Re: [PATCH] gpiolib-acpi: introduce acpi_get_gpio_by_index() helper

[Mika Westerberg <mika.westerberg@linux.intel.com>]

On Thu, Apr 04, 2013 at 11:19:53AM +0200, Benjamin Tissoires wrote:
> Hi Mika,
> 
> On Wed, Apr 3, 2013 at 12:56 PM, Mika Westerberg
> <mika.westerberg@linux.intel.com> wrote:
> > Instead of open-coding ACPI GPIO resource lookup in each driver, we provide
> > a helper function analogous to Device Tree version that allows drivers to
> > specify which GPIO resource they are interested (using an index to the GPIO
> > resources). The function then finds out the correct resource, translates
> > the ACPI GPIO number to the corresponding Linux GPIO number and returns
> > that.
> >
> > Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
> > ---
> >  Documentation/acpi/enumeration.txt |   32 ++++++++++++++-
> >  drivers/gpio/gpiolib-acpi.c        |   77 ++++++++++++++++++++++++++++++++++++
> >  include/linux/acpi_gpio.h          |   17 ++++++++
> >  3 files changed, 125 insertions(+), 1 deletion(-)
> >
> > diff --git a/Documentation/acpi/enumeration.txt b/Documentation/acpi/enumeration.txt
> > index 94a6561..b0d5410 100644
> > --- a/Documentation/acpi/enumeration.txt
> > +++ b/Documentation/acpi/enumeration.txt
> > @@ -199,6 +199,8 @@ the device to the driver. For example:
> >         {
> >                 Name (SBUF, ResourceTemplate()
> >                 {
> > +                       ...
> > +                       // Used to power on/off the device
> >                         GpioIo (Exclusive, PullDefault, 0x0000, 0x0000,
> >                                 IoRestrictionOutputOnly, "\\_SB.PCI0.GPI0",
> >                                 0x00, ResourceConsumer,,)
> > @@ -206,10 +208,20 @@ the device to the driver. For example:
> >                                 // Pin List
> >                                 0x0055
> >                         }
> > +
> > +                       // Interrupt for the device
> > +                       GpioInt (Edge, ActiveHigh, ExclusiveAndWake, PullNone,
> > +                                0x0000, "\\_SB.PCI0.GPI0", 0x00, ResourceConsumer,,)
> 
> Sorry for coming late in the GPIO ACPI discussion, but when I see this
> documentation, I wonder:
> wouldn't it be feasible to find the correct GPIO by its type? Here, we
> have a GpioIo and a GpioInt, and I bet this would be sometime more
> useful to request the first GpioInt without knowing the correct order
> of declarations.

Why not. But then again you can always check the type returned in the
acpi_gpio_info structure and pick the first GpioInt (if you have multiple
GPIO resources).

> It may be feasible by walking the tree, but a helper would be of great
> help (thinking at i2c-hid here, which can not rely on indexes in the
> DSDT).

Well, index is the only thing we can rely on unfortunately. There's nothing
like names or anything like that.

What I've seen from ACPI enumerated i2c-hid devices there is only one GPIO
resource (GpioInt) declared.