Make the systemd service bind to the backlight and display devices

This ensures that the service won't be started until both the backlight
and display devices are present, and that it will be stopped when one of
them disappears

Author: kekrby

etc/systemd/system/tiny-dfr.service

@@ -1,8 +1,7 @@
 [Unit]
 Description=Tiny Apple silicon touch bar daemon
 After=systemd-user-sessions.service [email protected] plymouth-quit.service systemd-logind.service
-StartLimitIntervalSec=30
-StartLimitBurst=2
+BindsTo=dev-tiny_dfr_display.device dev-tiny_dfr_backlight.device
 
 [Service]
 ExecStart=/usr/bin/tiny-dfr

etc/udev/rules.d/99-touchbar-tiny-dfr.rules

@@ -1,2 +1,6 @@
 SUBSYSTEM=="input", ATTR{name}=="MacBookPro17,1 Touch Bar", TAG+="systemd", ENV{SYSTEMD_WANTS}="tiny-dfr.service"
 SUBSYSTEM=="input", ATTR{name}=="Mac14,7 Touch Bar", TAG+="systemd", ENV{SYSTEMD_WANTS}="tiny-dfr.service"
+
+SUBSYSTEM=="drm", KERNEL=="card[0-9]*", DRIVERS=="adp", TAG+="systemd", ENV{SYSTEMD_ALIAS}="/dev/tiny_dfr_display"
+
+SUBSYSTEM=="backlight", KERNEL=="228200000.display-pipe.0", DRIVERS=="panel-summit", TAG+="systemd", ENV{SYSTEMD_ALIAS}="/dev/tiny_dfr_backlight"