py: Switch to non-blocking eventfd

Blocking wait can be easily implemented on top in Python, so rather than
supporting only blocking reads, or supporting both non-blocking and
blocking reads, let's support only non-blocking reads.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

1 files changed, 10 insertions, 2 deletions

diff --git a/src/py/examples/simple-capture.py b/src/py/examples/simple-capture.py
index a6a9b33e..5f93574f 100755
--- a/src/py/examples/simple-capture.py
+++ b/src/py/examples/simple-capture.py
@@ -14,6 +14,7 @@
 
 import argparse
 import libcamera as libcam
+import selectors
 import sys
 
 # Number of frames to capture
@@ -107,11 +108,18 @@ def main():
     # The main loop. Wait for the queued Requests to complete, process them,
     # and re-queue them again.
 
+    sel = selectors.DefaultSelector()
+    sel.register(cm.event_fd, selectors.EVENT_READ)
+
     while frames_done < TOTAL_FRAMES:
-        # cm.get_ready_requests() blocks until there is an event and returns
-        # all the ready requests. Here we should almost always get a single
+        # cm.get_ready_requests() does not block, so we use a Selector to wait
+        # for a camera event. Here we should almost always get a single
         # Request, but in some cases there could be multiple or none.
 
+        events = sel.select()
+        if not events:
+            continue
+
         reqs = cm.get_ready_requests()
 
         for req in reqs: