rt2x00: Don't queue ieee80211 work after USB removal

This prevents the rt2x00 driver from queueing ieee80211 work after the  
USB card has been removed, preventing a kernel panic.
Signed-off-by: Sean Cross <sean@chumby.com>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rt2x00/rt2x00dev.c

@@ -815,6 +815,8 @@ int rt2x00lib_probe_dev(struct rt2x00_dev *rt2x00dev)
 
 	mutex_init(&rt2x00dev->csr_mutex);
 
+	set_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags);
+
 	/*
 	 * Make room for rt2x00_intf inside the per-interface
 	 * structure ieee80211_vif.
@@ -871,8 +873,6 @@ int rt2x00lib_probe_dev(struct rt2x00_dev *rt2x00dev)
 	rt2x00leds_register(rt2x00dev);
 	rt2x00debug_register(rt2x00dev);
 
-	set_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags);
-
 	return 0;
 
 exit:

drivers/net/wireless/rt2x00/rt2x00link.c

@@ -362,6 +362,7 @@ void rt2x00link_start_tuner(struct rt2x00_dev *rt2x00dev)
 
 	rt2x00link_reset_tuner(rt2x00dev, false);
 
+	if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags))
 		ieee80211_queue_delayed_work(rt2x00dev->hw,
 					     &link->work, LINK_TUNE_INTERVAL);
 }
@@ -469,6 +470,8 @@ static void rt2x00link_tuner(struct work_struct *work)
 	 * Increase tuner counter, and reschedule the next link tuner run.
 	 */
 	link->count++;
+
+	if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags))
 		ieee80211_queue_delayed_work(rt2x00dev->hw,
 					     &link->work, LINK_TUNE_INTERVAL);
 }

drivers/net/wireless/rt2x00/rt2x00usb.c

@@ -47,6 +47,8 @@ int rt2x00usb_vendor_request(struct rt2x00_dev *rt2x00dev,
 	    (requesttype == USB_VENDOR_REQUEST_IN) ?
 	    usb_rcvctrlpipe(usb_dev, 0) : usb_sndctrlpipe(usb_dev, 0);
 
+	if (!test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags))
+		return -ENODEV;
 
 	for (i = 0; i < REGISTER_BUSY_COUNT; i++) {
 		status = usb_control_msg(usb_dev, pipe, request, requesttype,
@@ -60,9 +62,11 @@ int rt2x00usb_vendor_request(struct rt2x00_dev *rt2x00dev,
 		 * -ENODEV: Device has disappeared, no point continuing.
 		 * All other errors: Try again.
 		 */
-		else if (status == -ENODEV)
+		else if (status == -ENODEV) {
+			clear_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags);
 			break;
 		}
+	}
 
 	ERROR(rt2x00dev,
 	      "Vendor Request 0x%02x failed for offset 0x%04x with error %d.\n",
@@ -161,6 +165,9 @@ int rt2x00usb_regbusy_read(struct rt2x00_dev *rt2x00dev,
 {
 	unsigned int i;
 
+	if (!test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags))
+		return -ENODEV;
+
 	for (i = 0; i < REGISTER_BUSY_COUNT; i++) {
 		rt2x00usb_register_read_lock(rt2x00dev, offset, reg);
 		if (!rt2x00_get_field32(*reg, field))