Re: Newbie Kernel Programmer looking for first project.

[Tim Rightnour <root%garbled.net@localhost>]

On 03-Jul-2008 Michael Litchard wrote:
> When I see a pattern like this:
> 
>#idef DEBUG
>    printf("foo"...);
>#endif
> 
> I replace those three line with
>    aprint_debug("foo...");
> 
> the reasoning being that aprint_debug uses AB_DEBUG to govern behavior,
> and a new convention is replacing the old.
> 
> But I'm starting to question this. I see more complex preprocessor commands,
> and now I wonder if I should just leave them alone. Could you give me some
> feedback?

These are a tough case.  One thing you see alot is something where we do a
ifdef DEBUG printf, but the arguments to the printf aren't defined unless DEBUG
is defined.  So you would run into some compile issues there.

Additionally, some of the DEBUG stuff is pretty heavyweight, and is there for
true debugging, not casual use through dmesg.

I'm inclined to say leave most of them working the way they currently do.  Ie,
in the case above, change it to:

#idef DEBUG
    aprint_normal("foo"...);
#endif

aprint_debug is more or less for cases where it doesn't require any additional
processing to just print out some additional data that we already happen to
have.

src/sys/arch/ofppc/ofppc/mainbus.c is a relatively good example of different
uses, though not a perfect example.  In init_openpic() you can see how we use
verbose to note the enabling of interrupts on an SMP machine, and then verbose
to note the address where the openpic was found.  (however, I see one is marked
normal, oops). Finally, down in init_ofppc_interrupt() you see where we use
debug.  (I say relatively good example, because there are a few bad uses, and
it looks like 1-2 printfs are still in there.  Bad Tim.)

Alot of these are judgement calls.  You kinda have to do your best.  I would
convert 1 or 2 files, and then mail the diffs to tech-kern for review.  With a
little feedback from some of us, you will get the hang of it quickly.

---
Tim Rightnour <root%garbled.net@localhost>
NetBSD: Free multi-architecture OS http://www.netbsd.org/
Genecys: Open Source 3D MMORPG: http://www.genecys.org/