1 files changed, 60 insertions, 0 deletions

diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index be845873e23d..381515572235 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -923,6 +923,7 @@ static int ftdi_get_icount(struct tty_struct *tty,
 static int  ftdi_ioctl(struct tty_struct *tty,
                         unsigned int cmd, unsigned long arg);
 static void ftdi_break_ctl(struct tty_struct *tty, int break_state);
+static int ftdi_chars_in_buffer(struct tty_struct *tty);
 
 static unsigned short int ftdi_232am_baud_base_to_divisor(int baud, int base);
 static unsigned short int ftdi_232am_baud_to_divisor(int baud);
@@ -957,6 +958,7 @@ static struct usb_serial_driver ftdi_sio_device = {
         .ioctl =                ftdi_ioctl,
         .set_termios =          ftdi_set_termios,
         .break_ctl =            ftdi_break_ctl,
+        .chars_in_buffer =      ftdi_chars_in_buffer,
 };
 
 static struct usb_serial_driver * const serial_drivers[] = {
@@ -2089,6 +2091,64 @@ static void ftdi_break_ctl(struct tty_struct *tty, int break_state)
 
 }
 
+static int ftdi_chars_in_buffer(struct tty_struct *tty)
+{
+        struct usb_serial_port *port = tty->driver_data;
+        struct ftdi_private *priv = usb_get_serial_port_data(port);
+        unsigned long flags;
+        int chars;
+        unsigned char *buf;
+        int ret;
+
+        /* Check software buffer (code from
+         * usb_serial_generic_chars_in_buffer()) */
+        spin_lock_irqsave(&port->lock, flags);
+        chars = kfifo_len(&port->write_fifo) + port->tx_bytes;
+        spin_unlock_irqrestore(&port->lock, flags);
+
+        /* Check hardware buffer */
+        switch (priv->chip_type) {
+        case FT8U232AM:
+        case FT232BM:
+        case FT2232C:
+        case FT232RL:
+        case FT2232H:
+        case FT4232H:
+        case FT232H:
+        case FTX:
+                break;
+        case SIO:
+        default:
+                return chars;
+        }
+
+        buf = kmalloc(2, GFP_KERNEL);
+        if (!buf) {
+                dev_err(&port->dev, "kmalloc failed");
+                return chars;
+        }
+
+        ret = usb_control_msg(port->serial->dev,
+                                usb_rcvctrlpipe(port->serial->dev, 0),
+                                FTDI_SIO_GET_MODEM_STATUS_REQUEST,
+                                FTDI_SIO_GET_MODEM_STATUS_REQUEST_TYPE,
+                                0, priv->interface,
+                                buf, 2, WDR_TIMEOUT);
+
+        if (ret < 2) {
+                dev_err(&port->dev, "Unable to read modem and line status: "
+                        "%i\n", ret);
+                goto chars_in_buffer_out;
+        }
+
+        if (!(buf[1] & FTDI_RS_TEMT))
+                chars++;
+
+chars_in_buffer_out:
+        kfree(buf);
+        return chars;
+}
+
 /* old_termios contains the original termios settings and tty->termios contains
  * the new setting to be used
  * WARNING: set_termios calls this with old_termios in kernel space