4L2_CID_TEST_PATTERN);
-	if (v4l2TestPattern == controls().end()) {
-		LOG(CameraSensor, Debug) << "V4L2_CID_TEST_PATTERN is not supported";
-		return;
-	}
-
-	const auto &testPatternModes = staticProps_->testPatternModes;
-	if (testPatternModes.empty()) {
-		/*
-		 * The camera sensor supports test patterns but we don't know
-		 * how to map them so this should be fixed.
-		 */
-		LOG(CameraSensor, Debug) << "No static test pattern map for \'"
-					 << model() << "\'";
-		return;
-	}
-
-	/*
-	 * Create a map that associates the V4L2 control index to the test
-	 * pattern mode by reversing the testPatternModes map provided by the
-	 * camera sensor properties. This makes it easier to verify if the
-	 * control index is supported in the below for loop that creates the
-	 * list of supported test patterns.
-	 */
-	std::map<int32_t, controls::draft::TestPatternModeEnum> indexToTestPatternMode;
-	for (const auto &it : testPatternModes)
-		indexToTestPatternMode[it.second] = it.first;
-
-	for (const ControlValue &value : v4l2TestPattern->second.values()) {
-		const int32_t index = value.get<int32_t>();
-
-		const auto it = indexToTestPatternMode.find(index);
-		if (it == indexToTestPatternMode.end()) {
-			LOG(CameraSensor, Debug)
-				<< "Test pattern mode " << index << " ignored";
-			continue;
-		}
-
-		testPatternModes_.push_back(it->second);
-	}
-}
-
-int CameraSensor::initProperties()
-{
-	model_ = subdev_->model();
-	properties_.set(properties::Model, utils::toAscii(model_));
-
-	/* Generate a unique ID for the sensor. */
-	int ret = generateId();
-	if (ret)
-		return ret;
-
-	/* Initialize the static properties from the sensor database. */
-	initStaticProperties();
-
-	/* Retrieve and register properties from the kernel interface. */
-	const ControlInfoMap &controls = subdev_->controls();
-
-	const auto &orientation = controls.find(V4L2_CID_CAMERA_ORIENTATION);
-	if (orientation != controls.end()) {
-		int32_t v4l2Orientation = orientation->second.def().get<int32_t>();
-		int32_t propertyValue;
-
-		switch (v4l2Orientation) {
-		default:
-			LOG(CameraSensor, Warning)
-				<< "Unsupported camera location "
-				<< v4l2Orientation << ", setting to External";
-			[[fallthrough]];
-		case V4L2_CAMERA_ORIENTATION_EXTERNAL:
-			propertyValue = properties::CameraLocationExternal;
-			break;
-		case V4L2_CAMERA_ORIENTATION_FRONT:
-			propertyValue = properties::CameraLocationFront;
-			break;
-		case V4L2_CAMERA_ORIENTATION_BACK:
-			propertyValue = properties::CameraLocationBack;
-			break;
-		}
-		properties_.set(properties::Location, propertyValue);
-	} else {
-		LOG(CameraSensor, Warning) << "Failed to retrieve the camera location";
-	}
-
-	const auto &rotationControl = controls.find(V4L2_CID_CAMERA_SENSOR_ROTATION);
-	if (rotationControl != controls.end()) {
-		int32_t propertyValue = rotationControl->second.def().get<int32_t>();
-
-		/*
-		 * Cache the Transform associated with the camera mounting
-		 * rotation for later use in computeTransform().
-		 */
-		bool success;
-		mountingOrientation_ = orientationFromRotation(propertyValue, &success);
-		if (!success) {
-			LOG(CameraSensor, Warning)
-				<< "Invalid rotation of " << propertyValue
-				<< " degrees - ignoring";
-			mountingOrientation_ = Orientation::Rotate0;
-		}
-
-		properties_.set(properties::Rotation, propertyValue);
-	} else {
-		LOG(CameraSensor, Warning)
-			<< "Rotation control not available, default to 0 degrees";
-		properties_.set(properties::Rotation, 0);
-		mountingOrientation_ = Orientation::Rotate0;
-	}
-
-	properties_.set(properties::PixelArraySize, pixelArraySize_);
-	properties_.set(properties::PixelArrayActiveAreas, { activeArea_ });
-
-	/* Color filter array pattern, register only for RAW sensors. */
-	if (bayerFormat_) {
-		int32_t cfa;
-		switch (bayerFormat_->order) {
-		case BayerFormat::BGGR:
-			cfa = properties::draft::BGGR;
-			break;
-		case BayerFormat::GBRG:
-			cfa = properties::draft::GBRG;
-			break;
-		case BayerFormat::GRBG:
-			cfa = properties::draft::GRBG;
-			break;
-		case BayerFormat::RGGB:
-			cfa = properties::draft::RGGB;
-			break;
-		case BayerFormat::MONO:
-			cfa = properties::draft::MONO;
-			break;
-		}
-
-		properties_.set(properties::draft::ColorFilterArrangement, cfa);
-	}
-
-	return 0;
-}
-
-/**
- * \brief Check for and initialise any ancillary devices
- *
- * Sensors sometimes have ancillary devices such as a Lens or Flash that could
- * be linked to their MediaEntity by the kernel. Search for and handle any
- * such device.
- *
- * \todo Handle MEDIA_ENT_F_FLASH too.
- */
-int CameraSensor::discoverAncillaryDevices()
-{
-	int ret;
-
-	for (MediaEntity *ancillary : entity_->ancillaryEntities()) {
-		switch (ancillary->function()) {
-		case MEDIA_ENT_F_LENS:
-			focusLens_ = std::make_unique<CameraLens>(ancillary);
-			ret = focusLens_->init();
-			if (ret) {
-				LOG(CameraSensor, Error)
-					<< "Lens initialisation failed, lens disabled";
-				focusLens_.reset();
-			}
-			break;
-
-		default:
-			LOG(CameraSensor, Warning)
-				<< "Unsupported ancillary entity function "
-				<< ancillary->function();
-			break;
-		}
-	}
-
-	return 0;
-}
+CameraSensor::~CameraSensor() = default;
 
 /**
  * \fn CameraSensor::model()
@@ -622,29 +89,15 @@ int CameraSensor::discoverAncillaryDevices()
  */
 
 /**
+ * \fn CameraSensor::sizes()
  * \brief Retrieve the supported frame sizes for a media bus code
  * \param[in] mbusCode The media bus code for which sizes are requested
  *
  * \return The supported frame sizes for \a mbusCode sorted in increasing order
  */
-std::vector<Size> CameraSensor::sizes(unsigned int mbusCode) const
-{
-	std::vector<Size> sizes;
-
-	const auto &format = formats_.find(mbusCode);
-	if (format == formats_.end())
-		return sizes;
-
-	const std::vector<SizeRange> &ranges = format->second;
-	std::transform(ranges.begin(), ranges.end(), std::back_inserter(sizes),
-		       [](const SizeRange &range) { return range.max; });
-
-	std::sort(sizes.begin(), sizes.end());
-
-	return sizes;
-}
 
 /**
+ * \fn CameraSensor::resolution()
  * \brief Retrieve the camera sensor resolution
  *
  * The camera sensor resolution is the active pixel area size, clamped to the
@@ -657,12 +110,9 @@ std::vector<Size> CameraSensor::sizes(unsigned int mbusCode) const
  *
  * \return The camera sensor resolution in pixels
  */
-Size CameraSensor::resolution() const
-{
-	return std::min(sizes_.back(), activeArea_.size());
-}
 
 /**
+ * \fn CameraSensor::getFormat()
  * \brief Retrieve the best sensor format for a desired output
  * \param[in] mbusCodes The list of acceptable media bus codes
  * \param[in] size The desired size
@@ -698,59 +148,9 @@ Size CameraSensor::resolution() const
  * \return The best sensor output format matching the desired media bus codes
  * and size on success, or an empty format otherwise.
  */
-V4L2SubdeviceFormat CameraSensor::getFormat(const std::vector<unsigned int> &mbusCodes,
-					    const Size &size) const
-{
-	unsigned int desiredArea = size.width * size.height;
-	unsigned int bestArea = UINT_MAX;
-	float desiredRatio = static_cast<float>(size.width) / size.height;
-	float bestRatio = FLT_MAX;
-	const Size *bestSize = nullptr;
-	uint32_t bestCode = 0;
-
-	for (unsigned int code : mbusCodes) {
-		const auto formats = formats_.find(code);
-		if (formats == formats_.end())
-			continue;
-
-		for (const SizeRange &range : formats->second) {
-			const Size &sz = range.max;
-
-			if (sz.width < size.width || sz.height < size.height)
-				continue;
-
-			float ratio = static_cast<float>(sz.width) / sz.height;
-			float ratioDiff = std::abs(ratio - desiredRatio);
-			unsigned int area = sz.width * sz.height;
-			unsigned int areaDiff = area - desiredArea;
-
-			if (ratioDiff > bestRatio)
-				continue;
-
-			if (ratioDiff < bestRatio || areaDiff < bestArea) {
-				bestRatio = ratioDiff;
-				bestArea = areaDiff;
-				bestSize = &sz;
-				bestCode = code;
-			}
-		}
-	}
-
-	if (!bestSize) {
-		LOG(CameraSensor, Debug) << "No supported format or size found";
-		return {};
-	}
-
-	V4L2SubdeviceFormat format{
-		.code = bestCode,
-		.size = *bestSize,
-		.colorSpace = ColorSpace::Raw,
-	};
-
-	return format;
-}
 
 /**
+ * \fn CameraSensor::setFormat()
  * \brief Set the sensor output format
  * \param[in] format The desired sensor output format
  * \param[in] transform The transform to be applied on the sensor.
@@ -765,32 +165,9 @@ V4L2SubdeviceFormat CameraSensor::getFormat(const std::vector<unsigned int> &mbu
  *
  * \return 0 on success or a negative error code otherwise
  */
-int CameraSensor::setFormat(V4L2SubdeviceFormat *format, Transform transform)
-{
-	/* Configure flips if the sensor supports that. */
-	if (supportFlips_) {
-		ControlList flipCtrls(subdev_->controls());
-
-		flipCtrls.set(V4L2_CID_HFLIP,
-			      static_cast<int32_t>(!!(transform & Transform::HFlip)));
-		flipCtrls.set(V4L2_CID_VFLIP,
-			      static_cast<int32_t>(!!(transform & Transform::VFlip)));
-
-		int ret = subdev_->setControls(&flipCtrls);
-		if (ret)
-			return ret;
-	}
-
-	/* Apply format on the subdev. */
-	int ret = subdev_->setFormat(pad_, format);
-	if (ret)
-		return ret;
-
-	subdev_->updateControlInfo();
-	return 0;
-}
 
 /**
+ * \fn CameraSensor::tryFormat()
  * \brief Try the sensor output format
  * \param[in] format The desired sensor output format
  *
@@ -801,13 +178,9 @@ int CameraSensor::setFormat(V4L2SubdeviceFormat *format, Transform transform)
  *
  * \return 0 on success or a negative error code otherwise
  */
-int CameraSensor::tryFormat(V4L2SubdeviceFormat *format) const
-{
-	return subdev_->setFormat(pad_, format,
-				  V4L2Subdevice::Whence::TryFormat);
-}
 
 /**
+ * \fn CameraSensor::applyConfiguration()
  * \brief Apply a sensor configuration to the camera sensor
  * \param[in] config The sensor configuration
  * \param[in] transform The transform to be applied on the sensor.
@@ -822,74 +195,6 @@ int CameraSensor::tryFormat(V4L2SubdeviceFormat *format) const
  * \return 0 if \a config is applied correctly to the camera sensor, a negative
  * error code otherwise
  */
-int CameraSensor::applyConfiguration(const SensorConfiguration &config,
-				     Transform transform,
-				     V4L2SubdeviceFormat *sensorFormat)
-{
-	if (!config.isValid()) {
-		LOG(CameraSensor, Error) << "Invalid sensor configuration";
-		return -EINVAL;
-	}
-
-	std::vector<unsigned int> filteredCodes;
-	std::copy_if(mbusCodes_.begin(), mbusCodes_.end(),
-		     std::back_inserter(filteredCodes),
-		     [&config](unsigned int mbusCode) {
-			     BayerFormat bayer = BayerFormat::fromMbusCode(mbusCode);
-			     if (bayer.bitDepth == config.bitDepth)
-				     return true;
-			     return false;
-		     });
-	if (filteredCodes.empty()) {
-		LOG(CameraSensor, Error)
-			<< "Cannot find any format with bit depth "
-			<< config.bitDepth;
-		return -EINVAL;
-	}
-
-	/*
-	 * Compute the sensor's data frame size by applying the cropping
-	 * rectangle, subsampling and output crop to the sensor's pixel array
-	 * size.
-	 *
-	 * \todo The actual size computation is for now ignored and only the
-	 * output size is considered. This implies that resolutions obtained
-	 * with two different cropping/subsampling will look identical and
-	 * only the first found one will be considered.
-	 */
-	V4L2SubdeviceFormat subdevFormat = {};
-	for (unsigned int code : filteredCodes) {
-		for (const Size &size : sizes(code)) {
-			if (size.width != config.outputSize.width ||
-			    size.height != config.outputSize.height)
-				continue;
-
-			subdevFormat.code = code;
-			subdevFormat.size = size;
-			break;
-		}
-	}
-	if (!subdevFormat.code) {
-		LOG(CameraSensor, Error) << "Invalid output size in sensor configuration";
-		return -EINVAL;
-	}
-
-	int ret = setFormat(&subdevFormat, transform);
-	if (ret)
-		return ret;
-
-	/*
-	 * Return to the caller the format actually applied to the sensor.
-	 * This is relevant if transform has changed the bayer pattern order.
-	 */
-	if (sensorFormat)
-		*sensorFormat = subdevFormat;
-
-	/* \todo Handle AnalogCrop. Most sensors do not support set_selection */
-	/* \todo Handle scaling in the digital domain. */
-
-	return 0;
-}
 
 /**
  * \fn CameraSensor::properties()
@@ -898,6 +203,7 @@ int CameraSensor::applyConfiguration(const SensorConfiguration &config,
  */
 
