raid5 xor help

Hello,

I was going thru the raid5 code in the linux software raid. I could
not figure out the parity computation. The mothod 'compute_parity' is
somehow calling functions like 'do_2' , 'do_3' , etc - but I could not
find their defnitions anywhere. Is there any documentation about the
raid implementations in linux? Could you please help me out in this
regard. Thanks.

Regards,