// SPDX-License-Identifier: GPL-2.0
/*
 *  Native support for the I/O-Warrior USB devices
 *
 *  Copyright (c) 2003-2005, 2020  Code Mercenaries GmbH
 *  written by Christian Lucht <lucht@codemercs.com> and
 *  Christoph Jung <jung@codemercs.com>
 *
 *  based on

 *  usb-skeleton.c by Greg Kroah-Hartman  <greg@kroah.com>
 *  brlvger.c by Stephane Dalton  <sdalton@videotron.ca>
 *           and Stephane Doyon   <s.doyon@videotron.ca>
 *
 *  Released under the GPLv2.
 */

#include <linux/module.h>
#include <linux/usb.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/mutex.h>
#include <linux/poll.h>
#include <linux/usb/iowarrior.h>

#define DRIVER_AUTHOR "Christian Lucht <lucht@codemercs.com>"
#define DRIVER_DESC "USB IO-Warrior driver"

#define USB_VENDOR_ID_CODEMERCS         1984
/* low speed iowarrior */
#define USB_DEVICE_ID_CODEMERCS_IOW40   0x1500
#define USB_DEVICE_ID_CODEMERCS_IOW24   0x1501
#define USB_DEVICE_ID_CODEMERCS_IOWPV1  0x1511
#define USB_DEVICE_ID_CODEMERCS_IOWPV2  0x1512
/* full speed iowarrior */
#define USB_DEVICE_ID_CODEMERCS_IOW56   0x1503
/* fuller speed iowarrior */
#define USB_DEVICE_ID_CODEMERCS_IOW28   0x1504
#define USB_DEVICE_ID_CODEMERCS_IOW28L  0x1505
#define USB_DEVICE_ID_CODEMERCS_IOW100  0x1506

/* OEMed devices */
#define USB_DEVICE_ID_CODEMERCS_IOW24SAG        0x158a
#define USB_DEVICE_ID_CODEMERCS_IOW56AM         0x158b

/* Get a minor range for your devices from the usb maintainer */
#ifdef CONFIG_USB_DYNAMIC_MINORS
#define IOWARRIOR_MINOR_BASE    0
#else
#define IOWARRIOR_MINOR_BASE    208     // SKELETON_MINOR_BASE 192 + 16, not official yet
#endif

/* interrupt input queue size */
#define MAX_INTERRUPT_BUFFER 16
/*
   maximum number of urbs that are submitted for writes at the same time,
   this applies to the IOWarrior56 only!
   IOWarrior24 and IOWarrior40 use synchronous usb_control_msg calls.
*/
#define MAX_WRITES_IN_FLIGHT 4

MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE("GPL");

static struct usb_driver iowarrior_driver;

/*--------------*/
/*     data     */
/*--------------*/

/* Structure to hold all of our device specific stuff */
struct iowarrior {
        struct mutex mutex;                     /* locks this structure */
        struct usb_device *udev;                /* save off the usb device pointer */
        struct usb_interface *interface;        /* the interface for this device */
        unsigned char minor;                    /* the starting minor number for this device */
        struct usb_endpoint_descriptor *int_out_endpoint;       /* endpoint for reading (needed for IOW56 only) */
        struct usb_endpoint_descriptor *int_in_endpoint;        /* endpoint for reading */
        struct urb *int_in_urb;         /* the urb for reading data */
        unsigned char *int_in_buffer;   /* buffer for data to be read */
        unsigned char serial_number;    /* to detect lost packages */
        unsigned char *read_queue;      /* size is MAX_INTERRUPT_BUFFER * packet size */
        wait_queue_head_t read_wait;
        wait_queue_head_t write_wait;   /* wait-queue for writing to the device */
        atomic_t write_busy;            /* number of write-urbs submitted */
        atomic_t read_idx;
        atomic_t intr_idx;
        atomic_t overflow_flag;         /* signals an index 'rollover' */
        int present;                    /* this is 1 as long as the device is connected */
        int opened;                     /* this is 1 if the device is currently open */
        char chip_serial[9];            /* the serial number string of the chip connected */
        int report_size;                /* number of bytes in a report */
        u16 product_id;
        struct usb_anchor submitted;
};

