a script to enable powersaving options

rc.powersave

#!/bin/sh
# A script to enable laptop power saving features for #! & Debian GNU+linux.
# http://crunchbanglinux.org/forums/topic/11954

# List of modules to unload, space seperated. Edit depending on your hardware and preferences.
modlist="nsc_ircc uhci_hcd"
# Bus list for runtime pm. Probably shouldn't touch this.
buslist="pci i2c"

case "$1" in
    true|on)
    # Enable some power saving settings while on battery
       # Enable laptop mode
        echo 5 > /proc/sys/vm/laptop_mode
       # Less VM disk activity. Suggested by powertop
        echo 1500 > /proc/sys/vm/dirty_writeback_centisecs
       # Intel power saving
        echo Y > /sys/module/snd_hda_intel/parameters/power_save_controller
        echo 1 > /sys/module/snd_hda_intel/parameters/power_save
       # Set backlight brightness to 50%
        echo 4 > /sys/class/backlight/acpi_video0/brightness
       # USB powersaving
        for i in /sys/bus/usb/devices/*/power/autosuspend; do
            echo 1 > $i
        done
       # SATA power saving
        for i in /sys/class/scsi_host/host*/link_power_management_policy; do
            echo min_power > $i
        done
       # Disable hardware modules to save power
        for mod in $modlist; do
            grep $mod /proc/modules >/dev/null || continue
            modprobe -q -r $mod 2>/dev/null
        done
       # Enable runtime power management. Suggested by powertop.
        for bus in $buslist; do
            for i in /sys/bus/$bus/devices/*/power/control; do
                echo auto > $i
            done
        done
    ;;
    false|off)
       #Return settings to default on AC power
        echo 0 > /proc/sys/vm/laptop_mode
        echo 500 > /proc/sys/vm/dirty_writeback_centisecs
        echo N > /sys/module/snd_hda_intel/parameters/power_save_controller
        echo 0 > /sys/module/snd_hda_intel/parameters/power_save
        echo 7 > /sys/class/backlight/acpi_video0/brightness
        for i in /sys/bus/usb/devices/*/power/autosuspend; do
            echo 5 > $i
        done
        for i in /sys/class/scsi_host/host*/link_power_management_policy
            do echo max_performance > $i
        done
        for mod in $modlist; do
            modprobe -q $mod 2>/dev/null
        done
        for bus in $buslist; do
            for i in /sys/bus/$bus/devices/*/power/control; do
                echo on > $i
            done
        done
    ;;
    auto)
        ON_AC=`</sys/class/power_supply/AC/online`
        [ "$ON_AC" -eq 1 ] && $0 off || $0 on
    ;;
    *)
        echo "Usage: $(basename $0) on|off|auto"
    ;;
esac

exit 0