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

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Message-Id: <1218011716.20769.12.camel@localhost>
Date:	Wed, 06 Aug 2008 10:35:16 +0200
From:	Martin Schwidefsky <schwidefsky@...ibm.com>
To:	Greg KH <gregkh@...e.de>
Cc:	Kay Sievers <kay.sievers@...y.org>, 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>,
	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, 2008-08-05 at 15:31 -0700, Greg KH wrote:
> On Thu, Jul 31, 2008 at 11:10:04AM +0200, Martin Schwidefsky wrote:
> > On Wed, 2008-07-30 at 15:04 -0700, Greg KH wrote:
> > > On Thu, Jul 31, 2008 at 12:02:04AM +0200, Kay Sievers wrote:
> > > > On Wed, Jul 30, 2008 at 18:56, Martin Schwidefsky
> > > > <schwidefsky@...ibm.com> wrote:
> > > > 
> > > > > +#define kmsg_dev_alert(id, dev, format, arg...) \
> > > > > +       printk(__KMSG_CHECK(ALERT, id) KMSG_COMPONENT \
> > > > > +               ": %s: " format, (dev)->bus_id , ## arg)
> > > > 
> > > > Care to use dev_name(), bus_id will be removed soon.
> > > 
> > > Hm, just use dev_printk() instead, it handles all of these kinds of
> > > changes automatically.
> > 
> > Using dev_printk won't work because of the order of the elements of the
> > printk. The kmsg tag should not have a "random" position in the printk
> > but should be the first element. If we use dev_printk the kmsg tag will
> > be the third element, for other kmsg printks it will be the first. In
> > addition the kmsg message tag for the device drivers already includes
> > the driver name ..
> 
> But the structure of dev_printk() is well definied and should be pretty
> trival to parse even with missing fields.

The missing field is the message tag. Which is the key for the message
lookup. As far as the kmsg catalog is concerned this is a pretty
important field that may not be missing from the printk itself.

> And if not, fix up dev_printk() to properly delinate when we have
> missing fields, why create a totally new thing here that we need to
> convert subsystems into?

To "fix" dev_printk would mean to add the message tag. Which requires to
change all callers. The better approach is to add a new printk wrapper
and decide for each subsystem if it shouuld be converted. I'm not
advocating to change everything. The kmsg macros is a way to document
the message from a piece of code if you choose to use these macros. 

What could be done is to move the kmsg_dev_xxx macros to
include/linux/device.h if you want to keep all device printk related
definitions in one place. Would that be more acceptable ?

-- 
blue skies,
  Martin.

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


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