 /**
+ * \fn CameraSensor::sensorInfo()
  * \brief Assemble and return the camera sensor info
  * \param[out] info The camera sensor info
  *
@@ -911,82 +217,9 @@ int CameraSensor::applyConfiguration(const SensorConfiguration &config,
  *
  * \return 0 on success, a negative error code otherwise
  */
-int CameraSensor::sensorInfo(IPACameraSensorInfo *info) const
-{
-	if (!bayerFormat_)
-		return -EINVAL;
-
-	info->model = model();
-
-	/*
-	 * The active area size is a static property, while the crop
-	 * rectangle needs to be re-read as it depends on the sensor
-	 * configuration.
-	 */
-	info->activeAreaSize = { activeArea_.width, activeArea_.height };
-
-	/*
-	 * \todo Support for retreiving the crop rectangle is scheduled to
-	 * become mandatory. For the time being use the default value if it has
-	 * been initialized at sensor driver validation time.
-	 */
-	int ret = subdev_->getSelection(pad_, V4L2_SEL_TGT_CROP, &info->analogCrop);
-	if (ret) {
-		info->analogCrop = activeArea_;
-		LOG(CameraSensor, Warning)
-			<< "The analogue crop rectangle has been defaulted to the active area size";
-	}
-
-	/*
-	 * IPACameraSensorInfo::analogCrop::x and IPACameraSensorInfo::analogCrop::y
-	 * are defined relatively to the active pixel area, while V4L2's
-	 * TGT_CROP target is defined in respect to the full pixel array.
-	 *
-	 * Compensate it by subtracting the active area offset.
-	 */
-	info->analogCrop.x -= activeArea_.x;
-	info->analogCrop.y -= activeArea_.y;
-
-	/* The bit depth and image size depend on the currently applied format. */
-	V4L2SubdeviceFormat format{};
-	ret = subdev_->getFormat(pad_, &format);
-	if (ret)
-		return ret;
-
-	info->bitsPerPixel = MediaBusFormatInfo::info(format.code).bitsPerPixel;
-	info->outputSize = format.size;
-
-	std::optional<int32_t> cfa = properties_.get(properties::draft::ColorFilterArrangement);
-	info->cfaPattern = cfa ? *cfa : properties::draft::RGB;
-
-	/*
-	 * Retrieve the pixel rate, line length and minimum/maximum frame
-	 * duration through V4L2 controls. Support for the V4L2_CID_PIXEL_RATE,
-	 * V4L2_CID_HBLANK and V4L2_CID_VBLANK controls is mandatory.
-	 */
-	ControlList ctrls = subdev_->getControls({ V4L2_CID_PIXEL_RATE,
-						   V4L2_CID_HBLANK,
-						   V4L2_CID_VBLANK });
-	if (ctrls.empty()) {
-		LOG(CameraSensor, Error)
-			<< "Failed to retrieve camera info controls";
-		return -EINVAL;
-	}
-
-	info->pixelRate = ctrls.get(V4L2_CID_PIXEL_RATE).get<int64_t>();
-
-	const ControlInfo hblank = ctrls.infoMap()->at(V4L2_CID_HBLANK);
-	info->minLineLength = info->outputSize.width + hblank.min().get<int32_t>();
-	info->maxLineLength = info->outputSize.width + hblank.max().get<int32_t>();
-
-	const ControlInfo vblank = ctrls.infoMap()->at(V4L2_CID_VBLANK);
-	info->minFrameLength = info->outputSize.height + vblank.min().get<int32_t>();
-	info->maxFrameLength = info->outputSize.height + vblank.max().get<int32_t>();
-
-	return 0;
-}
 
 /**
+ * \fn CameraSensor::computeTransform()
  * \brief Compute the Transform that gives the requested \a orientation
  * \param[inout] orientation The desired image orientation
  *
@@ -1012,40 +245,9 @@ int CameraSensor::sensorInfo(IPACameraSensorInfo *info) const
  * \return A Transform instance that applied to the CameraSensor produces images
  * with \a orientation
  */
-Transform CameraSensor::computeTransform(Orientation *orientation) const
-{
-	/*
-	 * If we cannot do any flips we cannot change the native camera mounting
-	 * orientation.
-	 */
-	if (!supportFlips_) {
-		*orientation = mountingOrientation_;
-		return Transform::Identity;
-	}
-
-	/*
-	 * Now compute the required transform to obtain 'orientation' starting
-	 * from the mounting rotation.
-	 *
-	 * As a note:
-	 * 	orientation / mountingOrientation_ = transform
-	 * 	mountingOrientation_ * transform = orientation
-	 */
-	Transform transform = *orientation / mountingOrientation_;
-
-	/*
-	 * If transform contains any Transpose we cannot do it, so adjust
-	 * 'orientation' to report the image native orientation and return Identity.
-	 */
-	if (!!(transform & Transform::Transpose)) {
-		*orientation = mountingOrientation_;
-		return Transform::Identity;
-	}
-
-	return transform;
-}
 
 /**
+ * \fn CameraSensor::bayerOrder()
  * \brief Compute the Bayer order that results from the given Transform
  * \param[in] t The Transform to apply to the sensor
  *
@@ -1057,23 +259,9 @@ Transform CameraSensor::computeTransform(Orientation *orientation) const
  *
  * \return The Bayer order produced by the sensor when the Transform is applied
  */
-BayerFormat::Order CameraSensor::bayerOrder(Transform t) const
-{
-	/* Return a defined by meaningless value for non-Bayer sensors. */
-	if (!bayerFormat_)
-		return BayerFormat::Order::BGGR;
-
-	if (!flipsAlterBayerOrder_)
-		return bayerFormat_->order;
-
-	/*
-	 * Apply the transform to the native (i.e. untransformed) Bayer order,
-	 * using the rest of the Bayer format supplied by the caller.
-	 */
-	return bayerFormat_->transform(t).order;
-}
 
 /**
+ * \fn CameraSensor::controls()
  * \brief Retrieve the supported V4L2 controls and their information
  *
  * Control information is updated automatically to reflect the current sensor
@@ -1082,12 +270,9 @@ BayerFormat::Order CameraSensor::bayerOrder(Transform t) const
  *
  * \return A map of the V4L2 controls supported by the sensor
  */
-const ControlInfoMap &CameraSensor::controls() const
-{
-	return subdev_->controls();
-}
 
 /**
+ * \fn CameraSensor::getControls()
  * \brief Read V4L2 controls from the sensor
  * \param[in] ids The list of controls to read, specified by their ID
  *
@@ -1105,12 +290,9 @@ const ControlInfoMap &CameraSensor::controls() const
  * \return The control values in a ControlList on success, or an empty list on
  * error
  */
-ControlList CameraSensor::getControls(const std::vector<uint32_t> &ids)
-{
-	return subdev_->getControls(ids);
-}
 
 /**
+ * \fn CameraSensor::setControls()
  * \brief Write V4L2 controls to the sensor
  * \param[in] ctrls The list of controls to write
  *
@@ -1135,10 +317,6 @@ ControlList CameraSensor::getControls(const std::vector<uint32_t> &ids)
  * \retval -EINVAL One of the control is not supported or not accessible
  * \retval i The index of the control that failed
  */
-int CameraSensor::setControls(ControlList *ctrls)
-{
-	return subdev_->setControls(ctrls);
-}
 
 /**
  * \fn CameraSensor::testPatternModes()
@@ -1149,6 +327,7 @@ int CameraSensor::setControls(ControlList *ctrls)
  */
 
 /**
+ * \fn CameraSensor::setTestPatternMode()
  * \brief Set the test pattern mode for the camera sensor
  * \param[in] mode The test pattern mode
  *
@@ -1156,84 +335,6 @@ int CameraSensor::setControls(ControlList *ctrls)
  * pattern mode. Otherwise, this function is a no-op. Setting the same test
  * pattern mode for every frame thus incurs no performance penalty.
  */
-int CameraSensor::setTestPatternMode(controls::draft::TestPatternModeEnum mode)
-{
-	if (testPatternMode_ == mode)
-		return 0;
-
-	if (testPatternModes_.empty()) {
-		LOG(CameraSensor, Error)
-			<< "Camera sensor does not support test pattern modes.";
-		return -EINVAL;
-	}
-
-	return applyTestPatternMode(mode);
-}
-
-int CameraSensor::applyTestPatternMode(controls::draft::TestPatternModeEnum mode)
-{
-	if (testPatternModes_.empty())
-		return 0;
-
-	auto it = std::find(testPatternModes_.begin(), testPatternModes_.end(),
-			    mode);
-	if (it == testPatternModes_.end()) {
-		LOG(CameraSensor, Error) << "Unsupported test pattern mode "
-					 << mode;
-		return -EINVAL;
-	}
-
-	LOG(CameraSensor, Debug) << "Apply test pattern mode " << mode;
-
-	int32_t index = staticProps_->testPatternModes.at(mode);
-	ControlList ctrls{ controls() };
-	ctrls.set(V4L2_CID_TEST_PATTERN, index);
-
-	int ret = setControls(&ctrls);
-	if (ret)
-		return ret;
-
-	testPatternMode_ = mode;
-
-	return 0;
-}
-
-std::string CameraSensor::logPrefix() const
-{
-	return "'" + entity_->name() + "'";
-}
-
-namespace {
-
-/* Transitory default camera sensor implementation */
-class CameraSensorDefault : public CameraSensor
-{
-public:
-	CameraSensorDefault(MediaEntity *entity)
-		: CameraSensor(entity)
-	{
-	}
-
-	static bool match([[maybe_unused]] const MediaEntity *entity)
-	{
-		return true;
-	}
-
-	static std::unique_ptr<CameraSensorDefault> create(MediaEntity *entity)
-	{
-		std::unique_ptr<CameraSensorDefault> sensor =
-			std::make_unique<CameraSensorDefault>(entity);
-
-		if (sensor->init())
-			return nullptr;
-
-		return sensor;
-	}
-};
-
-REGISTER_CAMERA_SENSOR(CameraSensorDefault)
-
-}; /* namespace */
 
