[libcamera-devel] [PATCH v2 6/6] libcamera: v4l2_videodevice: Empty the V4L2 buffer cache on streamOff()

[Naushir Patuck]

When streamOff() is called, ensure the cache entires for the remaining queued
buffers are freed since this will not happen via the dequeueBuffer() mechanism.

Additionally, add a V4L2BufferCache::isEmpty() function and assert that the
cache is empty at the end of the streamOff() call.

Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
Tested-by: David Plowman <david.plowman at raspberrypi.com>
---
 include/libcamera/internal/v4l2_videodevice.h |  1 +
 src/libcamera/v4l2_videodevice.cpp            | 16 ++++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/include/libcamera/internal/v4l2_videodevice.h b/include/libcamera/internal/v4l2_videodevice.h
index 2d2ccc477c91..37747c0b2f27 100644
--- a/include/libcamera/internal/v4l2_videodevice.h
+++ b/include/libcamera/internal/v4l2_videodevice.h
@@ -126,6 +126,7 @@ public:
 
 	int get(const FrameBuffer &buffer);
 	void put(unsigned int index);
+	bool isEmpty() const;
 
 private:
 	class Entry
diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
index 5f36ee20710d..9da82697e7f0 100644
--- a/src/libcamera/v4l2_videodevice.cpp
+++ b/src/libcamera/v4l2_videodevice.cpp
@@ -262,6 +262,19 @@ void V4L2BufferCache::put(unsigned int index)
 	cache_[index].free_ = true;
 }
 
+/**
+ * \brief Check if all the entries in the cache are unused
+ */
+bool V4L2BufferCache::isEmpty() const
+{
+	for (auto const &entry : cache_) {
+		if (!entry.free_)
+			return false;
+	}
+
+	return true;
+}
+
 V4L2BufferCache::Entry::Entry()
 	: free_(true), lastUsed_(0)
 {
@@ -1832,10 +1845,13 @@ int V4L2VideoDevice::streamOff()
 	for (auto it : queuedBuffers_) {
 		FrameBuffer *buffer = it.second;
 
+		cache_->put(it.first);
 		buffer->metadata_.status = FrameMetadata::FrameCancelled;
 		bufferReady.emit(buffer);
 	}
 
+	ASSERT(cache_->isEmpty());
+
 	queuedBuffers_.clear();
 	fdBufferNotifier_->setEnabled(false);
 	streaming_ = false;
-- 
2.25.1