/usr/share/laptop-mode-tools/modules/ac97-powersave is in laptop-mode-tools 1.64-1ubuntu1.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 | #! /bin/sh
#
# Laptop mode tools module: Intel AC97 integrated audio power saving mode.
#
if [ x$CONTROL_AC97_POWER = x1 ] || [ x$ENABLE_AUTO_MODULES = x1 -a x$CONTROL_AC97_POWER = xauto ]; then
if [ -w /sys/module/snd_ac97_codec/parameters/power_save ]; then
echo 1 > /sys/module/snd_ac97_codec/parameters/power_save
log "VERBOSE" "AC97 power save mode enabled."
if [ -c /dev/dsp ]; then
# This can fail if the audio device is busy.
# Since this failure is non-fatal (worst case is that the timer changes
# don't get activated), we don't bother if it was successful or not
#(exec 2>/dev/null; echo 1 > /dev/dsp;)
# Better way
echo 1 2>/dev/null >/dev/dsp
log "VERBOSE" "Initialize timer change by close/open /dev/dsp"
fi
else
log "VERBOSE" "AC97 power saving is not available. Perhaps CONFIG_SND_AC97_POWER_SAVE option"
log "VERBOSE" "is not set in the kernel config, or the snd_ac97_codec module is not loaded."
fi
else
log "VERBOSE" "AC97 audio power setting is disabled."
fi
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