Commit 87e77e46 authored by Dirk Behme's avatar Dirk Behme Committed by Linus Walleij

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: default avatarDirk Behme <dirk.behme@gmail.com>
Acked-by: default avatarAlexandre Courbot <acourbot@nvidia.com>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
parent 69de52ba
...@@ -48,6 +48,15 @@ This property will make GPIOs 15, 16 and 17 available to the driver under the ...@@ -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. 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). 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
---- ----
ACPI also supports function names for GPIOs in a similar fashion to DT. ACPI also supports function names for GPIOs in a similar fashion to DT.
......
...@@ -39,6 +39,9 @@ device that displays digits), an additional index argument can be specified: ...@@ -39,6 +39,9 @@ device that displays digits), an additional index argument can be specified:
const char *con_id, unsigned int idx, const char *con_id, unsigned int idx,
enum gpiod_flags flags) 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 The flags parameter is used to optionally specify a direction and initial value
for the GPIO. Values can be: for the GPIO. Values can be:
......
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