[ltp] Re: Applying undervolting patches

[Andrew Barr]

On Wed, 2006-08-23 at 07:29 -0400, David Abrahams wrote:
> Andrew Barr <andrew.james.barr@gmail.com> writes:
> 
> > Hardware disappearing is because you don't have a driver for it. 
> 
> Something suddenly ripped the ipw3945 driver that comes with ubuntu
> out of my stock kernel?

The ipw3945 driver is not in mainline yet. You need to get it from
http://ipw3945.sourceforge.net/ and compile it for your stock kernel.

> > You need to find out what the driver is that your wireless card uses
> > and recompile it for the new kernel (or enable in the configuration
> > it if it is in-tree).
> 
> Yeah, but why is it gone for the old kernel?

If the kernel version strings are the same (output of 'uname -r') then
perhaps the module directories are clobbering each other. It's also
possible that the ipw3945 build system (if you are compiling it
yourself) is being too smart for its own good and deleting any old
ipw3945.ko files it finds.

> > I don't know about the ATI driver. Out of tree modules, proprietary or
> > not, that use kernel APIs extensively (like device drivers) tend to
> > break between kernel versions easily. Many times looking at communities
> > (forums, mailing lists, wikis) that have a large number of users of a
> > particular third-party module will have a patch to update them for new
> > kernel versions.
> 
> At the moment I'm using the same kernel version with just a few minor
> patches.  The question is why it stops working in one kernel when I
> install it for the other kernel.  Don't they have separate modules
> directories?

This is an issue with the ATI driver specifically. You'll have to ask
the ATI mailing list/web forum/whatever for help there. I've been
bedeviled by a similar issue trying to upgrade my home theater PC box to
2.6.17. It uses the proprietary nVidia display driver.

These drivers and their components (GL libraries, DDX drivers, kernel
modules) are packaged as a unit and rather fragile. If you change
something out from under them they tend to break.

> Seen that, but none for my CPU.  I took mine from NHC.  Although I
> can't be 100% sure I know what those frequency scaling factors 6, 7,
>  ...13 NHC uses are, I just assumed that 13 was 100% of the rated speed
> and scaled down linearly from there.  NHC seems to have 8 steps while
> linux-phc only seems to recognize 4.  Not sure what that means.

Windows, I think, uses the "throttling" feature of your processor to
drive the clock speed down even more. This is, from what I've seen on
the linux-acpi mailing list, a questionable move because it carries
minimal or no power-saving benefits.

I saw Windows take an older laptop I had down to 200 MHz where the
cpufreq driver only went down to 600 MHz.

-- 
Andrew Barr | http://www.oakcourt.dyndns.org/~andrew/

All parts should go together without forcing. You must remember that
the parts you are reassembling were disassembled by you. Therefore, if
you can't get them together again, there must be a reason. By all
means, do not use a hammer.
  -- IBM maintenance manual (1925)