[libcamera-devel] [PATCH v3 2/8] libcamera: request: Add Request::cancel()

[Jacopo Mondi]

Add a cancel() function to the Request class that allows to forcefully
complete the request and its associated buffers in error state.

Only pending requests can be forcefully cancelled. Enforce that
by asserting the request state to be RequestPending.

Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
Reviewed-by: Hirokazu Honda <hiroh at chromium.org>
---
 .../libcamera/internal/tracepoints/request.tp |  8 ++++++
 include/libcamera/request.h                   |  1 +
 src/libcamera/request.cpp                     | 28 +++++++++++++++++++
 3 files changed, 37 insertions(+)

diff --git a/include/libcamera/internal/tracepoints/request.tp b/include/libcamera/internal/tracepoints/request.tp
index 9e872951374d..9c841b97438a 100644
--- a/include/libcamera/internal/tracepoints/request.tp
+++ b/include/libcamera/internal/tracepoints/request.tp
@@ -66,6 +66,14 @@ TRACEPOINT_EVENT_INSTANCE(
 	)
 )
 
+TRACEPOINT_EVENT_INSTANCE(
+	libcamera,
+	request,
+	request_cancel,
+	TP_ARGS(
+		libcamera::Request *, req
+	)
+)
 
 TRACEPOINT_EVENT(
 	libcamera,
diff --git a/include/libcamera/request.h b/include/libcamera/request.h
index 4cf5ff3f7d3b..5596901ddd8e 100644
--- a/include/libcamera/request.h
+++ b/include/libcamera/request.h
@@ -65,6 +65,7 @@ private:
 	friend class PipelineHandler;
 
 	void complete();
+	void cancel();
 
 	bool completeBuffer(FrameBuffer *buffer);
 
diff --git a/src/libcamera/request.cpp b/src/libcamera/request.cpp
index ce2dd7b17f10..69b2d0172e3d 100644
--- a/src/libcamera/request.cpp
+++ b/src/libcamera/request.cpp
@@ -292,6 +292,34 @@ void Request::complete()
 	LIBCAMERA_TRACEPOINT(request_complete, this);
 }
 
+/**
+ * \brief Cancel a queued request
+ *
+ * Mark the request and its associated buffers as cancelled and complete it.
+ *
+ * Set each pending buffer in error state and emit the buffer completion signal
+ * before completing the Request.
+ */
+void Request::cancel()
+{
+	LIBCAMERA_TRACEPOINT(request_cancel, this);
+
+	ASSERT(status_ == RequestPending);
+
+	/*
+	 * We can't simply loop and call completeBuffer() as the erase() call
+	 * invalidates pointers and iterators, so we have to manually cancel the
+	 * buffer from the pending buffers list.
+	 */
+	for (auto buffer = pending_.begin(); buffer != pending_.end();) {
+		(*buffer)->cancel();
+		camera_->bufferCompleted.emit(this, *buffer);
+		buffer = pending_.erase(buffer);
+	}
+
+	cancelled_ = true;
+}
+
 /**
  * \brief Complete a buffer for the request
  * \param[in] buffer The buffer that has completed
-- 
2.31.1