linux-kernel - Re: [patch 1/3] kmsg: Kernel message catalog macros.

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Message-Id: <1218733457.2651.11.camel@localhost>
Date:	Thu, 14 Aug 2008 19:04:17 +0200
From:	Martin Schwidefsky <schwidefsky@...ibm.com>
To:	Tim Hockin <thockin@...kin.org>
Cc:	linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
	lf_kernel_messages@...ts.linux-foundation.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michael Holzheu <holzheu@...ibm.com>,
	Gerrit Huizenga <gh@...ibm.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	Jan Kara <jack@...e.cz>, Pavel Machek <pavel@....cz>,
	Sam Ravnborg <sam@...nborg.org>, Joe Perches <joe@...ches.com>,
	Jochen Voß <jochen.voss@...glemail.com>,
	Kunai Takashi <kunai@...ux-foundation.jp>,
	Tim Bird <tim.bird@...sony.com>
Subject: Re: [patch 1/3] kmsg: Kernel message catalog macros.

On Tue, 2008-08-12 at 17:35 -0700, Tim Hockin wrote:
> On Wed, Jul 30, 2008 at 9:56 AM, Martin Schwidefsky
> <schwidefsky@...ibm.com> wrote:
> > From: Michael Holzheu <holzheu@...ibm.com>
> > From: Martin Schwidefsky <schwidefsky@...ibm.com>
> >
> > Introduce a new family of printk macros which prefixes each kmsg message
> > with a component name and allows to tag the printk with a message id.
> 
> We've been talking about doing something like this, just this week.  AKPM
> pointed me at this thread.  Good timing. :)

Good to hear that we are not the only one working on this.

> > +#define kmsg_dev_alert(id, dev, format, arg...) \
> > +    printk(__KMSG_CHECK(ALERT, id) KMSG_COMPONENT \
> > +        ": %s: " format, (dev)->bus_id , ## arg)
> 
> Rather than the gcc-specific '## arg', shouldn't we use the standard C99
> form: '##__VA_ARGS__'  ?

Ok, I changed the macros accordingly.

> As a format, I would argue to leave out the spaces after colons, making
> the inevitable string splitting even easier.

Makes sense and it does not make the message harder to read.

> I don't care for the magic file-global KMSG_COMPONENT.  It just feels
> wrong.  In most cases, I want the prefix to be hierarchical.  For example,
> rather than "tg3" I want "net.tg3" or "netdev:tg3" or something.

But what is the alternative to the #define to specify the base name of
the message tag? KBUILD_MODNAME has been proposed but I don't think this
is a good idea since I want the message tags to be independent of the
code structure.

> Further, We want to make a clearer denotation between "just another
> printk()" and these things, which are really "important events".  Maybe a
> global prefix that makes it easy to seperate them out?  Or a parallel
> "event" interface that logs to printk() and a netlink socket?

Well the kmsg macros distinguish between id==0 and id>0 messages. For a
id==0 message there is no documentation required and the kmsg prefix
will be just the KMSG_COMPONENT. You could consider that to be "just
another printk". For id>0 the kmsg macros will create the tuppel
KMSG_COMPONENT.ID so you already can separate "normal" and "important"
prinkts.

-- 
blue skies,
  Martin.

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


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