/*****************************************************************************
 *                          USBLCD Kernel Driver                             *
 *                            Version 1.05                                   *
 *             (C) 2005 Georges Toth <g.toth@e-biz.lu>                       *
 *                                                                           *
 *     This file is licensed under the GPL. See COPYING in the package.      *
 * Based on usb-skeleton.c 2.0 by Greg Kroah-Hartman (greg@kroah.com)        *
 *                                                                           *
 *                                                                           *
 * 28.02.05 Complete rewrite of the original usblcd.c driver,                *
 *          based on usb_skeleton.c.                                         *
 *          This new driver allows more than one USB-LCD to be connected     *
 *          and controlled, at once                                          *
 *****************************************************************************/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <asm/uaccess.h>
#include <linux/usb.h>

#define DRIVER_VERSION "USBLCD Driver Version 1.05"

#define USBLCD_MINOR		144

#define IOCTL_GET_HARD_VERSION	1
#define IOCTL_GET_DRV_VERSION	2


static struct usb_device_id id_table [] = {
	{ .idVendor = 0x10D2, .match_flags = USB_DEVICE_ID_MATCH_VENDOR, },
	{ },
};
MODULE_DEVICE_TABLE (usb, id_table);


struct usb_lcd {
	struct usb_device *	udev;			/* init: probe_lcd */
	struct usb_interface *  interface;		/* the interface for this device */
	unsigned char *         bulk_in_buffer;		/* the buffer to receive data */
	size_t			bulk_in_size;		/* the size of the receive buffer */
	__u8			bulk_in_endpointAddr;	/* the address of the bulk in endpoint */
	__u8			bulk_out_endpointAddr;	/* the address of the bulk out endpoint */
	struct kref		kref;
	struct semaphore	limit_sem;		/* to stop writes at full throttle from
							 * using up all RAM */
};
#define to_lcd_dev(d) container_of(d, struct usb_lcd, kref)

#define USB_LCD_CONCURRENT_WRITES	5

static struct usb_driver lcd_driver;
static DEFINE_MUTEX(usb_lcd_open_mutex);


static void lcd_delete(struct kref *kref)
{
	struct usb_lcd *dev = to_lcd_dev(kref);

	usb_put_dev(dev->udev);
	kfree (dev->bulk_in_buffer);
	kfree (dev);
}


static int lcd_open(struct inode *inode, struct file *file)
{
	struct usb_lcd *dev;
	struct usb_interface *interface;
	int subminor;
	int retval = 0;

	subminor = iminor(inode);

	mutex_lock(&usb_lcd_open_mutex);
	interface = usb_find_interface(&lcd_driver, subminor);
	if (!interface) {
		err ("USBLCD: %s - error, can't find device for minor %d",
		     __FUNCTION__, subminor);
		retval = -ENODEV;
		goto exit;
	}

	dev = usb_get_intfdata(interface);
	if (!dev) {
		retval = -ENODEV;
		goto exit;
	}

	/* increment our usage count for the device */
	kref_get(&dev->kref);

	/* save our object in the file's private structure */
	file->private_data = dev;

exit:
	mutex_unlock(&usb_lcd_open_mutex);
	return retval;
}

static int lcd_release(struct inode *inode, struct file *file)
{
	struct usb_lcd *dev;

	dev = (struct usb_lcd *)file->private_data;
	if (dev == NULL)
		return -ENODEV;

	/* decrement the count on our device */
	kref_put(&dev->kref, lcd_delete);
	return 0;
}

static ssize_t lcd_read(struct file *file, char __user * buffer, size_t count, loff_t *ppos)
{
	struct usb_lcd *dev;
	int retval = 0;
	int bytes_read;

	dev = (struct usb_lcd *)file->private_data;

	/* do a blocking bulk read to get data from the device */
	retval = usb_bulk_msg(dev->udev, 
			      usb_rcvbulkpipe(dev->udev, dev->bulk_in_endpointAddr),
			      dev->bulk_in_buffer,
			      min(dev->bulk_in_size, count),
			      &bytes_read, 10000);

	/* if the read was successful, copy the data to userspace */
	if (!retval) {
		if (copy_to_user(buffer, dev->bulk_in_buffer, bytes_read))
			retval = -EFAULT;
		else
			retval = bytes_read;
	}

	return retval;
}

static int lcd_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg)
{
	struct usb_lcd *dev;
	u16 bcdDevice;
	char buf[30];

	dev = (struct usb_lcd *)file->private_data;
	if (dev == NULL)
		return -ENODEV;
	
	switch (cmd) {
	case IOCTL_GET_HARD_VERSION:
		bcdDevice = le16_to_cpu((dev->udev)->descriptor.bcdDevice);
		sprintf(buf,"%1d%1d.%1d%1d",
			(bcdDevice & 0xF000)>>12,
			(bcdDevice & 0xF00)>>8,
			(bcdDevice & 0xF0)>>4,
			(bcdDevice & 0xF));
		if (copy_to_user((void __user *)arg,buf,strlen(buf))!=0)
			return -EFAULT;
		break;
	case IOCTL_GET_DRV_VERSION:
		sprintf(buf,DRIVER_VERSION);
		if (copy_to_user((void __user *)arg,buf,strlen(buf))!=0)
			return -EFAULT;
		break;
	default:
		return -ENOTTY;
		break;
	}

	return 0;
}

static void lcd_write_bulk_callback(struct urb *urb)
{
	struct usb_lcd *dev;

	dev = (struct usb_lcd *)urb->context;

	/* sync/async unlink faults aren't errors */
	if (urb->status &&
	    !(urb->status == -ENOENT ||
	      urb->status == -ECONNRESET ||
              urb->status == -ESHUTDOWN)) {
		dbg("USBLCD: %s - nonzero write bulk status received: %d",
		    __FUNCTION__, urb->status);
	}

	/* free up our allocated buffer */
	usb_buffer_free(urb->dev, urb->transfer_buffer_length,
			urb->transfer_buffer, urb->transfer_dma);
	up(&dev->limit_sem);
}

static ssize_t lcd_write(struct file *file, const char __user * user_buffer, size_t count, loff_t *ppos)
{
	struct usb_lcd *dev;
        int retval = 0, r;
	struct urb *urb = NULL;
	char *buf = NULL;
	
	dev = (struct usb_lcd *)file->private_data;
	
	/* verify that we actually have some data to write */
	if (count == 0)
		goto exit;

	r = down_interruptible(&dev->limit_sem);
	if (r < 0)
		return -EINTR;

	/* create a urb, and a buffer for it, and copy the data to the urb */
	urb = usb_alloc_urb(0, GFP_KERNEL);
	if (!urb) {
		retval = -ENOMEM;
		goto err_no_buf;
	}
	
	buf = usb_buffer_alloc(dev->udev, count, GFP_KERNEL, &urb->transfer_dma);
	if (!buf) {
		retval = -ENOMEM;
		goto error;
	}
	
	if (copy_from_user(buf, user_buffer, count)) {
		retval = -EFAULT;
		goto error;
	}
	
	/* initialize the urb properly */
	usb_fill_bulk_urb(urb, dev->udev,
			  usb_sndbulkpipe(dev->udev, dev->bulk_out_endpointAddr),
			  buf, count, lcd_write_bulk_callback, dev);
	urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
	
	/* send the data out the bulk port */
	retval = usb_submit_urb(urb, GFP_KERNEL);
	if (retval) {
		err("USBLCD: %s - failed submitting write urb, error %d", __FUNCTION__, retval);
		goto error;
	}
	
	/* release our reference to this urb, the USB core will eventually free it entirely */
	usb_free_urb(urb);

exit:
	return count;

error:
	usb_buffer_free(dev->udev, count, buf, urb->transfer_dma);
	usb_free_urb(urb);
err_no_buf:
	up(&dev->limit_sem);
	return retval;
}

static const struct file_operations lcd_fops = {
        .owner =        THIS_MODULE,
        .read =         lcd_read,
        .write =        lcd_write,
        .open =         lcd_open,
	.ioctl =        lcd_ioctl,
        .release =      lcd_release,
};

/*
 * usb class driver info in order to get a minor number from the usb core,
 * and to have the device registered with the driver core
 */
static struct usb_class_driver lcd_class = {
        .name =         "lcd%d",
        .fops =         &lcd_fops,
        .minor_base =   USBLCD_MINOR,
};

static int lcd_probe(struct usb_interface *interface, const struct usb_device_id *id)
{
	struct usb_lcd *dev = NULL;
	struct usb_host_interface *iface_desc;
	struct usb_endpoint_descriptor *endpoint;
	size_t buffer_size;
	int i;
	int retval = -ENOMEM;

