Input: alps - use guard notation when acquiring mutex

This makes the code more compact and error handling more robust
by ensuring that mutexes are released in all code paths when control
leaves critical section.

Acked-by: Pali Rohár <pali@kernel.org>
Link: https://lore.kernel.org/r/ZsrBkWIpyEqzClUG@google.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Author: dtor

drivers/input/mouse/alps.c

@@ -1396,24 +1396,16 @@ static bool alps_is_valid_package_ss4_v2(struct psmouse *psmouse)
 
 static DEFINE_MUTEX(alps_mutex);
 
-static void alps_register_bare_ps2_mouse(struct work_struct *work)
+static int alps_do_register_bare_ps2_mouse(struct alps_data *priv)
 {
-	struct alps_data *priv =
-		container_of(work, struct alps_data, dev3_register_work.work);
 	struct psmouse *psmouse = priv->psmouse;
 	struct input_dev *dev3;
-	int error = 0;
-
-	mutex_lock(&alps_mutex);
-
-	if (priv->dev3)
-		goto out;
+	int error;
 
 	dev3 = input_allocate_device();
 	if (!dev3) {
 		psmouse_err(psmouse, "failed to allocate secondary device\n");
-		error = -ENOMEM;
-		goto out;
+		return -ENOMEM;
 	}
 
 	snprintf(priv->phys3, sizeof(priv->phys3), "%s/%s",
@@ -1446,21 +1438,35 @@ static void alps_register_bare_ps2_mouse(struct work_struct *work)
 		psmouse_err(psmouse,
 			    "failed to register secondary device: %d\n",
 			    error);
-		input_free_device(dev3);
-		goto out;
+		goto err_free_input;
 	}
 
 	priv->dev3 = dev3;
+	return 0;
 
-out:
-	/*
-	 * Save the error code so that we can detect that we
-	 * already tried to create the device.
-	 */
-	if (error)
-		priv->dev3 = ERR_PTR(error);
+err_free_input:
+	input_free_device(dev3);
+	return error;
+}
 
-	mutex_unlock(&alps_mutex);
+static void alps_register_bare_ps2_mouse(struct work_struct *work)
+{
+	struct alps_data *priv = container_of(work, struct alps_data,
+					      dev3_register_work.work);
+	int error;
+
+	guard(mutex)(&alps_mutex);
+
+	if (!priv->dev3) {
+		error = alps_do_register_bare_ps2_mouse(priv);
+		if (error) {
+			/*
+			 * Save the error code so that we can detect that we
+			 * already tried to create the device.
+			 */
+			priv->dev3 = ERR_PTR(error);
+		}
+	}
 }
 
 static void alps_report_bare_ps2_packet(struct psmouse *psmouse,