 /**
  * \class CameraSensorFactoryBase
@@ -1247,11 +348,13 @@ REGISTER_CAMERA_SENSOR(CameraSensorDefault)
 
 /**
  * \brief Construct a camera sensor factory base
+ * \param[in] name The camera sensor factory name
  *
  * Creating an instance of the factory base registers it with the global list of
  * factories, accessible through the factories() function.
  */
-CameraSensorFactoryBase::CameraSensorFactoryBase()
+CameraSensorFactoryBase::CameraSensorFactoryBase(const char *name)
+	: name_(name)
 {
 	registerFactory(this);
 }
@@ -1269,24 +372,34 @@ std::unique_ptr<CameraSensor> CameraSensorFactoryBase::create(MediaEntity *entit
 		CameraSensorFactoryBase::factories();
 
 	for (const CameraSensorFactoryBase *factory : factories) {
-		if (!factory->match(entity))
-			continue;
+		std::variant<std::unique_ptr<CameraSensor>, int> result =
+			factory->match(entity);
 
-		std::unique_ptr<CameraSensor> sensor = factory->createInstance(entity);
-		if (!sensor) {
+		if (std::holds_alternative<std::unique_ptr<CameraSensor>>(result)) {
+			LOG(CameraSensor, Debug)
+				<< "Entity '" << entity->name() << "' matched by "
+				<< factory->name();
+			return std::get<std::unique_ptr<CameraSensor>>(std::move(result));
+		}
+
+		if (std::get<int>(result)) {
 			LOG(CameraSensor, Error)
 				<< "Failed to create sensor for '"
-				<< entity->name();
+				<< entity->name() << ": " << std::get<int>(result);
 			return nullptr;
 		}
-
-		return sensor;
 	}
 
 	return nullptr;
 }
 
 /**
+ * \fn CameraSensorFactoryBase::name()
+ * \brief Retrieve the camera sensor factory name
+ * \return The name of the factory
+ */
+
+/**
  * \brief Retrieve the list of all camera sensor factories
  * \return The list of camera sensor factories
  */
@@ -1336,32 +449,26 @@ void CameraSensorFactoryBase::registerFactory(CameraSensorFactoryBase *factory)
  */
 
 /**
- * \fn CameraSensorFactory::createInstance() const
- * \brief Create an instance of the CameraSensor corresponding to the factory
- *
- * \return A unique pointer to a newly constructed instance of the CameraSensor
- * subclass corresponding to the factory
- */
-
-/**
  * \def REGISTER_CAMERA_SENSOR(sensor)
  * \brief Register a camera sensor type to the sensor factory
  * \param[in] sensor Class name of the CameraSensor derived class to register
  *
  * Register a CameraSensor subclass with the factory and make it available to
- * try and match sensors. The subclass needs to implement two static functions:
+ * try and match sensors. The subclass needs to implement a static match
+ * function:
  *
  * \code{.cpp}
- * static bool match(const MediaEntity *entity);
- * static std::unique_ptr<sensor> create(MediaEntity *entity);
+ * static std::variant<std::unique_ptr<CameraSensor>, int> match(MediaEntity *entity);
  * \endcode
  *
- * The match() function tests if the sensor class supports the camera sensor
- * identified by a MediaEntity.
+ * The function tests if the sensor class supports the camera sensor identified
+ * by a MediaEntity. If so, it creates a new instance of the sensor class. The
+ * return value is a variant that contains
  *
- * The create() function creates a new instance of the sensor class. It may
- * return a null pointer if initialization of the instance fails. It will only
- * be called if the match() function has returned true for the given entity.
+ * - A new instance of the camera sensor class if the entity matched and
+ *   creation succeeded ;
+ * - A non-zero error code if the entity matched and the creation failed ; or
+ * - A zero error code if the entity didn't match.
  */
 
