udev: Store original value for audio powersaving and restore it

This allows users to override values.

Signed-off-by: Vasiliy Stelmachenok <[email protected]>

Author: ventureoo

usr/lib/udev/rules.d/20-audio-pm.rules

@@ -2,7 +2,10 @@
 # running on battery power. This is needed because it prevents audio cracks on
 # some hardware.
 SUBSYSTEM=="power_supply", ENV{POWER_SUPPLY_ONLINE}=="0", TEST=="/sys/module/snd_hda_intel", \
-    RUN+="/bin/sh -c 'echo 0 > /sys/module/snd_hda_intel/parameters/power_save'"
+    RUN+="/bin/sh -c 'echo $$(cat /run/udev/snd-hda-intel-powersave 2>/dev/null || \
+        echo 10) > /sys/module/snd_hda_intel/parameters/power_save'"
 
 SUBSYSTEM=="power_supply", ENV{POWER_SUPPLY_ONLINE}=="1", TEST=="/sys/module/snd_hda_intel", \
-    RUN+="/bin/sh -c 'echo 10 > /sys/module/snd_hda_intel/parameters/power_save'"
+    RUN+="/bin/sh -c '[[ $$(cat /sys/module/snd_hda_intel/parameters/power_save) != 0 ]] && \
+        echo $$(cat /sys/module/snd_hda_intel/parameters/power_save) > /run/udev/snd-hda-intel-powersave; \
+        echo 0 > /sys/module/snd_hda_intel/parameters/power_save'"