`!=` doesn't seem to be the exact inverse of `==`. To prove this I added
the following to the udev rules. On a system with the community firmware
both COMM_FW and NOT_COMM_FW were set to true, with the quectel firmware
only NOT_COMM_FW was true.
ATTRS{serial}=="community_fw", ENV{COMM_FW}="true"
ATTRS{serial}!="community_fw", ENV{NOT_COMM_FW}="true"
When using the community-maintained firmware, some attributes need to be
set with different values than what works best with the stock firmware:
this is the case of the `power/control` attribute which should be set to
"on". Similarly, on the PPP `power/persist` should be set to "1".
This commit reworks the udev rules so we can differentiate between
firmwares and host devices.
Quectel advises to configure the USB autosuspend feature as:
- power/control: auto
- power/autosuspend_delay_ms: 3000
Futhermore, the following settings are also needed:
- power/wakeup: enabled
- power/persist: 0
- avoid_reset_quirk: 1
