pytests: test_cameras: update to runtime pm sysfs interface

in newer kernels camera drivers with proper runtime pm are loaded by default.

pytests/test_cameras.py

+from contextlib import contextmanager
 import subprocess
-import glob
-import os
-
 import pytest
 
 from . import boardtype
 
 
-def are_cameras_enabled():
-    for result in glob.iglob('/sys/class/regulator/*/'):
-        with open(os.path.join(result, "name")) as f:
-            if "CAMERA" in f.read():
-                with open(os.path.join(result, "state")) as g:
-                    if "enabled" in g.read():
-                        return True
-    return False
+def set_power(on):
+    value = 'on' if on else 'auto'
+    address = '10' if boardtype.is_birch() else '2d'
+    with open('/sys/bus/i2c/devices/2-0020/power/control', 'w') as f:
+        f.write(value)
+    with open('/sys/bus/i2c/devices/3-00' + address + '/power/control', 'w') as f:
+        f.write(value)
+
+
+@contextmanager
+def power_up():
+    set_power(True)
+    try:
+        yield
+    finally:
+        set_power(False)
 
 
 @pytest.mark.skipif(
     boardtype.is_birch(),
     reason="Birch is missing the connection to the shutdown line.")
 @pytest.mark.skipif(not boardtype.is_librem5(), reason="Not a phone")
-@pytest.mark.skipif(not are_cameras_enabled(), reason="Cameras disabled")
 def test_selfie_camera_i2c():
-    # TODO: bringup depends on the kernel
-    readout = subprocess.check_output([
-        'i2ctransfer',
-        '-f',  # don't let the loaded driver prevent the test
-        '-y', '2',
-        'w2@0x20', '0x0f', '0x16', 'r2'])
-    assert(readout == b'0x46 0x08\n')
+    with power_up():
+        # TODO: bringup depends on the kernel
+        readout = subprocess.check_output([
+            'i2ctransfer',
+            '-f',  # don't let the loaded driver prevent the test
+            '-y', '2',
+            'w2@0x20', '0x0f', '0x16', 'r2'])
+        assert(readout == b'0x46 0x08\n')
 
 
 @pytest.mark.skipif(not boardtype.is_librem5(), reason="Not a phone")
-@pytest.mark.skipif(not are_cameras_enabled(), reason="Cameras disabled")
 def test_big_camera_i2c():
-    address = '0x10' if boardtype.is_birch() else '0x2d'
-    readout = subprocess.check_output([
-        'i2ctransfer',
-        '-f',  # don't let the loaded driver prevent the test
-        '-y', '3',
-        'w2@' + address, '0x00', '0x00', 'r2'])
-    assert(readout == b'0x30 0xc6\n')
+    with power_up():
+        address = '0x10' if boardtype.is_birch() else '0x2d'
+        readout = subprocess.check_output([
+            'i2ctransfer',
+            '-f',  # don't let the loaded driver prevent the test
+            '-y', '3',
+            'w2@' + address, '0x00', '0x00', 'r2'])
+        assert(readout == b'0x30 0xc6\n')
 
 
 @pytest.mark.skipif(not boardtype.is_librem5(), reason="Not a phone")
-@pytest.mark.skipif(not are_cameras_enabled(), reason="Cameras disabled")
 def test_big_camera_focus_driver():
     """Tests the focus driver based on observed behaviour."""
 
@@ -59,13 +64,14 @@ def test_big_camera_focus_driver():
             '-y', '3',
             'w2@' + address, byte1, byte2, 'r2'])
 
-    # Set config bits.
-    readout = regsetread('0x00', '0x0f')
-    assert(readout == b'0x00 0x0f\n')
-    # Switch to "Ringing setting" mode,
-    # which probably means "Change settings".
-    readout = regsetread('0xec', '0xa3')
-    assert(readout == b'0x00 0x00\n')
-    # Switch back to drive mode.
-    readout = regsetread('0xdc', '0x51')
-    assert(readout == b'0x00 0x0f\n')
+    with power_up():
+        # Set config bits.
+        readout = regsetread('0x00', '0x0f')
+        assert(readout == b'0x00 0x0f\n')
+        # Switch to "Ringing setting" mode,
+        # which probably means "Change settings".
+        readout = regsetread('0xec', '0xa3')
+        assert(readout == b'0x00 0x00\n')
+        # Switch back to drive mode.
+        readout = regsetread('0xdc', '0x51')
+        assert(readout == b'0x00 0x0f\n')