The con_id parameter has to match the GPIO description and is automatically extended by the GPIO suffix if not NULL. I had to look into the code to understand this and properly find the GPIO I've been looking for, so document this.
Signed-off-by: Dirk Behme <[email protected]> --- Documentation/gpio/board.txt | 36 ++++++++++++++++++++++++++++++++++++ Documentation/gpio/consumer.txt | 3 +++ 2 files changed, 39 insertions(+) diff --git a/Documentation/gpio/board.txt b/Documentation/gpio/board.txt index 7605773..eac78fc 100644 --- a/Documentation/gpio/board.txt +++ b/Documentation/gpio/board.txt @@ -48,6 +48,42 @@ This property will make GPIOs 15, 16 and 17 available to the driver under the 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). +If in the consumer device's node the property doesn't have a <function>- prefix, +the second parameter (con_id) of the gpiod_get*() functions has to be NULL: + +E.g. if in the above device tree example the GPIO array is just called 'gpios' + + foo_device { + compatible = "acme,foo"; + ... + gpios = <&gpio 15 GPIO_ACTIVE_HIGH>, /* red */ + <&gpio 16 GPIO_ACTIVE_HIGH>, /* green */ + <&gpio 17 GPIO_ACTIVE_HIGH>; /* blue */ + }; + +the gpiod_get*() calls will be: + + struct gpio_desc *red, *green, *blue, *power; + + red = gpiod_get_index(dev, NULL, 0, GPIOD_OUT_HIGH); + green = gpiod_get_index(dev, NULL, 1, GPIOD_OUT_HIGH); + blue = gpiod_get_index(dev, NULL, 2, GPIOD_OUT_HIGH); + +To summarize: + +The con_id string parameter has to be either NULL or the <function>-prefix +of the GPIO suffixes ("gpios" or "gpio", automatically looked up by the +gpiod functions internally): + +* If the GPIO description is just named with one of the GPIO suffixes + ("gpios" or "gpio"), use NULL. +* If the GPIO description is prefixed with anything, e.g. "led-gpios", use the + prefix without the "-" as con_id parameter (in this example "led"). + +In case con_id is not NULL, 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. diff --git a/Documentation/gpio/consumer.txt b/Documentation/gpio/consumer.txt index 75542b9..47ce4fd 100644 --- a/Documentation/gpio/consumer.txt +++ b/Documentation/gpio/consumer.txt @@ -39,6 +39,9 @@ device that displays digits), an additional index argument can be specified: const char *con_id, unsigned int idx, enum gpiod_flags flags) +For a more detailed description of the con_id parameter in the DeviceTree case +see Documentation/gpio/board.txt + The flags parameter is used to optionally specify a direction and initial value for the GPIO. Values can be: -- 2.4.6 -- To unsubscribe from this list: send the line "unsubscribe linux-gpio" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