/*--------------*/
/*    globals   */
/*--------------*/

#define USB_REQ_GET_REPORT  0x01
//#if 0
static int usb_get_report(struct usb_device *dev,
                          struct usb_host_interface *inter, unsigned char type,
                          unsigned char id, void *buf, int size)
{
        return usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
                               USB_REQ_GET_REPORT,
                               USB_DIR_IN | USB_TYPE_CLASS |
                               USB_RECIP_INTERFACE, (type << 8) + id,
                               inter->desc.bInterfaceNumber, buf, size,
                               USB_CTRL_GET_TIMEOUT);
}
//#endif

#define USB_REQ_SET_REPORT 0x09

static int usb_set_report(struct usb_interface *intf, unsigned char type,
                          unsigned char id, void *buf, int size)
{
        return usb_control_msg(interface_to_usbdev(intf),
                               usb_sndctrlpipe(interface_to_usbdev(intf), 0),
                               USB_REQ_SET_REPORT,
                               USB_TYPE_CLASS | USB_RECIP_INTERFACE,
                               (type << 8) + id,
                               intf->cur_altsetting->desc.bInterfaceNumber, buf,
                               size, 1000);
}

/*---------------------*/
/* driver registration */
/*---------------------*/
/* table of devices that work with this driver */
static const struct usb_device_id iowarrior_ids[] = {
        {USB_DEVICE(USB_VENDOR_ID_CODEMERCS, USB_DEVICE_ID_CODEMERCS_IOW40)},
        {USB_DEVICE(USB_VENDOR_ID_CODEMERCS, USB_DEVICE_ID_CODEMERCS_IOW24)},
        {USB_DEVICE(USB_VENDOR_ID_CODEMERCS, USB_DEVICE_ID_CODEMERCS_IOWPV1)},
        {USB_DEVICE(USB_VENDOR_ID_CODEMERCS, USB_DEVICE_ID_CODEMERCS_IOWPV2)},
        {USB_DEVICE(USB_VENDOR_ID_CODEMERCS, USB_DEVICE_ID_CODEMERCS_IOW56)},
        {USB_DEVICE(USB_VENDOR_ID_CODEMERCS, USB_DEVICE_ID_CODEMERCS_IOW24SAG)},
        {USB_DEVICE(USB_VENDOR_ID_CODEMERCS, USB_DEVICE_ID_CODEMERCS_IOW56AM)},
        {USB_DEVICE(USB_VENDOR_ID_CODEMERCS, USB_DEVICE_ID_CODEMERCS_IOW28)},
        {USB_DEVICE(USB_VENDOR_ID_CODEMERCS, USB_DEVICE_ID_CODEMERCS_IOW28L)},
        {USB_DEVICE(USB_VENDOR_ID_CODEMERCS, USB_DEVICE_ID_CODEMERCS_IOW100)},
        {}                      /* Terminating entry */
};
MODULE_DEVICE_TABLE(usb, iowarrior_ids);

/*
 * USB callback handler for reading data
 */
static void iowarrior_callback(struct urb *urb)
{
        struct iowarrior *dev = urb->context;
        int intr_idx;
        int read_idx;
        int aux_idx;
        int offset;
        int status = urb->status;
        int retval;

        switch (status) {
        case 0:
                /* success */
                break;
        case -ECONNRESET:
        case -ENOENT:
        case -ESHUTDOWN:
                return;
        default:
                goto exit;
        }

        intr_idx = atomic_read(&dev->intr_idx);
        /* aux_idx become previous intr_idx */
        aux_idx = (intr_idx == 0) ? (MAX_INTERRUPT_BUFFER - 1) : (intr_idx - 1);
        read_idx = atomic_read(&dev->read_idx);

