linux-kernel - Re: [RESEND PATCH v4 3/8] gpio: 104-dio-48e: Utilize for_each_set

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Date:   Mon, 15 Oct 2018 13:59:33 +0200
From:   Rasmus Villemoes <linux@...musvillemoes.dk>
To:     William Breathitt Gray <vilhelm.gray@...il.com>
Cc:     linus.walleij@...aro.org, akpm@...ux-foundation.org,
        linux-gpio@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org, andriy.shevchenko@...ux.intel.com
Subject: Re: [RESEND PATCH v4 3/8] gpio: 104-dio-48e: Utilize
 for_each_set_clump macro

On 2018-10-14 06:19, William Breathitt Gray wrote:

> a bit value of 0 in the
> bits array does not necessarily mean the input was not requested, but
> may instead mean that the value at the input is 0;

sure enough, but...

> therefore, the caller
> must keep track of the requested inputs rather than try to deduce them
> from the values in the bits array.

...I don't agree that this logically follows. A caller might reasonably
expect not to find any bits set in positions other than those in mask. A
simple example would be caller that just tried to ask "are any of
_these_ inputs set"; it would be reasonable to implement that using
bitmap_empty() on the returned bitset, without first having to mask by
the mask he passed in.

Rasmus