Re: [PATCH 2/2] lib/test_bits.c: Add tests for GENMASK_U128()

[Arnd Bergmann]

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@xxxxxxxxxxxxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> ---
>  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