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Documentation: gpio: board: describe the con_id parameter
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 <dirk.behme@gmail.com> Acked-by: Alexandre Courbot <acourbot@nvidia.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
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@ -48,6 +48,15 @@ This property will make GPIOs 15, 16 and 17 available to the driver under the
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The led GPIOs will be active-high, while the power GPIO will be active-low (i.e.
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gpiod_is_active_low(power) will be true).
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The second parameter of the gpiod_get() functions, the con_id string, has to be
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the <function>-prefix of the GPIO suffixes ("gpios" or "gpio", automatically
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looked up by the gpiod functions internally) used in the device tree. With above
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"led-gpios" example, use the prefix without the "-" as con_id parameter: "led".
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Internally, the GPIO subsystem prefixes the GPIO suffix ("gpios" or "gpio")
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with the string passed in con_id to get the resulting string
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(snprintf(... "%s-%s", con_id, gpio_suffixes[]).
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ACPI
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----
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ACPI also supports function names for GPIOs in a similar fashion to DT.
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@ -39,6 +39,9 @@ device that displays digits), an additional index argument can be specified:
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const char *con_id, unsigned int idx,
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enum gpiod_flags flags)
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For a more detailed description of the con_id parameter in the DeviceTree case
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see Documentation/gpio/board.txt
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The flags parameter is used to optionally specify a direction and initial value
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for the GPIO. Values can be:
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