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#!/bin/sh
. "${PM_FUNCTIONS}"
SATA_ALPM_ENABLE=${SATA_ALPM_ENABLE:-true}
help() {
cat <<EOF
$0: SATA link power management
This hook tries to save power by allowing SATA controllers to
reduce power usage when the SATA subsystem is otherwise idle.
This adds a little bit of latency to drive accesses in
exchange for moderate power savings if you are not using the drive.
This hook has 1 parameter:
SATA_ALPM_ENABLE = whether to use SATA ALPM on battery.
Defaults to "true".
EOF
}
set_sata_alpm() {
# see kernel commit 6013efd8860bf15c1f86f365332642cfe557152f
kv="$(uname -r)"
[ "$kv" ] || exit $NA #for paranoia's sake
[ "${kv%-*}" \< "2.6.33" ] && exit $NA # avoid fs corruption
for f in /sys/class/scsi_host/host*; do
[ -w "$f/link_power_management_policy" ] || continue
printf "Setting SATA APLM on %s to %s..." "${f##*/}" "$1"
echo "$1" > "$f/link_power_management_policy" && echo Done. || \
echo Failed.
done
}
case $1 in
true) [ "$SATA_ALPM_ENABLE" = true ] && set_sata_alpm min_power;;
false) set_sata_alpm max_performance;;
help) help;;
*) exit $NA;;
esac
exit 0
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