test_cros_ec_pwm_backlight: Test backlight brightness behaviour

This patch adds a function to check that the backlight brightness affects
value of duty cycle of the PWM in debugfs.
Signed-off-by: Fabien Lahoudere <fabien.lahoudere@collabora.com>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>

test-cros-ec.py

@@ -366,6 +366,47 @@ class TestCrosEC(unittest.TestCase):
                     self.assertEqual(os.path.exists("/sys/class/rtc/" + devname + "/" + filename), 1)
         self.assertNotEqual(match,0)
 
+    def test_cros_ec_pwm_backlight(self):
+        if not os.path.exists("/sys/class/backlight/backlight/max_brightness"):
+            self.skipTest("No backlight pwm found, skipping")
+        is_ec_pwm = False
+        fd = open("/sys/kernel/debug/pwm", 'r')
+        line = fd.readline()
+        while line and not is_ec_pwm:
+            if line[0] != ' ' and ":ec-pwm" in line:
+                line = fd.readline()
+                while line:
+                    if line[0] == '\n':
+                        is_ec_pwm = False
+                        break
+                    if "backlight" in line:
+                        is_ec_pwm = True
+                        break
+                    line = fd.readline()
+            line = fd.readline()
+        fd.close()
+        if not is_ec_pwm:
+            self.skipTest("No EC backlight pwm found, skipping")
+        fd = open("/sys/class/backlight/backlight/max_brightness", 'r')
+        brightness = int(int(fd.read()) / 2)
+        fd.close()
+        fd = open("/sys/class/backlight/backlight/brightness", 'w')
+        fd.write(str(brightness))
+        fd.close()
+        fd = open("/sys/kernel/debug/pwm", 'r')
+        line = fd.readline()
+        while line:
+            if "backlight" in line:
+                start = line.find("duty") + 6
+                self.assertNotEqual(start,5)
+                end = start + line[start:].find(" ")
+                self.assertNotEqual(start,end)
+                duty = int(line[start:end])
+                self.assertNotEqual(duty,0)
+                break
+            line = fd.readline()
+        fd.close()
+
 if __name__ == '__main__':
     unittest.main(testRunner=LavaTestRunner(),
         # these make sure that some options that are not applicable