linux-kernel - Re: [RFC][PATCHv2 2/3] lib: printf: append support of '%*p[Mm][FR]'

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Date:	Tue, 3 Jul 2012 21:32:42 +0300
From:	Andy Shevchenko <andy.shevchenko@...il.com>
To:	Joe Perches <joe@...ches.com>
Cc:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>, proski@....org,
	Andrei Emeltchenko <andrei.emeltchenko@...el.com>,
	linux-wireless@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCHv2 2/3] lib: printf: append support of '%*p[Mm][FR]'

On Tue, Jul 3, 2012 at 6:33 PM, Joe Perches <joe@...ches.com> wrote:
> On Tue, 2012-07-03 at 13:06 +0300, Andy Shevchenko wrote:
>> There are many places in the kernel where the drivers print small buffers as a
>> hex string. This patch adds a support of the variable width buffer to print it
>> as a hex string with a delimiter. The idea came from Pavel Roskin here:
>> http://www.digipedia.pl/usenet/thread/18835/17449/
>>
>> Sample output of
>>       pr_info("buf[%d:%d] %*pM\n", from, len, len, &buf[from]);
>> could be look like this:
>>       [ 0.726130] buf[51:8] e8:16:b6:ef:e3:74:45:6e
>>       [ 0.750736] buf[59:15] 31:81:b8:3f:35:49:06:ae:df:32:06:05:4a:af:55
>>       [ 0.757602] buf[17:5] ac:16:d5:2c:ef

> It might be more sensible to use new, distinct
> "%*pH" and "%*ph" functions and not touch the
> mac address function at all.  Will anyone ever
> really want to emit the buffer in reverse?
> I don't think so.
Yeah, probably it's only the case for the Bluetooth addresses.

> Perhaps when using a hex_string_buffer func the
> separator should be a space/no-space with %*pHh.
What I learned from today's linux-next is the most used separators are
' ' (space), '' (nothing), ':' and '-'. We have dozens of the cases
for first three. The '-' support could not be implemented
nevertheless.
So, might be %*pHh[CDS] C for 'colon', S for 'space', D for 'dash' looks better.
'Hh' for capital/small letters than?

> You could extend the max to 128 or larger now.
I don't think it is really needed. Most of the current cases usually
print not more than ~30bytes (in average) per time. And I couldn't
imagine good looking printing for long lines anyway.


-- 
With Best Regards,
Andy Shevchenko
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