diff options
Diffstat (limited to 'Documentation/gpio/board.txt')
| -rw-r--r-- | Documentation/gpio/board.txt | 40 |
1 files changed, 25 insertions, 15 deletions
diff --git a/Documentation/gpio/board.txt b/Documentation/gpio/board.txt index b80606de545a..f59c43b6411b 100644 --- a/Documentation/gpio/board.txt +++ b/Documentation/gpio/board.txt @@ -21,8 +21,8 @@ exact way to do it depends on the GPIO controller providing the GPIOs, see the device tree bindings for your controller. GPIOs mappings are defined in the consumer device's node, in a property named -<function>-gpios, where <function> is the function the driver will request -through gpiod_get(). For example: +either <function>-gpios or <function>-gpio, where <function> is the function +the driver will request through gpiod_get(). For example: foo_device { compatible = "acme,foo"; @@ -31,7 +31,7 @@ through gpiod_get(). For example: <&gpio 16 GPIO_ACTIVE_HIGH>, /* green */ <&gpio 17 GPIO_ACTIVE_HIGH>; /* blue */ - power-gpios = <&gpio 1 GPIO_ACTIVE_LOW>; + power-gpio = <&gpio 1 GPIO_ACTIVE_LOW>; }; This property will make GPIOs 15, 16 and 17 available to the driver under the @@ -39,15 +39,24 @@ This property will make GPIOs 15, 16 and 17 available to the driver under the 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 +151,14 @@ 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. |
