RE: How to use an ACPI declared GPIO in a userspace ...

Flavio Suligoi
2020-09-29T16:10:58Z

Hi Bartosz,

> > I need to expose to the userspace a GPIO, physically connected to a
> board
> > push-button. This GPIO must expose a pre-defined name, such as
> > "user-push-button", so that the userspace applications can use it
> without
> > know any physical GPIO details.
> >
> > I can customize the board BIOS and so my goal is to add an ACPI table
> with
> > a content like this:
> >
> > ...
> > Scope (\_SB.GPO1)
> > {
> > Device (BTNS)
> > {
> > Name (_HID, "PRP0001")
> > Name (_DDN, "GPIO buttons device")
> >
> > Name (_CRS, ResourceTemplate ()
> > {
> > GpioIo (
> > Exclusive, // Not shared
> > PullNone, // No need for
> pulls
> > 0, // Debounce
> timeout
> > 0, // Drive
> strength
> > IoRestrictionInputOnly, // Only used as
> input
> > "\\_SB.GPO1", // GPIO
> controller
> > 0, ResourceConsumer, , ) // Must be 0
> > {
> > 25, // GPIO number
> > }
> > ...
> >
> > I know that this GPIO can be used from other drivers.
> > For example I successfully tested it using the "gpio-keys" device
> driver,
> > giving to my GPIO a key-code and emulating in this way a keyboard key.
> > This could be a possible solution.
> >
> > But I prefer to expose my GPIO as a classic GPIO, not as a keyboard key.
> >
> > I was wondering if there is a generic GPIO driver that I can use to
> expose
> > this GPIO with its pre-defined name (caming from the ACPI table
> declaration),
> > to the userspace...
> >
> > Best regards,
> >
> > Flavio
>
> Adding Andy who knows ACPI GPIO well.
>
> In general, the "gpio-line-names" property is used for that and it's
> supported both for device tree as well as ACPI, although I have only
> ever used the former.
>
> Bartosz

Thanks! I'll try!!!

Flavio