[libcamera-devel] [RFC PATCH] libcamera: v4l2_videodevice: Track streaming state

[Kieran Bingham]

Track the state of streamon/streamoff calls to simplify error paths.

Ensuring that streamOff() can be called on non-streaming streams facilitates simpler
error code paths, where a set of devices can all call streamOff regardless of their
initialisation state.

Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
---

This is a patch I have while developing the RPi ISP handler.
It means I can do the following for error paths:

	data->isp_.stats_->streamOff();
	data->isp_.capture1_->streamOff();
 	data->isp_.capture0_->streamOff();
 	data->isp_.output_->streamOff();
 	data->unicam_->streamOff();

which essentially means I can just call stop(camera) for cleanup, without
having to track which ones were successfully started or not.

So - Reasonable or not ?

Patch will not apply directly to master, as it's currently based on my dev
branch, hence RFC

 src/libcamera/include/v4l2_videodevice.h | 2 ++
 src/libcamera/v4l2_videodevice.cpp       | 9 ++++++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/libcamera/include/v4l2_videodevice.h b/src/libcamera/include/v4l2_videodevice.h
index 60fca01670c6..d6e0c0e7bf02 100644
--- a/src/libcamera/include/v4l2_videodevice.h
+++ b/src/libcamera/include/v4l2_videodevice.h
@@ -188,6 +188,8 @@ private:
 	std::map<unsigned int, Buffer *> queuedBuffers_;
 
 	EventNotifier *fdEvent_;
+
+	bool streaming_;
 };
 
 class V4L2M2MDevice
diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
index 71c32766fc2d..01e11597cfb0 100644
--- a/src/libcamera/v4l2_videodevice.cpp
+++ b/src/libcamera/v4l2_videodevice.cpp
@@ -273,7 +273,7 @@ const std::string V4L2DeviceFormat::toString() const
  */
 V4L2VideoDevice::V4L2VideoDevice(const std::string &deviceNode)
 	: V4L2Device(deviceNode), multiPlanar_(false), bufferPool_(nullptr),
-	  fdEvent_(nullptr)
+	  fdEvent_(nullptr), streaming_(false)
 {
 	/*
 	 * We default to an MMAP based CAPTURE video device, however this will
@@ -1197,6 +1197,8 @@ int V4L2VideoDevice::streamOn()
 		return ret;
 	}
 
+	streaming_ = true;
+
 	return 0;
 }
 
@@ -1214,6 +1216,9 @@ int V4L2VideoDevice::streamOff()
 {
 	int ret;
 
+	if (!streaming_)
+		return 0;
+
 	ret = ioctl(VIDIOC_STREAMOFF, &bufferType_);
 	if (ret < 0) {
 		LOG(V4L2, Error)
@@ -1234,6 +1239,8 @@ int V4L2VideoDevice::streamOff()
 	queuedBuffers_.clear();
 	fdEvent_->setEnabled(false);
 
+	streaming_ = false;
+
 	return 0;
 }
 
-- 
2.20.1