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-rw-r--r--Documentation/serial/driver25
1 files changed, 25 insertions, 0 deletions
diff --git a/Documentation/serial/driver b/Documentation/serial/driver
index c3a7689a90e6..3bba1aeb799c 100644
--- a/Documentation/serial/driver
+++ b/Documentation/serial/driver
@@ -429,3 +429,28 @@ thus:
struct uart_port port;
int my_stuff;
};
+
+Modem control lines via GPIO
+----------------------------
+
+Some helpers are provided in order to set/get modem control lines via GPIO.
+
+mctrl_gpio_init(dev, idx):
+ This will get the {cts,rts,...}-gpios from device tree if they are
+ present and request them, set direction etc, and return an
+ allocated structure. devm_* functions are used, so there's no need
+ to call mctrl_gpio_free().
+
+mctrl_gpio_free(dev, gpios):
+ This will free the requested gpios in mctrl_gpio_init().
+ As devm_* function are used, there's generally no need to call
+ this function.
+
+mctrl_gpio_to_gpiod(gpios, gidx)
+ This returns the gpio structure associated to the modem line index.
+
+mctrl_gpio_set(gpios, mctrl):
+ This will sets the gpios according to the mctrl state.
+
+mctrl_gpio_get(gpios, mctrl):
+ This will update mctrl with the gpios values.