/*
 * USB Skeleton driver - 2.0
 *
 * Copyright (C) 2001-2004 Greg Kroah-Hartman (greg@kroah.com)
 *
 *      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, version 2.
 *
 * This driver is based on the 2.6.3 version of drivers/usb/usb-skeleton.c 
 * but has been rewritten to be easy to read and use, as no locks are now
 * needed anymore.
 *
 */

#include <linux/config.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/kref.h>
#include <asm/uaccess.h>
#include <linux/usb.h>


/* Define these values to match your devices */
#define USB_SKEL_VENDOR_ID      0xfff0
#define USB_SKEL_PRODUCT_ID     0xfff0

/* table of devices that work with this driver */
static struct usb_device_id skel_table [] = {
        { USB_DEVICE(USB_SKEL_VENDOR_ID, USB_SKEL_PRODUCT_ID) },
        { }                                     /* Terminating entry */
};
MODULE_DEVICE_TABLE (usb, skel_table);


/* Get a minor range for your devices from the usb maintainer */
#define USB_SKEL_MINOR_BASE     192

/* Structure to hold all of our device specific stuff */
struct usb_skel {
        struct usb_device *     udev;                   /* the usb device for this device */
        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;
};
#define to_skel_dev(d) container_of(d, struct usb_skel, kref)

static struct usb_driver skel_driver;

static void skel_delete(struct kref *kref)
{       
        struct usb_skel *dev = to_skel_dev(kref);

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

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

        subminor = iminor(inode);

        interface = usb_find_interface(&skel_driver, subminor);
        if (!interface) {
                err ("%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:
        return retval;
}

static int skel_release(struct inode *inode, struct file *file)
{
        struct usb_skel *dev;

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

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

static ssize_t skel_read(struct file *file, char *buffer, size_t count, loff_t *ppos)
{
        struct usb_skel *dev;
        int retval = 0;

        dev = (struct usb_skel *)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),
                              &count, HZ*10);

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

        return retval;
}

static void skel_write_bulk_callback(struct urb *urb, struct pt_regs *regs)
{
        struct usb_skel *dev;

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

        /* sync/async unlink faults aren't errors */
        if (urb->status && 
            !(urb->status == -ENOENT || 
              urb->status == -ECONNRESET ||
              urb->status == -ESHUTDOWN)) {
                dbg("%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);
}

static ssize_t skel_write(struct file *file, const char *user_buffer, size_t count, loff_t *ppos)
{
        struct usb_skel *dev;
        int retval = 0;
        struct urb *urb = NULL;
        char *buf = NULL;

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

        /* verify that we actually have some data to write */
        if (count == 0)
                goto exit;

        /* 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 error;
        }

        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, skel_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("%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);
        return retval;
}

static struct file_operations skel_fops = {
        .owner =        THIS_MODULE,
        .read =         skel_read,
        .write =        skel_write,
        .open =         skel_open,
        .release =      skel_release,
};

/* 
 * usb class driver info in order to get a minor number from the usb core,
 * and to have the device registered with devfs and the driver core
 */
static struct usb_class_driver skel_class = {
        .name =         "usb/skel%d",
        .fops =         &skel_fops,
        .mode =         S_IFCHR | S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH,
        .minor_base =   USB_SKEL_MINOR_BASE,
};

static int skel_probe(struct usb_interface *interface, const struct usb_device_id *id)
{
        struct usb_skel *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 = kmalloc(sizeof(*dev), GFP_KERNEL);
        if (dev == NULL) {
                err("Out of memory");
                goto error;
        }
        memset(dev, 0x00, sizeof(*dev));
        kref_init(&dev->kref);

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

        /* 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 &&
                    (endpoint->bEndpointAddress & USB_DIR_IN) &&
                    ((endpoint->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK)
                                        == USB_ENDPOINT_XFER_BULK)) {
                        /* 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 &&
                    !(endpoint->bEndpointAddress & USB_DIR_IN) &&
                    ((endpoint->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK)
                                        == USB_ENDPOINT_XFER_BULK)) {
                        /* 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, &skel_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;
        }

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

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

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

        /* prevent skel_open() from racing skel_disconnect() */
        lock_kernel();

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

        /* give back our minor */
        usb_deregister_dev(interface, &skel_class);

        unlock_kernel();

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

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

static struct usb_driver skel_driver = {
        .owner =        THIS_MODULE,
        .name =         "skeleton",
        .probe =        skel_probe,
        .disconnect =   skel_disconnect,
        .id_table =     skel_table,
};

static int __init usb_skel_init(void)
{
        int result;

        /* register this driver with the USB subsystem */
        result = usb_register(&skel_driver);
        if (result)
                err("usb_register failed. Error number %d", result);

        return result;
}

static void __exit usb_skel_exit(void)
{
        /* deregister this driver with the USB subsystem */
        usb_deregister(&skel_driver);
}

module_init (usb_skel_init);
module_exit (usb_skel_exit);

MODULE_LICENSE("GPL");