Input: preallocate memory to hold event values

Preallocate memory for holding event values (input_dev->vals) so that
there is no need to check if it was allocated or not in the event
processing code.

The amount of memory will be adjusted after input device has been fully
set up upon registering device with the input core.

Reviewed-by: Jeff LaBundy <[e-mail]>
Reviewed-by: Benjamin Tissoires <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/input.c

···
 	if ((disposition & INPUT_PASS_TO_DEVICE) && dev->event)
 		dev->event(dev, type, code, value);
 
-	if (!dev->vals)
-		return;
-
 	if (disposition & INPUT_PASS_TO_HANDLERS) {
 		struct input_value *v;
 
···
 	if (!dev)
 		return NULL;
 
+	/*
+	 * Start with space for SYN_REPORT + 7 EV_KEY/EV_MSC events + 2 spare,
+	 * see input_estimate_events_per_packet(). We will tune the number
+	 * when we register the device.
+	 */
+	dev->max_vals = 10;
+	dev->vals = kcalloc(dev->max_vals, sizeof(*dev->vals), GFP_KERNEL);
+	if (!dev->vals) {
+		kfree(dev);
+		return NULL;
+	}
+
 	mutex_init(&dev->mutex);
 	spin_lock_init(&dev->event_lock);
 	timer_setup(&dev->timer, NULL, 0);
···
 }
 EXPORT_SYMBOL_GPL(input_device_enabled);
 
+static int input_device_tune_vals(struct input_dev *dev)
+{
+	struct input_value *vals;
+	unsigned int packet_size;
+	unsigned int max_vals;
+
+	packet_size = input_estimate_events_per_packet(dev);
+	if (dev->hint_events_per_packet < packet_size)
+		dev->hint_events_per_packet = packet_size;
+
+	max_vals = dev->hint_events_per_packet + 2;
+	if (dev->max_vals >= max_vals)
+		return 0;
+
+	vals = kcalloc(max_vals, sizeof(*vals), GFP_KERNEL);
+	if (!vals)
+		return -ENOMEM;
+
+	spin_lock_irq(&dev->event_lock);
+	dev->max_vals = max_vals;
+	swap(dev->vals, vals);
+	spin_unlock_irq(&dev->event_lock);
+
+	/* Because of swap() above, this frees the old vals memory */
+	kfree(vals);
+
+	return 0;
+}
+
 /**
  * input_register_device - register device with input core
  * @dev: device to be registered
···
 {
 	struct input_devres *devres = NULL;
 	struct input_handler *handler;
-	unsigned int packet_size;
 	const char *path;
 	int error;
 
···
 	/* Make sure that bitmasks not mentioned in dev->evbit are clean. */
 	input_cleanse_bitmasks(dev);
 
-	packet_size = input_estimate_events_per_packet(dev);
-	if (dev->hint_events_per_packet < packet_size)
-		dev->hint_events_per_packet = packet_size;
-
-	dev->max_vals = dev->hint_events_per_packet + 2;
-	dev->vals = kcalloc(dev->max_vals, sizeof(*dev->vals), GFP_KERNEL);
-	if (!dev->vals) {
-		error = -ENOMEM;
+	error = input_device_tune_vals(dev);
+	if (error)
 		goto err_devres_free;
-	}
 
 	/*
 	 * If delay and period are pre-set by the driver, then autorepeating
···
 
 	error = device_add(&dev->dev);
 	if (error)
-		goto err_free_vals;
+		goto err_devres_free;
 
 	path = kobject_get_path(&dev->dev.kobj, GFP_KERNEL);
 	pr_info("%s as %s\n",
···
 
 err_device_del:
 	device_del(&dev->dev);
-err_free_vals:
-	kfree(dev->vals);
-	dev->vals = NULL;
 err_devres_free:
 	devres_free(devres);
 	return error;