These changes are the raw update to linux-4.4.6-rt14. Kernel sources

[kvmfornfv.git] / kernel / Documentation / gpio / board.txt

diff --git a/kernel/Documentation/gpio/board.txt b/kernel/Documentation/gpio/board.txt
index b80606d..3092178 100644 (file)
--- 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.