[PATCH v2] libcamera: software_isp: Handle signals in the proper thread

[Milan Zamazal]

inputBufferReady ready signal in the simple pipeline is handled in the
pipeline handler thread.  outputBufferReady and ispStatsReady signals
should be handled there too.

Rather than relying on the user of the SoftwareIsp instance, let
SoftwareIsp inherits Object.  SoftwareIsp serves as a signal proxy, the
signals above are emitted from signal handlers.  This means that if
SoftwareIsp inherits Object then the slots are invoked in SoftwareIsp
thread.  Which is the camera manager thread because the SoftwareIsp
instance is created there.

Signed-off-by: Milan Zamazal <mzamazal at redhat.com>
---
 .../internal/software_isp/software_isp.h      |  3 ++-
 src/libcamera/pipeline/simple/simple.cpp      | 19 ++++++-------------
 2 files changed, 8 insertions(+), 14 deletions(-)

diff --git a/include/libcamera/internal/software_isp/software_isp.h b/include/libcamera/internal/software_isp/software_isp.h
index d51b03fd..440a296d 100644
--- a/include/libcamera/internal/software_isp/software_isp.h
+++ b/include/libcamera/internal/software_isp/software_isp.h
@@ -18,6 +18,7 @@
 
 #include <libcamera/base/class.h>
 #include <libcamera/base/log.h>
+#include <libcamera/base/object.h>
 #include <libcamera/base/signal.h>
 #include <libcamera/base/thread.h>
 
@@ -43,7 +44,7 @@ struct StreamConfiguration;
 
 LOG_DECLARE_CATEGORY(SoftwareIsp)
 
-class SoftwareIsp
+class SoftwareIsp : public Object
 {
 public:
 	SoftwareIsp(PipelineHandler *pipe, const CameraSensor *sensor,
diff --git a/src/libcamera/pipeline/simple/simple.cpp b/src/libcamera/pipeline/simple/simple.cpp
index 8ac24e6e..fade8fda 100644
--- a/src/libcamera/pipeline/simple/simple.cpp
+++ b/src/libcamera/pipeline/simple/simple.cpp
@@ -538,20 +538,13 @@ int SimpleCameraData::init()
 			swIsp_.reset();
 		} else {
 			/*
-			 * The inputBufferReady signal is emitted from the soft ISP thread,
-			 * and needs to be handled in the pipeline handler thread. Signals
-			 * implement queued delivery, but this works transparently only if
-			 * the receiver is bound to the target thread. As the
-			 * SimpleCameraData class doesn't inherit from the Object class, it
-			 * is not bound to any thread, and the signal would be delivered
-			 * synchronously. Instead, connect the signal to a lambda function
-			 * bound explicitly to the pipe, which is bound to the pipeline
-			 * handler thread. The function then simply forwards the call to
-			 * conversionInputDone().
+			 * The connected signals should be handled by the camera manager
+			 * thread. This method is called in the camera manager thread and
+			 * instantiates the SoftwareIsp instance, which inherits Object and
+			 * emits the signals from the instance's own signal handlers; thus
+			 * the slots here are invoked in the camera manager thread.
 			 */
-			swIsp_->inputBufferReady.connect(pipe, [this](FrameBuffer *buffer) {
-				this->conversionInputDone(buffer);
-			});
+			swIsp_->inputBufferReady.connect(this, &SimpleCameraData::conversionInputDone);
 			swIsp_->outputBufferReady.connect(this, &SimpleCameraData::conversionOutputDone);
 			swIsp_->ispStatsReady.connect(this, &SimpleCameraData::ispStatsReady);
 			swIsp_->setSensorControls.connect(this, &SimpleCameraData::setSensorControls);
-- 
2.48.1