drivers/input/misc/input-polldev.c

/*
 * 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>

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);