linux-kernel - RE: [PATCH 0/1] Add KUnit tests for lib/crc16.c

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Message-ID: <7f67ae7f15524e4eab6b15cdfd750a04@AcuMS.aculab.com>
Date: Thu, 26 Sep 2024 16:21:12 +0000
From: David Laight <David.Laight@...LAB.COM>
To: 'Vinicius Peixoto' <vpeixoto@...amp.dev>, André Almeida
	<andrealmeid@...eup.net>
CC: Brendan Higgins <brendan.higgins@...ux.dev>, "~lkcamp/patches@...ts.sr.ht"
	<~lkcamp/patches@...ts.sr.ht>, Rae Moar <rmoar@...gle.com>, David Gow
	<davidgow@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>,
	"kunit-dev@...glegroups.com" <kunit-dev@...glegroups.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>
Subject: RE: [PATCH 0/1] Add KUnit tests for lib/crc16.c

...
> The checksums for the randomly-generated test cases were calculated
> using a reference implementation [1] and this test compares them against
> the values yielded by the kernel's implementation.

I'd just use a naïve implementation - doesn't really matter
if it is a bit slow.

Slow is relative - this code only takes 35ms to crc-64 over 5MB of data.

{
    volatile const uint32_t *r = (const void *)buf;
    for (crc = 0; r < (const uint32_t *)buf_end; r++) {
        uint64_t val = le32toh(*r);
        crc ^= bswap64(val);
        for (i = 0; i < 32; i++) {
            if (crc & (1ull << 63))
                crc = (crc << 1) ^ 0x42f0e1eba9ea3693ull;
            else
                crc = crc << 1;
        }
    }
}

	David

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