firmware: Handle devices without ALS

Devices without internal display like Mac mini, Studio and Pro do not
have an ambient light sensor. The ioreg subprocess will not produce any
output but return with exit status 0.
Handle this gracefully. This might hide unexpected cases on devices with
ALS but a simple solution without listing devices.

Fixes: 766ecc0 ("Extract and store ALS calibration")
Signed-off-by: Janne Grunau <[email protected]>

Author: jannau

asahi_firmware/als.py

@@ -16,6 +16,9 @@ def load(self):
         if ioreg.returncode != 0:
             log.warning("Unable to run ioreg, ambient light sensor calibration will not be saved")
             return
+        if len(ioreg.stdout) == 0:
+            log.info("ioreg without 'als' object. Possibly a device without ambient light sensor.")
+            return
         tree = plistlib.loads(ioreg.stdout)
         try:
             cal_data = tree[0]["IORegistryEntryChildren"][0]["IORegistryEntryChildren"][0]["IORegistryEntryChildren"][0]["CalibrationData"]