tty/serial: Add GPIOLIB helpers for controlling modem lines
This patch add some helpers to control modem lines (CTS/RTS/DSR...) via
GPIO.
This will be useful for many boards which have a serial controller that
only handle CTS/RTS pins (or even just RX/TX).
Signed-off-by: Richard Genoud <richard.genoud@gmail.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Tested-by: Yegor Yefremov <yegorslists@googlemail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/Documentation/serial/driver b/Documentation/serial/driver
index c3a7689..3bba1ae 100644
--- a/Documentation/serial/driver
+++ b/Documentation/serial/driver
@@ -429,3 +429,28 @@
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.