[libcamera-devel] [PATCH v1] v4l2_videodevice: Disable the watchdog timer when no buffers are queued

[Naushir Patuck]

Only enable/reset the watchdog timer when there are buffers queued in the V4L2
device. Otherwise, we may trigger spurious warnings when the watchdog times out
even if there are no buffers queued in the device.

Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
---
 src/libcamera/v4l2_videodevice.cpp | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
index 5b4637b1a39e..430715afd554 100644
--- a/src/libcamera/v4l2_videodevice.cpp
+++ b/src/libcamera/v4l2_videodevice.cpp
@@ -1662,8 +1662,11 @@ int V4L2VideoDevice::queueBuffer(FrameBuffer *buffer)
 		return ret;
 	}
 
-	if (queuedBuffers_.empty())
+	if (queuedBuffers_.empty()) {
 		fdBufferNotifier_->setEnabled(true);
+		if (watchdogDuration_)
+			watchdog_.start(std::chrono::duration_cast<std::chrono::milliseconds>(watchdogDuration_));
+	}
 
 	queuedBuffers_[buf.index] = buffer;
 
@@ -1742,16 +1745,21 @@ FrameBuffer *V4L2VideoDevice::dequeueBuffer()
 		return nullptr;
 	}
 
-	if (watchdogDuration_.count())
-		watchdog_.start(std::chrono::duration_cast<std::chrono::milliseconds>(watchdogDuration_));
-
 	cache_->put(buf.index);
 
 	FrameBuffer *buffer = it->second;
 	queuedBuffers_.erase(it);
 
-	if (queuedBuffers_.empty())
+	if (queuedBuffers_.empty()) {
 		fdBufferNotifier_->setEnabled(false);
+		watchdog_.stop();
+	} else if (watchdogDuration_) {
+		/*
+		 * Restart the watchdog timer if there are buffers still queued
+		 * in the device.
+		 */
+		watchdog_.start(std::chrono::duration_cast<std::chrono::milliseconds>(watchdogDuration_));
+	}
 
 	buffer->metadata_.status = buf.flags & V4L2_BUF_FLAG_ERROR
 				 ? FrameMetadata::FrameError
@@ -1847,7 +1855,7 @@ int V4L2VideoDevice::streamOn()
 	}
 
 	state_ = State::Streaming;
-	if (watchdogDuration_.count())
+	if (watchdogDuration_ && !queuedBuffers_.empty())
 		watchdog_.start(std::chrono::duration_cast<std::chrono::milliseconds>(watchdogDuration_));
 
 	return 0;
@@ -1924,7 +1932,7 @@ void V4L2VideoDevice::setDequeueTimeout(utils::Duration timeout)
 	watchdogDuration_ = timeout;
 
 	watchdog_.stop();
-	if (watchdogDuration_.count() && state_ == State::Streaming)
+	if (watchdogDuration_ && state_ == State::Streaming && !queuedBuffers_.empty())
 		watchdog_.start(std::chrono::duration_cast<std::chrono::milliseconds>(timeout));
 }
 
-- 
2.25.1