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

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Date:   Mon, 22 May 2017 19:33:35 +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 Sun, May 21, 2017 at 2:43 PM, Jan Kiszka <jan.kiszka@...mens.com> wrote:
> On 2017-05-18 19:43, Andy Shevchenko wrote:
>> 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

>>> +       pdata.first_gpio = first_gpio;
>>> +       pdata.ngpio = ngpio;
>>
>> Still thinking about device properties ("ngpios" and something like
>> "exar8250,gpio-start").
>
> Changed back to properties, removing all platform data.
>
> But what's the purpose of prefixing the name here? This does not have
> anything to do with device trees. It's a private parameter channel
> between the creating device driver and the gpio driver, and there will
> be no other bindings.

To avoid potential collision with registered official property, that's
why better to use prefix.
(I didn't find anything like GPIO start / pin in registered
properties, maybe there is one)

>>> +       unsigned int first_gpio;
>>> +       unsigned int ngpio;
>>
>> u16 ?

> If we do that, then we would rather have to choose u8. But this is
> pointless restriction. I prefer to stay with the native type.

Still for properties it would be u32, wouldn't it?

-- 
With Best Regards,
Andy Shevchenko