HID: google: switch to devm when registering keyboard backlight LED

We can use devm to register keyboard backlight LED on hammer devices, this
will allow us to use HID's driver data for something else later.

Link: https://lore.kernel.org/r/[e-mail]
Tested-by: Stephen Boyd <[e-mail]> # coachz, wormdingler
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/hid/hid-google-hammer.c

···
 static int hammer_register_leds(struct hid_device *hdev)
 {
 	struct hammer_kbd_leds *kbd_backlight;
-	int error;
 
-	kbd_backlight = kzalloc(sizeof(*kbd_backlight), GFP_KERNEL);
+	kbd_backlight = devm_kzalloc(&hdev->dev, sizeof(*kbd_backlight),
+				     GFP_KERNEL);
 	if (!kbd_backlight)
 		return -ENOMEM;
 
···
 	/* Set backlight to 0% initially. */
 	hammer_kbd_brightness_set_blocking(&kbd_backlight->cdev, 0);
 
-	error = led_classdev_register(&hdev->dev, &kbd_backlight->cdev);
-	if (error)
-		goto err_free_mem;
-
-	hid_set_drvdata(hdev, kbd_backlight);
-	return 0;
-
-err_free_mem:
-	kfree(kbd_backlight);
-	return error;
-}
-
-static void hammer_unregister_leds(struct hid_device *hdev)
-{
-	struct hammer_kbd_leds *kbd_backlight = hid_get_drvdata(hdev);
-
-	if (kbd_backlight) {
-		led_classdev_unregister(&kbd_backlight->cdev);
-		kfree(kbd_backlight);
-	}
+	return devm_led_classdev_register(&hdev->dev, &kbd_backlight->cdev);
 }
 
 #define HID_UP_GOOGLEVENDOR	0xffd10000
···
 	kfree(buf);
 }
 
+static void hammer_stop(void *hdev)
+{
+	hid_hw_stop(hdev);
+}
+
 static int hammer_probe(struct hid_device *hdev,
 			const struct hid_device_id *id)
 {
···
 		return error;
 
 	error = hid_hw_start(hdev, HID_CONNECT_DEFAULT);
+	if (error)
+		return error;
+
+	error = devm_add_action(&hdev->dev, hammer_stop, hdev);
 	if (error)
 		return error;
 
···
 		spin_unlock_irqrestore(&cbas_ec_lock, flags);
 	}
 
-	hammer_unregister_leds(hdev);
-
-	hid_hw_stop(hdev);
+	/* Unregistering LEDs and stopping the hardware is done via devm */
 }
 
 static const struct hid_device_id hammer_devices[] = {