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gpio/dt: Refine GPIO device tree binding

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Allow for multiple named gpio properties

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
This commit is contained in:
Grant Likely 2011-06-03 11:07:16 -06:00
parent 33300571b1
commit bf859f84a1
1 changed files with 37 additions and 9 deletions
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46
Documentation/devicetree/bindings/gpio/gpio.txt
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@ -4,17 +4,45 @@ Specifying GPIO information for devices
1) gpios property
-----------------
Nodes that makes use of GPIOs should define them using `gpios' property,
format of which is: <&gpio-controller1-phandle gpio1-specifier
&gpio-controller2-phandle gpio2-specifier
0 /* holes are permitted, means no GPIO 3 */
&gpio-controller4-phandle gpio4-specifier
...>;
Nodes that makes use of GPIOs should specify them using one or more
properties, each containing a 'gpio-list':
Note that gpio-specifier length is controller dependent.
gpio-list ::= <single-gpio> [gpio-list]
single-gpio ::= <gpio-phandle> <gpio-specifier>
gpio-phandle : phandle to gpio controller node
gpio-specifier : Array of #gpio-cells specifying specific gpio
(controller specific)
GPIO properties should be named "[<name>-]gpios". Exact
meaning of each gpios property must be documented in the device tree
binding for each device.
For example, the following could be used to describe gpios pins to use
as chip select lines; with chip selects 0, 1 and 3 populated, and chip
select 2 left empty:
gpio1: gpio1 {
gpio-controller
#gpio-cells = <2>;
};
gpio2: gpio2 {
gpio-controller
#gpio-cells = <1>;
};
[...]
chipsel-gpios = <&gpio1 12 0>,
<&gpio1 13 0>,
<0>, /* holes are permitted, means no GPIO 2 */
<&gpio2 2>;
Note that gpio-specifier length is controller dependent. In the
above example, &gpio1 uses 2 cells to specify a gpio, while &gpio2
only uses one.
gpio-specifier may encode: bank, pin position inside the bank,
whether pin is open-drain and whether pin is logically inverted.
Exact meaning of each specifier cell is controller specific, and must
be documented in the device tree binding for the device.
Example of the node using GPIOs:
@ -28,8 +56,8 @@ and empty GPIO flags as accepted by the "qe_pio_e" gpio-controller.
2) gpio-controller nodes
------------------------
Every GPIO controller node must have #gpio-cells property defined,
this information will be used to translate gpio-specifiers.
Every GPIO controller node must both an empty "gpio-controller"
property, and have #gpio-cells contain the size of the gpio-specifier.
Example of two SOC GPIO banks defined as gpio-controller nodes: