drivers/hid/hid-roccat.c - third_party/linux - Git at Google

 /*
  * Roccat driver for Linux
  *
  * Copyright (c) 2010 Stefan Achatz <erazor_de@users.sourceforge.net>
  */

 /*
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License as published by the Free
  * Software Foundation; either version 2 of the License, or (at your option)
  * any later version.
  */

 /*
  * Module roccat is a char device used to report special events of roccat
  * hardware to userland. These events include requests for on-screen-display of
  * profile or dpi settings or requests for execution of macro sequences that are
  * not stored in device. The information in these events depends on hid device
  * implementation and contains data that is not available in a single hid event
  * or else hidraw could have been used.
  * It is inspired by hidraw, but uses only one circular buffer for all readers.
  */

 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

 #include <linux/cdev.h>
 #include <linux/poll.h>
 #include <linux/sched/signal.h>
 #include <linux/hid-roccat.h>
 #include <linux/module.h>

 #define ROCCAT_FIRST_MINOR 0
 #define ROCCAT_MAX_DEVICES 8

 /* should be a power of 2 for performance reason */
 #define ROCCAT_CBUF_SIZE 16

 struct roccat_report {
 	uint8_t *value;
 };

 struct roccat_device {
 	unsigned int minor;
 	int report_size;
 	int open;
 	int exist;
 	wait_queue_head_t wait;
 	struct device *dev;
 	struct hid_device *hid;
 	struct list_head readers;
 	/* protects modifications of readers list */
 	struct mutex readers_lock;

 	/*
 	 * circular_buffer has one writer and multiple readers with their own
 	 * read pointers
 	 */
 	struct roccat_report cbuf[ROCCAT_CBUF_SIZE];
 	int cbuf_end;
 	struct mutex cbuf_lock;
 };

 struct roccat_reader {
 	struct list_head node;
 	struct roccat_device *device;
 	int cbuf_start;
 };

 static int roccat_major;
 static struct cdev roccat_cdev;

 static struct roccat_device *devices[ROCCAT_MAX_DEVICES];
 /* protects modifications of devices array */
 static DEFINE_MUTEX(devices_lock);

 static ssize_t roccat_read(struct file *file, char __user *buffer,
 		size_t count, loff_t *ppos)
 {
 	struct roccat_reader *reader = file->private_data;
 	struct roccat_device *device = reader->device;
 	struct roccat_report *report;
 	ssize_t retval = 0, len;
 	DECLARE_WAITQUEUE(wait, current);

 	mutex_lock(&device->cbuf_lock);

 	/* no data? */
 	if (reader->cbuf_start == device->cbuf_end) {
 		add_wait_queue(&device->wait, &wait);
 		set_current_state(TASK_INTERRUPTIBLE);

 		/* wait for data */
 		while (reader->cbuf_start == device->cbuf_end) {
 			if (file->f_flags & O_NONBLOCK) {
 				retval = -EAGAIN;
 				break;
 			}
 			if (signal_pending(current)) {
 				retval = -ERESTARTSYS;
 				break;
 			}
 			if (!device->exist) {
 				retval = -EIO;
 				break;
 			}

 			mutex_unlock(&device->cbuf_lock);
 			schedule();
 			mutex_lock(&device->cbuf_lock);
 			set_current_state(TASK_INTERRUPTIBLE);
 		}

 		set_current_state(TASK_RUNNING);
 		remove_wait_queue(&device->wait, &wait);
 	}

 	/* here we either have data or a reason to return if retval is set */
 	if (retval)
 		goto exit_unlock;

 	report = &device->cbuf[reader->cbuf_start];
 	/*
 	 * If report is larger than requested amount of data, rest of report
 	 * is lost!
 	 */
 	len = device->report_size > count ? count : device->report_size;

 	if (copy_to_user(buffer, report->value, len)) {
 		retval = -EFAULT;
 		goto exit_unlock;
 	}
 	retval += len;
 	reader->cbuf_start = (reader->cbuf_start + 1) % ROCCAT_CBUF_SIZE;

 exit_unlock:
 	mutex_unlock(&device->cbuf_lock);
 	return retval;
 }

 static __poll_t roccat_poll(struct file *file, poll_table *wait)
 {
 	struct roccat_reader *reader = file->private_data;
 	poll_wait(file, &reader->device->wait, wait);
 	if (reader->cbuf_start != reader->device->cbuf_end)
 		return POLLIN | POLLRDNORM;
 	if (!reader->device->exist)
 		return POLLERR | POLLHUP;
 	return 0;
 }

