USB: ti_usb_3410_5052: query hardware-buffer status in chars_in_buffer

Query hardware-buffer status in chars_in_buffer should the write fifo be
empty.

This is needed to make the tty layer wait for hardware buffers to drain
on close.

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

diff --git a/drivers/usb/serial/ti_usb_3410_5052.c b/drivers/usb/serial/ti_usb_3410_5052.c
index 3ed8eca..062b6d8 100644 (file)
--- a/drivers/usb/serial/ti_usb_3410_5052.c
+++ b/drivers/usb/serial/ti_usb_3410_5052.c
@@ -687,6 +687,8 @@ static int ti_chars_in_buffer(struct tty_struct *tty)
        struct ti_port *tport = usb_get_serial_port_data(port);
        int chars = 0;
        unsigned long flags;
+       int ret;
+       u8 lsr;
 
        if (tport == NULL)
                return 0;
@@ -695,6 +697,12 @@ static int ti_chars_in_buffer(struct tty_struct *tty)
        chars = kfifo_len(&tport->write_fifo);
        spin_unlock_irqrestore(&tport->tp_lock, flags);
 
+       if (!chars) {
+               ret = ti_get_lsr(tport, &lsr);
+               if (!ret && !(lsr & TI_LSR_TX_EMPTY))
+                       chars = 1;
+       }
+
        dev_dbg(&port->dev, "%s - returns %d\n", __func__, chars);
        return chars;
 }