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

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Date:   Fri, 26 Apr 2019 21:26:50 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
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 8:52 PM Manivannan Sadhasivam
<manivannan.sadhasivam@...aro.org> wrote:
> 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 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.

It can be easily broken by shuffling DT, kernel cnfiguration and
adding some GPIO expanders. Note, no C-code mangling is involved.

>
> 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!


-- 
With Best Regards,
Andy Shevchenko