linux-kernel - Re: [RFC] move #define pr_fmt KBUILD_MODNAME and KMSG

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Message-ID: <20091001130219.7f0db35d@mschwide.boeblingen.de.ibm.com>
Date:	Thu, 1 Oct 2009 13:02:19 +0200
From:	Martin Schwidefsky <schwidefsky@...ibm.com>
To:	Joe Perches <joe@...ches.com>
Cc:	Sam Ravnborg <sam@...nborg.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] move #define pr_fmt KBUILD_MODNAME and KMSG_COMPONENT to
 Makefiles?

On Wed, 30 Sep 2009 07:52:58 -0700
Joe Perches <joe@...ches.com> wrote:

> On Wed, 2009-09-30 at 11:20 +0200, Martin Schwidefsky wrote:
> > On Wed, 30 Sep 2009 00:54:59 -0700
> > Joe Perches <joe@...ches.com> wrote:
> > > If something like were added to a module Makefile:
> > > 	ccflags-y += -D "pr_fmt(fmt)=KBUILD_MODNAME \": \" fmt"
> > 
> > Where is the difference between the definition of the macro in the 
> > source file? It's still one additional line, no?
> 
> Look at net/netfilter/ipvs for instance.
> 
> It would have been possible to add:
> 
> 	ccflags-y += -D "KMSG_COMPONENT=IPVS"
> 	ccflags-y += -D "pr_fmt(fmt)=KMSG_COMPONENT \": \" fmt"
> 
> to net/netfilter/ipvs/Makefile instead of adding it
> to 23 files.

That can make sense if you have lots of files that use the same
KMSG_COMPONENT. 

> Same sort of thing for drivers/s390/char/Makefile,
> though it's less beneficial there.
> 
> Multiple
> 	CFLAGS_foo.o += -D "KMSG_COMPONENT=foo"
> and a single
> 	ccflags-y += -D "pr_fmt(fmt)=KMSG_COMPONENT \": \" fmt"
> 
> > And if you are dreaming of converting all source files
> > to the pr_fmt mechanism, this is a big effort ..
> 
> I think it could be a useful mechanism to define pr_fmt
> for individual module Makefiles and there's no rush...

If you need multiple
	CFLAGS_foo.o += -D "KMSG_COMPONENT=foo"
lines the benefit of the Makfile method is limited. In general I find
the code to be less clear if I have to search for the message prefix in
the Makefile instead of the start of the C file. Personal preference I
guess.

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.

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