linux-kernel - Re: [PATCH] bitmap: simplify GENMASK(size

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Message-ID: <adcdf79d-e50c-2fb0-e105-67b384189999@quicinc.com>
Date:   Tue, 26 Oct 2021 11:26:14 -0400
From:   Qian Cai <quic_qiancai@...cinc.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
CC:     Yury Norov <yury.norov@...il.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] bitmap: simplify GENMASK(size - 1, 0) lines



On 10/26/21 11:10 AM, Andy Shevchenko wrote:
> On Tue, Oct 26, 2021 at 10:41:08AM -0400, Qian Cai wrote:
>> Since "size" is an "unsigned int", the rvalue "size - 1" will still be
>> "unsigned int" according to the C standard (3.2.1.5 Usual arithmetic
>> conversions). Therefore, GENMASK(size - 1, 0) will always return 0UL.
> 
> Huh?!
> 
> Have you run test_bitmap et al., btw?

Not yet. I'll setup a VM to run it soon.