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

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Message-ID: <CA+55aFyjGZ=PLOBfyFub4kS3r2vJ0SFD58rTf21koPodFTSARQ@mail.gmail.com>
Date:	Wed, 9 May 2012 10:15:11 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Igor Mammedov <imammedo@...hat.com>, Jiang Liu <liuj97@...il.com>,
	linux-kernel@...r.kernel.org, mingo@...nel.org, pjt@...gle.com,
	tglx@...utronix.de, seto.hidetoshi@...fujitsu.com,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC][PATCH] printk: Add %pb to print bitmaps

On Wed, May 9, 2012 at 6:27 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> + * - 'b' For a bitmap, consumes 2 args, second is int
> + * - 'bc' For a cpumask
> + * - 'bn' For a nodemask

Hard NAK.

No way. The "consumes 2 args" is fundamentally idiotic, since it
forces compiler warnings. The whole idea of %pXX was that you can give
it any pointer, because all that the compiler cares about is the "%p"
part, so random pointers to stuff won't break.

Your patch breaks the whole point of the extension.

The "bc" and "bn" would work, except for the fact that I doubt they
are printed out enough to matter.

A "%.*pb" is the only interface that can work for a "sized" bitmap
(with obviously fixed-length ones being possible with a "%.32bp" like
thing)

But the whole va_args games you play are not acceptable. %p *will*
continue to take a void *, and nothing else.

                 Linus
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