linux-kernel - Re: [PATCH v2 5/6] gpio-exar/8250-exar: Make set of exported GPIOs configurable

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Date:   Thu, 18 May 2017 20:43:36 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Jan Kiszka <jan.kiszka@...mens.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Alexandre Courbot <gnurou@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        Sudip Mukherjee <sudip.mukherjee@...ethink.co.uk>,
        Sascha Weisenberger <sascha.weisenberger@...mens.com>
Subject: Re: [PATCH v2 5/6] gpio-exar/8250-exar: Make set of exported GPIOs configurable

On Thu, May 18, 2017 at 5:59 PM, Jan Kiszka <jan.kiszka@...mens.com> wrote:
> On the SIMATIC, IOT2040 only a single pin is exportable as GPIO, the
> rest is required to operate the UART. To allow modeling this case,
> expand the platform device data structure to specify a (consecutive) pin
> subset for exporting by the gpio-exar driver.

> +       unsigned int first_gpio;

Perhaps pin?
Or shift?

Because first_gpio a bit confusing with Linux side of GPIO.

> -       unsigned int bank = offset / 8;
> -       unsigned int addr;
> +       struct exar_gpio_chip *exar_gpio = gpiochip_get_data(chip);
> +       unsigned int bank, addr;
>
> +       offset += exar_gpio->first_gpio;
> +       bank = offset / 8;

Can't we instead do something like the following:

struct exar_gpio_chip *exar_gpio = gpiochip_get_data(chip);
unsigned int bank = (offset + exar_gpio->pin) / 8;
unsigned int line = (offset + exar_gpio->pin) % 8;


> +       pdata.first_gpio = first_gpio;
> +       pdata.ngpio = ngpio;

Still thinking about device properties ("ngpios" and something like
"exar8250,gpio-start").

> +       unsigned int first_gpio;
> +       unsigned int ngpio;

u16 ?

-- 
With Best Regards,
Andy Shevchenko