resource/udev: read uncached sysfs value via pyudev

pyudev allows unsetting cached attribute values since
d935e2c ("Add device attribute unset()") [1], introduced in pyudev
v0.24.4.

Instead of working around udev and reading via sysfs, use that feature
in USBResource.read_attr() now and bump the pyudev version requirement
accordingly.

[1] pyudev/pyudev@d935e2c

Signed-off-by: Bastian Krause <bst@pengutronix.de>

Author: Bastian-Krause

labgrid/resource/udev.py

@@ -1,4 +1,3 @@
-import os
 import queue
 import warnings
 from collections import OrderedDict
@@ -214,16 +213,10 @@ def model_id(self):
         return None
 
     def read_attr(self, attribute):
-        """read uncached attribute value from sysfs
-
-        pyudev currently supports only cached access to attributes, so we read
-        directly from sysfs.
-        """
-        # FIXME update pyudev to support udev_device_set_sysattr_value(dev,
-        # attr, None) to clear the cache
+        """read uncached attribute value"""
         if self.device is not None:
-            with open(os.path.join(self.device.sys_path, attribute), 'rb') as f:
-                return f.read().rstrip(b'\n') # drop trailing newlines
+            self.device.attributes.unset(attribute)
+            return self.device.attributes.get(attribute)
 
         return None
 

pyproject.toml

@@ -42,7 +42,7 @@ dependencies = [
     "pexpect>=4.8.0",
     "pyserial-labgrid>=3.4.0.1",
     "pytest>=7.0.0",
-    "pyudev>=0.22.0",
+    "pyudev>=0.24.4",
     "pyusb>=1.2.1",
     "PyYAML>=6.0.1",
     "requests>=2.26.0",