This is a bit of a long shot, but is there a document anywhere 
that explains  how a driver is constructed?

In particular, I'm trying to understand how the eap driver works on i386,
with a mind to adding a new codec (using FreeBSD's pcm(4) as a reference,
although their driver isn't designed the same way).

Trouble is I'm finding it hard to follow the source alone - it's quite
difficult to see where the codecs are defined for example
(I stress this is PEBKAC, not a problem with the NetBSD source; C-wise,
I'm just past the 'teach yourself XX in 24 hours' level).

I'd rather have a crack at hacking it myself than buy a new card,
plus I've needed an excuse to look into the kernel source for ages...
 - just thought I'd aks if there were any useful docs I should know about,
and figured you guys must've learnt somewhere....
 
 Google seemed to draw a blank, so thought I'd ask here.

-- 
Rasputin :: Jack of All Trades - Master of Nuns