ipa: libipa: Add OV2685 Camera Sensor Helper

Provide a CameraSensorHelper for the OV2685, along with the
corresponding camera sensor properties.

Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/ipa/libipa/camera_sensor_helper.cpp

@@ -450,6 +450,21 @@ public:
 };
 REGISTER_CAMERA_SENSOR_HELPER("imx477", CameraSensorHelperImx477)
 
+class CameraSensorHelperOv2685 : public CameraSensorHelper
+{
+public:
+	CameraSensorHelperOv2685()
+	{
+		/*
+		 * The Sensor Manual doesn't appear to document the gain model.
+		 * This has been validated with some empirical testing only.
+		 */
+		gainType_ = AnalogueGainLinear;
+		gainConstants_.linear = { 1, 0, 0, 128 };
+	}
+};
+REGISTER_CAMERA_SENSOR_HELPER("ov2685", CameraSensorHelperOv2685)
+
 class CameraSensorHelperOv2740 : public CameraSensorHelper
 {
 public:

src/libcamera/camera_sensor_properties.cpp

@@ -133,6 +133,20 @@ const CameraSensorProperties *CameraSensorProperties::get(const std::string &sen
 				{ controls::draft::TestPatternModePn9, 4 },
 			},
 		} },
+		{ "ov2685", {
+			.unitCellSize = { 1750, 1750 },
+			.testPatternModes = {
+				{ controls::draft::TestPatternModeOff, 0 },
+				{ controls::draft::TestPatternModeColorBars, 1},
+				{ controls::draft::TestPatternModeColorBarsFadeToGray, 2 },
+				/*
+				 * No corresponding test pattern mode for:
+				 * 3: "Random Data"
+				 * 4: "Black White Square"
+				 * 5: "Color Square"
+				 */
+			},
+		} },
 		{ "ov2740", {
 			.unitCellSize = { 1400, 1400 },
 			.testPatternModes = {