gpiolib / ACPI: document the GPIO descriptor based interface

In addition to the existing ACPI specific GPIO interface, document the new
descriptor based GPIO interface in Documentation/acpi/enumeration.txt, so
it is clear that this new interface is preferred over the ACPI specific
version.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 22 insertions, 4 deletions

diff --git a/Documentation/acpi/enumeration.txt b/Documentation/acpi/enumeration.txt
index aca4e69121b7..b994bcb32b92 100644
--- a/Documentation/acpi/enumeration.txt
+++ b/Documentation/acpi/enumeration.txt
@@ -295,10 +295,6 @@ 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.
 
-The driver can do this by including <linux/acpi_gpio.h> and then calling
-acpi_get_gpio(path, gpio). This will return the Linux GPIO number or
-negative errno if there was no translation found.
-
 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
@@ -322,3 +318,25 @@ 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:
+
+        #include <linux/gpio/consumer.h>
+        ...
+
+        struct gpio_desc *irq_desc, *power_desc;
+
+        irq_desc = gpiod_get_index(dev, NULL, 1);
+        if (IS_ERR(irq_desc))
+                /* handle error */
+
+        power_desc = gpiod_get_index(dev, NULL, 0);
+        if (IS_ERR(power_desc))
+                /* handle error */
+
+        /* Now we can use the GPIO descriptors */
+
+See also Documentation/gpio.txt.