 static int roccat_open(struct inode *inode, struct file *file)
 {
 	unsigned int minor = iminor(inode);
 	struct roccat_reader *reader;
 	struct roccat_device *device;
 	int error = 0;

 	reader = kzalloc(sizeof(struct roccat_reader), GFP_KERNEL);
 	if (!reader)
 		return -ENOMEM;

 	mutex_lock(&devices_lock);

 	device = devices[minor];

 	if (!device) {
 		pr_emerg("roccat device with minor %d doesn't exist\n", minor);
 		error = -ENODEV;
 		goto exit_err_devices;
 	}

 	mutex_lock(&device->readers_lock);

 	if (!device->open++) {
 		/* power on device on adding first reader */
 		error = hid_hw_power(device->hid, PM_HINT_FULLON);
 		if (error < 0) {
 			--device->open;
 			goto exit_err_readers;
 		}

 		error = hid_hw_open(device->hid);
 		if (error < 0) {
 			hid_hw_power(device->hid, PM_HINT_NORMAL);
 			--device->open;
 			goto exit_err_readers;
 		}
 	}

 	reader->device = device;
 	/* new reader doesn't get old events */
 	reader->cbuf_start = device->cbuf_end;

 	list_add_tail(&reader->node, &device->readers);
 	file->private_data = reader;

 exit_err_readers:
 	mutex_unlock(&device->readers_lock);
 exit_err_devices:
 	mutex_unlock(&devices_lock);
 	if (error)
 		kfree(reader);
 	return error;
 }

 static int roccat_release(struct inode *inode, struct file *file)
 {
 	unsigned int minor = iminor(inode);
 	struct roccat_reader *reader = file->private_data;
 	struct roccat_device *device;

 	mutex_lock(&devices_lock);

 	device = devices[minor];
 	if (!device) {
 		mutex_unlock(&devices_lock);
 		pr_emerg("roccat device with minor %d doesn't exist\n", minor);
 		return -ENODEV;
 	}

 	mutex_lock(&device->readers_lock);
 	list_del(&reader->node);
 	mutex_unlock(&device->readers_lock);
 	kfree(reader);

 	if (!--device->open) {
 		/* removing last reader */
 		if (device->exist) {
 			hid_hw_power(device->hid, PM_HINT_NORMAL);
 			hid_hw_close(device->hid);
 		} else {
 			kfree(device);
 		}
 	}

 	mutex_unlock(&devices_lock);

 	return 0;
 }

 /*
  * roccat_report_event() - output data to readers
  * @minor: minor device number returned by roccat_connect()
  * @data: pointer to data
  *
  * Return value is zero on success, a negative error code on failure.
  *
  * This is called from interrupt handler.
  */
 int roccat_report_event(int minor, u8 const *data)
 {
 	struct roccat_device *device;
 	struct roccat_reader *reader;
 	struct roccat_report *report;
 	uint8_t *new_value;

 	device = devices[minor];

 	new_value = kmemdup(data, device->report_size, GFP_ATOMIC);
 	if (!new_value)
 		return -ENOMEM;

 	report = &device->cbuf[device->cbuf_end];

 	/* passing NULL is safe */
 	kfree(report->value);

 	report->value = new_value;
 	device->cbuf_end = (device->cbuf_end + 1) % ROCCAT_CBUF_SIZE;

 	list_for_each_entry(reader, &device->readers, node) {
 		/*
 		 * As we already inserted one element, the buffer can't be
 		 * empty. If start and end are equal, buffer is full and we
 		 * increase start, so that slow reader misses one event, but
 		 * gets the newer ones in the right order.
 		 */
 		if (reader->cbuf_start == device->cbuf_end)
 			reader->cbuf_start = (reader->cbuf_start + 1) % ROCCAT_CBUF_SIZE;
 	}

 	wake_up_interruptible(&device->wait);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(roccat_report_event);

