libcamera: camera_sensor: Add tryFormat()

Add a function to the CameraSensor class that allows to test a format
without applying it to the subdevice and without modifying any control
value associated with the camera sensor.

Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

2 files changed, 18 insertions, 0 deletions

diff --git a/include/libcamera/internal/camera_sensor.h b/include/libcamera/internal/camera_sensor.h
index 928c61af..02c77ab0 100644
--- a/include/libcamera/internal/camera_sensor.h
+++ b/include/libcamera/internal/camera_sensor.h
@@ -56,6 +56,7 @@ public:
 				      const Size &size) const;
 	int setFormat(V4L2SubdeviceFormat *format,
 		      Transform transform = Transform::Identity);
+	int tryFormat(V4L2SubdeviceFormat *format) const;
 
 	const ControlInfoMap &controls() const;
 	ControlList getControls(const std::vector<uint32_t> &ids);
diff --git a/src/libcamera/camera_sensor.cpp b/src/libcamera/camera_sensor.cpp
index e442b89d..06f31521 100644
--- a/src/libcamera/camera_sensor.cpp
+++ b/src/libcamera/camera_sensor.cpp
@@ -796,6 +796,23 @@ int CameraSensor::setFormat(V4L2SubdeviceFormat *format, Transform transform)
 }
 
 /**
+ * \brief Try the sensor output format
+ * \param[in] format The desired sensor output format
+ *
+ * The ranges of any controls associated with the sensor are not updated.
+ *
+ * \todo Add support for Transform by changing the format's Bayer ordering
+ * before calling subdev_->setFormat().
+ *
+ * \return 0 on success or a negative error code otherwise
+ */
+int CameraSensor::tryFormat(V4L2SubdeviceFormat *format) const
+{
+	return subdev_->setFormat(pad_, format,
+				  V4L2Subdevice::Whence::TryFormat);
+}
+
+/**
  * \brief Retrieve the supported V4L2 controls and their information
  *
  * Control information is updated automatically to reflect the current sensor