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authorDirk Behme <dirk.behme@gmail.com>2015-09-02 21:07:10 +0300
committerLinus Walleij <linus.walleij@linaro.org>2015-09-14 10:12:03 +0300
commit87e77e46c61a9333227ab41cdefb1875758a4f13 (patch)
treeaff0adbf941230d730c489b6532a1fdec1f13986 /Documentation/gpio/board.txt
parent69de52ba321dda8dd7f632d1e480983494325ba0 (diff)
downloadlinux-87e77e46c61a9333227ab41cdefb1875758a4f13.tar.xz
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>
Diffstat (limited to 'Documentation/gpio/board.txt')
-rw-r--r--Documentation/gpio/board.txt9
1 files changed, 9 insertions, 0 deletions
diff --git a/Documentation/gpio/board.txt b/Documentation/gpio/board.txt
index 9edd5af31b3a..5fa069a80171 100644
--- a/Documentation/gpio/board.txt
+++ b/Documentation/gpio/board.txt
@@ -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.