Automatic building kernel module against kernel in archive

[Resul Cetin <Resul-Cetin@gmx.net>]

Hi,
I have a source package with a userspace part and a kernelland part. From this 
package I create a xyz-source package and a xyz package. The user can now use 
m-a to build a xyz-modules-... package.
I saw that the last step could be done by our great build farm and the user 
has a direct usable kernel module. Randall Donald seems to have done that for 
his nvidia-graphics-drivers package, but I cannot figure out by looking at the 
source package how he done it.
Does there exist a description how this can be done and when should we 
generate binary kernel module packages.

Regards,
Resul Cetin

P.S.: I cc this to Randall Donald because he has done it and maybe can comment 
on the procedure.