linux-kernel - Re: [RFC][PATCH] printk: Add %pb to print bitmaps

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Message-ID: <1336581561.1905.3.camel@joe2Laptop>
Date:	Wed, 09 May 2012 09:39:21 -0700
From:	Joe Perches <joe@...ches.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Igor Mammedov <imammedo@...hat.com>,
	Jiang Liu <liuj97@...il.com>, linux-kernel@...r.kernel.org,
	pjt@...gle.com, tglx@...utronix.de, seto.hidetoshi@...fujitsu.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [RFC][PATCH] printk: Add %pb to print bitmaps

On Wed, 2012-05-09 at 18:06 +0200, Peter Zijlstra wrote:
> On Wed, 2012-05-09 at 17:41 +0200, Ingo Molnar wrote:
> > * Peter Zijlstra <peterz@...radead.org> wrote:
> > 
> > > On Wed, 2012-05-09 at 16:15 +0200, Ingo Molnar wrote:
> > > > > I guess I should use %.*pb and keep the field_width in case someone
> > > > > manages to actually make bitmap_scnlistprintf() conform to it. The
> > > > > precision is unused anyway.
> > > > 
> > > > That's a cute trick, and it's intuitive as well. 
> > > 
> > > kernel/sched/core.c:5570:3: warning: precision used with ‘%p’ gnu_printf format [-Wformat]
> > > 
> > > /me curses a bit.. anybody?
> > 
> > Yeah, that's a floating point precision thing (or for strings, 
> > right-align) - could you use %30pb, etc?
> 
> %*pb you mean? Yeah that works, field width is allowed for %p. It does
> mean we cannot ever make bitmaps respect field width though.

You could also fill a new struct with info
about the bitmap and pass a pointer to that.

struct print_bitmap_info {
	int foo;
	int precision;
	int width;
	void *bitmap;
};
...
	struct print_bitmap_info bi;
	bi.foo = bar;
	...
	bi.bitmap = &bitmap;
...
	printk("%pb", &bi);


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