sc16is7xx: implemented get_mctrl

Add support for manual getting the modem control lines.
Signed-off-by: NMaarten Brock <m.brock@vanmierlo.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/sc16is7xx.c

@@ -822,10 +822,16 @@ static unsigned int sc16is7xx_tx_empty(struct uart_port *port)
 
 static unsigned int sc16is7xx_get_mctrl(struct uart_port *port)
 {
-	/* DCD and DSR are not wired and CTS/RTS is handled automatically
-	 * so just indicate DSR and CAR asserted
-	 */
-	return TIOCM_DSR | TIOCM_CAR;
+	unsigned int msr;
+	unsigned int ret = 0;
+
+	msr = sc16is7xx_port_read(port, SC16IS7XX_MSR_REG);
+
+	ret |= (msr & SC16IS7XX_MSR_CTS_BIT) ? TIOCM_CTS : 0;
+	ret |= (msr & SC16IS7XX_MSR_DSR_BIT) ? TIOCM_DSR : 0;
+	ret |= (msr & SC16IS7XX_MSR_RI_BIT)  ? TIOCM_RNG : 0;
+	ret |= (msr & SC16IS7XX_MSR_CD_BIT)  ? TIOCM_CAR : 0;
+	return ret;
 }
 
 static void sc16is7xx_set_mctrl(struct uart_port *port, unsigned int mctrl)