Applying correct hdparm values on resume

[Arthur A <arthur.machlas@gmail.com>]

Hi list,

I'm using Debian Lenny with Laptop-mode tools that I've configured to 
manage my laptop's hd, which is controlled by firmware that gives insane 
load cycle values. Thus, I've enabled laptop-mode-tools and it currently 
applies a setting of 254 (disabled) when running on AC and 128 (enabled 
and aggressive pm settings) when running on battery. This works fine on 
boot, and when removing or inserting the AC power. However, upon resume 
a setting of 128 is applied regardless of the machine's powerstate.

I believe that laptop-mode is being restarted correctly since if I 
remove and reinsert the AC cord the correct hdparm settings (254) are 
applied. My guess is that something is also being re-initialized upon 
resume from suspend that is over-riding laptop-mode-tools. In any event, 
I thought that the simplest fix for this would be to add a script to 
/etc/pm/sleep.d/01-hdparm-power-check which would do nothing if going to 
sleep, and if resuming would check whether the computer was running on 
ac, and if so apply hdparm -B 254 /dev/sda

My problem lies in this second part, as I'm not sure how to correctly do 
a check, the rest of it I can steal from other scripts included under 
/usr/lib/pm-utils/sleep.d/

This is what I think 01-hdparm-power-check would look like:
=====================================
#
#!/bin/sh
# Check to see if we are running on AC power, and if so,
# override mystery program overriding laptop-mode.conf

. "${PM_FUNCTIONS}"

if cat /proc/acpi/ac_adapter/C1AB/state = off-line || exit $NA

case "$1" in
   hibernate|suspend)
      
       ;;
   thaw|resume)
       hdparm -B 254 /dev/sda
       ;;
   *) exit $NA
       ;;
esac
======================================

As you can see, I don't know much (anything) about bash scripting. Your 
advice, assistance, criticism or concerns would be greatly appreciated.

Best,

AA