The role of Machine Quirks is to read DMI info from the kernel at runtime, and then activate the relevant prefs to that machine. This is necessary for the use case of the reven board, that supports a wide range of devices from different manufacturers. Further background can be found at go/machine-quirks-design.
On the machine, when powerd initializes, first it checks if the kHasMachineQuirksPref is activated by the board to see if it should move on.
Next, the MachineQuirks class collects DMI info from the following location:
/sys/class/dmi/id/product_name
It compares the value of product_name with the kSuspendToIdleListPref and the kSuspendPreventionListPref. If a match is found, then either kSuspendToIdlePref or kDisableIdleSuspendPref is set to true via the Prefs class.
machine_quirks.h
machine_quirks.cc
machine_quirks_stub.cc
machine_quirks_stub.h
machine_quirks_test.cc
The MachineQuirks feature is currently activated via chromeos-config in the overlay, using model.yaml in chromeos-config-bsp. In the future, activation may be moved to boxster.
The machine quirk lists can be modified by creating files in /var/lib/power_manager to test out device fixes*.
cat /sys/class/dmi/id/product_name > /var/lib/power_manager/suspend_to_idle_models restart powerd
Refer to logs in /var/log/power_manager/powerd.LATEST and look at arguments passed into powerd_setuid_helper to confirm if the --suspend-to-idle flag was passed.
# after test, clear settings again rm /var/lib/power_manager/suspend_to_idle_models restart powerd
cat /sys/class/dmi/id/product_name > /var/lib/power_manager/suspend_prevention_models restart powerd
When suspend prevention is enabled, after suspend the power button remains on, and the screen immediately turns on upon user interaction on the keyboard.
# after test, clear settings again rm /var/lib/power_manager/suspend_prevention_models restart powerd
*has_machine_quirks should be set to 1 for the above to work.
