serial: mctrl_gpio: add modem control read routine

mctrl_gpio_get_outputs() returns the state of following signals:

RTS, DTR

While defining the routine for reading outputs, fix the comment for
mctrl_gpio_get() routine as it returns only the state of the input
signals.

Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/serial_mctrl_gpio.c

@@ -86,6 +86,24 @@ unsigned int mctrl_gpio_get(struct mctrl_gpios *gpios, unsigned int *mctrl)
 }
 EXPORT_SYMBOL_GPL(mctrl_gpio_get);
 
+unsigned int
+mctrl_gpio_get_outputs(struct mctrl_gpios *gpios, unsigned int *mctrl)
+{
+	enum mctrl_gpio_idx i;
+
+	for (i = 0; i < UART_GPIO_MAX; i++) {
+		if (gpios->gpio[i] && mctrl_gpios_desc[i].dir_out) {
+			if (gpiod_get_value(gpios->gpio[i]))
+				*mctrl |= mctrl_gpios_desc[i].mctrl;
+			else
+				*mctrl &= ~mctrl_gpios_desc[i].mctrl;
+		}
+	}
+
+	return *mctrl;
+}
+EXPORT_SYMBOL_GPL(mctrl_gpio_get_outputs);
+
 struct mctrl_gpios *mctrl_gpio_init_noauto(struct device *dev, unsigned int idx)
 {
 	struct mctrl_gpios *gpios;

drivers/tty/serial/serial_mctrl_gpio.h

@@ -48,11 +48,18 @@ struct mctrl_gpios;
 void mctrl_gpio_set(struct mctrl_gpios *gpios, unsigned int mctrl);
 
 /*
- * Get state of the modem control output lines from GPIOs.
+ * Get state of the modem control input lines from GPIOs.
  * The mctrl flags are updated and returned.
  */
 unsigned int mctrl_gpio_get(struct mctrl_gpios *gpios, unsigned int *mctrl);
 
+/*
+ * Get state of the modem control output lines from GPIOs.
+ * The mctrl flags are updated and returned.
+ */
+unsigned int
+mctrl_gpio_get_outputs(struct mctrl_gpios *gpios, unsigned int *mctrl);
+
 /*
  * Returns the associated struct gpio_desc to the modem line gidx
  */
@@ -107,6 +114,12 @@ unsigned int mctrl_gpio_get(struct mctrl_gpios *gpios, unsigned int *mctrl)
 	return *mctrl;
 }
 
+static inline unsigned int
+mctrl_gpio_get_outputs(struct mctrl_gpios *gpios, unsigned int *mctrl)
+{
+	return *mctrl;
+}
+
 static inline
 struct gpio_desc *mctrl_gpio_to_gpiod(struct mctrl_gpios *gpios,
 				      enum mctrl_gpio_idx gidx)