Re: How do I set user space GPIO polarity (active state) via device tree?

[Bartosz Golaszewski <brgl@xxxxxxxx>]

2018-02-14 15:59 GMT+01:00 Jonas Mark (ST-FIR/ENG1) <Mark.Jonas@xxxxxxxxxxxx>:
> Hello,
>
>> tl;dr: How do I set the polarity (active state) of a GPIO in the device
>> tree and use it from user space?
>
> I am still not able to declare the polarity of a GPIO via device tree
> so it can be used from user space using libgpio.
>
> I read the kernel documentation and did not find hint how to do this.
> What I found is how to set the polarity of a GPIO for a gpio-hog or a
> kernel driver. But that prevents the GPIO being used from user space.
>
> Thank you in advance for your help,
> Mark Jonas
>
> Mit freundlichen Grüßen / Best regards
>
>  Mark Jonas
>
> Security Systems, Panel Software Fire (ST-FIR/ENG1)
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Hi Jonas,

the active state of a GPIO line is a consumer-specific setting. For
example: you want to indicate to the GPIO push button driver that the
line it's using is active-low so that it correctly interprets the
falling edge event as a button *press* instead of a *release*.

It doesn't make sense to set it globally for a line in the kernel.

Hope that helps,
Bartosz
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