USB: serial: add modem-status-change wait queue

Add modem-status-change wait queue to struct usb_serial_port that
subdrivers can use to implement TIOCMIWAIT.

Currently subdrivers use a private wait queue which may have been
released when waking up after device disconnected.

Note that we're adding a new wait queue rather than reusing the tty-port
one as we do not want to get woken up at hangup (yet).

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

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/usb/serial.h b/include/linux/usb/serial.h
index ef9be7e1e190..1819b59aab2a 100644
--- a/include/linux/usb/serial.h
+++ b/include/linux/usb/serial.h
@@ -66,6 +66,7 @@
  *      port.
  * @flags: usb serial port flags
  * @write_wait: a wait_queue_head_t used by the port.
+ * @delta_msr_wait: modem-status-change wait queue
  * @work: work queue entry for the line discipline waking up.
  * @throttled: nonzero if the read urb is inactive to throttle the device
  * @throttle_req: nonzero if the tty wants to throttle us
@@ -112,6 +113,7 @@ struct usb_serial_port {
 
         unsigned long           flags;
         wait_queue_head_t       write_wait;
+        wait_queue_head_t       delta_msr_wait;
         struct work_struct      work;
         char                    throttled;
         char                    throttle_req;