Many IBM Thinkpad T4* models and some R* and X* with radeon video cards draw
too much power when suspended to RAM, reducing drastically the battery
lifetime.  The solution is to enable suspend-to-D2 on these machines.  They
are whitelisted through their subsystem vendor/device ID.  This fixes
http://bugzilla.kernel.org/show_bug.cgi?id=3022

The patch introduces a framework to alter the pm_mode and reinit_func fields
of the radeonfb_info structure based on a whitelist.  This should facilitate
future hardware-dependent workarounds.  The workaround for the Samsung P35
that is already in the radeonfb code has been rewritten using this framework.

The behavior can be overridden with module options:

i)  video=radeonfb:force_sleep=1
    enable suspend-to-D2 also on non-whitelisted machines (useful for
    testing new notebook models),

ii) video=radeonfb:ignore_devlist=1
    Disable checking the whitelist and do not apply any workarounds.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>