linux-kernel - Re: [PATCH] lib/crc32: remove unused combination support

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Message-ID: <20250608234741.GF1259@sol>
Date: Sun, 8 Jun 2025 16:47:41 -0700
From: Eric Biggers <ebiggers@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: linux-crypto@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>
Subject: Re: [PATCH] lib/crc32: remove unused combination support

On Fri, Jun 06, 2025 at 08:22:28PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@...gle.com>
> 
> Remove crc32_le_combine() and crc32_le_shift(), since they are no longer
> used.
> 
> Although combination is an interesting thing that can be done with CRCs,
> it turned out that none of the users of it in the kernel were even close
> to being worthwhile.  All were much better off simply chaining the CRCs
> or processing zeroes.
> 
> Let's remove the CRC32 combination code for now.  It can come back
> (potentially optimized with carryless multiplication instructions) if
> there is ever a case where it would actually be worthwhile.
> 
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>
> ---
>  include/linux/crc32.h | 25 ----------------
>  lib/crc32.c           | 67 -------------------------------------------
>  lib/tests/crc_kunit.c | 39 +------------------------
>  3 files changed, 1 insertion(+), 130 deletions(-)

Applied to https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git/log/?h=crc-next

- Eric