ThinkPad R40 hangs during ACPI power down

[Nate Lawson]

> I've got an IBM ThinkPad R40 that hangs when I do a "shutdown -p".  It
> wedges after printing "Powering system off using ACPI".
>
> Attempting to use 'acpiconf -s" to suspend produces similar hangs.

Your system is halting correctly but powering off is failing.  A cursory
glance at your ASL shows nothing particularly amiss.  It's very similar to
my laptop (T23).

> I tried compiling a version of the kernel with the ACPI_DEBUG option
> listed in NOTES, but buildkernel dies

This was fixed on Sept 21 so cvsup and recompile.  Set hw.acpi.verbose=1
in loader.conf to get more messages.

To debug this, please boot a newer kernel with the ACPI_DEBUG option with
the following options in loader.conf:

    debug.acpi.layer="ACPI_ALL_COMPONENTS ACPI_ALL_DRIVERS"
    debug.acpi.level="ACPI_LV_FUNCTIONS"

You'll get spammed with way too many messages on boot but just ignore
these.  Then do shutdown -p and log the printed messages (hopefully you
have a serial console).

I'll map the debugging tunables to a sysctl since it would be better if
you could just set this just before testing rather than for the full boot.

-Nate