Distro: Gentoo RC4
Kernel: Gentoo-sources 2.4.20-r1
I did some reading and investigating about acpi:
wally root # cat /proc/acpi/event
When the power button is pressed acpi registers this event
|button/power PWRF 00000080 00000001
When the Fn+Esc (Sleep/Moon) is pressed acpi registers this event
|button/sleep SLPB 00000080 00000001
However no acpi event is registered when the LCD switch. I'm guessing that since it doesn't register then acpi can't handle it.
Some more information:
Doing a cat /proc/acpi/sleep
wally root # cat /proc/acpi/sleep
S0 S3 S4 S5
S3 - "Suspend to RAM"
All power to the cpu is shut off, and the contents of its registers are flushed to RAM, which remains on. In Microsoft Windows, the "Standby" command can be associated with this state if enabled in the BIOS. Because it requires a high degree of coordination between the cpu, chipset, devices, OS, BIOS, and OS device drivers, this system state is the most prone to errors and instability.
S4 - "Suspend to Disk"
CPU power shut off as in S3, but RAM is written to disk and shut off as well. In Microsoft Windows, the "Hibernate" command is associated with this state. A variation called S4BIOS is most prevalent, where the system image is stored and loaded by the BIOS instead of the OS. Because the contents of RAM are written out to disk, system context is maintained. For example, unsaved files would not be lost following an S4 transition.
S5 - "Soft Off"
System is shut down, however some power may be supplied to certain devices to generate a wake event, for example to support automatic startup from a LAN or USB device. In Microsoft Windows, the "Shut down" command is associated with this state. Mechanical power can usually be removed or restored with no ill effects.
Source:ACPI Sleep States
Doing an /bin/echo 5 /proc/acpi/sleep immediately turned my machine (yikes)
3,4 gave an invalid device error
Supposedly kernel 2.5 supports Suspend to RAM function.