        /* queue is not empty and it's interface 0 */
        if ((intr_idx != read_idx)
            && (dev->interface->cur_altsetting->desc.bInterfaceNumber == 0)) {
                /* + 1 for serial number */
                offset = aux_idx * (dev->report_size + 1);
                if (!memcmp
                    (dev->read_queue + offset, urb->transfer_buffer,
                     dev->report_size)) {
                        /* equal values on interface 0 will be ignored */
                        goto exit;
                }
        }

        /* aux_idx become next intr_idx */
        aux_idx = (intr_idx == (MAX_INTERRUPT_BUFFER - 1)) ? 0 : (intr_idx + 1);
        if (read_idx == aux_idx) {
                /* queue full, dropping oldest input */
                read_idx = (++read_idx == MAX_INTERRUPT_BUFFER) ? 0 : read_idx;
                atomic_set(&dev->read_idx, read_idx);
                atomic_set(&dev->overflow_flag, 1);
        }

        /* +1 for serial number */
        offset = intr_idx * (dev->report_size + 1);
        memcpy(dev->read_queue + offset, urb->transfer_buffer,
               dev->report_size);
        *(dev->read_queue + offset + (dev->report_size)) = dev->serial_number++;

        atomic_set(&dev->intr_idx, aux_idx);
        /* tell the blocking read about the new data */
        wake_up_interruptible(&dev->read_wait);

exit:
        retval = usb_submit_urb(urb, GFP_ATOMIC);
        if (retval)
                dev_err(&dev->interface->dev, "%s - usb_submit_urb failed with result %d\n",
                        __func__, retval);

}

/*
 * USB Callback handler for write-ops
 */
static void iowarrior_write_callback(struct urb *urb)
{
        struct iowarrior *dev;
        int status = urb->status;

        dev = urb->context;
        /* sync/async unlink faults aren't errors */
        if (status &&
            !(status == -ENOENT ||
              status == -ECONNRESET || status == -ESHUTDOWN)) {
                dev_dbg(&dev->interface->dev,
                        "nonzero write bulk status received: %d\n", status);
        }
        /* free up our allocated buffer */
        usb_free_coherent(urb->dev, urb->transfer_buffer_length,
                          urb->transfer_buffer, urb->transfer_dma);
        /* tell a waiting writer the interrupt-out-pipe is available again */
        atomic_dec(&dev->write_busy);
        wake_up_interruptible(&dev->write_wait);
}

/*
 *      iowarrior_delete
 */
static inline void iowarrior_delete(struct iowarrior *dev)
{
        dev_dbg(&dev->interface->dev, "minor %d\n", dev->minor);
        kfree(dev->int_in_buffer);
        usb_free_urb(dev->int_in_urb);
        kfree(dev->read_queue);
        usb_put_intf(dev->interface);
        kfree(dev);
}

/*---------------------*/
/* fops implementation */
/*---------------------*/

static int read_index(struct iowarrior *dev)
{
        int intr_idx, read_idx;

        read_idx = atomic_read(&dev->read_idx);
        intr_idx = atomic_read(&dev->intr_idx);

        return (read_idx == intr_idx ? -1 : read_idx);
}

/*
 *  iowarrior_read
 */
static ssize_t iowarrior_read(struct file *file, char __user *buffer,
                              size_t count, loff_t *ppos)
{
        struct iowarrior *dev;
        int read_idx;
        int offset;

        dev = file->private_data;

        /* verify that the device wasn't unplugged */
        if (!dev || !dev->present)
                return -ENODEV;

        dev_dbg(&dev->interface->dev, "minor %d, count = %zd\n",
                dev->minor, count);

        /* read count must be packet size (+ time stamp) */
        if ((count != dev->report_size)
            && (count != (dev->report_size + 1)))
                return -EINVAL;

        /* repeat until no buffer overrun in callback handler occur */
        do {
                atomic_set(&dev->overflow_flag, 0);
                if ((read_idx = read_index(dev)) == -1) {
                        /* queue empty */
                        if (file->f_flags & O_NONBLOCK)
                                return -EAGAIN;
                        else {
                                //next line will return when there is either new data, or the device is unplugged
                                int r = wait_event_interruptible(dev->read_wait,
                                                                 (!dev->present
                                                                  || (read_idx =
                                                                      read_index
                                                                      (dev)) !=
                                                                  -1));
                                if (r) {
                                        //we were interrupted by a signal
                                        return -ERESTART;
                                }
                                if (!dev->present) {
                                        //The device was unplugged
                                        return -ENODEV;
                                }
                                if (read_idx == -1) {
                                        // Can this happen ???
                                        return 0;
                                }
                        }
                }

                offset = read_idx * (dev->report_size + 1);
                if (copy_to_user(buffer, dev->read_queue + offset, count)) {
                        return -EFAULT;
                }
        } while (atomic_read(&dev->overflow_flag));

        read_idx = ++read_idx == MAX_INTERRUPT_BUFFER ? 0 : read_idx;
        atomic_set(&dev->read_idx, read_idx);
        return count;
}

/*
 * iowarrior_write
 */
static ssize_t iowarrior_write(struct file *file,
                               const char __user *user_buffer,
                               size_t count, loff_t *ppos)
{
        struct iowarrior *dev;
        int retval = 0;
        char *buf = NULL;       /* for IOW24 and IOW56 we need a buffer */
        struct urb *int_out_urb = NULL;

        dev = file->private_data;

