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Subject[PATCH 3.4 057/134] USB: serial: add modem-status-change wait queue
3.4-stable review patch.  If anyone has any objections, please let me know.


From: Johan Hovold <>

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 <>
Signed-off-by: Ben Hutchings <>
Cc: Yang Yingliang <>
Signed-off-by: Greg Kroah-Hartman <>

include/linux/usb/serial.h | 2 ++
1 file changed, 2 insertions(+)

--- 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;

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