[ltp] Workarounds and tips for thinkpads running 2.6.23/2.6.24

[Henrique de Moraes Holschuh]

Here's a bunch of tips and workaround for issues plaguing thinkpads on
2.6.24 and possibly on 2.6.23.  Not all of them apply to every model of
thinkpad.


Bay and dock handling:

1. You may need to give the kernel parameter libata.noacpi=1 to work around
an issue in the ACPI subsystem.  Possible side-effects when you *use* that
parameter are different behaviour when sleeping/hibernating/waking up, as
Linux won't use ACPI information to set up the disks for sleep/resume
anymore.  Most thinkpads won't really care or need this libata function
anyway (if it worked in 2.6.22, chances are it doesn't need it at all).
Test it first, especially if you use an HD password in BIOS or something
like that.

2. ACPI generic bay and dock are *MUCH* better than thinkpad-acpi's
deprecated bay and dock handling.  Try them.  Bay/dock handling will be gone
from thinkpad-acpi soon.  ACPI generic bay/dock send events over udev
instead of over acpid, though.


Hotkeys:

1. Always have acpid running. You need it for a lot of stuff, like the sleep
and power buttons, display LID, and a lot of other stuff.

2. Unless you know better (and you have patched acpid), you *NEED* the
"deprecated /proc/acpi/event" support, so make sure to compile it in on
2.6.24.

3. Volume hotkeys won't work right on newew Lenovos unless you are using the
latest BIOS.  You have been warned.

4. Volume hotkeys in newer Lenovos are sent to userspace, they don't "just
work" like they did on IBM thinkpad and early Lenovo models.  You will need
to configure userspace properly to act on them (see past emails on this
list).

5. Brightness keys *do* work, but there is a major mess about who handles
them, and usually this means they won't do the right thing out-of-the-box.
Your best bet is to use the video ACPI module, *and* map these keys in
userspace to call xbacklight or xrandr when running a new-enough X server
(which will block the BIOS calls used by thinkpad-acpi and ACPI video to
change the brightness).

6. On 2.6.23, give the kernel the acpi_osi="Linux" command line if you have
a newer lenovo thinkpad.  On 2.6.24, you may or may not need that, as at
least one thinkpad was whitelisted already.  If you *do* need it, send
email.  This will immediately change the behaviour of the Mute keys, and
possibly, of the video during resume (maybe even fixing the
display-remains-off issue!).

Misc:

When you buy a thinkpad, get one with either Intel graphics, or ATI
graphics.  ATI has opened the specs of *most* stuff in their newest chips,
and proper drivers are on the works.  Intel has opened the specs of their
chips a lot of time ago, and drivers are very good and mostly mature.
nVidia is a lost case right now, please do the community a big favour and
avoid them like the plague.  Besides, AFAIK ATIs are better at power
conservation than nVidia anyway (wtf Lenovo switched to nVidia?!), and
nobody can beat the slower Intel GPUs at power conservation, so if you don't
require 3D speed that much, get Intel.

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh