libcamera: v4l2_videodevice: Track streaming state

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@ideasonboard.com>
Signed-off-by: Umang Jain <email@uajain.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

2 files changed, 13 insertions, 1 deletions

diff --git a/include/libcamera/internal/v4l2_videodevice.h b/include/libcamera/internal/v4l2_videodevice.h
index 529ca0e3..626dfbcd 100644
--- a/include/libcamera/internal/v4l2_videodevice.h
+++ b/include/libcamera/internal/v4l2_videodevice.h
@@ -249,6 +249,8 @@ private:
 	std::map<unsigned int, FrameBuffer *> queuedBuffers_;
 
 	EventNotifier *fdBufferNotifier_;
+
+	bool streaming_;
 };
 
 class V4L2M2MDevice
diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
index baf683d6..a9509bff 100644
--- a/src/libcamera/v4l2_videodevice.cpp
+++ b/src/libcamera/v4l2_videodevice.cpp
@@ -481,7 +481,8 @@ const std::string V4L2DeviceFormat::toString() const
  * \param[in] deviceNode The file-system path to the video device node
  */
 V4L2VideoDevice::V4L2VideoDevice(const std::string &deviceNode)
-	: V4L2Device(deviceNode), cache_(nullptr), fdBufferNotifier_(nullptr)
+	: V4L2Device(deviceNode), cache_(nullptr), fdBufferNotifier_(nullptr),
+	  streaming_(false)
 {
 	/*
 	 * We default to an MMAP based CAPTURE video device, however this will
@@ -1554,6 +1555,8 @@ int V4L2VideoDevice::streamOn()
 		return ret;
 	}
 
+	streaming_ = true;
+
 	return 0;
 }
 
@@ -1565,12 +1568,18 @@ int V4L2VideoDevice::streamOn()
  * and the bufferReady signal is emitted for them. The order in which those
  * buffers are dequeued is not specified.
  *
+ * This will be a no-op if the stream is not started in the first place and
+ * has no queued buffers.
+ *
  * \return 0 on success or a negative error code otherwise
  */
 int V4L2VideoDevice::streamOff()
 {
 	int ret;
 
+	if (!streaming_ && queuedBuffers_.empty())
+		return 0;
+
 	ret = ioctl(VIDIOC_STREAMOFF, &bufferType_);
 	if (ret < 0) {
 		LOG(V4L2, Error)
@@ -1588,6 +1597,7 @@ int V4L2VideoDevice::streamOff()
 
 	queuedBuffers_.clear();
 	fdBufferNotifier_->setEnabled(false);
+	streaming_ = false;
 
 	return 0;
 }