[libcamera-devel] [PATCH v3 7/8] libcamera: camera_sensor: Initialize frame durations

[Jacopo Mondi]

Calculate the camera minimum and maximum frame durations, and register
the corresponding FrameDurationLimits property with those values.

Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
---
 src/libcamera/camera_sensor.cpp | 74 +++++++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)

diff --git a/src/libcamera/camera_sensor.cpp b/src/libcamera/camera_sensor.cpp
index b9428175c55e..b144940f047d 100644
--- a/src/libcamera/camera_sensor.cpp
+++ b/src/libcamera/camera_sensor.cpp
@@ -283,6 +283,80 @@ int CameraSensor::initProperties()
 		propertyValue = 0;
 	properties_.set(properties::Rotation, propertyValue);
 
+	/* Frame durations. */
+	std::map<uint32_t, const ControlInfo *> controlLimits;
+	std::array<uint32_t, 3> controlIds = {
+		V4L2_CID_VBLANK,
+		V4L2_CID_HBLANK,
+		V4L2_CID_PIXEL_RATE
+	};
+	for (uint32_t controlId : controlIds) {
+		/*
+		 * Make sure the subdevice reports VBLANK, HBLANK and PIXEL_RATE
+		 * controls and collect the control information.
+		 */
+		auto it = controls.find(controlId);
+		if (it == controls.end()) {
+			LOG(CameraSensor, Error)
+				<< "Camera sensor does not support control "
+				<< controlId;
+			return -EINVAL;
+		}
+
+		controlLimits[controlId] = &it->second;
+	}
+
+	/*
+	 * While the maximum line and frame sizes can be calculated by adding
+	 * each control's maximum supported value to the current configuration,
+	 * the minimum sizes shall be calculated by using the minimum available
+	 * resolution. Get the current and smalles available size then calculate
+	 * the frame durations.
+	 */
+	V4L2SubdeviceFormat fmt{};
+	int ret = subdev_->getFormat(0, &fmt);
+	if (ret)
+		return ret;
+	const Size &currentSize = fmt.size;
+	const Size &minSize = *sizes_.begin();
+
+	std::vector<int32_t> durations;
+	int32_t duration;
+
+	/*
+	 * Pixel rate is reported in Hz while frame duration is expressed in
+	 * nanoseconds. Adjust it and calculate the minimum and maximum
+	 * durations.
+	 */
+	int64_t pixelRate = controlLimits[V4L2_CID_PIXEL_RATE]->max().get<int64_t>();
+	float rate = static_cast<float>(pixelRate) / 1e9F;
+
+	/* Minimum frame duration: higher frame rate. */
+	duration = (minSize.width +
+		    controlLimits[V4L2_CID_HBLANK]->min().get<int32_t>())
+		 * (minSize.height +
+		    controlLimits[V4L2_CID_VBLANK]->min().get<int32_t>());
+	duration = static_cast<int32_t>(static_cast<float>(duration) / rate);
+	durations.push_back(duration);
+
+	pixelRate = controlLimits[V4L2_CID_PIXEL_RATE]->min().get<int64_t>();
+	rate = static_cast<float>(pixelRate) / 1e9F;
+
+	/* Maximum frame duration: lower frame rate. */
+	duration = (currentSize.width +
+		    controlLimits[V4L2_CID_HBLANK]->max().get<int32_t>())
+		 * (currentSize.height +
+		    controlLimits[V4L2_CID_VBLANK]->max().get<int32_t>());
+	duration = static_cast<int32_t>(static_cast<float>(duration) / rate);
+	durations.push_back(duration);
+
+	properties_.set(properties::FrameDurationLimits, durations);
+
+	LOG(CameraSensor, Debug) << "Frame durations interval = ["
+				 << durations[0] << " - "
+				 << durations[1] << "]";
+
+	return 0;
 }
 
 /**
-- 
2.27.0