linux-kernel - Re: About multi-line printk and the need (not) to repeat loglevel markers [Was: Re: [PATCH] ARM: mx3/pcm037: properly allocate memory for mx3-camera]

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Date:	Tue, 23 Nov 2010 11:58:30 +0100
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	linux-arm-kernel@...ts.infradead.org, kernel@...gutronix.de,
	linux-kernel@...r.kernel.org,
	Arjan van de Ven <arjan@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: About multi-line printk and the need (not) to repeat loglevel
	markers [Was: Re: [PATCH] ARM: mx3/pcm037: properly allocate memory
	for mx3-camera]

On Tue, Nov 23, 2010 at 11:39:40AM +0100, Uwe Kleine-König wrote:
> Hello,
> 
> [extended the audience to lkml and a few more]
> 
> On Tue, Nov 23, 2010 at 10:12:11AM +0000, Russell King - ARM Linux wrote:
> > On Tue, Nov 23, 2010 at 10:43:02AM +0100, Uwe Kleine-König wrote:
> > > There is no need to memzero the buffer because dma_alloc_coherent zeros
> > > the memory for us.
> > > 
> > > This fixes:
> > > 
> > > 	BUG: Your driver calls ioremap() on system memory.  This leads
> > > 	<4>to architecturally unpredictable behaviour on ARMv6+, and ioremap()
> > > 	<4>will fail in the next kernel release.  Please fix your driver.
> > > 
> > > Tested-by: Michael Grzeschik <mgr@...gutronix.de>
> > > Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> > > ---
> > [...]
> > > I assume sending a patch to remove the <4> is just a waste of time,
> > > isn't it?
> (this message is generated by:
> 
> 	printk(KERN_WARNING "BUG: Your driver calls ioremap() on system memory.  This leads\n"
> 	       KERN_WARNING "to architecturally unpredictable behaviour on ARMv6+, and ioremap()\n"
> 	       KERN_WARNING "will fail in the next kernel release.  Please fix your driver.\n");
> 
> in arch/arm/mm/ioremap.c.)
> 
> > Hmm, someone changed the behaviour of printk - it used to require the
> > tag after each newline.  It seems that it only requires it as the first
> > few characters now, which is a pain in the backside if you split
> > printk's.
> > 
> > IOW:
> > 
> > 	printk(KERN_ERR "foo bar baz ");
> > 	printk("buz\n" KERN_WARNING "fiz\n");
> > 
> > used to result in "foo bar baz buz" being printed at error level, and
> > "fiz" at warning level.  Today, you'll get "foo bar baz buz" at error
> > level, and "<4>fiz" at the default level.
BTW, I just noticed that Linus wrote:

	Additionally, if no newline existed, one is added (unless the
	log-level is the explicit KERN_CONT marker, to explicitly show
	that it's a continuation of a previous line).

This seems to be unimplemented, otherwise the output of

	printk(KERN_ERR "foo bar baz ");
	printk("buz\n" KERN_WARNING "fiz\n");

should be

	"foo bar baz \n" at error level
	"buz\n<4>fiz\n" at default level

useless_mail_counter++;

Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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