mei: support polling for event notification

Polling on priority events is translated on waiting for event
notification. One need to enable notification prior for
calling select or poll system call otherwise process
will not wait.

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/mei/main.c

@@ -608,6 +608,7 @@ static unsigned int mei_poll(struct file *file, poll_table *wait)
 	struct mei_cl *cl = file->private_data;
 	struct mei_device *dev;
 	unsigned int mask = 0;
+	bool notify_en;
 
 	if (WARN_ON(!cl || !cl->dev))
 		return POLLERR;
@@ -616,6 +617,7 @@ static unsigned int mei_poll(struct file *file, poll_table *wait)
 
 	mutex_lock(&dev->device_lock);
 
+	notify_en = cl->notify_en && (req_events & POLLPRI);
 
 	if (dev->dev_state != MEI_DEV_ENABLED ||
 	    !mei_cl_is_connected(cl)) {
@@ -628,6 +630,12 @@ static unsigned int mei_poll(struct file *file, poll_table *wait)
 		goto out;
 	}
 
+	if (notify_en) {
+		poll_wait(file, &cl->ev_wait, wait);
+		if (cl->notify_ev)
+			mask |= POLLPRI;
+	}
+
 	if (req_events & (POLLIN | POLLRDNORM)) {
 		poll_wait(file, &cl->rx_wait, wait);