linux-kernel - Re: [PATCH 2/2] gpio: sch: Add interrupt support

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Date:   Fri, 26 Apr 2019 23:22:40 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Jan Kiszka <jan.kiszka@...mens.com>,
        "Enrico Weigelt, metux IT consult" <lkml@...ux.net>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH 2/2] gpio: sch: Add interrupt support

On Fri, Apr 26, 2019 at 08:44:36PM +0300, Andy Shevchenko wrote:
> On Fri, Apr 26, 2019 at 8:33 PM Manivannan Sadhasivam
> <manivannan.sadhasivam@...aro.org> wrote:
> > On Fri, Apr 26, 2019 at 08:20:19PM +0300, Andy Shevchenko wrote:
> > > On Fri, Apr 26, 2019 at 7:05 PM Jan Kiszka <jan.kiszka@...mens.com> wrote:
> > > > On 26.04.19 16:42, Enrico Weigelt, metux IT consult wrote:
> > > > > On 26.04.19 15:36, Jan Kiszka wrote:
> 
> > > The problem here is opaque number. This has to be chip + *relative* pin number/
> > > See this:
> > > https://stackoverflow.com/questions/55532410/how-do-linux-gpio-numbers-get-their-values/55579640#55579640
> > >
> >
> > But for platform like 96Boards we don't need controller specific lookup, these
> > are all handled by the platform code [1] so that the users can use the standard
> > pinout number to access GPIOs.
> 
> This is a complete mistake.
> 
> There is *no* global GPIO numbers anymore in Linux. (I don't count
> very old legacy platforms)
> Read above, it applies to DT or whatever resource provider.
> 

I think you misunderstood what I said. I referred the standard 96Boards
pinout and in the MRAA platform code, individual boards just map their
GPIO chip and line number based on that. I didn't mean the deprecated
global linux numbering.

https://github.com/intel-iot-devkit/mraa/blob/master/src/arm/96boards.c#L109

And of couse as Jan mentioned, the chip number will change when some
other external GPIO controller got probed before but so far we haven't
got to it!

Regards,
Mani

> > For instance, pin 23 on the Low Speed expansion
> > header is the GPIO for all 96Boards platform, so the user can access that pin
> > using 23 itself in the application and it will run across all supported
> > 96Boards.
> >
> > That's one of the reason why we prefer MRAA.
> 
> > [1] https://github.com/intel-iot-devkit/mraa/blob/master/src/arm/96boards.c#L75
> 
> -- 
> With Best Regards,
> Andy Shevchenko