 } /* namespace libcamera */
diff --git a/src/libcamera/sensor/camera_sensor_legacy.cpp b/src/libcamera/sensor/camera_sensor_legacy.cpp
new file mode 100644
index 00000000..68c94533
--- /dev/null
+++ b/src/libcamera/sensor/camera_sensor_legacy.cpp
@@ -0,0 +1,1015 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * camera_sensor_legacy.cpp - A V4L2-backed camera sensor
+ */
+
+#include <algorithm>
+#include <cmath>
+#include <float.h>
+#include <iomanip>
+#include <limits.h>
+#include <map>
+#include <memory>
+#include <string.h>
+#include <string>
+#include <vector>
+
+#include <libcamera/base/class.h>
+#include <libcamera/base/log.h>
+#include <libcamera/base/utils.h>
+
+#include <libcamera/camera.h>
+#include <libcamera/control_ids.h>
+#include <libcamera/controls.h>
+#include <libcamera/geometry.h>
+#include <libcamera/orientation.h>
+#include <libcamera/property_ids.h>
+#include <libcamera/transform.h>
+
+#include <libcamera/ipa/core_ipa_interface.h>
+
+#include "libcamera/internal/bayer_format.h"
+#include "libcamera/internal/camera_lens.h"
+#include "libcamera/internal/camera_sensor.h"
+#include "libcamera/internal/camera_sensor_properties.h"
+#include "libcamera/internal/formats.h"
+#include "libcamera/internal/media_device.h"
+#include "libcamera/internal/sysfs.h"
+#include "libcamera/internal/v4l2_subdevice.h"
+
+namespace libcamera {
+
+class BayerFormat;
+class CameraLens;
+class MediaEntity;
+class SensorConfiguration;
+
+struct CameraSensorProperties;
+
+enum class Orientation;
+
+LOG_DECLARE_CATEGORY(CameraSensor)
+
+class CameraSensorLegacy : public CameraSensor, protected Loggable
+{
+public:
+	CameraSensorLegacy(const MediaEntity *entity);
+	~CameraSensorLegacy();
+
+	static std::variant<std::unique_ptr<CameraSensor>, int>
+	match(MediaEntity *entity);
+
+	const std::string &model() const override { return model_; }
+	const std::string &id() const override { return id_; }
+
+	const MediaEntity *entity() const override { return entity_; }
+	V4L2Subdevice *device() override { return subdev_.get(); }
+
+	CameraLens *focusLens() override { return focusLens_.get(); }
+
+	const std::vector<unsigned int> &mbusCodes() const override { return mbusCodes_; }
+	std::vector<Size> sizes(unsigned int mbusCode) const override;
+	Size resolution() const override;
+
+	V4L2SubdeviceFormat getFormat(const std::vector<unsigned int> &mbusCodes,
+				      const Size &size) const override;
+	int setFormat(V4L2SubdeviceFormat *format,
+		      Transform transform = Transform::Identity) override;
+	int tryFormat(V4L2SubdeviceFormat *format) const override;
+
+	int applyConfiguration(const SensorConfiguration &config,
+			       Transform transform = Transform::Identity,
+			       V4L2SubdeviceFormat *sensorFormat = nullptr) override;
+
+	const ControlList &properties() const override { return properties_; }
+	int sensorInfo(IPACameraSensorInfo *info) const override;
+	Transform computeTransform(Orientation *orientation) const override;
+	BayerFormat::Order bayerOrder(Transform t) const override;
+
+	const ControlInfoMap &controls() const override;
+	ControlList getControls(const std::vector<uint32_t> &ids) override;
+	int setControls(ControlList *ctrls) override;
+
+	const std::vector<controls::draft::TestPatternModeEnum> &
+	testPatternModes() const override { return testPatternModes_; }
+	int setTestPatternMode(controls::draft::TestPatternModeEnum mode) override;
+
+protected:
+	std::string logPrefix() const override;
+
+private:
+	LIBCAMERA_DISABLE_COPY(CameraSensorLegacy)
+
+	int init();
+	int generateId();
+	int validateSensorDriver();
+	void initVimcDefaultProperties();
+	void initStaticProperties();
+	void initTestPatternModes();
+	int initProperties();
+	int applyTestPatternMode(controls::draft::TestPatternModeEnum mode);
+	int discoverAncillaryDevices();
+
+	const MediaEntity *entity_;
+	std::unique_ptr<V4L2Subdevice> subdev_;
+	unsigned int pad_;
+
+	const CameraSensorProperties *staticProps_;
+
+	std::string model_;
+	std::string id_;
+
+	V4L2Subdevice::Formats formats_;
+	std::vector<unsigned int> mbusCodes_;
+	std::vector<Size> sizes_;
+	std::vector<controls::draft::TestPatternModeEnum> testPatternModes_;
+	controls::draft::TestPatternModeEnum testPatternMode_;
+
+	Size pixelArraySize_;
+	Rectangle activeArea_;
+	const BayerFormat *bayerFormat_;
+	bool supportFlips_;
+	bool flipsAlterBayerOrder_;
+	Orientation mountingOrientation_;
+
+	ControlList properties_;
+
+	std::unique_ptr<CameraLens> focusLens_;
+};
+
+/**
+ * \class CameraSensorLegacy
+ * \brief A camera sensor based on V4L2 subdevices
+ *
+ * The implementation is currently limited to sensors that expose a single V4L2
+ * subdevice with a single pad. It will be extended to support more complex
+ * devices as the needs arise.
+ */
+
+CameraSensorLegacy::CameraSensorLegacy(const MediaEntity *entity)
+	: entity_(entity), pad_(UINT_MAX), staticProps_(nullptr),
+	  bayerFormat_(nullptr), supportFlips_(false),
+	  flipsAlterBayerOrder_(false), properties_(properties::properties)
+{
+}
+
+CameraSensorLegacy::~CameraSensorLegacy() = default;
+
+std::variant<std::unique_ptr<CameraSensor>, int>
+CameraSensorLegacy::match(MediaEntity *entity)
+{
+	std::unique_ptr<CameraSensorLegacy> sensor =
+		std::make_unique<CameraSensorLegacy>(entity);
+
+	int ret = sensor->init();
+	if (ret)
+		return { ret };
+
+	return { std::move(sensor) };
+}
+
+int CameraSensorLegacy::init()
+{
+	for (const MediaPad *pad : entity_->pads()) {
+		if (pad->flags() & MEDIA_PAD_FL_SOURCE) {
+			pad_ = pad->index();
+			break;
+		}
+	}
+
+	if (pad_ == UINT_MAX) {
+		LOG(CameraSensor, Error)
+			<< "Sensors with more than one pad are not supported";
+		return -EINVAL;
+	}
+
+	switch (entity_->function()) {
+	case MEDIA_ENT_F_CAM_SENSOR:
+	case MEDIA_ENT_F_PROC_VIDEO_ISP:
+		break;
+
+	default:
+		LOG(CameraSensor, Error)
+			<< "Invalid sensor function "
+			<< utils::hex(entity_->function());
+		return -EINVAL;
+	}
+
+	/* Create and open the subdev. */
+	subdev_ = std::make_unique<V4L2Subdevice>(entity_);
+	int ret = subdev_->open();
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * Clear any flips to be sure we get the "native" Bayer order. This is
+	 * harmless for sensors where the flips don't affect the Bayer order.
+	 */
+	ControlList ctrls(subdev_->controls());
+	if (subdev_->controls().find(V4L2_CID_HFLIP) != subdev_->controls().end())
+		ctrls.set(V4L2_CID_HFLIP, 0);
+	if (subdev_->controls().find(V4L2_CID_VFLIP) != subdev_->controls().end())
+		ctrls.set(V4L2_CID_VFLIP, 0);
+	subdev_->setControls(&ctrls);
+
+	/* Enumerate, sort and cache media bus codes and sizes. */
+	formats_ = subdev_->formats(pad_);
+	if (formats_.empty()) {
+		LOG(CameraSensor, Error) << "No image format found";
+		return -EINVAL;
+	}
+
+	mbusCodes_ = utils::map_keys(formats_);
+	std::sort(mbusCodes_.begin(), mbusCodes_.end());
+
+	for (const auto &format : formats_) {
+		const std::vector<SizeRange> &ranges = format.second;
+		std::transform(ranges.begin(), ranges.end(), std::back_inserter(sizes_),
+			       [](const SizeRange &range) { return range.max; });
+	}
+
+	std::sort(sizes_.begin(), sizes_.end());
+
+	/* Remove duplicates. */
+	auto last = std::unique(sizes_.begin(), sizes_.end());
+	sizes_.erase(last, sizes_.end());
+
+	/*
