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

[Joe Perches <joe@perches.com>]

On Tue, 2012-07-03 at 21:32 +0300, Andy Shevchenko wrote:
> On Tue, Jul 3, 2012 at 6:33 PM, Joe Perches <joe@perches.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.

Maybe use a space default.

> 'Hh' for capital/small letters than?

If you want, though I'd hope nobody uses upper case.

> > You could extend the max to 128 or larger now.
> I don't think it is really needed.

I hope it's not, but I just don't see the need to limit it.

> 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.

Yup, they'd be ugly.
print_hex_dump() should be favored anyway.

cheers, Joe