linux-kernel - Re: [RFC PATCHv3] printk: add %pM format specifier for MAC addresses

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Message-Id: <1225144515.5269.40.camel@localhost>
Date:	Mon, 27 Oct 2008 14:55:15 -0700
From:	Joe Perches <joe@...ches.com>
To:	Harvey Harrison <harvey.harrison@...il.com>
Cc:	David Miller <davem@...emloft.net>, johannes@...solutions.net,
	anders@...uras.de, netdev@...r.kernel.org,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCHv3] printk: add %pM format specifier for MAC
 addresses

On Mon, 2008-10-27 at 12:59 -0700, Harvey Harrison wrote:

The changes to use %p4 aren't too bad.
I did that last year using a similar style
to print_mac.  80 or so files.
http://repo.or.cz/w/linux-2.6/trivial-mods.git?a=shortlog;h=refs/heads/print_ipv4
ipv6 was 30 or so files
http://repo.or.cz/w/linux-2.6/trivial-mods.git?a=shortlog;h=refs/heads/print_ipv6

> I was wondering if perhaps it would be
> better to allow a length to be specified as well, which would allow:
[]
> But if that was added, it may be more natural to call it 
> %pB (bytes)
> %pW (words)

I think length would not be good addition.
print_dump_hex already does a fine job.
There are also BE/LE expectation problems with pW.

The %p6 pointer should be in6_addr *
The %p4 pointer should be __be32 *.
Printing an ipv4 address should use %u.%u.%u.%u

I've been doodling with sparse to check
calls with __attribute__(format(printf
parsing the format strings for %p<FOO>
and match the argument types.

I'll post it if anything comes of it.

> +static char *mac_address(char *buf, char *end, u8 *addr, int field_width,
> +			 int precision, int flags)
> +{

mac_address_string please.

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