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authorMika Westerberg <mika.westerberg@linux.intel.com>2015-03-17 12:40:12 +0200
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2015-03-18 02:02:35 +0100
commit56b858dfad9b97aea88f9fe87b1468ddaf154c94 (patch)
treec4919642d14b34370eae96187253f0cd814fed18 /Documentation/acpi
parent06e5801b8cb3fc057d88cb4dc03c0b64b2744cda (diff)
downloadkernel-56b858dfad9b97aea88f9fe87b1468ddaf154c94.tar.gz
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>
Diffstat (limited to 'Documentation/acpi')
-rw-r--r--Documentation/acpi/enumeration.txt26
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