when source code isn't enough

[Peter Jay Salzman <p@dirac.org>]

i've been finding some kernel source code extremely lacking in comments.
i'm trying to figure out how usb keyboards work, meaning i'm going back to
input.c (written by same person).

in input.c,

/*
 * Event types
 */

#define EV_RST       0x00
#define EV_KEY       0x01
#define EV_REL       0x02
#define EV_ABS       0x03
#define EV_LED       0x11
#define EV_SND       0x12
#define EV_REP       0x14
#define EV_MAX       0x1f


it's not clear to me what all these events mean.  this is more of a meta
question than a specific one -- are there resources out there that try to
document stuff like this?  a "google" or "yahoo" for kernel programming?

also, i'm wondering if !! is a double negation or something about C which
i've never learned:

#define input_report_key(a,b,c) input_event(a, EV_KEY, b, !!(c))

if it's a double negation, what possible purpose could it serve?

thanks!

pete


-- 
"Coffee... I've conquered the Borg on coffee!"               p@dirac.org
       -- Kathryn Janeway on the virtues of coffee           www.dirac.org/p
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