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

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Date:	Wed, 30 Sep 2009 00:54:59 -0700
From:	Joe Perches <joe@...ches.com>
To:	Sam Ravnborg <sam@...nborg.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [RFC] move #define pr_fmt KBUILD_MODNAME and KMSG_COMPONENT to
 Makefiles?

On Wed, 2009-09-30 at 08:55 +0200, Sam Ravnborg wrote:
> On Tue, Sep 29, 2009 at 11:15:04AM -0700, Joe Perches wrote:
> > There are starting to be more uses of
> > #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> > and
> > #define KMSG_COMPONENT "foo"
> > #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
> > in kernel sources.
> > 
> > Perhaps it would be better to put these
> > defines in the appropriate Makefile and not
> > sprinkle the sources with them multiple times?
> 
> Maybe I'm a bit dense but I do not quite follow you
> here. What is it you want moved to kbuild here?
> 
> To me it looks more like a logical extension to the
> pr_* macros based on info we already have available.

Hi Sam.

I agree it's a logical extension to what exists
already, unfortunately there are already many
uses of pr_<level> calls, some that use pr_fmt(),
some that use an embedded constant string,
and some with nothing.  Using a predeclared
standardized pr_fmt would be a problem for
those calls that use embedded constant strings.

So today, every file in a module that uses
pr_fmt #defines pr_fmt before the #includes.

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

There are starting to be a lot of these and
likely there will be a lot more unless the
defines are standardized somehow.

Per Makefile ccflags would allow a gradual
conversion of the many pr_<level> calls that
are already prefixed with nothing, or constant
strings, or already use pr_fmt with either
KBUILD_MODNAME, KMSG_COMPONENT, or some
other fixed string.

If something like were added to a module Makefile:

	ccflags-y += -D "pr_fmt(fmt)=KBUILD_MODNAME \": \" fmt"

or if necessary a per-file entry in the Makefile:

	CFLAGS_foo.o += -D "pr_fmt(fmt)=KBUILD_MODNAME \": \" fmt"

the number of these #defines pr_fmt in source could be
reduced.

These new Makefiles -D entries could later be stripped
and the pr_fmt define standardized perhaps in the top
level Makefile after the existing pr_<level> calls with
embedded prefix strings in source are modified as necessary.

Something similar could be done in the Makefiles for
KMSG_COMPONENT uses as well.

cheers, Joe

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