[linux-lvm] How to create a device mapper patch?

[wim at unetix.nl]

Hello,

I tried to find out to make a patch for my kernel , 2.4.22,
but there seems to be no documentation available how
to generate a device mapper kernel patch. 
From the INSTALL file:
---
If your kernel does not already contain device-mapper, patch,
   configure and build a new kernel with it
----
Now this is nice , but doesn't explain how to generate a patch
for the kernel. The patches directory only contains patches
for 2.4.20 en 21 so, how do I generate a patch for 2.4.22?
Device mapper is version 1.00.05

TIA

WB