linux-kernel - Re: [PATCH] gpio: aggregator: Wrap access to gpiochip

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Date:   Mon, 4 Oct 2021 16:22:17 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Geert Uytterhoeven <geert+renesas@...der.be>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] gpio: aggregator: Wrap access to gpiochip_fwd.tmp[]

On Mon, Oct 4, 2021 at 3:47 PM Geert Uytterhoeven
<geert+renesas@...der.be> wrote:
>
> The tmp[] member of the gpiochip_fwd structure is used to store both the
> temporary values bitmap and the desc pointers for operations on multiple
> GPIOs.  As both are arrays with sizes unknown at compile-time, accessing
> them requires offset calculations, which are currently duplicated in
> gpio_fwd_get_multiple() and gpio_fwd_set_multiple().
>
> Introduce (a) accessors for both arrays and (b) a macro to calculate the
> needed storage size.  This confines the layout of the tmp[] member into
> a single spot, to ease maintenance.

...

> +#define fwd_tmp_descs(fwd)     (void *)&(fwd)->tmp[BITS_TO_LONGS((fwd)->chip.ngpio)]
> +
> +#define fwd_tmp_size(ngpios)   (BITS_TO_LONGS((ngpios)) + (ngpios))

...

> -       fwd = devm_kzalloc(dev, struct_size(fwd, tmp,
> -                          BITS_TO_LONGS(ngpios) + ngpios), GFP_KERNEL);
> +       fwd = devm_kzalloc(dev, struct_size(fwd, tmp, fwd_tmp_size(ngpios)),
> +                          GFP_KERNEL);

Shouldn't we rather use devm_bitmap_zalloc() / bitmap_free()?

>         if (!fwd)
>                 return ERR_PTR(-ENOMEM);


-- 
With Best Regards,
Andy Shevchenko