 /*
  * roccat_connect() - create a char device for special event output
  * @class: the class thats used to create the device. Meant to hold device
  * specific sysfs attributes.
  * @hid: the hid device the char device should be connected to.
  * @report_size: size of reports
  *
  * Return value is minor device number in Range [0, ROCCAT_MAX_DEVICES] on
  * success, a negative error code on failure.
  */
 int roccat_connect(struct class *klass, struct hid_device *hid, int report_size)
 {
 	unsigned int minor;
 	struct roccat_device *device;
 	int temp;

 	device = kzalloc(sizeof(struct roccat_device), GFP_KERNEL);
 	if (!device)
 		return -ENOMEM;

 	mutex_lock(&devices_lock);

 	for (minor = 0; minor < ROCCAT_MAX_DEVICES; ++minor) {
 		if (devices[minor])
 			continue;
 		break;
 	}

 	if (minor < ROCCAT_MAX_DEVICES) {
 		devices[minor] = device;
 	} else {
 		mutex_unlock(&devices_lock);
 		kfree(device);
 		return -EINVAL;
 	}

 	device->dev = device_create(klass, &hid->dev,
 			MKDEV(roccat_major, minor), NULL,
 			"%s%s%d", "roccat", hid->driver->name, minor);

 	if (IS_ERR(device->dev)) {
 		devices[minor] = NULL;
 		mutex_unlock(&devices_lock);
 		temp = PTR_ERR(device->dev);
 		kfree(device);
 		return temp;
 	}

 	mutex_unlock(&devices_lock);

 	init_waitqueue_head(&device->wait);
 	INIT_LIST_HEAD(&device->readers);
 	mutex_init(&device->readers_lock);
 	mutex_init(&device->cbuf_lock);
 	device->minor = minor;
 	device->hid = hid;
 	device->exist = 1;
 	device->cbuf_end = 0;
 	device->report_size = report_size;

 	return minor;
 }
 EXPORT_SYMBOL_GPL(roccat_connect);

 /* roccat_disconnect() - remove char device from hid device
  * @minor: the minor device number returned by roccat_connect()
  */
 void roccat_disconnect(int minor)
 {
 	struct roccat_device *device;

 	mutex_lock(&devices_lock);
 	device = devices[minor];
 	mutex_unlock(&devices_lock);

 	device->exist = 0; /* TODO exist maybe not needed */

 	device_destroy(device->dev->class, MKDEV(roccat_major, minor));

 	mutex_lock(&devices_lock);
 	devices[minor] = NULL;
 	mutex_unlock(&devices_lock);

 	if (device->open) {
 		hid_hw_close(device->hid);
 		wake_up_interruptible(&device->wait);
 	} else {
 		kfree(device);
 	}
 }
 EXPORT_SYMBOL_GPL(roccat_disconnect);

 static long roccat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
 	struct inode *inode = file_inode(file);
 	struct roccat_device *device;
 	unsigned int minor = iminor(inode);
 	long retval = 0;

 	mutex_lock(&devices_lock);

 	device = devices[minor];
 	if (!device) {
 		retval = -ENODEV;
 		goto out;
 	}

 	switch (cmd) {
 	case ROCCATIOCGREPSIZE:
 		if (put_user(device->report_size, (int __user *)arg))
 			retval = -EFAULT;
 		break;
 	default:
 		retval = -ENOTTY;
 	}
 out:
 	mutex_unlock(&devices_lock);
 	return retval;
 }

 static const struct file_operations roccat_ops = {
 	.owner = THIS_MODULE,
 	.read = roccat_read,
 	.poll = roccat_poll,
 	.open = roccat_open,
 	.release = roccat_release,
 	.llseek = noop_llseek,
 	.unlocked_ioctl = roccat_ioctl,
 };

 static int __init roccat_init(void)
 {
 	int retval;
 	dev_t dev_id;

 	retval = alloc_chrdev_region(&dev_id, ROCCAT_FIRST_MINOR,
 			ROCCAT_MAX_DEVICES, "roccat");
 	if (retval < 0) {
 		pr_warn("can't get major number\n");
 		goto error;
 	}

 	roccat_major = MAJOR(dev_id);

 	cdev_init(&roccat_cdev, &roccat_ops);
 	retval = cdev_add(&roccat_cdev, dev_id, ROCCAT_MAX_DEVICES);

 	if (retval < 0) {
 		pr_warn("cannot add cdev\n");
 		goto cleanup_alloc_chrdev_region;
 	}
 	return 0;


  cleanup_alloc_chrdev_region:
 	unregister_chrdev_region(dev_id, ROCCAT_MAX_DEVICES);
  error:
 	return retval;
 }

 static void __exit roccat_exit(void)
 {
 	dev_t dev_id = MKDEV(roccat_major, 0);

 	cdev_del(&roccat_cdev);
 	unregister_chrdev_region(dev_id, ROCCAT_MAX_DEVICES);
 }

 module_init(roccat_init);
 module_exit(roccat_exit);

