diff options
Diffstat (limited to 'Documentation/devicetree/bindings/gpio/gpio.txt')
| -rw-r--r-- | Documentation/devicetree/bindings/gpio/gpio.txt | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/Documentation/devicetree/bindings/gpio/gpio.txt b/Documentation/devicetree/bindings/gpio/gpio.txt index 5788d5cf1252..63b1b9039ce8 100644 --- a/Documentation/devicetree/bindings/gpio/gpio.txt +++ b/Documentation/devicetree/bindings/gpio/gpio.txt @@ -52,9 +52,13 @@ 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. Use the macros -defined in include/dt-bindings/gpio/gpio.h whenever possible: +be documented in the device tree binding for the device. + +Most controllers are however specifying a generic flag bitfield +in the last cell, so for these, use the macros defined in +include/dt-bindings/gpio/gpio.h whenever possible: Example of a node using GPIOs: @@ -65,6 +69,15 @@ Example of a node using GPIOs: GPIO_ACTIVE_HIGH is 0, so in this example gpio-specifier is "18 0" and encodes GPIO pin number, and GPIO flags as accepted by the "qe_pio_e" gpio-controller. +Optional standard bitfield specifiers for the last cell: + +- Bit 0: 0 means active high, 1 means active low +- Bit 1: 1 means single-ended wiring, see: + https://en.wikipedia.org/wiki/Single-ended_triode + When used with active-low, this means open drain/collector, see: + https://en.wikipedia.org/wiki/Open_collector + When used with active-high, this means open source/emitter + 1.1) GPIO specifier best practices ---------------------------------- |