/*
   * 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.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 unsigned int 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
  ", 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
  ", 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");
  
  	roccat_major = MAJOR(dev_id);
  
  	if (retval < 0) {
  		pr_warn("can't get major number
  ");
  		goto error;
  	}
  
  	cdev_init(&roccat_cdev, &roccat_ops);
  	retval = cdev_add(&roccat_cdev, dev_id, ROCCAT_MAX_DEVICES);
  
  	if (retval < 0) {
  		pr_warn("cannot add cdev
  ");
  		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");