 MODULE_AUTHOR("Stefan Achatz");
 MODULE_DESCRIPTION("USB Roccat char device");
 MODULE_LICENSE("GPL v2");
	/*
	* Roccat driver for Linux
	*
	* Copyright (c) 2010 Stefan Achatz <erazor_de@users.sourceforge.net>
	*/

	/*
	* This program is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License as published by the Free
	* Software Foundation; either version 2 of the License, or (at your option)
	* any later version.
	*/

	/*
	* Module roccat is a char device used to report special events of roccat
	* hardware to userland. These events include requests for on-screen-display of
	* profile or dpi settings or requests for execution of macro sequences that are
	* not stored in device. The information in these events depends on hid device
	* implementation and contains data that is not available in a single hid event
	* or else hidraw could have been used.
	* It is inspired by hidraw, but uses only one circular buffer for all readers.
	*/

	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

	#include <linux/cdev.h>
	#include <linux/poll.h>
	#include <linux/sched/signal.h>
	#include <linux/hid-roccat.h>
	#include <linux/module.h>

	#define ROCCAT_FIRST_MINOR 0
	#define ROCCAT_MAX_DEVICES 8

	/* should be a power of 2 for performance reason */
	#define ROCCAT_CBUF_SIZE 16

	struct roccat_report {
	uint8_t *value;
	};

	struct roccat_device {
	unsigned int minor;
	int report_size;
	int open;
	int exist;
	wait_queue_head_t wait;
	struct device *dev;
	struct hid_device *hid;
	struct list_head readers;
	/* protects modifications of readers list */
	struct mutex readers_lock;

	/*
	* circular_buffer has one writer and multiple readers with their own
	* read pointers
	*/
	struct roccat_report cbuf[ROCCAT_CBUF_SIZE];
	int cbuf_end;
	struct mutex cbuf_lock;
	};

	struct roccat_reader {
	struct list_head node;
	struct roccat_device *device;
	int cbuf_start;
	};

	static int roccat_major;
	static struct cdev roccat_cdev;

	static struct roccat_device *devices[ROCCAT_MAX_DEVICES];
	/* protects modifications of devices array */
	static DEFINE_MUTEX(devices_lock);

	static ssize_t roccat_read(struct file file, char __user buffer,
	size_t count, loff_t *ppos)
	{
	struct roccat_reader *reader = file->private_data;
	struct roccat_device *device = reader->device;
	struct roccat_report *report;
	ssize_t retval = 0, len;
	DECLARE_WAITQUEUE(wait, current);

	mutex_lock(&device->cbuf_lock);

	/* no data? */
	if (reader->cbuf_start == device->cbuf_end) {
	add_wait_queue(&device->wait, &wait);
	set_current_state(TASK_INTERRUPTIBLE);

	/* wait for data */
	while (reader->cbuf_start == device->cbuf_end) {
	if (file->f_flags & O_NONBLOCK) {
	retval = -EAGAIN;
	break;
	}
	if (signal_pending(current)) {
	retval = -ERESTARTSYS;
	break;
	}
	if (!device->exist) {
	retval = -EIO;
	break;
	}

	mutex_unlock(&device->cbuf_lock);
	schedule();
	mutex_lock(&device->cbuf_lock);
	set_current_state(TASK_INTERRUPTIBLE);
	}

	set_current_state(TASK_RUNNING);
	remove_wait_queue(&device->wait, &wait);
	}

	/* here we either have data or a reason to return if retval is set */
	if (retval)
	goto exit_unlock;

	report = &device->cbuf[reader->cbuf_start];
	/*
	* If report is larger than requested amount of data, rest of report
	* is lost!
	*/
	len = device->report_size > count ? count : device->report_size;

	if (copy_to_user(buffer, report->value, len)) {
	retval = -EFAULT;
	goto exit_unlock;
	}
	retval += len;
	reader->cbuf_start = (reader->cbuf_start + 1) % ROCCAT_CBUF_SIZE;

	exit_unlock:
	mutex_unlock(&device->cbuf_lock);
	return retval;
	}

	static __poll_t roccat_poll(struct file file, poll_table wait)
	{
	struct roccat_reader *reader = file->private_data;
	poll_wait(file, &reader->device->wait, wait);
	if (reader->cbuf_start != reader->device->cbuf_end)
	return POLLIN \| POLLRDNORM;
	if (!reader->device->exist)
	return POLLERR \| POLLHUP;
	return 0;
	}

