Re: MM kernels - how to keep on the bleeding edge?

[Michael Krufky <mkrufky@m1k.net>]

Andrew Morton wrote:

> Michael Krufky <mkrufky@m1k.net> wrote:
>  
>
> > [ tracking mm stuff ]
> >    
While we're on the topic of how -mm works, I have a question for you.  
How can I test a kernel source tree (during compilation) to determine 
whether it is a -mm tree or a -linus tree?
I will give you an example of what I am trying to do:

video4linux cvs is backwards compatible with older 2.6 kernels.  We keep 
backwards compatibility so that users can install newer device drivers 
without having to compile an entire kernel.  There are things like:
#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,13)

...all over the code that allows it to compile cleanly with many 
different versions.  Our patching scripts eliminate these "compatibility 
tests" from the source when building patches, and only presents the code 
compatible with the correct kernel version, so this doesn't interfere 
with development or the patching process.
However, sometimes there are patches in -mm that are incompatable with 
-linus.  An example of this is "Pavel's pm_message_t mangling" ... 
Testing for the numbered 2.6.x version isn't enough of a test in a case 
like this, but it would be nice to be able to develop against the most 
recent version of both the -mm tree and the -linus tree without having 
to revert patches.  Of course, v4l has chosen to maintain compatibility 
with -mm, for the sake of patch generation, and I have a handy 
-linus-compat.patch on the side for now if I want to build cvs against 
-linus, until Pavel's patches get merged later on.  But I'm sure things 
like this must happen all the time.  How do others deal with issues like 
these automatically?
It doesn't matter which -mm version or which -linus version it is... I 
can already test for 2.6.x ... All that matters is if it is -mm or 
-linus.  If there isn't already an answer to this question, maybe you 
can create a /linux/.mm file, or something like that.  A Makefile can 
test for the presence of that file... or is there already a file present 
that is unique to the -mm tree?
--
Michael Krufky

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