netdev - Re: [PATCH] add %pM printf format specifier

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Date:	Sun, 26 Oct 2008 09:30:22 +0100
From:	Johannes Berg <johannes@...solutions.net>
To:	David Miller <davem@...emloft.net>
Cc:	anders@...uras.de, netdev@...r.kernel.org
Subject: Re: [PATCH] add %pM printf format specifier

On Sun, 2008-10-26 at 09:21 +0100, Johannes Berg wrote:

> Of course, actually adding, say, %p4 and %p6 would be trivial, but
> making lots of code use it so it's useful would be another mass
> conversion I'm not too keen to do again right away :)

Actually... At least for ipv6 that isn't true, just do something like
this:

@@ include/linux/kernel.h
-#define NIP6(addr) \
-...
+#define NIP6(addr) &addr

-#define NIP6_FMT "%04x:%04x:%04x:%04x:%04x:%04x:%04x:%04x"
-#define NIP6_SEQFMT "%04x%04x%04x%04x%04x%04x%04x%04x"
+#define NIP6_FMT "%p6"
+#define NIP6_SEQFMT "%#p6"

and then add the correct stuff to pointer() in lib/vsprintf.c, something
like

static char *ip6_string(char *buf, char *end, be16 *addr, int field_width, int precision, int flags)
{
	char ip6[8*5];
	char *p = ip6;
	int i;
	u16 tmp;

	for (i=0; i<7; i++) {
		tmp = cpu_to_le16(addr[i]);
		p = pack_hex_byte(p, tmp >> 8);
		p = pack_hex_byte(p, tmp & 0xFF);
		if (!(flags & SPECIAL))
			*p++ = ':';
	}
	tmp = cpu_to_le16(addr[7]);
	p = pack_hex_byte(p, tmp >> 8);
	p = pack_hex_byte(p, tmp & 0xFF);
	*p = '\0';

	return string(buf, end, ip6, field_width, precision, flags & ~SPECIAL);
}


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