linux-kernel - Re: [PATCH 2/2] lib/test_bits.c: Add tests for GENMASK

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Message-Id: <83972212-c8b6-4888-8574-4eb153008109@app.fastmail.com>
Date: Wed, 24 Jul 2024 12:45:55 +0200
From: "Arnd Bergmann" <arnd@...db.de>
To: "Anshuman Khandual" <anshuman.khandual@....com>,
 linux-kernel@...r.kernel.org
Cc: "Andrew Morton" <akpm@...ux-foundation.org>,
 "Yury Norov" <yury.norov@...il.com>,
 "Rasmus Villemoes" <linux@...musvillemoes.dk>,
 Linux-Arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH 2/2] lib/test_bits.c: Add tests for GENMASK_U128()

On Wed, Jul 24, 2024, at 12:31, Anshuman Khandual wrote:
> This adds GENMASK_U128() tests although currently only 64 bit wide masks
> are being tested.
>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---
>  lib/test_bits.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
>
> diff --git a/lib/test_bits.c b/lib/test_bits.c
> index 01313980f175..2515ddc34409 100644
> --- a/lib/test_bits.c
> +++ b/lib/test_bits.c
> @@ -39,6 +39,24 @@ static void genmask_ull_test(struct kunit *test)
>  #endif
>  }
> 
> +static void genmask_u128_test(struct kunit *test)
> +{
> +	/* Tests mask generation only when the mask width is within 64 bits */
> +	KUNIT_EXPECT_EQ(test, 0x0000000000ff0000ULL, GENMASK_U128(87, 80) >> 64);
> +	KUNIT_EXPECT_EQ(test, 0x0000000000ffffffULL, GENMASK_U128(87, 64) >> 64);
> +	KUNIT_EXPECT_EQ(test, 0x0000000000000001ULL, GENMASK_U128(0, 0));

This looks like it would need an #ifdef check for either
__SIZEOF_INT128__ or CONFIG_ARCH_SUPPORTS_INT128, otherwise
it will fail to build on all 32-bit architectures and possibly
old compiler versions on some 64-bit ones. I think I checked
in the past which targets support __u128, but I don't remember
the result.

    Arnd