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Documentation: gpio: board: describe the con_id parameter

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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>
This commit is contained in:
Dirk Behme 2015-09-02 20:07:10 +02:00 committed by Linus Walleij
parent 69de52ba32
commit 87e77e46c6
2 changed files with 12 additions and 0 deletions
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9
Documentation/gpio/board.txt
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@ -48,6 +48,15 @@ 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).
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.

3
Documentation/gpio/consumer.txt
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@ -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: