[yocto] How do I patch the kernel before it is built?

[autif khan]

I could not find a way to patch the kernel source before its is built.

I promise to update the Yocto wiki's How do I section when I have a
working solution for the following :-)

Here is what I am trying to do:

1) Patch the kernel (add VID/PID to hid_ignore_list in
drivers/hid/hid-core.c and also to add the VID/PID to .h file)
2) Build the kernel - no change here - standard kernel build
3) Build a kernel module

I have a meta layer where I am keeping my changes. I am guessing that I need to:

a) write a bbappend file to accomplish #1
b) write a recipe to accomplish #3

I have written recipes before, but just for libraries and autotools
based applications. Not for a kernel module. If there is a recipe out
there for some other module, I would be happy to steal from it.

Please advise how I can go about patching the kernel and if there is a
recipe for a kernel module - please point me to it.

Thank you

Autif