+	 * VIMC is a bit special, as it does not yet support all the mandatory
+	 * requirements regular sensors have to respect.
+	 *
+	 * Do not validate the driver if it's VIMC and initialize the sensor
+	 * properties with static information.
+	 *
+	 * \todo Remove the special case once the VIMC driver has been
+	 * updated in all test platforms.
+	 */
+	if (entity_->device()->driver() == "vimc") {
+		initVimcDefaultProperties();
+
+		ret = initProperties();
+		if (ret)
+			return ret;
+
+		return discoverAncillaryDevices();
+	}
+
+	/* Get the color filter array pattern (only for RAW sensors). */
+	for (unsigned int mbusCode : mbusCodes_) {
+		const BayerFormat &bayerFormat = BayerFormat::fromMbusCode(mbusCode);
+		if (bayerFormat.isValid()) {
+			bayerFormat_ = &bayerFormat;
+			break;
+		}
+	}
+
+	ret = validateSensorDriver();
+	if (ret)
+		return ret;
+
+	ret = initProperties();
+	if (ret)
+		return ret;
+
+	ret = discoverAncillaryDevices();
+	if (ret)
+		return ret;
+
+	/*
+	 * Set HBLANK to the minimum to start with a well-defined line length,
+	 * allowing IPA modules that do not modify HBLANK to use the sensor
+	 * minimum line length in their calculations.
+	 */
+	const struct v4l2_query_ext_ctrl *hblankInfo = subdev_->controlInfo(V4L2_CID_HBLANK);
+	if (hblankInfo && !(hblankInfo->flags & V4L2_CTRL_FLAG_READ_ONLY)) {
+		ControlList ctrl(subdev_->controls());
+
+		ctrl.set(V4L2_CID_HBLANK, static_cast<int32_t>(hblankInfo->minimum));
+		ret = subdev_->setControls(&ctrl);
+		if (ret)
+			return ret;
+	}
+
+	return applyTestPatternMode(controls::draft::TestPatternModeEnum::TestPatternModeOff);
+}
+
+int CameraSensorLegacy::generateId()
+{
+	const std::string devPath = subdev_->devicePath();
+
+	/* Try to get ID from firmware description. */
+	id_ = sysfs::firmwareNodePath(devPath);
+	if (!id_.empty())
+		return 0;
+
+	/*
+	 * Virtual sensors not described in firmware
+	 *
+	 * Verify it's a platform device and construct ID from the device path
+	 * and model of sensor.
+	 */
+	if (devPath.find("/sys/devices/platform/", 0) == 0) {
+		id_ = devPath.substr(strlen("/sys/devices/")) + " " + model();
+		return 0;
+	}
+
+	LOG(CameraSensor, Error) << "Can't generate sensor ID";
+	return -EINVAL;
+}
+
+int CameraSensorLegacy::validateSensorDriver()
+{
+	int err = 0;
+
+	/*
+	 * Optional controls are used to register optional sensor properties. If
+	 * not present, some values will be defaulted.
+	 */
+	static constexpr uint32_t optionalControls[] = {
+		V4L2_CID_CAMERA_SENSOR_ROTATION,
+	};
+
+	const ControlIdMap &controls = subdev_->controls().idmap();
+	for (uint32_t ctrl : optionalControls) {
+		if (!controls.count(ctrl))
+			LOG(CameraSensor, Debug)
+				<< "Optional V4L2 control " << utils::hex(ctrl)
+				<< " not supported";
+	}
+
+	/*
+	 * Recommended controls are similar to optional controls, but will
+	 * become mandatory in the near future. Be loud if they're missing.
+	 */
+	static constexpr uint32_t recommendedControls[] = {
+		V4L2_CID_CAMERA_ORIENTATION,
+	};
+
+	for (uint32_t ctrl : recommendedControls) {
+		if (!controls.count(ctrl)) {
+			LOG(CameraSensor, Warning)
+				<< "Recommended V4L2 control " << utils::hex(ctrl)
+				<< " not supported";
+			err = -EINVAL;
+		}
+	}
+
+	/*
+	 * Verify if sensor supports horizontal/vertical flips
+	 *
+	 * \todo Handle horizontal and vertical flips independently.
+	 */
+	const struct v4l2_query_ext_ctrl *hflipInfo = subdev_->controlInfo(V4L2_CID_HFLIP);
+	const struct v4l2_query_ext_ctrl *vflipInfo = subdev_->controlInfo(V4L2_CID_VFLIP);
+	if (hflipInfo && !(hflipInfo->flags & V4L2_CTRL_FLAG_READ_ONLY) &&
+	    vflipInfo && !(vflipInfo->flags & V4L2_CTRL_FLAG_READ_ONLY)) {
+		supportFlips_ = true;
+
+		if (hflipInfo->flags & V4L2_CTRL_FLAG_MODIFY_LAYOUT ||
+		    vflipInfo->flags & V4L2_CTRL_FLAG_MODIFY_LAYOUT)
+			flipsAlterBayerOrder_ = true;
+	}
+
+	if (!supportFlips_)
+		LOG(CameraSensor, Debug)
+			<< "Camera sensor does not support horizontal/vertical flip";
+
+	/*
+	 * 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
+	 * IPACameraSensorInfo for the IPA module, won't be supported.
+	 *
+	 * \todo Make support for selection targets mandatory as soon as all
+	 * test platforms have been updated.
+	 */
+	Rectangle rect;
+	int ret = subdev_->getSelection(pad_, V4L2_SEL_TGT_CROP_BOUNDS, &rect);
+	if (ret) {
+		/*
+		 * Default the pixel array size to the largest size supported
+		 * by the sensor. The sizes_ vector is sorted in ascending
+		 * order, the largest size is thus the last element.
+		 */
+		pixelArraySize_ = sizes_.back();
+
+		LOG(CameraSensor, Warning)
+			<< "The PixelArraySize property has been defaulted to "
+			<< pixelArraySize_;
+		err = -EINVAL;
+	} else {
+		pixelArraySize_ = rect.size();
+	}
+
+	ret = subdev_->getSelection(pad_, V4L2_SEL_TGT_CROP_DEFAULT, &activeArea_);
+	if (ret) {
+		activeArea_ = Rectangle(pixelArraySize_);
+		LOG(CameraSensor, Warning)
+			<< "The PixelArrayActiveAreas property has been defaulted to "
+			<< activeArea_;
+		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";
+	}
+
+	if (!bayerFormat_)
+		return 0;
+
+	/*
+	 * For raw sensors, make sure the sensor driver supports the controls
+	 * required by the CameraSensor class.
+	 */
+	static constexpr uint32_t mandatoryControls[] = {
+		V4L2_CID_ANALOGUE_GAIN,
+		V4L2_CID_EXPOSURE,
+		V4L2_CID_HBLANK,
+		V4L2_CID_PIXEL_RATE,
+		V4L2_CID_VBLANK,
+	};
+
+	err = 0;
+	for (uint32_t ctrl : mandatoryControls) {
+		if (!controls.count(ctrl)) {
+			LOG(CameraSensor, Error)
+				<< "Mandatory V4L2 control " << utils::hex(ctrl)
+				<< " not available";
+			err = -EINVAL;
+		}
+	}
+
+	if (err) {
+		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 err;
+	}
+
+	return 0;
+}
+
+void CameraSensorLegacy::initVimcDefaultProperties()
+{
+	/* Use the largest supported size. */
+	pixelArraySize_ = sizes_.back();
+	activeArea_ = Rectangle(pixelArraySize_);
+}
+
+void CameraSensorLegacy::initStaticProperties()
+{
+	staticProps_ = CameraSensorProperties::get(model_);
+	if (!staticProps_)
+		return;
+
+	/* Register the properties retrieved from the sensor database. */
+	properties_.set(properties::UnitCellSize, staticProps_->unitCellSize);
+
+	initTestPatternModes();
+}
+
+void CameraSensorLegacy::initTestPatternModes()
+{
+	const auto &v4l2TestPattern = controls().find(V4L2_CID_TEST_PATTERN);
+	if (v4l2TestPattern == controls().end()) {
+		LOG(CameraSensor, Debug) << "V4L2_CID_TEST_PATTERN is not supported";
+		return;
+	}
+
+	const auto &testPatternModes = staticProps_->testPatternModes;
+	if (testPatternModes.empty()) {
+		/*
+		 * The camera sensor supports test patterns but we don't know
+		 * how to map them so this should be fixed.
+		 */
+		LOG(CameraSensor, Debug) << "No static test pattern map for \'"
+					 << model() << "\'";
+		return;
+	}
+
+	/*
+	 * Create a map that associates the V4L2 control index to the test
+	 * pattern mode by reversing the testPatternModes map provided by the
+	 * camera sensor properties. This makes it easier to verify if the
+	 * control index is supported in the below for loop that creates the
+	 * list of supported test patterns.
+	 */
+	std::map<int32_t, controls::draft::TestPatternModeEnum> indexToTestPatternMode;
+	for (const auto &it : testPatternModes)
+		indexToTestPatternMode[it.second] = it.first;
