greybus: hid: remove custom locking from gb_hid_open/close

Now that HID core enforces serialization of transport driver open/close
calls we can remove custom locking from greybus hid driver.
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/staging/greybus/hid.c

@@ -32,8 +32,6 @@ struct gb_hid {
 	char				*inbuf;
 };
 
-static DEFINE_MUTEX(gb_hid_open_mutex);
-
 /* Routines to get controller's information over greybus */
 
 /* Operations performed on greybus */
@@ -346,19 +344,14 @@ static void gb_hid_stop(struct hid_device *hid)
 static int gb_hid_open(struct hid_device *hid)
 {
 	struct gb_hid *ghid = hid->driver_data;
-	int ret = 0;
-
-	mutex_lock(&gb_hid_open_mutex);
-	if (!hid->open++) {
-		ret = gb_hid_set_power(ghid, GB_HID_TYPE_PWR_ON);
-		if (ret < 0)
-			hid->open--;
-		else
-			set_bit(GB_HID_STARTED, &ghid->flags);
-	}
-	mutex_unlock(&gb_hid_open_mutex);
+	int ret;
 
-	return ret;
+	ret = gb_hid_set_power(ghid, GB_HID_TYPE_PWR_ON);
+	if (ret < 0)
+		return ret;
+
+	set_bit(GB_HID_STARTED, &ghid->flags);
+	return 0;
 }
 
 static void gb_hid_close(struct hid_device *hid)
@@ -366,21 +359,13 @@ static void gb_hid_close(struct hid_device *hid)
 	struct gb_hid *ghid = hid->driver_data;
 	int ret;
 
-	/*
-	 * Protecting hid->open to make sure we don't restart data acquistion
-	 * due to a resumption we no longer care about..
-	 */
-	mutex_lock(&gb_hid_open_mutex);
-	if (!--hid->open) {
-		clear_bit(GB_HID_STARTED, &ghid->flags);
-
-		/* Save some power */
-		ret = gb_hid_set_power(ghid, GB_HID_TYPE_PWR_OFF);
-		if (ret)
-			dev_err(&ghid->connection->bundle->dev,
-				"failed to power off (%d)\n", ret);
-	}
-	mutex_unlock(&gb_hid_open_mutex);
+	clear_bit(GB_HID_STARTED, &ghid->flags);
+
+	/* Save some power */
+	ret = gb_hid_set_power(ghid, GB_HID_TYPE_PWR_OFF);
+	if (ret)
+		dev_err(&ghid->connection->bundle->dev,
+			"failed to power off (%d)\n", ret);
 }
 
 static int gb_hid_power(struct hid_device *hid, int lvl)