libcamera: ipc: unix: Make socket operation asynchronous

Blocking socket operation when receiving messages may lead to long
delays, and possibly a complete deadlock, if the remote side delays
sending of the payload after the header, or doesn't send the payload at
all. To avoid this, make the socket non-blocking and implement a simple
state machine to receive the header synchronously with the socket read
notification. The payload read is still synchronous with the receive()
method to avoid data copies.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/libcamera/include/ipc_unixsocket.h b/src/libcamera/include/ipc_unixsocket.h
index ef166d74..03e9fe49 100644
--- a/src/libcamera/include/ipc_unixsocket.h
+++ b/src/libcamera/include/ipc_unixsocket.h
@@ -49,6 +49,8 @@ private:
 	void dataNotifier(EventNotifier *notifier);
 
 	int fd_;
+	bool headerReceived_;
+	struct Header header_;
 	EventNotifier *notifier_;
 };