	static int roccat_open(struct inode inode, struct file file)
	{
	unsigned int minor = iminor(inode);
	struct roccat_reader *reader;
	struct roccat_device *device;
	int error = 0;

	reader = kzalloc(sizeof(struct roccat_reader), GFP_KERNEL);
	if (!reader)
	return -ENOMEM;

	mutex_lock(&devices_lock);

	device = devices[minor];

	if (!device) {
	pr_emerg("roccat device with minor %d doesn't exist\n", minor);
	error = -ENODEV;
	goto exit_err_devices;
	}

	mutex_lock(&device->readers_lock);

	if (!device->open++) {
	/* power on device on adding first reader */
	error = hid_hw_power(device->hid, PM_HINT_FULLON);
	if (error < 0) {
	--device->open;
	goto exit_err_readers;
	}

	error = hid_hw_open(device->hid);
	if (error < 0) {
	hid_hw_power(device->hid, PM_HINT_NORMAL);
	--device->open;
	goto exit_err_readers;
	}
	}

	reader->device = device;
	/* new reader doesn't get old events */
	reader->cbuf_start = device->cbuf_end;

	list_add_tail(&reader->node, &device->readers);
	file->private_data = reader;

	exit_err_readers:
	mutex_unlock(&device->readers_lock);
	exit_err_devices:
	mutex_unlock(&devices_lock);
	if (error)
	kfree(reader);
	return error;
	}

	static int roccat_release(struct inode inode, struct file file)
	{
	unsigned int minor = iminor(inode);
	struct roccat_reader *reader = file->private_data;
	struct roccat_device *device;

	mutex_lock(&devices_lock);

	device = devices[minor];
	if (!device) {
	mutex_unlock(&devices_lock);
	pr_emerg("roccat device with minor %d doesn't exist\n", minor);
	return -ENODEV;
	}

	mutex_lock(&device->readers_lock);
	list_del(&reader->node);
	mutex_unlock(&device->readers_lock);
	kfree(reader);

	if (!--device->open) {
	/* removing last reader */
	if (device->exist) {
	hid_hw_power(device->hid, PM_HINT_NORMAL);
	hid_hw_close(device->hid);
	} else {
	kfree(device);
	}
	}

	mutex_unlock(&devices_lock);

	return 0;
	}

	/*
	* roccat_report_event() - output data to readers
	* @minor: minor device number returned by roccat_connect()
	* @data: pointer to data
	*
	* Return value is zero on success, a negative error code on failure.
	*
	* This is called from interrupt handler.
	*/
	int roccat_report_event(int minor, u8 const *data)
	{
	struct roccat_device *device;
	struct roccat_reader *reader;
	struct roccat_report *report;
	uint8_t *new_value;

	device = devices[minor];

	new_value = kmemdup(data, device->report_size, GFP_ATOMIC);
	if (!new_value)
	return -ENOMEM;

	report = &device->cbuf[device->cbuf_end];

	/* passing NULL is safe */
	kfree(report->value);

	report->value = new_value;
	device->cbuf_end = (device->cbuf_end + 1) % ROCCAT_CBUF_SIZE;

	list_for_each_entry(reader, &device->readers, node) {
	/*
	* As we already inserted one element, the buffer can't be
	* empty. If start and end are equal, buffer is full and we
	* increase start, so that slow reader misses one event, but
	* gets the newer ones in the right order.
	*/
	if (reader->cbuf_start == device->cbuf_end)
	reader->cbuf_start = (reader->cbuf_start + 1) % ROCCAT_CBUF_SIZE;
	}

	wake_up_interruptible(&device->wait);
	return 0;
	}
	EXPORT_SYMBOL_GPL(roccat_report_event);

