linux-kernel - Re: [PATCH v2 5/8] pinctrl: nuvoton: Add driver for WPCM450

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Date:   Thu, 9 Dec 2021 08:26:24 +0000
From:   Zev Weiss <zweiss@...inix.com>
To:     Jonathan Neuschäfer <j.neuschaefer@....net>
CC:     Andy Shevchenko <andy.shevchenko@...il.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Tomer Maimon <tmaimon77@...il.com>,
        "openbmc@...ts.ozlabs.org" <openbmc@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v2 5/8] pinctrl: nuvoton: Add driver for WPCM450

On Wed, Dec 08, 2021 at 05:58:30AM PST, Jonathan Neuschäfer wrote:
>Hi,
>
>On Wed, Dec 08, 2021 at 01:24:18PM +0200, Andy Shevchenko wrote:
>> On Tuesday, December 7, 2021, Jonathan Neuschäfer <j.neuschaefer@....net>
>
><snip>
>
>> > +static void wpcm450_gpio_irqhandler(struct irq_desc *desc)
>> > +{
>> > +       struct wpcm450_gpio *gpio = gpiochip_get_data(irq_desc_
>> > get_handler_data(desc));
>> > +       struct wpcm450_pinctrl *pctrl = gpio->pctrl;
>> > +       struct irq_chip *chip = irq_desc_get_chip(desc);
>> > +       unsigned long pending;
>> > +       unsigned long flags;
>> > +       unsigned long ours;
>> > +       unsigned int bit;
>> > +
>> > +       ours = ((1UL << gpio->num_irqs) - 1) << gpio->first_irq_bit;
>>
>>
>> BIT()
>
>I'll use it, but in this case, I think it doesn't simplify much the
>whole expression all that much. Is there perhaps a macro that
>constructs a continuous bitmask of N bits, perhaps additionally
>left-shifted by M bits?
>
>Maybe somewhere in the bitmap_* API...
>

There's GENMASK(), though it takes a high bit and low bit rather than a
bit position and count, so it'd require a small bit of arithmetic, e.g.

  lastbit = gpio->first_irq_bit + gpio->num_irqs - 1;
  ours = GENMASK(lastbit, gpio->first_irq_bit);

or a manual shift:

  ours = GENMASK(gpio->num_irqs - 1, 0) << gpio->first_irq_bit;

(I don't have any terribly strong opinions on which of these is best,
personally.)



Zev