	/* allocate memory for our device state and initialize it */
	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
	if (dev == NULL) {
		err("Out of memory");
		goto error;
	}
	kref_init(&dev->kref);
	sema_init(&dev->limit_sem, USB_LCD_CONCURRENT_WRITES);

	dev->udev = usb_get_dev(interface_to_usbdev(interface));
	dev->interface = interface;

	if (le16_to_cpu(dev->udev->descriptor.idProduct) != 0x0001) {
		warn(KERN_INFO "USBLCD model not supported.");
		return -ENODEV;
	}
	
	/* set up the endpoint information */
	/* use only the first bulk-in and bulk-out endpoints */
	iface_desc = interface->cur_altsetting;
	for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {
		endpoint = &iface_desc->endpoint[i].desc;

		if (!dev->bulk_in_endpointAddr &&
		    usb_endpoint_is_bulk_in(endpoint)) {
			/* we found a bulk in endpoint */
			buffer_size = le16_to_cpu(endpoint->wMaxPacketSize);
			dev->bulk_in_size = buffer_size;
			dev->bulk_in_endpointAddr = endpoint->bEndpointAddress;
			dev->bulk_in_buffer = kmalloc(buffer_size, GFP_KERNEL);
			if (!dev->bulk_in_buffer) {
				err("Could not allocate bulk_in_buffer");
				goto error;
			}
		}

		if (!dev->bulk_out_endpointAddr &&
		    usb_endpoint_is_bulk_out(endpoint)) {
			/* we found a bulk out endpoint */
			dev->bulk_out_endpointAddr = endpoint->bEndpointAddress;
		}
	}
	if (!(dev->bulk_in_endpointAddr && dev->bulk_out_endpointAddr)) {
		err("Could not find both bulk-in and bulk-out endpoints");
		goto error;
	}

	/* save our data pointer in this interface device */
	usb_set_intfdata(interface, dev);

	/* we can register the device now, as it is ready */
	retval = usb_register_dev(interface, &lcd_class);
	if (retval) {
		/* something prevented us from registering this driver */
		err("Not able to get a minor for this device.");
		usb_set_intfdata(interface, NULL);
		goto error;
	}

	i = le16_to_cpu(dev->udev->descriptor.bcdDevice);

	info("USBLCD Version %1d%1d.%1d%1d found at address %d",
		(i & 0xF000)>>12,(i & 0xF00)>>8,(i & 0xF0)>>4,(i & 0xF),
		dev->udev->devnum);

	/* let the user know what node this device is now attached to */
	info("USB LCD device now attached to USBLCD-%d", interface->minor);
	return 0;

error:
	if (dev)
		kref_put(&dev->kref, lcd_delete);
	return retval;
}

static void lcd_disconnect(struct usb_interface *interface)
{
	struct usb_lcd *dev;
        int minor = interface->minor;

        /* prevent skel_open() from racing skel_disconnect() */
        mutex_lock(&usb_lcd_open_mutex);

        dev = usb_get_intfdata(interface);
        usb_set_intfdata(interface, NULL);

        /* give back our minor */
        usb_deregister_dev(interface, &lcd_class);
 
	mutex_unlock(&usb_lcd_open_mutex);

	/* decrement our usage count */
	kref_put(&dev->kref, lcd_delete);

	info("USB LCD #%d now disconnected", minor);
}

static struct usb_driver lcd_driver = {
	.name =		"usblcd",
	.probe =	lcd_probe,
	.disconnect =	lcd_disconnect,
	.id_table =	id_table,
};

static int __init usb_lcd_init(void)
{
	int result;
	
	result = usb_register(&lcd_driver);
	if (result)
		err("usb_register failed. Error number %d", result);

	return result;
}


static void __exit usb_lcd_exit(void)
{
	usb_deregister(&lcd_driver);
}

module_init(usb_lcd_init);
module_exit(usb_lcd_exit);

MODULE_AUTHOR("Georges Toth <g.toth@e-biz.lu>");
MODULE_DESCRIPTION(DRIVER_VERSION);
MODULE_LICENSE("GPL");