	/*
	* roccat_connect() - create a char device for special event output
	* @class: the class thats used to create the device. Meant to hold device
	* specific sysfs attributes.
	* @hid: the hid device the char device should be connected to.
	* @report_size: size of reports
	*
	* Return value is minor device number in Range [0, ROCCAT_MAX_DEVICES] on
	* success, a negative error code on failure.
	*/
	int roccat_connect(struct class klass, struct hid_device hid, int report_size)
	{
	unsigned int minor;
	struct roccat_device *device;
	int temp;

	device = kzalloc(sizeof(struct roccat_device), GFP_KERNEL);
	if (!device)
	return -ENOMEM;

	mutex_lock(&devices_lock);

	for (minor = 0; minor < ROCCAT_MAX_DEVICES; ++minor) {
	if (devices[minor])
	continue;
	break;
	}

	if (minor < ROCCAT_MAX_DEVICES) {
	devices[minor] = device;
	} else {
	mutex_unlock(&devices_lock);
	kfree(device);
	return -EINVAL;
	}

	device->dev = device_create(klass, &hid->dev,
	MKDEV(roccat_major, minor), NULL,
	"%s%s%d", "roccat", hid->driver->name, minor);

	if (IS_ERR(device->dev)) {
	devices[minor] = NULL;
	mutex_unlock(&devices_lock);
	temp = PTR_ERR(device->dev);
	kfree(device);
	return temp;
	}

	mutex_unlock(&devices_lock);

	init_waitqueue_head(&device->wait);
	INIT_LIST_HEAD(&device->readers);
	mutex_init(&device->readers_lock);
	mutex_init(&device->cbuf_lock);
	device->minor = minor;
	device->hid = hid;
	device->exist = 1;
	device->cbuf_end = 0;
	device->report_size = report_size;

	return minor;
	}
	EXPORT_SYMBOL_GPL(roccat_connect);

	/* roccat_disconnect() - remove char device from hid device
	* @minor: the minor device number returned by roccat_connect()
	*/
	void roccat_disconnect(int minor)
	{
	struct roccat_device *device;

	mutex_lock(&devices_lock);
	device = devices[minor];
	mutex_unlock(&devices_lock);

	device->exist = 0; /* TODO exist maybe not needed */

	device_destroy(device->dev->class, MKDEV(roccat_major, minor));

	mutex_lock(&devices_lock);
	devices[minor] = NULL;
	mutex_unlock(&devices_lock);

	if (device->open) {
	hid_hw_close(device->hid);
	wake_up_interruptible(&device->wait);
	} else {
	kfree(device);
	}
	}
	EXPORT_SYMBOL_GPL(roccat_disconnect);

	static long roccat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
	{
	struct inode *inode = file_inode(file);
	struct roccat_device *device;
	unsigned int minor = iminor(inode);
	long retval = 0;

	mutex_lock(&devices_lock);

	device = devices[minor];
	if (!device) {
	retval = -ENODEV;
	goto out;
	}

	switch (cmd) {
	case ROCCATIOCGREPSIZE:
	if (put_user(device->report_size, (int __user *)arg))
	retval = -EFAULT;
	break;
	default:
	retval = -ENOTTY;
	}
	out:
	mutex_unlock(&devices_lock);
	return retval;
	}

	static const struct file_operations roccat_ops = {
	.owner = THIS_MODULE,
	.read = roccat_read,
	.poll = roccat_poll,
	.open = roccat_open,
	.release = roccat_release,
	.llseek = noop_llseek,
	.unlocked_ioctl = roccat_ioctl,
	};

	static int __init roccat_init(void)
	{
	int retval;
	dev_t dev_id;

	retval = alloc_chrdev_region(&dev_id, ROCCAT_FIRST_MINOR,
	ROCCAT_MAX_DEVICES, "roccat");
	if (retval < 0) {
	pr_warn("can't get major number\n");
	goto error;
	}

	roccat_major = MAJOR(dev_id);

	cdev_init(&roccat_cdev, &roccat_ops);
	retval = cdev_add(&roccat_cdev, dev_id, ROCCAT_MAX_DEVICES);

	if (retval < 0) {
	pr_warn("cannot add cdev\n");
	goto cleanup_alloc_chrdev_region;
	}
	return 0;


	cleanup_alloc_chrdev_region:
	unregister_chrdev_region(dev_id, ROCCAT_MAX_DEVICES);
	error:
	return retval;
	}

	static void __exit roccat_exit(void)
	{
	dev_t dev_id = MKDEV(roccat_major, 0);

	cdev_del(&roccat_cdev);
	unregister_chrdev_region(dev_id, ROCCAT_MAX_DEVICES);
	}

	module_init(roccat_init);
	module_exit(roccat_exit);

	MODULE_AUTHOR("Stefan Achatz");
	MODULE_DESCRIPTION("USB Roccat char device");
	MODULE_LICENSE("GPL v2");