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

[Jan Kiszka]

On 26.04.19 19:20, Andy Shevchenko wrote:
> On Fri, Apr 26, 2019 at 7:05 PM Jan Kiszka <jan.kiszka@xxxxxxxxxxx> wrote:
> > On 26.04.19 16:42, Enrico Weigelt, metux IT consult wrote:
> > > On 26.04.19 15:36, Jan Kiszka wrote:
> > >
> > > > At the same time, there are no real alternatives - to my> knowledge - for the value it brings (various bindings) to simply
> > > switch> the engine.
> > > Which value exactly does that collection of crude wrappers and broken
> > > attempts to buypass the kernel (driving gpios via /dev/mem *facepalm*)
> > > provide ?
> >
> > Leaving that blunt hack aside:
> >
> > import mraa
> >
> > pin = mraa.Gpio(13)
> > pin.dir(mraa.DIR_OUT)
> > pin.write(1)
> >
> > And the same goes for nodejs, java and c++.
> >
> > Moreover, this allows you to abstract away where "Pin 13" actually came from on
> > that board if the kernel changes (BSP -> upstream...) or the extension board or
> > ...
>
> 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

...and device path based discovery of the base:

https://github.com/siemens/mraa/commits/jan/queue

And I think that makes good use cases for application-level abstractions like in 
mraa. You don't want all user having to learn those nasty details, for 
devicetree, ACPI, and even worse stuff.

Jan

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