linux-kernel - Re: [PATCH 05/17] Blackfin: convert to generic checksum code

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Date:	Wed, 24 Jun 2009 00:06:09 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Mike Frysinger <vapier.adi@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	uclinux-dist-devel@...ckfin.uclinux.org,
	Michal Simek <monstr@...str.eu>,
	Paul Mundt <lethal@...ux-sh.org>
Subject: Re: [PATCH 05/17] Blackfin: convert to generic checksum code

On Tuesday 23 June 2009, Mike Frysinger wrote:
> and this is an internal tester ... if we're going to let arches
> override it, then its function signature are pretty much set in stone.
> i agree we should test every checksum function, but i think only
> testing do_csum indirectly would be detrimental to the people who
> would want to use this -- arch maintainers looking to implement
> do_csum() themselves.  otherwise they need to step through the
> surrounding functions a bit to find the exact values given to
> do_csum() and the exact value expected back such that the calling
> function still works.  and every arch guy is going to do this same
> thing.

It depends on how we want to use it. If it's only for testing architecture
that have moved to the generic checksum code, that's fine. I was
thinking we could also use it for architectures that want to keep
their own code, but we don't have to.

> i'm a bit of a nub here wrt checksuming.  the test module i came up
> with by simply flooding my board and copying & pasting mismatched
> buffers ;).  are you saying the following should be OK ?
> -    if (tret != do_csum_data[i].ret) {
> +    if (tret != le16_to_cpu(do_csum_data[i].ret)) {

yes, that should work.

> unless there is a macro i could use that'd do the expansion at CPP
> time so i'd write the test data as:
> static struct do_csum_data __initdata do_csum_data[] = {
>         DO_CSUM_DATA(1, le16_to_cpu(0x0020)),
> ...

Ah, right that won't. I tested only on x86 (little-endian), so
le16_to_cpu() is an identity function that can be evaluated for
constants, but on big-endian that would break.

	Arnd <><
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