Re: [gentoo-dev] Patches and the 2.4->2.6 move

[Kumba]

Donnie Berkholz wrote:

> I'd like some input on this:
>
> I have a patch that fixes SSE problems on 2.4 kernels. However, on 2.6
> kernels it breaks OpenGL (applications segfault).
>
> Currently I'm applying this patch if /usr/src/linux is linked to a 2.4
> kernel at compile-time.
>
> This means that if a user emerges xfree when linked to a 2.4 kernel,
> that user will need to remerge xfree after moving to 2.6 kernels. This
> takes about 40 minutes on a ~2GHz x86. However, if this patch is not
> applied, the bug will continue to exist for all Gentoo users on 2.4
> kernels.
>
> My request to you is:
> 1) Is this acceptable?
> 2) If not, what is a better solution? Dropping the patch entirely? Note
> that I don't know Mesa/programming well enough to write a patch
> compatible for both 2.4 and 2.6 kernels.
>
> Thanks,
> Donnie


Here's an idea.  Bit demented, though.

First, why check /usr/src/linux?  IMHO, that link may or may not always 
be there or be correct.  I recommend instead using the get_KV and 
KV_to_int functions defined in /sbin/functions.sh to determine what the 
machine is currently running.

The second part is where to apply the patch, and how.  This is the 
difficult part.  I'd first say to apply it from the kernel.eclass file, 
but this likely goes against some odd policy somewheres, which means 
most modern 2.4 ebuilds would need updating to use this patch.  Alot of 
work is involved in tweaking all the 2.4 sources ebuilds.

The third part is How to know when to apply the patch?  In pseudo-codish 
form, here is what I can come up with.

if KV_to_int(get_KV) <= KV_to_int(2.4.99) then
	if (use x86) && (use xfree) then
		epatch <patch>
		echo "${BAD}*${NORMAL} "
		echo "${BAD}*${NORMAL} BIG FAT WARNING: You are running Xfree on an 
x86  system and are running a 2.4 kernel.
		echo "${BAD}*${NORMAL} Because of this, a patch has been applied to 
the kernel to fix some SSE/3DNOW problems."
		echo "${BAD}*${NORMAL} This patch requires you to rebuild Xfree in 
order to take advantage of the patch's"
		echo "${BAD}*${NORMAL} benefits.  Please note that this patch is only 
for 2.4 kernels.  If you move to a 2.6"
		echo "${BAD}*${NORMAL} kernel, you WILL need to re-merge Xfree, 
otherwise OpenGL-based applications"
		echo "${BAD}*${NORMAL} will fail in X."
		echo "${BAD}*${NORMAL} "
	fi
fi


That should go into pkg_postinst, and probably include a sleep delay 
timer + bell dinging like on portage and baselayout ebuilds to get the 
attention of users.

All speculation, of course, but it's a slow night and I'm in brainstorm 
mode.


--Kumba

-- 
"Such is oft the course of deeds that move the wheels of the world: 
small hands do them because they must, while the eyes of the great are 
elsewhere."  --Elrond


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