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";
<&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
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.
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.