        mutex_lock(&dev->mutex);
        /* verify that the device wasn't unplugged */
        if (!dev->present) {
                retval = -ENODEV;
                goto exit;
        }
        dev_dbg(&dev->interface->dev, "minor %d, count = %zd\n",
                dev->minor, count);
        /* if count is 0 we're already done */
        if (count == 0) {
                retval = 0;
                goto exit;
        }
        /* We only accept full reports */
        if (count != dev->report_size) {
                retval = -EINVAL;
                goto exit;
        }
        switch (dev->product_id) {
        case USB_DEVICE_ID_CODEMERCS_IOW24:
        case USB_DEVICE_ID_CODEMERCS_IOW24SAG:
        case USB_DEVICE_ID_CODEMERCS_IOWPV1:
        case USB_DEVICE_ID_CODEMERCS_IOWPV2:
        case USB_DEVICE_ID_CODEMERCS_IOW40:
                /* IOW24 and IOW40 use a synchronous call */
                buf = memdup_user(user_buffer, count);
                if (IS_ERR(buf)) {
                        retval = PTR_ERR(buf);
                        goto exit;
                }
                retval = usb_set_report(dev->interface, 2, 0, buf, count);
                kfree(buf);
                goto exit;
        case USB_DEVICE_ID_CODEMERCS_IOW56:
        case USB_DEVICE_ID_CODEMERCS_IOW56AM:
        case USB_DEVICE_ID_CODEMERCS_IOW28:
        case USB_DEVICE_ID_CODEMERCS_IOW28L:
        case USB_DEVICE_ID_CODEMERCS_IOW100:
                /* The IOW56 uses asynchronous IO and more urbs */
                if (atomic_read(&dev->write_busy) == MAX_WRITES_IN_FLIGHT) {
                        /* Wait until we are below the limit for submitted urbs */
                        if (file->f_flags & O_NONBLOCK) {
                                retval = -EAGAIN;
                                goto exit;
                        } else {
                                retval = wait_event_interruptible(dev->write_wait,
                                                                  (!dev->present || (atomic_read (&dev-> write_busy) < MAX_WRITES_IN_FLIGHT)));
                                if (retval) {
                                        /* we were interrupted by a signal */
                                        retval = -ERESTART;
                                        goto exit;
                                }
                                if (!dev->present) {
                                        /* The device was unplugged */
                                        retval = -ENODEV;
                                        goto exit;
                                }
                                if (!dev->opened) {
                                        /* We were closed while waiting for an URB */
                                        retval = -ENODEV;
                                        goto exit;
                                }
                        }
                }
                atomic_inc(&dev->write_busy);
                int_out_urb = usb_alloc_urb(0, GFP_KERNEL);
                if (!int_out_urb) {
                        retval = -ENOMEM;
                        goto error_no_urb;
                }
                buf = usb_alloc_coherent(dev->udev, dev->report_size,
                                         GFP_KERNEL, &int_out_urb->transfer_dma);
                if (!buf) {
                        retval = -ENOMEM;
                        dev_dbg(&dev->interface->dev,
                                "Unable to allocate buffer\n");
                        goto error_no_buffer;
                }
                usb_fill_int_urb(int_out_urb, dev->udev,
                                 usb_sndintpipe(dev->udev,
                                                dev->int_out_endpoint->bEndpointAddress),
                                 buf, dev->report_size,
                                 iowarrior_write_callback, dev,
                                 dev->int_out_endpoint->bInterval);
                int_out_urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
                if (copy_from_user(buf, user_buffer, count)) {
                        retval = -EFAULT;
                        goto error;
                }
                usb_anchor_urb(int_out_urb, &dev->submitted);
                retval = usb_submit_urb(int_out_urb, GFP_KERNEL);
                if (retval) {
                        dev_dbg(&dev->interface->dev,
                                "submit error %d for urb nr.%d\n",
                                retval, atomic_read(&dev->write_busy));
                        usb_unanchor_urb(int_out_urb);
                        goto error;
                }
                /* submit was ok */
                retval = count;
                usb_free_urb(int_out_urb);
                goto exit;
        default:
                /* what do we have here ? An unsupported Product-ID ? */
                dev_err(&dev->interface->dev, "%s - not supported for product=0x%x\n",
                        __func__, dev->product_id);
                retval = -EFAULT;
                goto exit;
        }
error:
        usb_free_coherent(dev->udev, dev->report_size, buf,
                          int_out_urb->transfer_dma);
error_no_buffer:
        usb_free_urb(int_out_urb);
error_no_urb:
        atomic_dec(&dev->write_busy);
        wake_up_interruptible(&dev->write_wait);
exit:
        mutex_unlock(&dev->mutex);
        return retval;
}

/*
 *      iowarrior_ioctl
 */
static long iowarrior_ioctl(struct file *file, unsigned int cmd,
                                                        unsigned long arg)
{
        struct iowarrior *dev = NULL;
        __u8 *buffer;
        __u8 __user *user_buffer;
        int retval;
        int io_res;             /* checks for bytes read/written and copy_to/from_user results */

        dev = file->private_data;
        if (!dev)
                return -ENODEV;

        buffer = kzalloc(dev->report_size, GFP_KERNEL);
        if (!buffer)
                return -ENOMEM;

        mutex_lock(&dev->mutex);

        /* verify that the device wasn't unplugged */
        if (!dev->present) {
                retval = -ENODEV;
                goto error_out;
        }

        dev_dbg(&dev->interface->dev, "minor %d, cmd 0x%.4x, arg %ld\n",
                dev->minor, cmd, arg);

