howto debug scsi device driver ?

Hi,

I have a LSI MegaRAID i4 (511 series) IDE RAID card (I believe it is the 
same than DELL CERC card). This card works well on a 2.6.11.6 vanilla 
kernel, with the old megaraid module.

But I tried to upgrade the kernel to the last release (2.6.20) with 
almost the same config (I done a 'make oldconfig' command) and the card 
doesn't work anymore (the scsi host is not found on dmesg)

I diff-ed megaraid.c from both versions and I noticed megaraid release 
from 2.6.11.6 is 2.00.3 while release from 2.6.20 is 2.00.4... I looked 
on the code with my little coding skills, and I understood the main 
differences are :

* changing naming conventions for some data structures,
* hardening some pieces of code when saving/restoring IRQs
* adding some code for handling SCSI SENSE (don't know what it is for...)

I never hacked linux kernel, nor scsi low-level drivers, so I have 
absolutelly no ideas of the way of debugging this code... So I wondered 
some kernel gurus here would be kind enough to give me some hints (maybe 
a howto or a cookbook exists ?) to try to debug by myself this module !

Thanks !

PS: I added an entry #7999 on http://bugzilla.kernel.org

-- 
Rico

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