In order for a serial function to add flags to the poll() mask of their
tty files, propagate the poll() callback to the next layer so it can
return a mask if it sees fit to do so.

Signed-off-by: Tal Shorer <tal.sho...@gmail.com>
---
 drivers/usb/gadget/function/u_serial.c | 16 ++++++++++++++++
 drivers/usb/gadget/function/u_serial.h |  3 +++
 2 files changed, 19 insertions(+)

diff --git a/drivers/usb/gadget/function/u_serial.c 
b/drivers/usb/gadget/function/u_serial.c
index 9b0805f..d466f58 100644
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -1025,6 +1025,21 @@ static int gs_break_ctl(struct tty_struct *tty, int 
duration)
        return status;
 }
 
+static unsigned int gs_poll(struct tty_struct *tty, struct file *file,
+       poll_table *wait)
+{
+       struct gs_port *port = tty->driver_data;
+       struct gserial *gser;
+       unsigned int mask = 0;
+
+       spin_lock_irq(&port->port_lock);
+       gser = port->port_usb;
+       if (gser && gser->poll)
+               mask |= gser->poll(gser, file, wait);
+       spin_unlock_irq(&port->port_lock);
+       return mask;
+}
+
 static const struct tty_operations gs_tty_ops = {
        .open =                 gs_open,
        .close =                gs_close,
@@ -1035,6 +1050,7 @@ static const struct tty_operations gs_tty_ops = {
        .chars_in_buffer =      gs_chars_in_buffer,
        .unthrottle =           gs_unthrottle,
        .break_ctl =            gs_break_ctl,
+       .poll =                 gs_poll,
 };
 
 /*-------------------------------------------------------------------------*/
diff --git a/drivers/usb/gadget/function/u_serial.h 
b/drivers/usb/gadget/function/u_serial.h
index c20210c..ce00840 100644
--- a/drivers/usb/gadget/function/u_serial.h
+++ b/drivers/usb/gadget/function/u_serial.h
@@ -12,6 +12,7 @@
 #ifndef __U_SERIAL_H
 #define __U_SERIAL_H
 
+#include <linux/poll.h>
 #include <linux/usb/composite.h>
 #include <linux/usb/cdc.h>
 
@@ -50,6 +51,8 @@ struct gserial {
        void (*connect)(struct gserial *p);
        void (*disconnect)(struct gserial *p);
        int (*send_break)(struct gserial *p, int duration);
+       unsigned int (*poll)(struct gserial *p, struct file *file,
+                               poll_table *wait);
 };
 
 /* utilities to allocate/free request and buffer */
-- 
2.7.4

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