+
+	for (const ControlValue &value : v4l2TestPattern->second.values()) {
+		const int32_t index = value.get<int32_t>();
+
+		const auto it = indexToTestPatternMode.find(index);
+		if (it == indexToTestPatternMode.end()) {
+			LOG(CameraSensor, Debug)
+				<< "Test pattern mode " << index << " ignored";
+			continue;
+		}
+
+		testPatternModes_.push_back(it->second);
+	}
+}
+
+int CameraSensorLegacy::initProperties()
+{
+	model_ = subdev_->model();
+	properties_.set(properties::Model, utils::toAscii(model_));
+
+	/* Generate a unique ID for the sensor. */
+	int ret = generateId();
+	if (ret)
+		return ret;
+
+	/* Initialize the static properties from the sensor database. */
+	initStaticProperties();
+
+	/* Retrieve and register properties from the kernel interface. */
+	const ControlInfoMap &controls = subdev_->controls();
+
+	const auto &orientation = controls.find(V4L2_CID_CAMERA_ORIENTATION);
+	if (orientation != controls.end()) {
+		int32_t v4l2Orientation = orientation->second.def().get<int32_t>();
+		int32_t propertyValue;
+
+		switch (v4l2Orientation) {
+		default:
+			LOG(CameraSensor, Warning)
+				<< "Unsupported camera location "
+				<< v4l2Orientation << ", setting to External";
+			[[fallthrough]];
+		case V4L2_CAMERA_ORIENTATION_EXTERNAL:
+			propertyValue = properties::CameraLocationExternal;
+			break;
+		case V4L2_CAMERA_ORIENTATION_FRONT:
+			propertyValue = properties::CameraLocationFront;
+			break;
+		case V4L2_CAMERA_ORIENTATION_BACK:
+			propertyValue = properties::CameraLocationBack;
+			break;
+		}
+		properties_.set(properties::Location, propertyValue);
+	} else {
+		LOG(CameraSensor, Warning) << "Failed to retrieve the camera location";
+	}
+
+	const auto &rotationControl = controls.find(V4L2_CID_CAMERA_SENSOR_ROTATION);
+	if (rotationControl != controls.end()) {
+		int32_t propertyValue = rotationControl->second.def().get<int32_t>();
+
+		/*
+		 * Cache the Transform associated with the camera mounting
+		 * rotation for later use in computeTransform().
+		 */
+		bool success;
+		mountingOrientation_ = orientationFromRotation(propertyValue, &success);
+		if (!success) {
+			LOG(CameraSensor, Warning)
+				<< "Invalid rotation of " << propertyValue
+				<< " degrees - ignoring";
+			mountingOrientation_ = Orientation::Rotate0;
+		}
+
+		properties_.set(properties::Rotation, propertyValue);
+	} else {
+		LOG(CameraSensor, Warning)
+			<< "Rotation control not available, default to 0 degrees";
+		properties_.set(properties::Rotation, 0);
+		mountingOrientation_ = Orientation::Rotate0;
+	}
+
+	properties_.set(properties::PixelArraySize, pixelArraySize_);
+	properties_.set(properties::PixelArrayActiveAreas, { activeArea_ });
+
+	/* Color filter array pattern, register only for RAW sensors. */
+	if (bayerFormat_) {
+		int32_t cfa;
+		switch (bayerFormat_->order) {
+		case BayerFormat::BGGR:
+			cfa = properties::draft::BGGR;
+			break;
+		case BayerFormat::GBRG:
+			cfa = properties::draft::GBRG;
+			break;
+		case BayerFormat::GRBG:
+			cfa = properties::draft::GRBG;
+			break;
+		case BayerFormat::RGGB:
+			cfa = properties::draft::RGGB;
+			break;
+		case BayerFormat::MONO:
+			cfa = properties::draft::MONO;
+			break;
+		}
+
+		properties_.set(properties::draft::ColorFilterArrangement, cfa);
+	}
+
+	return 0;
+}
+
+int CameraSensorLegacy::discoverAncillaryDevices()
+{
+	int ret;
+
+	for (MediaEntity *ancillary : entity_->ancillaryEntities()) {
+		switch (ancillary->function()) {
+		case MEDIA_ENT_F_LENS:
+			focusLens_ = std::make_unique<CameraLens>(ancillary);
+			ret = focusLens_->init();
+			if (ret) {
+				LOG(CameraSensor, Error)
+					<< "Lens initialisation failed, lens disabled";
+				focusLens_.reset();
+			}
+			break;
+
+		default:
+			LOG(CameraSensor, Warning)
+				<< "Unsupported ancillary entity function "
+				<< ancillary->function();
+			break;
+		}
+	}
+
+	return 0;
+}
+
+std::vector<Size> CameraSensorLegacy::sizes(unsigned int mbusCode) const
+{
+	std::vector<Size> sizes;
+
+	const auto &format = formats_.find(mbusCode);
+	if (format == formats_.end())
+		return sizes;
+
+	const std::vector<SizeRange> &ranges = format->second;
+	std::transform(ranges.begin(), ranges.end(), std::back_inserter(sizes),
+		       [](const SizeRange &range) { return range.max; });
+
+	std::sort(sizes.begin(), sizes.end());
+
+	return sizes;
+}
+
+Size CameraSensorLegacy::resolution() const
+{
+	return std::min(sizes_.back(), activeArea_.size());
+}
+
+V4L2SubdeviceFormat
+CameraSensorLegacy::getFormat(const std::vector<unsigned int> &mbusCodes,
+			      const Size &size) const
+{
+	unsigned int desiredArea = size.width * size.height;
+	unsigned int bestArea = UINT_MAX;
+	float desiredRatio = static_cast<float>(size.width) / size.height;
+	float bestRatio = FLT_MAX;
+	const Size *bestSize = nullptr;
+	uint32_t bestCode = 0;
+
+	for (unsigned int code : mbusCodes) {
+		const auto formats = formats_.find(code);
+		if (formats == formats_.end())
+			continue;
+
+		for (const SizeRange &range : formats->second) {
+			const Size &sz = range.max;
+
+			if (sz.width < size.width || sz.height < size.height)
+				continue;
+
+			float ratio = static_cast<float>(sz.width) / sz.height;
+			float ratioDiff = std::abs(ratio - desiredRatio);
+			unsigned int area = sz.width * sz.height;
+			unsigned int areaDiff = area - desiredArea;
+
+			if (ratioDiff > bestRatio)
+				continue;
+
+			if (ratioDiff < bestRatio || areaDiff < bestArea) {
+				bestRatio = ratioDiff;
+				bestArea = areaDiff;
+				bestSize = &sz;
+				bestCode = code;
+			}
+		}
+	}
+
+	if (!bestSize) {
+		LOG(CameraSensor, Debug) << "No supported format or size found";
+		return {};
+	}
+
+	V4L2SubdeviceFormat format{
+		.code = bestCode,
+		.size = *bestSize,
+		.colorSpace = ColorSpace::Raw,
+	};
+
+	return format;
+}
+
+int CameraSensorLegacy::setFormat(V4L2SubdeviceFormat *format, Transform transform)
+{
+	/* Configure flips if the sensor supports that. */
+	if (supportFlips_) {
+		ControlList flipCtrls(subdev_->controls());
+
+		flipCtrls.set(V4L2_CID_HFLIP,
+			      static_cast<int32_t>(!!(transform & Transform::HFlip)));
+		flipCtrls.set(V4L2_CID_VFLIP,
+			      static_cast<int32_t>(!!(transform & Transform::VFlip)));
+
+		int ret = subdev_->setControls(&flipCtrls);
+		if (ret)
+			return ret;
+	}
+
+	/* Apply format on the subdev. */
+	int ret = subdev_->setFormat(pad_, format);
+	if (ret)
+		return ret;
+
+	subdev_->updateControlInfo();
+	return 0;
+}
+
+int CameraSensorLegacy::tryFormat(V4L2SubdeviceFormat *format) const
+{
+	return subdev_->setFormat(pad_, format,
+				  V4L2Subdevice::Whence::TryFormat);
+}
+
+int CameraSensorLegacy::applyConfiguration(const SensorConfiguration &config,
+					   Transform transform,
+					   V4L2SubdeviceFormat *sensorFormat)
+{
+	if (!config.isValid()) {
+		LOG(CameraSensor, Error) << "Invalid sensor configuration";
+		return -EINVAL;
+	}
+
+	std::vector<unsigned int> filteredCodes;
+	std::copy_if(mbusCodes_.begin(), mbusCodes_.end(),
+		     std::back_inserter(filteredCodes),
+		     [&config](unsigned int mbusCode) {
+			     BayerFormat bayer = BayerFormat::fromMbusCode(mbusCode);
+			     if (bayer.bitDepth == config.bitDepth)
+				     return true;
+			     return false;
+		     });
+	if (filteredCodes.empty()) {
