[PATCH/RFC 21/32] libcamera: camera_sensor: Sort factories by priority
Laurent Pinchart
laurent.pinchart at ideasonboard.com
Fri Mar 1 22:21:10 CET 2024
In order to support a default implementation for camera sensors when no
better implementation matches, libcamera needs to try "specialized"
implementations first and pick the default last. Make this possible by
adding a priority value for factories. Newly registered factories are
inserted in the factories list sorted by descending priority, and the
default factory uses a negative priority to be inserted as the last
element.
This mechanism may be a bit overkill in the sense that there is no
expected use cases for priorities other than trying the default last,
but the implementation is simple and easy to understand.
Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
---
include/libcamera/internal/camera_sensor.h | 18 +++++++---
src/libcamera/sensor/camera_sensor.cpp | 34 +++++++++++++++++--
src/libcamera/sensor/camera_sensor_legacy.cpp | 2 +-
3 files changed, 45 insertions(+), 9 deletions(-)
diff --git a/include/libcamera/internal/camera_sensor.h b/include/libcamera/internal/camera_sensor.h
index d37e66773195..59785ff62019 100644
--- a/include/libcamera/internal/camera_sensor.h
+++ b/include/libcamera/internal/camera_sensor.h
@@ -79,11 +79,13 @@ public:
class CameraSensorFactoryBase
{
public:
- CameraSensorFactoryBase();
+ CameraSensorFactoryBase(int priority);
virtual ~CameraSensorFactoryBase() = default;
static std::unique_ptr<CameraSensor> create(MediaEntity *entity);
+ int priority() const { return priority_; }
+
private:
LIBCAMERA_DISABLE_COPY_AND_MOVE(CameraSensorFactoryBase)
@@ -93,14 +95,16 @@ private:
virtual std::variant<std::unique_ptr<CameraSensor>, int>
match(MediaEntity *entity) const = 0;
+
+ int priority_;
};
template<typename _CameraSensor>
class CameraSensorFactory final : public CameraSensorFactoryBase
{
public:
- CameraSensorFactory()
- : CameraSensorFactoryBase()
+ CameraSensorFactory(int priority = 0)
+ : CameraSensorFactoryBase(priority)
{
}
@@ -112,7 +116,11 @@ private:
}
};
-#define REGISTER_CAMERA_SENSOR(sensor) \
- static CameraSensorFactory<sensor> global_##sensor##Factory{};
+#ifndef __DOXYGEN__
+#define REGISTER_CAMERA_SENSOR(sensor, ...) \
+ static CameraSensorFactory<sensor> global_##sensor##Factory{ __VA_ARGS__ };
+#else
+#define REGISTER_CAMERA_SENSOR(sensor, priority)
+#endif
} /* namespace libcamera */
diff --git a/src/libcamera/sensor/camera_sensor.cpp b/src/libcamera/sensor/camera_sensor.cpp
index 7abbe2c76596..e7b526c2f050 100644
--- a/src/libcamera/sensor/camera_sensor.cpp
+++ b/src/libcamera/sensor/camera_sensor.cpp
@@ -348,11 +348,13 @@ CameraSensor::~CameraSensor() = default;
/**
* \brief Construct a camera sensor factory base
+ * \param[in] priority Priority order for factory selection
*
* Creating an instance of the factory base registers it with the global list of
* factories, accessible through the factories() function.
*/
-CameraSensorFactoryBase::CameraSensorFactoryBase()
+CameraSensorFactoryBase::CameraSensorFactoryBase(int priority)
+ : priority_(priority)
{
registerFactory(this);
}
@@ -361,6 +363,12 @@ CameraSensorFactoryBase::CameraSensorFactoryBase()
* \brief Create an instance of the CameraSensor corresponding to a media entity
* \param[in] entity The media entity on the source end of the sensor
*
+ * When multiple factories match the same \a entity, this function selects the
+ * matching factory with the highest priority as specified to the
+ * REGISTER_CAMERA_SENSOR() macro at factory registration time. If multiple
+ * matching factories have the same highest priority value, which factory gets
+ * selected is undefined and may vary between runs.
+ *
* \return A unique pointer to a new instance of the CameraSensor subclass
* matching the entity, or a null pointer if no such factory exists
*/
@@ -387,8 +395,17 @@ std::unique_ptr<CameraSensor> CameraSensorFactoryBase::create(MediaEntity *entit
return nullptr;
}
+/**
+ * \fn CameraSensorFactoryBase::priority()
+ * \brief Retrieve the priority value for the factory
+ * \return The priority value for the factory
+ */
+
/**
* \brief Retrieve the list of all camera sensor factories
+ *
+ * The factories are sorted in decreasing priority order.
+ *
* \return The list of camera sensor factories
*/
std::vector<CameraSensorFactoryBase *> &CameraSensorFactoryBase::factories()
@@ -411,7 +428,12 @@ void CameraSensorFactoryBase::registerFactory(CameraSensorFactoryBase *factory)
std::vector<CameraSensorFactoryBase *> &factories =
CameraSensorFactoryBase::factories();
- factories.push_back(factory);
+ auto pos = std::upper_bound(factories.begin(), factories.end(), factory,
+ [](const CameraSensorFactoryBase *value,
+ const CameraSensorFactoryBase *elem) {
+ return value->priority() > elem->priority();
+ });
+ factories.insert(pos, factory);
}
/**
@@ -437,9 +459,10 @@ void CameraSensorFactoryBase::registerFactory(CameraSensorFactoryBase *factory)
*/
/**
- * \def REGISTER_CAMERA_SENSOR(sensor)
+ * \def REGISTER_CAMERA_SENSOR(sensor, priority)
* \brief Register a camera sensor type to the sensor factory
* \param[in] sensor Class name of the CameraSensor derived class to register
+ * \param[in] priority Priority order for factory selection
*
* Register a CameraSensor subclass with the factory and make it available to
* try and match sensors. The subclass needs to implement a static match
@@ -457,6 +480,11 @@ void CameraSensorFactoryBase::registerFactory(CameraSensorFactoryBase *factory)
* 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.
+ *
+ * When multiple factories can support the same MediaEntity (as in the match()
+ * function of multiple factories returning true for the same entity), the \a
+ * priority argument selects which factory will be used. See
+ * CameraSensorFactoryBase::create() for more information.
*/
} /* namespace libcamera */
diff --git a/src/libcamera/sensor/camera_sensor_legacy.cpp b/src/libcamera/sensor/camera_sensor_legacy.cpp
index 34677339241c..f9f889a125d0 100644
--- a/src/libcamera/sensor/camera_sensor_legacy.cpp
+++ b/src/libcamera/sensor/camera_sensor_legacy.cpp
@@ -1010,6 +1010,6 @@ std::string CameraSensorLegacy::logPrefix() const
return "'" + entity_->name() + "'";
}
-REGISTER_CAMERA_SENSOR(CameraSensorLegacy)
+REGISTER_CAMERA_SENSOR(CameraSensorLegacy, -100)
} /* namespace libcamera */
--
Regards,
Laurent Pinchart
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