USB: serial: add wait_until_sent operation

Add wait_until_sent operation which can be used to wait for hardware
buffers to drain.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 18 insertions, 0 deletions

diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
index cf75beb1251b..31d27686151f 100644
--- a/drivers/usb/serial/usb-serial.c
+++ b/drivers/usb/serial/usb-serial.c
@@ -375,6 +375,22 @@ static int serial_chars_in_buffer(struct tty_struct *tty)
         return count;
 }
 
+static void serial_wait_until_sent(struct tty_struct *tty, int timeout)
+{
+        struct usb_serial_port *port = tty->driver_data;
+        struct usb_serial *serial = port->serial;
+
+        dev_dbg(tty->dev, "%s\n", __func__);
+
+        if (!port->serial->type->wait_until_sent)
+                return;
+
+        mutex_lock(&serial->disc_mutex);
+        if (!serial->disconnected)
+                port->serial->type->wait_until_sent(tty, timeout);
+        mutex_unlock(&serial->disc_mutex);
+}
+
 static void serial_throttle(struct tty_struct *tty)
 {
         struct usb_serial_port *port = tty->driver_data;
@@ -1191,6 +1207,7 @@ static const struct tty_operations serial_ops = {
         .unthrottle =           serial_unthrottle,
         .break_ctl =            serial_break,
         .chars_in_buffer =      serial_chars_in_buffer,
+        .wait_until_sent =      serial_wait_until_sent,
         .tiocmget =             serial_tiocmget,
         .tiocmset =             serial_tiocmset,
         .get_icount =           serial_get_icount,
diff --git a/include/linux/usb/serial.h b/include/linux/usb/serial.h
index b9b0f7b4e43b..afbb7eeaac5f 100644
--- a/include/linux/usb/serial.h
+++ b/include/linux/usb/serial.h
@@ -268,6 +268,7 @@ struct usb_serial_driver {
                         struct usb_serial_port *port, struct ktermios *old);
         void (*break_ctl)(struct tty_struct *tty, int break_state);
         int  (*chars_in_buffer)(struct tty_struct *tty);
+        void (*wait_until_sent)(struct tty_struct *tty, long timeout);
         void (*throttle)(struct tty_struct *tty);
         void (*unthrottle)(struct tty_struct *tty);
         int  (*tiocmget)(struct tty_struct *tty);