+		LOG(CameraSensor, Error)
+			<< "Cannot find any format with bit depth "
+			<< config.bitDepth;
+		return -EINVAL;
+	}
+
+	/*
+	 * Compute the sensor's data frame size by applying the cropping
+	 * rectangle, subsampling and output crop to the sensor's pixel array
+	 * size.
+	 *
+	 * \todo The actual size computation is for now ignored and only the
+	 * output size is considered. This implies that resolutions obtained
+	 * with two different cropping/subsampling will look identical and
+	 * only the first found one will be considered.
+	 */
+	V4L2SubdeviceFormat subdevFormat = {};
+	for (unsigned int code : filteredCodes) {
+		for (const Size &size : sizes(code)) {
+			if (size.width != config.outputSize.width ||
+			    size.height != config.outputSize.height)
+				continue;
+
+			subdevFormat.code = code;
+			subdevFormat.size = size;
+			break;
+		}
+	}
+	if (!subdevFormat.code) {
+		LOG(CameraSensor, Error) << "Invalid output size in sensor configuration";
+		return -EINVAL;
+	}
+
+	int ret = setFormat(&subdevFormat, transform);
+	if (ret)
+		return ret;
+
+	/*
+	 * Return to the caller the format actually applied to the sensor.
+	 * This is relevant if transform has changed the bayer pattern order.
+	 */
+	if (sensorFormat)
+		*sensorFormat = subdevFormat;
+
+	/* \todo Handle AnalogCrop. Most sensors do not support set_selection */
+	/* \todo Handle scaling in the digital domain. */
+
+	return 0;
+}
+
+int CameraSensorLegacy::sensorInfo(IPACameraSensorInfo *info) const
+{
+	if (!bayerFormat_)
+		return -EINVAL;
+
+	info->model = model();
+
+	/*
+	 * The active area size is a static property, while the crop
+	 * rectangle needs to be re-read as it depends on the sensor
+	 * configuration.
+	 */
+	info->activeAreaSize = { activeArea_.width, activeArea_.height };
+
+	/*
+	 * \todo Support for retreiving the crop rectangle is scheduled to
+	 * become mandatory. For the time being use the default value if it has
+	 * been initialized at sensor driver validation time.
+	 */
+	int ret = subdev_->getSelection(pad_, V4L2_SEL_TGT_CROP, &info->analogCrop);
+	if (ret) {
+		info->analogCrop = activeArea_;
+		LOG(CameraSensor, Warning)
+			<< "The analogue crop rectangle has been defaulted to the active area size";
+	}
+
+	/*
+	 * IPACameraSensorInfo::analogCrop::x and IPACameraSensorInfo::analogCrop::y
+	 * are defined relatively to the active pixel area, while V4L2's
+	 * TGT_CROP target is defined in respect to the full pixel array.
+	 *
+	 * Compensate it by subtracting the active area offset.
+	 */
+	info->analogCrop.x -= activeArea_.x;
+	info->analogCrop.y -= activeArea_.y;
+
+	/* The bit depth and image size depend on the currently applied format. */
+	V4L2SubdeviceFormat format{};
+	ret = subdev_->getFormat(pad_, &format);
+	if (ret)
+		return ret;
+	info->bitsPerPixel = MediaBusFormatInfo::info(format.code).bitsPerPixel;
+	info->outputSize = format.size;
+
+	std::optional<int32_t> cfa = properties_.get(properties::draft::ColorFilterArrangement);
+	info->cfaPattern = cfa ? *cfa : properties::draft::RGB;
+
+	/*
+	 * Retrieve the pixel rate, line length and minimum/maximum frame
+	 * duration through V4L2 controls. Support for the V4L2_CID_PIXEL_RATE,
+	 * V4L2_CID_HBLANK and V4L2_CID_VBLANK controls is mandatory.
+	 */
+	ControlList ctrls = subdev_->getControls({ V4L2_CID_PIXEL_RATE,
+						   V4L2_CID_HBLANK,
+						   V4L2_CID_VBLANK });
+	if (ctrls.empty()) {
+		LOG(CameraSensor, Error)
+			<< "Failed to retrieve camera info controls";
+		return -EINVAL;
+	}
+
+	info->pixelRate = ctrls.get(V4L2_CID_PIXEL_RATE).get<int64_t>();
+
+	const ControlInfo hblank = ctrls.infoMap()->at(V4L2_CID_HBLANK);
+	info->minLineLength = info->outputSize.width + hblank.min().get<int32_t>();
+	info->maxLineLength = info->outputSize.width + hblank.max().get<int32_t>();
+
+	const ControlInfo vblank = ctrls.infoMap()->at(V4L2_CID_VBLANK);
+	info->minFrameLength = info->outputSize.height + vblank.min().get<int32_t>();
+	info->maxFrameLength = info->outputSize.height + vblank.max().get<int32_t>();
+
+	return 0;
+}
+
+Transform CameraSensorLegacy::computeTransform(Orientation *orientation) const
+{
+	/*
+	 * If we cannot do any flips we cannot change the native camera mounting
+	 * orientation.
+	 */
+	if (!supportFlips_) {
+		*orientation = mountingOrientation_;
+		return Transform::Identity;
+	}
+
+	/*
+	 * Now compute the required transform to obtain 'orientation' starting
+	 * from the mounting rotation.
+	 *
+	 * As a note:
+	 * 	orientation / mountingOrientation_ = transform
+	 * 	mountingOrientation_ * transform = orientation
+	 */
+	Transform transform = *orientation / mountingOrientation_;
+
+	/*
+	 * If transform contains any Transpose we cannot do it, so adjust
+	 * 'orientation' to report the image native orientation and return Identity.
+	 */
+	if (!!(transform & Transform::Transpose)) {
+		*orientation = mountingOrientation_;
+		return Transform::Identity;
+	}
+
+	return transform;
+}
+
+BayerFormat::Order CameraSensorLegacy::bayerOrder(Transform t) const
+{
+	/* Return a defined by meaningless value for non-Bayer sensors. */
+	if (!bayerFormat_)
+		return BayerFormat::Order::BGGR;
+
+	if (!flipsAlterBayerOrder_)
+		return bayerFormat_->order;
+
+	/*
+	 * Apply the transform to the native (i.e. untransformed) Bayer order,
+	 * using the rest of the Bayer format supplied by the caller.
+	 */
+	return bayerFormat_->transform(t).order;
+}
+
+const ControlInfoMap &CameraSensorLegacy::controls() const
+{
+	return subdev_->controls();
+}
+
+ControlList CameraSensorLegacy::getControls(const std::vector<uint32_t> &ids)
+{
+	return subdev_->getControls(ids);
+}
+
+int CameraSensorLegacy::setControls(ControlList *ctrls)
+{
+	return subdev_->setControls(ctrls);
+}
+
+int CameraSensorLegacy::setTestPatternMode(controls::draft::TestPatternModeEnum mode)
+{
+	if (testPatternMode_ == mode)
+		return 0;
+
+	if (testPatternModes_.empty()) {
+		LOG(CameraSensor, Error)
+			<< "Camera sensor does not support test pattern modes.";
+		return -EINVAL;
+	}
+
+	return applyTestPatternMode(mode);
+}
+
+int CameraSensorLegacy::applyTestPatternMode(controls::draft::TestPatternModeEnum mode)
+{
+	if (testPatternModes_.empty())
+		return 0;
+
+	auto it = std::find(testPatternModes_.begin(), testPatternModes_.end(),
+			    mode);
+	if (it == testPatternModes_.end()) {
+		LOG(CameraSensor, Error) << "Unsupported test pattern mode "
+					 << mode;
+		return -EINVAL;
+	}
+
+	LOG(CameraSensor, Debug) << "Apply test pattern mode " << mode;
+
+	int32_t index = staticProps_->testPatternModes.at(mode);
+	ControlList ctrls{ controls() };
+	ctrls.set(V4L2_CID_TEST_PATTERN, index);
+
+	int ret = setControls(&ctrls);
+	if (ret)
+		return ret;
+
+	testPatternMode_ = mode;
+
+	return 0;
+}
+
+std::string CameraSensorLegacy::logPrefix() const
+{
+	return "'" + entity_->name() + "'";
+}
+
+REGISTER_CAMERA_SENSOR(CameraSensorLegacy)
+
+} /* namespace libcamera */
diff --git a/src/libcamera/sensor/meson.build b/src/libcamera/sensor/meson.build
index 61234e95..f0d58897 100644
--- a/src/libcamera/sensor/meson.build
+++ b/src/libcamera/sensor/meson.build
@@ -2,5 +2,6 @@
 
 libcamera_internal_sources += files([
     'camera_sensor.cpp',
+    'camera_sensor_legacy.cpp',
     'camera_sensor_properties.cpp',
 ])