On Sat, Oct 25, 2014 at 7:05 AM, Rafael J. Wysocki [off-list ref] wrote:

From: Rafael J. Wysocki <redacted>

Provide a way for device drivers using GPIOs described by ACPI
GpioIo resources in _CRS to tell the GPIO subsystem what names
(connection IDs) to associate with specific GPIO pins defined
in there.

To do that, a driver needs to define a mapping table as a
NULL-terminated array of struct acpi_gpio_mapping objects
that each contain a name, a pointer to an array of pin data
(struct acpi_gpio_params) objects and the size of that array.

Each struct acpi_gpio_params object consists of three fields,
crs_entry_index, pin_index, active_low, representing the index of
the target GpioIo()/GpioInt() resource in _CRS starting from zero,
the index of the target pin in that resource starting from zero,
and the active-low flag for that pin, respectively.

Next, the mapping table needs to be passed as the second argument to
acpi_dev_add_driver_gpios() that will register it with the ACPI device
object pointed to by its first argument.  That object must represent
the ACPI namespace node containing the _CRS object referred to by the
GPIO mapping.  That should be done in the driver's .probe() routine.

On removal, the driver should unregister its GPIO mapping table
by calling acpi_dev_remove_driver_gpios() on the ACPI device
object where that table was previously registered.

Included are fixes from Mika Westerberg.

Acked-by: Alexandre Courbot <acourbot@nvidia.com>

As we discussed already, this is a great idea. The only thing that is
missing is a paragraph in Documentation/gpio/consumer.txt with an
explanation of the global mechanism and a simple example to illustrate
how and when this should be used.