linux-kernel - Re: [PATCH] lib/hexdump

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Message-Id: <20070502160635.31dd91e6.akpm@linux-foundation.org>
Date:	Wed, 2 May 2007 16:06:35 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Randy Dunlap <randy.dunlap@...cle.com>
Cc:	lkml <linux-kernel@...r.kernel.org>, jwboyer@...ux.vnet.ibm.com,
	grant.likely@...retlab.ca, jketreno@...ux.intel.com
Subject: Re: [PATCH] lib/hexdump

On Wed, 02 May 2007 15:56:48 -0700
Randy Dunlap <randy.dunlap@...cle.com> wrote:

> Andrew Morton wrote:
> > On Wed, 2 May 2007 15:35:56 -0700
> > Randy Dunlap <randy.dunlap@...cle.com> wrote:
> > 
> >> From: Randy Dunlap <randy.dunlap@...cle.com>
> >>
> >> Based on ace_dump_mem() from Grant Likely for the Xilinx 
> >> SystemACE CompactFlash interface.
> >>
> >> Add hex_dumper() to lib/hexdump.c and linux/kernel.h.
> >>
> >> This patch adds the function 'hex_dumper' which can be used to perform a 
> >> hex + ASCII dump of data to syslog, in an easily viewable format, thus
> >> providing a common text hex dump format.
> >>
> >> It does not provide a hexdump_to_buffer() function.
> >> if someone needs that, we'll have to add it.
> >>
> >> Example usage:
> >> 	hex_dumper(KERN_DEBUG, data, length);
> >>
> > 
> > Fair enough.  This is the sort of thing one could easily overdesign ;)
> 
> The Intel version also returned the number of bytes printed.
> and they had a hexdump_to_buffer() for sysfs output.
> 

Yeah, that's where we get into creature feeping.  Really it should be
passed the address of a function which performs the per-char output and
which is passed a bunch of args so it can do its stuff.  But doing printk
of a single char at a time is a bit inefficient and produces mangled output
on SMP.  And then we don't know the length of the output and we'd like it
dynamically allocated and on and on.

Ho hum.  Perhaps a middle ground is to implement hexdump-to-memory as the
core function.  hex_dumper() becomes a simple wrapper around that.  (but
how big is its buffer?  One line would be OK, I guess)

> OK, that's one way to do it.  I'll wait a bit for other comments.

Good luck ;)

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