diff options
| -rw-r--r-- | Documentation/devicetree/bindings/gpio/gpio.txt | 17 | ||||
| -rw-r--r-- | include/dt-bindings/gpio/gpio.h | 12 |
2 files changed, 27 insertions, 2 deletions
diff --git a/Documentation/devicetree/bindings/gpio/gpio.txt b/Documentation/devicetree/bindings/gpio/gpio.txt index 5788d5c..63b1b90 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 ---------------------------------- diff --git a/include/dt-bindings/gpio/gpio.h b/include/dt-bindings/gpio/gpio.h index e6b1e0a..c673d2c 100644 --- a/include/dt-bindings/gpio/gpio.h +++ b/include/dt-bindings/gpio/gpio.h @@ -9,7 +9,19 @@ #ifndef _DT_BINDINGS_GPIO_GPIO_H #define _DT_BINDINGS_GPIO_GPIO_H +/* Bit 0 express polarity */ #define GPIO_ACTIVE_HIGH 0 #define GPIO_ACTIVE_LOW 1 +/* Bit 1 express single-endedness */ +#define GPIO_PUSH_PULL 0 +#define GPIO_SINGLE_ENDED 2 + +/* + * Open Drain/Collector is the combination of single-ended active low, + * Open Source/Emitter is the combination of single-ended active high. + */ +#define GPIO_OPEN_DRAIN (GPIO_SINGLE_ENDED | GPIO_ACTIVE_LOW) +#define GPIO_OPEN_SOURCE (GPIO_SINGLE_ENDED | GPIO_ACTIVE_HIGH) + #endif |