diff options
Diffstat (limited to 'kernel/Documentation/gpio/board.txt')
| -rw-r--r-- | kernel/Documentation/gpio/board.txt | 38 |
1 files changed, 26 insertions, 12 deletions
diff --git a/kernel/Documentation/gpio/board.txt b/kernel/Documentation/gpio/board.txt index b80606de5..309217862 100644 --- a/kernel/Documentation/gpio/board.txt +++ b/kernel/Documentation/gpio/board.txt @@ -34,20 +34,33 @@ through gpiod_get(). For example: power-gpios = <&gpio 1 GPIO_ACTIVE_LOW>; }; +Properties named <function>-gpio are also considered valid and old bindings use +it but are only supported for compatibility reasons and should not be used for +newer bindings since it has been deprecated. + This property will make GPIOs 15, 16 and 17 available to the driver under the "led" function, and GPIO 1 as the "power" GPIO: struct gpio_desc *red, *green, *blue, *power; - red = gpiod_get_index(dev, "led", 0); - green = gpiod_get_index(dev, "led", 1); - blue = gpiod_get_index(dev, "led", 2); + red = gpiod_get_index(dev, "led", 0, GPIOD_OUT_HIGH); + green = gpiod_get_index(dev, "led", 1, GPIOD_OUT_HIGH); + blue = gpiod_get_index(dev, "led", 2, GPIOD_OUT_HIGH); - power = gpiod_get(dev, "power"); + power = gpiod_get(dev, "power", GPIOD_OUT_HIGH); The led GPIOs will be active-high, while the power GPIO will be active-low (i.e. gpiod_is_active_low(power) will be true). +The second parameter of the gpiod_get() functions, the con_id string, has to be +the <function>-prefix of the GPIO suffixes ("gpios" or "gpio", automatically +looked up by the gpiod functions internally) used in the device tree. With above +"led-gpios" example, use the prefix without the "-" as con_id parameter: "led". + +Internally, the GPIO subsystem prefixes the GPIO suffix ("gpios" or "gpio") +with the string passed in con_id to get the resulting string +(snprintf(... "%s-%s", con_id, gpio_suffixes[]). + ACPI ---- ACPI also supports function names for GPIOs in a similar fashion to DT. @@ -142,13 +155,14 @@ The driver controlling "foo.0" will then be able to obtain its GPIOs as follows: struct gpio_desc *red, *green, *blue, *power; - red = gpiod_get_index(dev, "led", 0); - green = gpiod_get_index(dev, "led", 1); - blue = gpiod_get_index(dev, "led", 2); + red = gpiod_get_index(dev, "led", 0, GPIOD_OUT_HIGH); + green = gpiod_get_index(dev, "led", 1, GPIOD_OUT_HIGH); + blue = gpiod_get_index(dev, "led", 2, GPIOD_OUT_HIGH); - power = gpiod_get(dev, "power"); - gpiod_direction_output(power, 1); + power = gpiod_get(dev, "power", GPIOD_OUT_HIGH); -Since the "power" GPIO is mapped as active-low, its actual signal will be 0 -after this code. Contrary to the legacy integer GPIO interface, the active-low -property is handled during mapping and is thus transparent to GPIO consumers. +Since the "led" GPIOs are mapped as active-high, this example will switch their +signals to 1, i.e. enabling the LEDs. And for the "power" GPIO, which is mapped +as active-low, its actual signal will be 0 after this code. Contrary to the legacy +integer GPIO interface, the active-low property is handled during mapping and is +thus transparent to GPIO consumers. |