text: /*
   * Generic implementation of a polled input device
  
   * Copyright (c) 2007 Dmitry Torokhov
   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 as published by
   * the Free Software Foundation.
   */
  
  #include <linux/jiffies.h>
  #include <linux/mutex.h>
  #include <linux/input-polldev.h>
  
  MODULE_AUTHOR("Dmitry Torokhov <dtor@mail.ru>");
  MODULE_DESCRIPTION("Generic implementation of a polled input device");
  MODULE_LICENSE("GPL v2");
  MODULE_VERSION("0.1");
  
  static DEFINE_MUTEX(polldev_mutex);
  static int polldev_users;
  static struct workqueue_struct *polldev_wq;
  
  static int input_polldev_start_workqueue(void)
  {
  	int retval;
  
  	retval = mutex_lock_interruptible(&polldev_mutex);
  	if (retval)
  		return retval;
  
  	if (!polldev_users) {
  		polldev_wq = create_singlethread_workqueue("ipolldevd");
  		if (!polldev_wq) {
  			printk(KERN_ERR "input-polldev: failed to create "
  				"ipolldevd workqueue\n");
  			retval = -ENOMEM;
  			goto out;
  		}
  	}
  
  	polldev_users++;
  
   out:
  	mutex_unlock(&polldev_mutex);
  	return retval;
  }
  
  static void input_polldev_stop_workqueue(void)
  {
  	mutex_lock(&polldev_mutex);
  
  	if (!--polldev_users)
  		destroy_workqueue(polldev_wq);
  
  	mutex_unlock(&polldev_mutex);
  }
  
  static void input_polled_device_work(struct work_struct *work)
  {
  	struct input_polled_dev *dev =
  		container_of(work, struct input_polled_dev, work.work);
  
  	dev->poll(dev);
  	queue_delayed_work(polldev_wq, &dev->work,
  			   msecs_to_jiffies(dev->poll_interval));
  }
  
  static int input_open_polled_device(struct input_dev *input)
  {
  	struct input_polled_dev *dev = input->private;
  	int error;
  
  	error = input_polldev_start_workqueue();
  	if (error)
  		return error;
  
  	if (dev->flush)
  		dev->flush(dev);
  
  	queue_delayed_work(polldev_wq, &dev->work,
  			   msecs_to_jiffies(dev->poll_interval));
  
  	return 0;
  }
  
  static void input_close_polled_device(struct input_dev *input)
  {
  	struct input_polled_dev *dev = input->private;
  
  	cancel_rearming_delayed_workqueue(polldev_wq, &dev->work);
  	input_polldev_stop_workqueue();
  }
  
  /**
   * input_allocate_polled_device - allocated memory polled device
   *
   * The function allocates memory for a polled device and also
   * for an input device associated with this polled device.
   */
  struct input_polled_dev *input_allocate_polled_device(void)
  {
  	struct input_polled_dev *dev;
  
  	dev = kzalloc(sizeof(struct input_polled_dev), GFP_KERNEL);
  	if (!dev)
  		return NULL;
  
  	dev->input = input_allocate_device();
  	if (!dev->input) {
  		kfree(dev);
  		return NULL;
  	}
  
  	return dev;
  }
  EXPORT_SYMBOL(input_allocate_polled_device);
  
  /**
   * input_free_polled_device - free memory allocated for polled device
   * @dev: device to free
   *
   * The function frees memory allocated for polling device and drops
   * reference to the associated input device (if present).
   */
  void input_free_polled_device(struct input_polled_dev *dev)
  {
  	if (dev) {
  		input_free_device(dev->input);
  		kfree(dev);
  	}
  }
  EXPORT_SYMBOL(input_free_polled_device);
  
  /**
   * input_register_polled_device - register polled device
   * @dev: device to register
   *
   * The function registers previously initialized polled input device
   * with input layer. The device should be allocated with call to
   * input_allocate_polled_device(). Callers should also set up poll()
   * method and set up capabilities (id, name, phys, bits) of the
   * corresponing input_dev structure.
   */
  int input_register_polled_device(struct input_polled_dev *dev)
  {
  	struct input_dev *input = dev->input;
  
  	INIT_DELAYED_WORK(&dev->work, input_polled_device_work);
  	if (!dev->poll_interval)
  		dev->poll_interval = 500;
  	input->private = dev;
  	input->open = input_open_polled_device;
  	input->close = input_close_polled_device;
  
  	return input_register_device(input);
  }
  EXPORT_SYMBOL(input_register_polled_device);
  
  /**
   * input_unregister_polled_device - unregister polled device
   * @dev: device to unregister
   *
   * The function unregisters previously registered polled input
   * device from input layer. Polling is stopped and device is
   * ready to be freed with call to input_free_polled_device().
   * Callers should not attempt to access dev->input pointer
   * after calling this function.
   */
  void input_unregister_polled_device(struct input_polled_dev *dev)
  {
  	input_unregister_device(dev->input);
  	dev->input = NULL;
  }
  EXPORT_SYMBOL(input_unregister_polled_device);
  
  