py: Add CameraManager.read_event()

Add CameraManager.read_event() so that the user does not need to call
os.read().

We use eventfd, and we must always read 8 bytes. Hiding that inside
read_event() makes sense.

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>

src/py/cam/cam.py

@@ -9,7 +9,6 @@
 import argparse
 import binascii
 import libcamera as libcam
-import os
 import sys
 import traceback
 
@@ -294,7 +293,7 @@ def event_handler(state):
         cm = state['cm']
         contexts = state['contexts']
 
-        os.read(cm.efd, 8)
+        cm.read_event()
 
         reqs = cm.get_ready_requests()
 

src/py/libcamera/py_main.cpp

@@ -212,6 +212,14 @@ PYBIND11_MODULE(_libcamera, m)
 			return gEventfd;
 		})
 
+		.def("read_event", [](CameraManager &) {
+			uint8_t buf[8];
+
+			int ret = read(gEventfd, buf, 8);
+			if (ret != 8)
+				throw std::system_error(errno, std::generic_category());
+		})
+
 		.def("get_ready_requests", [](CameraManager &) {
 			std::vector<Request *> v;
 

test/py/unittests.py

@@ -7,7 +7,6 @@ from collections import defaultdict
 import errno
 import gc
 import libcamera as libcam
-import os
 import selectors
 import time
 import typing
@@ -278,7 +277,7 @@ class SimpleCaptureMethods(CameraTesterBase):
         while running:
             events = sel.select()
             for key, _ in events:
-                os.read(key.fd, 8)
+                cm.read_event()
 
                 ready_reqs = cm.get_ready_requests()