[libcamera-devel] [PATCH v3 2/5] libcamera: camera_sensor: Add frame length limits to CameraSensorInfo

[Naushir Patuck]

Sensor frame length is made up of active and inactive (blanking) lines.
The minimum and maximum frame length values may be used by pipeline
handlers to limit frame durations based on the sensor mode capabilities.

Store the minimum and maximum allowable frame length values (in lines)
in the CameraSensorInfo structure. These values are computed in
CameraSensor::sensorInfo() by querying the sensor subdevice
V4L2_CID_VBLANK control limits. This in turn means that V4L2_CID_VBLANK
is now a mandatory subdevice control.

Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
---
 include/libcamera/internal/camera_sensor.h |  3 ++
 src/libcamera/camera_sensor.cpp            | 43 ++++++++++++++++++++--
 test/ipa/ipa_wrappers_test.cpp             |  2 +
 3 files changed, 44 insertions(+), 4 deletions(-)

diff --git a/include/libcamera/internal/camera_sensor.h b/include/libcamera/internal/camera_sensor.h
index fed36bf26e47..5d8c9b1a3121 100644
--- a/include/libcamera/internal/camera_sensor.h
+++ b/include/libcamera/internal/camera_sensor.h
@@ -33,6 +33,9 @@ struct CameraSensorInfo {
 
 	uint64_t pixelRate;
 	uint32_t lineLength;
+
+	uint32_t minFrameLength;
+	uint32_t maxFrameLength;
 };
 
 class CameraSensor : protected Loggable
diff --git a/src/libcamera/camera_sensor.cpp b/src/libcamera/camera_sensor.cpp
index ab315bdc468c..f60d0cc9c6fa 100644
--- a/src/libcamera/camera_sensor.cpp
+++ b/src/libcamera/camera_sensor.cpp
@@ -113,6 +113,36 @@ LOG_DEFINE_CATEGORY(CameraSensor)
  * The total line length in pixel clock periods, including blanking.
  */
 
+/**
+ * \var CameraSensorInfo::minFrameLength
+ * \brief The minimum allowable frame length in units of lines
+ *
+ * The sensor frame length comprises of active output lines and blanking lines
+ * in a frame. The minimum frame length value dictates the minimum allowable
+ * frame duration of the sensor mode.
+ *
+ * To obtain the minimum frame duration:
+ *
+ * \verbatim
+	frameDuration(s) = minFrameLength(lines) * lineLength(pixels) / pixelRate(pixels per second)
+   \endverbatim
+ */
+
+/**
+ * \var CameraSensorInfo::maxFrameLength
+ * \brief The maximum allowable frame length in units of lines
+ *
+ * The sensor frame length comprises of active output lines and blanking lines
+ * in a frame. The maximum frame length value dictates the maximum allowable
+ * frame duration of the sensor mode.
+ *
+ * To obtain the maximum frame duration:
+ *
+ * \verbatim
+	frameDuration(s) = maxFrameLength(lines) * lineLength(pixels) / pixelRate(pixels per second)
+   \endverbatim
+ */
+
 /**
  * \class CameraSensor
  * \brief A camera sensor based on V4L2 subdevices
@@ -699,12 +729,13 @@ int CameraSensor::sensorInfo(CameraSensorInfo *info) const
 	info->outputSize = format.size;
 
 	/*
-	 * Retrieve the pixel rate and the line length through V4L2 controls.
-	 * Support for the V4L2_CID_PIXEL_RATE and V4L2_CID_HBLANK controls is
-	 * mandatory.
+	 * 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_HBLANK,
+						   V4L2_CID_VBLANK });
 	if (ctrls.empty()) {
 		LOG(CameraSensor, Error)
 			<< "Failed to retrieve camera info controls";
@@ -715,6 +746,10 @@ int CameraSensor::sensorInfo(CameraSensorInfo *info) const
 	info->lineLength = info->outputSize.width + hblank;
 	info->pixelRate = ctrls.get(V4L2_CID_PIXEL_RATE).get<int64_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;
 }
 
diff --git a/test/ipa/ipa_wrappers_test.cpp b/test/ipa/ipa_wrappers_test.cpp
index 47533d105d03..eb6d783e8489 100644
--- a/test/ipa/ipa_wrappers_test.cpp
+++ b/test/ipa/ipa_wrappers_test.cpp
@@ -313,6 +313,8 @@ protected:
 			.outputSize = { 2560, 1940 },
 			.pixelRate = 96000000,
 			.lineLength = 2918,
+			.minFrameLength = 1940,
+			.maxFrameLength = 2880
 		};
 		std::map<unsigned int, IPAStream> config{
 			{ 1, { V4L2_PIX_FMT_YUYV, { 1024, 768 } } },
-- 
2.25.1