From: Joe Perches <joe@perches.com>
Subject: Re: [PATCH 2/9] ext4: Use pr_fmt and pr_<level>
Date: Thu, 22 Mar 2012 10:42:32 -0700
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Cc: Jiri Slaby <jirislaby@gmail.com>, Ted Ts'o <tytso@mit.edu>,
	Andreas Dilger <adilger.kernel@dilger.ca>,
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To: Jiri Slaby <jslaby@suse.cz>
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On Thu, 2012-03-22 at 18:02 +0100, Jiri Slaby wrote:
> On 03/20/2012 10:46 AM, Joe Perches wrote:
> > On Tue, 2012-03-20 at 10:25 +0100, Jiri Slaby wrote:
> >> On 03/20/2012 10:21 AM, Joe Perches wrote:
> >>> the ath5k pr_ conversion patches are to
> >>> standardize prefixes and to reduce code size by
> >>> centralizing tests.
> >> What is the "standard" prefix?
> > KBUILD_MODNAME
> 
> Instead, we should switch as many printks to dev_* and similar as
> possible, right?

I believe logging message use should be selected
to be as specific as possible (from high to low):

o <subsystem>_<level>
o netif_<level>
o netdev_<level>
o dev_<level>
o pr_<level>
o printk(KERN_<LEVEL>

> They are standard and provide a good interface for
> extensions: one has a device to work with. This is something what pr_*
> does not offer.

I completely agree.

I'd like to see some new subsystem prefixes
created and used as well.  Maybe:

fs_<level> (like Ted's ext4_<foo>)
io_<level> (scsi/ide/mtd)
mm_<level>

There are probably a few others like
cpu/video/sound that might be useful.

> Frankly, moving the debug code to a separate function should make the
> code rather faster. By moving the unlikely code out of the instruction
> cache.

I think it's better still to eliminate debug
code altogether via if (0) when reasonable
or use dynamic_debug (jump_tables) when
overall code size isn't an issue.

cheers, Joe