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Backlight control; Suspend/Hibernate with nouveau on PowerBook G4?

I am trying to find a way to suspend my laptop to either ram or disk
or both and not having much luck. In the course of trying to get this
to work, I have discovered I have no control over the backlight
whatsoever. I would be grateful for any advice or pointers to

Laptop: 12" Aluminium G4 PowerBook from summer 2005 (1.5GHz with 1.25
GB maxed out ram and a nVIDIA GeForce FX Go5200 graphics card with AGP
bus, 64 MB vram and 32-bit colour)

I am using Wheezy with the occasional package from sid (about 6
application-level packages are from unstable - Iceweasel, mainly). I
am using the nouveau drivers. To get this working I am passing
on the kernel command line via yaboot.conf. The machine is dual
booting Wheezy and OS X.

I have tried installing and uninstalling various combinations of
applications with varying results. Nothing I've tried so much as
suggests that suspend to ram might work in any way whatsoever so I've
been concentrating on suspend to disk.

With uswsusp installed, suspend to disk seems to go fine but I have
problems on resume. Specifically, resume complains that the checksums
do not match. The two checksums displayed on the console look
identical to me but resume does not see things my way.

Uninstall uswsusp and force machine to use swsusp from the kernel.
Again, hibernate seems to go OK. This time, resume also works with
just one glitch. Just before powering off, the backlight is turned off
or low. (I think off.) On resume, it remains in this state so that it
is impossible to do anything without rebooting the machine. (With a
good lamp, it is possible to see that I am back to the desktop without
having logged in or started a new session so I think resume has worked
in some sense.)

The same issue occurs if I accidentally switch to battery power for a
moment - nothing will restore the backlight.

In general, I can find no way to control the backlight with Wheezy and
nouveau. (This did work with an earlier kernel but probably before I
got my graphics sorted out.)

/sys/class/backlight is empty.

/sbin/fblevel reports:

ioctl PMU_IOC_GET_BACKLIGHT: Invalid argument

/sbin/backlight reports;

  *************         WARNING         ************
  **  backlight is obsolete, please use fblevel   **
PMU_IOC_GET_BACKLIGHT ioctl: Invalid argument
Backlight level: 0

If this question is misdirected, a suggestion as to where it might
more appropriately be sent would be great.

A lot of the stuff I've found online seems to be out of date or to
apply only to non-ppc. After finding the updated Debian wiki page on
suspend, I have uninstalled hal since the notes for Wheezy say that
this can interfere with suspend. However, the next suggestion there is
to disable KMS but my understanding is that the nouveau drivers
*require* KMS so this isn't an option.

I am reaching the end of my resources and am not sure what to try
next. (Admittedly my resources are limited to poking around man
pages/documentation and possibly-related system files, googling
anything I can find to google and tearing out hair.)


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