        retval = 0;
        io_res = 0;
        switch (cmd) {
        case IOW_WRITE:
                if (dev->product_id == USB_DEVICE_ID_CODEMERCS_IOW24 ||
                    dev->product_id == USB_DEVICE_ID_CODEMERCS_IOW24SAG ||
                    dev->product_id == USB_DEVICE_ID_CODEMERCS_IOWPV1 ||
                    dev->product_id == USB_DEVICE_ID_CODEMERCS_IOWPV2 ||
                    dev->product_id == USB_DEVICE_ID_CODEMERCS_IOW40) {
                        user_buffer = (__u8 __user *)arg;
                        io_res = copy_from_user(buffer, user_buffer,
                                                dev->report_size);
                        if (io_res) {
                                retval = -EFAULT;
                        } else {
                                io_res = usb_set_report(dev->interface, 2, 0,
                                                        buffer,
                                                        dev->report_size);
                                if (io_res < 0)
                                        retval = io_res;
                        }
                } else {
                        retval = -EINVAL;
                        dev_err(&dev->interface->dev,
                                "ioctl 'IOW_WRITE' is not supported for product=0x%x.\n",
                                dev->product_id);
                }
                break;
        case IOW_READ:
                user_buffer = (__u8 __user *)arg;
                io_res = usb_get_report(dev->udev,
                                        dev->interface->cur_altsetting, 1, 0,
                                        buffer, dev->report_size);
                if (io_res < 0)
                        retval = io_res;
                else {
                        io_res = copy_to_user(user_buffer, buffer, dev->report_size);
                        if (io_res)
                                retval = -EFAULT;
                }
                break;
        case IOW_GETINFO:
                {
                        /* Report available information for the device */
                        struct iowarrior_info info;
                        /* needed for power consumption */
                        struct usb_config_descriptor *cfg_descriptor = &dev->udev->actconfig->desc;

                        memset(&info, 0, sizeof(info));
                        /* directly from the descriptor */
                        info.vendor = le16_to_cpu(dev->udev->descriptor.idVendor);
                        info.product = dev->product_id;
                        info.revision = le16_to_cpu(dev->udev->descriptor.bcdDevice);

                        /* 0==UNKNOWN, 1==LOW(usb1.1) ,2=FULL(usb1.1), 3=HIGH(usb2.0) */
                        info.speed = dev->udev->speed;
                        info.if_num = dev->interface->cur_altsetting->desc.bInterfaceNumber;
                        info.report_size = dev->report_size;

                        /* serial number string has been read earlier 8 chars or empty string */
                        memcpy(info.serial, dev->chip_serial,
                               sizeof(dev->chip_serial));
                        if (cfg_descriptor == NULL) {
                                info.power = -1;        /* no information available */
                        } else {
                                /* the MaxPower is stored in units of 2mA to make it fit into a byte-value */
                                info.power = cfg_descriptor->bMaxPower * 2;
                        }
                        io_res = copy_to_user((struct iowarrior_info __user *)arg, &info,
                                         sizeof(struct iowarrior_info));
                        if (io_res)
                                retval = -EFAULT;
                        break;
                }
        default:
                /* return that we did not understand this ioctl call */
                retval = -ENOTTY;
                break;
        }
error_out:
        /* unlock the device */
        mutex_unlock(&dev->mutex);
        kfree(buffer);
        return retval;
}

/*
 *      iowarrior_open
 */
static int iowarrior_open(struct inode *inode, struct file *file)
{
        struct iowarrior *dev = NULL;
        struct usb_interface *interface;
        int subminor;
        int retval = 0;

        subminor = iminor(inode);

        interface = usb_find_interface(&iowarrior_driver, subminor);
        if (!interface) {
                pr_err("%s - error, can't find device for minor %d\n",
                       __func__, subminor);
                return -ENODEV;
        }

        dev = usb_get_intfdata(interface);
        if (!dev)
                return -ENODEV;

        mutex_lock(&dev->mutex);

        /* Only one process can open each device, no sharing. */
        if (dev->opened) {
                retval = -EBUSY;
                goto out;
        }

        /* setup interrupt handler for receiving values */
        if ((retval = usb_submit_urb(dev->int_in_urb, GFP_KERNEL)) < 0) {
                dev_err(&interface->dev, "Error %d while submitting URB\n", retval);
                retval = -EFAULT;
                goto out;
        }
        /* increment our usage count for the driver */
        ++dev->opened;
        /* save our object in the file's private structure */
        file->private_data = dev;
        retval = 0;

out:
        mutex_unlock(&dev->mutex);
        return retval;
}

/*
 *      iowarrior_release
 */
static int iowarrior_release(struct inode *inode, struct file *file)
{
        struct iowarrior *dev;
        int retval = 0;

        dev = file->private_data;
        if (!dev)
                return -ENODEV;

        dev_dbg(&dev->interface->dev, "minor %d\n", dev->minor);

        /* lock our device */
        mutex_lock(&dev->mutex);

        if (dev->opened <= 0) {
                retval = -ENODEV;       /* close called more than once */
                mutex_unlock(&dev->mutex);
        } else {
                dev->opened = 0;        /* we're closing now */
                retval = 0;
                if (dev->present) {
                        /*
                           The device is still connected so we only shutdown
                           pending read-/write-ops.
                         */
                        usb_kill_urb(dev->int_in_urb);
                        wake_up_interruptible(&dev->read_wait);
                        wake_up_interruptible(&dev->write_wait);
                        mutex_unlock(&dev->mutex);
                } else {
                        /* The device was unplugged, cleanup resources */
                        mutex_unlock(&dev->mutex);
                        iowarrior_delete(dev);
                }
        }
        return retval;
}

static __poll_t iowarrior_poll(struct file *file, poll_table * wait)
{
        struct iowarrior *dev = file->private_data;
        __poll_t mask = 0;

        if (!dev->present)
                return EPOLLERR | EPOLLHUP;

        poll_wait(file, &dev->read_wait, wait);
        poll_wait(file, &dev->write_wait, wait);

        if (!dev->present)
                return EPOLLERR | EPOLLHUP;

        if (read_index(dev) != -1)
                mask |= EPOLLIN | EPOLLRDNORM;

        if (atomic_read(&dev->write_busy) < MAX_WRITES_IN_FLIGHT)
                mask |= EPOLLOUT | EPOLLWRNORM;
        return mask;
}

/*
 * File operations needed when we register this driver.
 * This assumes that this driver NEEDS file operations,
 * of course, which means that the driver is expected
 * to have a node in the /dev directory. If the USB
 * device were for a network interface then the driver
 * would use "struct net_driver" instead, and a serial
 * device would use "struct tty_driver".
 */
static const struct file_operations iowarrior_fops = {
        .owner = THIS_MODULE,
        .write = iowarrior_write,
        .read = iowarrior_read,
        .unlocked_ioctl = iowarrior_ioctl,
        .open = iowarrior_open,
        .release = iowarrior_release,
        .poll = iowarrior_poll,
        .llseek = noop_llseek,
};

static char *iowarrior_devnode(struct device *dev, umode_t *mode)
{
        return kasprintf(GFP_KERNEL, "usb/%s", dev_name(dev));
}

/*
 * 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 iowarrior_class = {
        .name = "iowarrior%d",
        .devnode = iowarrior_devnode,
        .fops = &iowarrior_fops,
        .minor_base = IOWARRIOR_MINOR_BASE,
};

/*---------------------------------*/
/*  probe and disconnect functions */
/*---------------------------------*/
/*
 *      iowarrior_probe
 *
 *      Called by the usb core when a new device is connected that it thinks
 *      this driver might be interested in.
 */
static int iowarrior_probe(struct usb_interface *interface,
                           const struct usb_device_id *id)
{
        struct usb_device *udev = interface_to_usbdev(interface);
        struct iowarrior *dev = NULL;
        struct usb_host_interface *iface_desc;
        int retval = -ENOMEM;
        int res;

