linux-kernel - Re: [PATCH v2 10/16] gpio: add a reusable generic gpio

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Message-ID: <CACRpkdZPZ4nFQ6B3tGG9wvceoTWqAkfY0r1UKs2pf_c=ZNBG=w@mail.gmail.com>
Date:   Thu, 16 Apr 2020 11:20:38 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Michael Walle <michael@...le.cc>
Cc:     Bartosz Golaszewski <bgolaszewski@...libre.com>,
        linux-gpio <linux-gpio@...r.kernel.org>,
        linux-devicetree <devicetree@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, linux-hwmon@...r.kernel.org,
        linux-pwm@...r.kernel.org,
        LINUXWATCHDOG <linux-watchdog@...r.kernel.org>,
        arm-soc <linux-arm-kernel@...ts.infradead.org>,
        Rob Herring <robh+dt@...nel.org>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Lee Jones <lee.jones@...aro.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Shawn Guo <shawnguo@...nel.org>, Li Yang <leoyang.li@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <maz@...nel.org>, Mark Brown <broonie@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v2 10/16] gpio: add a reusable generic gpio_chip using regmap

On Tue, Apr 14, 2020 at 9:57 PM Michael Walle <michael@...le.cc> wrote:

> So what about the following:
>
> #define GPIO_REGMAP_ADDR_ZERO (unsigned int)(-1)

Yeah with regmap explicitly using int I guess we can't use
S32_MAX, so that is fair.

> So this way the user might assign the base addresses the normal way
> except when he wants to use zero, in that case he has to use
>
>    ->base_adr = GPIO_REGMAP_ADDR_ZERO;
>
> gpio-regmap.c could use then:
>
> if (base_addr)
>    something_useful(gpio_regmap_addr(base_addr));
>
> unsigned int gpio_regmap_addr(unsigned int addr)
> {
>    return (addr == GPIO_REGMAP_ADDR_ZERO) ? 0 : addr;
> }

That's reasonably clean.

Yours,
Linus Walleij