[ 084/104] USB: serial: add modem-status-change wait queue

[Ben Hutchings]

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Johan Hovold <jhovold@xxxxxxxxx>

commit e5b33dc9d16053c2ae4c2c669cf008829530364b upstream.

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).

Signed-off-by: Johan Hovold <jhovold@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 include/linux/usb/serial.h |    2 ++
 1 file changed, 2 insertions(+)

--- a/include/linux/usb/serial.h
+++ b/include/linux/usb/serial.h
@@ -71,6 +71,7 @@ enum port_dev_state {
  *	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
@@ -114,6 +115,7 @@ 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;


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