modesetting feature status

[Kristian Høgsberg]

On Sat, 2008-09-20 at 06:18 +0200, Joshua C. wrote:
> 2008/9/19 Josh Boyer <jwboyer at gmail.com>:
> > On Fri, Sep 19, 2008 at 07:57:34PM +0200, Joshua C. wrote:
> >>I tried `strace -o /drm.strace modprobe drm debug=1` and got the
> >>output in the attached file. I tried the same with `strace -o
> >>/radeon.trace modprobe radeon modeset=1` but this time there's nothing
> >>in the file. How can I hook strace to the radeon driver?
> >
> > You can't.  All you're stracing is the modprobe command, not the driver
> > operation.
> >
> > Drivers don't operate in userspace, and don't make system calls.  So strace
> > just plain doesn't work.
> >
> > josh
> 
> 
> Ok, I cannot use ssh (just one mashine). What other options do I have
> to debug this thing? There should be a way to do this with just one
> computer.
> I read somewhere that the 2.6.26 kernel have some "new debugger" or
> so. I just need to make it write down the process to a file. After
> restart I can send you the log.
> After the drive loads I can only hard reset the computer. And if
> everything is in the ram, then I have to dump it to a file. Any other
> ideas?

When you're debugging graphics drivers that may crash and leave random
garbage on your screen, you generally need to ssh in from a second
computer.  Also, for kernel modesetting, you'll have to resort to
printk-debugging for the most cases and put up with a lot of rebooting.

The easiest way to debug this is to clone Daves kernel tree from here
http://git.kernel.org/?p=linux/kernel/git/airlied/drm-2.6.git and then
check out the drm-rawhide branch.  Something like this:

  $ git clone
git://git.kernel.org/pub/scm/linux/kernel/git/airlied/drm-2.6.git

  $ git checkout -b drm-rawhide origin/drm-rawhide

Or you may want to start from the drm-rawhide branch in my kernel repo
here: people.freedesktop.org/~krh/linux-2.6, which have a couple of
fixes that Dave hasn't pulled yet - or maybe he just didn't push them to
the kernel.org repo.  They're in rawhide though.

You then need the kernel-devel rpm for the kernel you're running and
then you should be able to build just the drm drivers from the kernel
tree against your current kernel like this:

  $ make -C /lib/modules/$(uname -r)/build
M=~/src/drm-2.6/drivers/gpu/drm

assuming your kernel tree clone lives in ~/src/drm-2.6.  Use

  $ insmod ~/src/drm-2.6/drivers/gpu/drm/drm.ko debug=1

  $ insmod ~/src/drm-2.6/drivers/gpu/drm/radeon/radeon.ko modeset=1

to load the drivers with debugging and modesetting enabled.  This will
let you change and recompile the drivers quickly and you can now add
printk statements (or use the DRM_ERROR macro) in the code to see how
far it gets etc.

Good luck :)
Kristian