[PATCH V1 4/6] USB: serial: f81232: Add tx_empty function

[Ji-Ze Hong (Peter Hong)]

Add tx_empty() function for F81232 & F81534A series.

Signed-off-by: Ji-Ze Hong (Peter Hong) <hpeter+linux_ker...@gmail.com>
---
 drivers/usb/serial/f81232.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/usb/serial/f81232.c b/drivers/usb/serial/f81232.c
index e9470fb0d691..7d1ec8f9d168 100644
--- a/drivers/usb/serial/f81232.c
+++ b/drivers/usb/serial/f81232.c
@@ -850,6 +850,24 @@ static void f81232_dtr_rts(struct usb_serial_port *port, 
int on)
                f81232_set_mctrl(port, 0, TIOCM_DTR | TIOCM_RTS);
 }
 
+static bool f81232_tx_empty(struct usb_serial_port *port)
+{
+       int status;
+       u8 tmp;
+       u8 both_empty = UART_LSR_TEMT | UART_LSR_THRE;
+
+       status = f81232_get_register(port, LINE_STATUS_REGISTER, &tmp);
+       if (status) {
+               dev_err(&port->dev, "get LSR status failed: %d\n", status);
+               return false;
+       }
+
+       if ((tmp & both_empty) != both_empty)
+               return false;
+
+       return true;
+}
+
 static int f81232_carrier_raised(struct usb_serial_port *port)
 {
        u8 msr;
@@ -1279,6 +1297,7 @@ static struct usb_serial_driver f81232_device = {
        .tiocmget =             f81232_tiocmget,
        .tiocmset =             f81232_tiocmset,
        .tiocmiwait =           usb_serial_generic_tiocmiwait,
+       .tx_empty =             f81232_tx_empty,
        .process_read_urb =     f81232_read_urb_proxy,
        .read_int_callback =    f81232_read_int_callback,
        .port_probe =           f81232_port_probe,
-- 
2.7.4