ACPI with CentOS 4.1 on IBM T42
-------------------------------
2005-07-07

This is based on a tip from http://www.linux-on-laptops.com and
http://www.cs.washington.edu/homes/klee/nix/thinkpad-t42/#power

1.  Edit /etc/grub.conf
	Change:
	kernel /vmlinuz-xxxxxxx ro root=LABEL=/ rhgb quiet
	(where xxxxxxx is the kernel version) to:
	kernel /vmlinuz-xxxxxxx ro root=LABEL=/ rhgb quiet acpi_sleep=s3_bios

2.  Create these files:
	/etc/acpi/events/lid.conf
---BEGIN---
# sleep on lid close
event=button[/]lid
action=/etc/acpi/actions/sleep.sh
---END---

	/etc/acpi/events/sleep.conf
---BEGIN---
# sleep on "sleep" key request
event=button[/]sleep
action=/etc/acpi/actions/sleep.sh
---END---

	/etc/acpi/actions/sleep.sh
---BEGIN---
#!/bin/sh
echo -n mem >/sys/power/state
#/sbin/modprobe -r usb_uhci
#/sbin/modprobe -i usb_uhci
#/usr/sbin/hwclock --hctosys
---END---

NOTE (from link above): The modprobe lines reload the USB driver, which has the
effect of making my USB mouse work again. You may need to add lines to reload
the other USB drivers, if you use non-HCI devices (e.g., USB drives). If I ever
get such a device, I'll update this page to reflect my experiences. The last
line fixes some problems I had with the system clock resetting itself to
strange values on resume.

NOTE: I do not have any issues with my external USB mouse (Dell Logitech
optical w/ scroll wheel) and I'm not having system clock reset problems, so I
have commented those lines but kept for other's reference.

3.  chmod 744 /etc/acpi/actions/sleep.sh

4.  Test it!
	- You will need to reboot b/c of the change to grub.conf
	- Push the lid button and hold to watch the system sleep, let go to
	  watch it resume
	- Fn+F4 also works for sleep/resume

NOTE: I'm not sure how this will affect the ipw2200 wifi yet, but I'll know soon!