ACPI: Update GPIO documentation to mention _DSD

Make sure that the ACPI enumeration.txt provides latest information on how
to describe and retrieve GPIOs now that we can take advantage of _DSD
device properties.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 23 insertions, 3 deletions

diff --git a/Documentation/acpi/enumeration.txt b/Documentation/acpi/enumeration.txt
index 9b121a569ab4..750401f91341 100644
--- a/Documentation/acpi/enumeration.txt
+++ b/Documentation/acpi/enumeration.txt
@@ -254,8 +254,13 @@ GPIO support
 ~~~~~~~~~~~~
 ACPI 5 introduced two new resources to describe GPIO connections: GpioIo
 and GpioInt. These resources are used be used to pass GPIO numbers used by
-the device to the driver. For example:
+the device to the driver. ACPI 5.1 extended this with _DSD (Device
+Specific Data) which made it possible to name the GPIOs among other things.
 
+For example:
+
+Device (DEV)
+{
         Method (_CRS, 0, NotSerialized)
         {
                 Name (SBUF, ResourceTemplate()
@@ -285,6 +290,18 @@ the device to the driver. For example:
                 Return (SBUF)
         }
 
+        // ACPI 5.1 _DSD used for naming the GPIOs
+        Name (_DSD, Package ()
+        {
+                ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+                Package ()
+                {
+                        Package () {"power-gpios", Package() {^DEV, 0, 0, 0 }},
+                        Package () {"irq-gpios", Package() {^DEV, 1, 0, 0 }},
+                }
+        })
+        ...
+
 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 corresponding Linux GPIO descriptors.
@@ -300,11 +317,11 @@ a code like this:
 
         struct gpio_desc *irq_desc, *power_desc;
 
-        irq_desc = gpiod_get_index(dev, NULL, 1);
+        irq_desc = gpiod_get(dev, "irq");
         if (IS_ERR(irq_desc))
                 /* handle error */
 
-        power_desc = gpiod_get_index(dev, NULL, 0);
+        power_desc = gpiod_get(dev, "power");
         if (IS_ERR(power_desc))
                 /* handle error */
 
@@ -313,6 +330,9 @@ a code like this:
 There are also devm_* versions of these functions which release the
 descriptors once the device is released.
 
+See Documentation/acpi/gpio-properties.txt for more information about the
+_DSD binding related to GPIOs.
+
 MFD devices
 ~~~~~~~~~~~
 The MFD devices register their children as platform devices. For the child