On Thursday 23 October 2014 15:10:55 Alexandre Courbot wrote:
> >
> > Then, the driver needs to do something like:
> >
> > if (!device_property_present(dev,
> > "known_property_that_should_be_present")
> > && ACPI_COMPANION(dev))
> > acpi_probe_gpios(dev);
> >
> > and in the acpi_probe_gpios() routine there may be checks like:
> >
> > if (device_has_id(dev, "MARY0001")) {
> > The first pin in the first GpioIo resource in _CRS is
> > "fred" and
> > it is active-low.
> > The third pin in the second GpioIo resource in _CRS is
> > "steve"
> > and it is not active-low.
> > } else if (device_has_id(dev, "JANE0002")) {
> > The first pin in the second GpioIo resource in _CRS is
> > "fred" and
> > it is not active-low.
> > The second pin in the first GpioIo resource in _CRS is
> > "steve"
> > and it is active-low.
> > }
> >
> > and so on. Of course, there may be drivers knowing that the meaning of the
> > GpioIo resources in _CRS is the same for all devices handled by them, in
> > which
> > case they will not need to check device IDs, but the core has now way of
> > knowing that. Only the drivers have that information and the core has now
> > way to figure out what to do for a given specific device.
> >
> > So here's a radical idea: Why don't we introduce something like
> >
> > acpi_enumerate_gpio(dev, name, GpioIo_index, pin_index, active_low)
> >
> > such that after calling, say, acpi_enumerate_gpio(dev, "fred", 0, 0, true)
> > the
> > driver can do something like:
> >
> > desc = get_gpiod_by_name(dev, "fred");
> >
> > and it'll all work. Then, the only part of the driver that really needs to
> > be
> > ACPI-specific will be the acpi_probe_gpios() function calling
> > acpi_enumerate_gpio()
> > in accordance with what the device ID is.
>
> I like this idea. It doesn't complicate the GPIO interface (i.e. no
> "if you are on ACPI and no _DSD is present then gpiod_get() will
> behave that way...") and does the plumbing behind the scenes.
>
> I will also allow us to finally push the use of names instead of
> indexes in the GPIO API. I'm all for it.
Yes, sounds good.
Arnd
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