[libcamera-devel] [PATCH v5 01/10] libcamera: property: Add MinNumRequests property

[Nícolas F. R. A. Prado]

The MinNumRequests property reports the bare minimum number of requests
needed in the camera pipeline for capture to be possible. It is equal to
the number of buffers required by the driver. At this quantity, there's
no guarantee that frames won't be dropped or that manual per-frame
controls will apply correctly. The quantity needed for those may be
added as separate properties in the future.

Signed-off-by: Nícolas F. R. A. Prado <nfraprado at collabora.com>
---
 src/libcamera/pipeline/ipu3/ipu3.cpp               | 6 ++++++
 src/libcamera/pipeline/raspberrypi/raspberrypi.cpp | 6 ++++++
 src/libcamera/pipeline/rkisp1/rkisp1.cpp           | 2 ++
 src/libcamera/pipeline/simple/simple.cpp           | 2 ++
 src/libcamera/pipeline/uvcvideo/uvcvideo.cpp       | 2 ++
 src/libcamera/pipeline/vimc/vimc.cpp               | 3 +++
 src/libcamera/property_ids.yaml                    | 9 +++++++++
 7 files changed, 30 insertions(+)

diff --git a/src/libcamera/pipeline/ipu3/ipu3.cpp b/src/libcamera/pipeline/ipu3/ipu3.cpp
index 76c3bb3d8aa9..017018c845fa 100644
--- a/src/libcamera/pipeline/ipu3/ipu3.cpp
+++ b/src/libcamera/pipeline/ipu3/ipu3.cpp
@@ -1111,6 +1111,12 @@ int PipelineHandlerIPU3::registerCameras()
 		/* Initialize the camera properties. */
 		data->properties_ = cio2->sensor()->properties();
 
+		/*
+		 * \todo Make sure this is correct even after the stream is
+		 * configured to CIO2
+		 */
+		data->properties_.set(properties::MinNumRequests, 1);
+
 		ret = initControls(data.get());
 		if (ret)
 			continue;
diff --git a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
index 082eb1ee1c23..f99a21de6918 100644
--- a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
+++ b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
@@ -1045,6 +1045,12 @@ bool PipelineHandlerRPi::match(DeviceEnumerator *enumerator)
 	/* Initialize the camera properties. */
 	data->properties_ = data->sensor_->properties();
 
+	/*
+	 * \todo Make sure this is correct after the stream is configured for
+	 * any of the roles
+	 */
+	data->properties_.set(properties::MinNumRequests, 1);
+
 	/*
 	 * Set a default value for the ScalerCropMaximum property to show
 	 * that we support its use, however, initialise it to zero because
diff --git a/src/libcamera/pipeline/rkisp1/rkisp1.cpp b/src/libcamera/pipeline/rkisp1/rkisp1.cpp
index 00df4f0b3e6b..b5cbf2394b1c 100644
--- a/src/libcamera/pipeline/rkisp1/rkisp1.cpp
+++ b/src/libcamera/pipeline/rkisp1/rkisp1.cpp
@@ -24,6 +24,7 @@
 #include <libcamera/ipa/core_ipa_interface.h>
 #include <libcamera/ipa/rkisp1_ipa_interface.h>
 #include <libcamera/ipa/rkisp1_ipa_proxy.h>
+#include <libcamera/property_ids.h>
 #include <libcamera/request.h>
 #include <libcamera/stream.h>
 
@@ -944,6 +945,7 @@ int PipelineHandlerRkISP1::createCamera(MediaEntity *sensor)
 
 	/* Initialize the camera properties. */
 	data->properties_ = data->sensor_->properties();
+	data->properties_.set(properties::MinNumRequests, 3);
 
 	/*
 	 * \todo Read dealy values from the sensor itself or from a
diff --git a/src/libcamera/pipeline/simple/simple.cpp b/src/libcamera/pipeline/simple/simple.cpp
index b29fff9820e5..c4adea61519f 100644
--- a/src/libcamera/pipeline/simple/simple.cpp
+++ b/src/libcamera/pipeline/simple/simple.cpp
@@ -25,6 +25,7 @@
 
 #include <libcamera/camera.h>
 #include <libcamera/control_ids.h>
+#include <libcamera/property_ids.h>
 #include <libcamera/request.h>
 #include <libcamera/stream.h>
 
@@ -436,6 +437,7 @@ int SimpleCameraData::init()
 	}
 
 	properties_ = sensor_->properties();
+	properties_.set(properties::MinNumRequests, 3);
 
 	return 0;
 }
diff --git a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
index 0f634b8da609..0258111ad6cf 100644
--- a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
+++ b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
@@ -525,6 +525,8 @@ int UVCCameraData::init(MediaDevice *media)
 	properties_.set(properties::PixelArraySize, resolution);
 	properties_.set(properties::PixelArrayActiveAreas, { Rectangle(resolution) });
 
+	properties_.set(properties::MinNumRequests, 1);
+
 	/* Initialise the supported controls. */
 	ControlInfoMap::Map ctrls;
 
diff --git a/src/libcamera/pipeline/vimc/vimc.cpp b/src/libcamera/pipeline/vimc/vimc.cpp
index 12f7517fd0ae..8c3f7ccb46bd 100644
--- a/src/libcamera/pipeline/vimc/vimc.cpp
+++ b/src/libcamera/pipeline/vimc/vimc.cpp
@@ -21,6 +21,7 @@
 #include <libcamera/control_ids.h>
 #include <libcamera/controls.h>
 #include <libcamera/formats.h>
+#include <libcamera/property_ids.h>
 #include <libcamera/request.h>
 #include <libcamera/stream.h>
 
@@ -517,6 +518,8 @@ int VimcCameraData::init()
 	/* Initialize the camera properties. */
 	properties_ = sensor_->properties();
 
+	properties_.set(properties::MinNumRequests, 2);
+
 	return 0;
 }
 
diff --git a/src/libcamera/property_ids.yaml b/src/libcamera/property_ids.yaml
index 12ecbce5eed4..4efa952ee393 100644
--- a/src/libcamera/property_ids.yaml
+++ b/src/libcamera/property_ids.yaml
@@ -678,6 +678,15 @@ controls:
         \todo Turn this property into a "maximum control value" for the
         ScalerCrop control once "dynamic" controls have been implemented.
 
+  - MinNumRequests:
+      type: int32_t
+      description: |
+        The bare minimum number of requests needed in the camera pipeline for
+        capture to be possible, as required by the driver. Note that this
+        quantity does not guarantee that frames won't be dropped or that manual
+        per-frame controls will be applied properly.
+
+
   # ----------------------------------------------------------------------------
   # Draft properties section
 
-- 
2.32.0