Documentation / ACPI: update to GPIO descriptor API

Update the documentation also to reflect the fact that there are no ACPI
specific GPIO interfaces anymore but drivers should instead use the
descriptor based GPIO APIs.

Signed-off-by: Mika Westerberg <[e-mail]>
Acked-by: Rafael J. Wysocki <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>

Documentation/acpi/enumeration.txt

···
 
 These GPIO numbers are controller relative and path "\\_SB.PCI0.GPI0"
 specifies the path to the controller. In order to use these GPIOs in Linux
-we need to translate them to the Linux GPIO numbers.
+we need to translate them to the corresponding Linux GPIO descriptors.
 
-In a simple case of just getting the Linux GPIO number from device
-resources one can use acpi_get_gpio_by_index() helper function. It takes
-pointer to the device and index of the GpioIo/GpioInt descriptor in the
-device resources list. For example:
+There is a standard GPIO API for that and is documented in
+Documentation/gpio.txt.
 
-	int gpio_irq, gpio_power;
-	int ret;
-
-	gpio_irq = acpi_get_gpio_by_index(dev, 1, NULL);
-	if (gpio_irq < 0)
-		/* handle error */
-
-	gpio_power = acpi_get_gpio_by_index(dev, 0, NULL);
-	if (gpio_power < 0)
-		/* handle error */
-
-	/* Now we can use the GPIO numbers */
-
-Other GpioIo parameters must be converted first by the driver to be
-suitable to the gpiolib before passing them.
-
-In case of GpioInt resource an additional call to gpio_to_irq() must be
-done before calling request_irq().
-
-Note that the above API is ACPI specific and not recommended for drivers
-that need to support non-ACPI systems. The recommended way is to use
-the descriptor based GPIO interfaces. The above example looks like this
-when converted to the GPIO desc:
+In the above example we can get the corresponding two GPIO descriptors with
+a code like this:
 
 	#include <linux/gpio/consumer.h>
 	...
···
 
 	/* Now we can use the GPIO descriptors */
 
-See also Documentation/gpio.txt.
+There are also devm_* versions of these functions which release the
+descriptors once the device is released.