linux-kernel - Re: [RFC] LZO de/compression support

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Date:	Thu, 31 May 2007 23:51:26 +0530
From:	"Satyam Sharma" <satyam.sharma@...il.com>
To:	"Nitin Gupta" <nitingupta910@...il.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Daniel Hazelton" <dhazelton@...er.net>,
	"Richard Purdie" <richard@...nedhand.com>,
	"Bret Towe" <magnade@...il.com>
Subject: Re: [RFC] LZO de/compression support - take 6

On 5/31/07, Nitin Gupta <nitingupta910@...il.com> wrote:
> [...]
> The author (Markus Oberhumer) of LZO  provided these comments for this patch:
>
> ---
> I've only briefly looked over it, but it's obvious that your version does not
> work on architechtures which do not allow unaligned access (arm, mips, ...).
>
> As for further quality assurance, your version should generate byte-identical
> object code to LZO 2.02 when using the same compiler & flags. So you could do
> some semi-automatic testing by compiling with -ffunction-sections and use
> "objcopy --only-section .text.XXX" to compare the md5sum of all generated
> functions. This also works fine with crosscompilers.
>
> Finally I'm not too happy that you renamed the functions and #defines like
> LZO1X_WORKMEM_SIZE - please stay compatible with the official library version.

As suggested by Johannes earlier, it'd be great if you could submit
the various changes (as per Changelog) as _individual patches_ on
the original userspace code. That would be easier for others to review,
and there's lesser chances of bugs / issues leaking in that way.

As for "byte-identical object code", I definitely do *not* think it is
necessarily a requirement / good idea. As long as all the changes
you make are reviewed individually / closely by people here on this
list, there's very low chances of any bugs creeping in. [ F.e. I see
nothing wrong in removing the usage of "register" -- that could clearly
lead to different object code, but with no bugs introduced. ]
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