linux-kernel - Re: [PATCHv8] gpio: Remove VLA from gpiolib

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Message-ID: <fc2fb457-57eb-d929-1061-5bc00ee218a8@redhat.com>
Date:   Mon, 21 May 2018 10:30:55 -0700
From:   Laura Abbott <labbott@...hat.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Kees Cook <keescook@...omium.org>,
        Lukas Wunner <lukas@...ner.de>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        kernel-hardening@...ts.openwall.com,
        Phil Reid <preid@...ctromag.com.au>
Subject: Re: [PATCHv8] gpio: Remove VLA from gpiolib

On 05/18/2018 02:12 PM, Andy Shevchenko wrote:
> On Sat, May 19, 2018 at 12:05 AM, Geert Uytterhoeven
> <geert@...ux-m68k.org> wrote:
>> On Fri, May 18, 2018 at 10:07 PM, Andy Shevchenko
>> <andy.shevchenko@...il.com> wrote:
>>> On Fri, May 18, 2018 at 8:53 PM, Laura Abbott <labbott@...hat.com> wrote:
> 
>>>> +               bits = mask + BITS_TO_LONGS(chip->ngpio);
>>>> +               memset(mask, 0, BITS_TO_LONGS(chip->ngpio) * sizeof(*mask));
>>>
>>> Wouldn't be better
>>>
>>> bitmap_zero(mask, chip->ngpio);
>>>
>>> ?
>>
>> chip->ngpio is never const, so bitmap_zero() would always fall back to
>> plain memset().
> 
> Yes. But it also much more readable and understandable here.
> 

I wasn't aware of that API. I'll switch to that.