        /* allocate memory for our device state and initialize it */
        dev = kzalloc(sizeof(struct iowarrior), GFP_KERNEL);
        if (!dev)
                return retval;

        mutex_init(&dev->mutex);

        atomic_set(&dev->intr_idx, 0);
        atomic_set(&dev->read_idx, 0);
        atomic_set(&dev->overflow_flag, 0);
        init_waitqueue_head(&dev->read_wait);
        atomic_set(&dev->write_busy, 0);
        init_waitqueue_head(&dev->write_wait);

        dev->udev = udev;
        dev->interface = usb_get_intf(interface);

        iface_desc = interface->cur_altsetting;
        dev->product_id = le16_to_cpu(udev->descriptor.idProduct);

        init_usb_anchor(&dev->submitted);

        res = usb_find_last_int_in_endpoint(iface_desc, &dev->int_in_endpoint);
        if (res) {
                dev_err(&interface->dev, "no interrupt-in endpoint found\n");
                retval = res;
                goto error;
        }

        if ((dev->product_id == USB_DEVICE_ID_CODEMERCS_IOW56) ||
            (dev->product_id == USB_DEVICE_ID_CODEMERCS_IOW56AM) ||
            (dev->product_id == USB_DEVICE_ID_CODEMERCS_IOW28) ||
            (dev->product_id == USB_DEVICE_ID_CODEMERCS_IOW28L) ||
            (dev->product_id == USB_DEVICE_ID_CODEMERCS_IOW100)) {
                res = usb_find_last_int_out_endpoint(iface_desc,
                                &dev->int_out_endpoint);
                if (res) {
                        dev_err(&interface->dev, "no interrupt-out endpoint found\n");
                        retval = res;
                        goto error;
                }
        }

        /* we have to check the report_size often, so remember it in the endianness suitable for our machine */
        dev->report_size = usb_endpoint_maxp(dev->int_in_endpoint);

        /*
         * Some devices need the report size to be different than the
         * endpoint size.
         */
        if (dev->interface->cur_altsetting->desc.bInterfaceNumber == 0) {
                switch (dev->product_id) {
                case USB_DEVICE_ID_CODEMERCS_IOW56:
                case USB_DEVICE_ID_CODEMERCS_IOW56AM:
                        dev->report_size = 7;
                        break;

                case USB_DEVICE_ID_CODEMERCS_IOW28:
                case USB_DEVICE_ID_CODEMERCS_IOW28L:
                        dev->report_size = 4;
                        break;

                case USB_DEVICE_ID_CODEMERCS_IOW100:
                        dev->report_size = 13;
                        break;
                }
        }

        /* create the urb and buffer for reading */
        dev->int_in_urb = usb_alloc_urb(0, GFP_KERNEL);
        if (!dev->int_in_urb)
                goto error;
        dev->int_in_buffer = kmalloc(dev->report_size, GFP_KERNEL);
        if (!dev->int_in_buffer)
                goto error;
        usb_fill_int_urb(dev->int_in_urb, dev->udev,
                         usb_rcvintpipe(dev->udev,
                                        dev->int_in_endpoint->bEndpointAddress),
                         dev->int_in_buffer, dev->report_size,
                         iowarrior_callback, dev,
                         dev->int_in_endpoint->bInterval);
        /* create an internal buffer for interrupt data from the device */
        dev->read_queue =
            kmalloc_array(dev->report_size + 1, MAX_INTERRUPT_BUFFER,
                          GFP_KERNEL);
        if (!dev->read_queue)
                goto error;
        /* Get the serial-number of the chip */
        memset(dev->chip_serial, 0x00, sizeof(dev->chip_serial));
        usb_string(udev, udev->descriptor.iSerialNumber, dev->chip_serial,
                   sizeof(dev->chip_serial));
        if (strlen(dev->chip_serial) != 8)
                memset(dev->chip_serial, 0x00, sizeof(dev->chip_serial));

        /* Set the idle timeout to 0, if this is interface 0 */
        if (dev->interface->cur_altsetting->desc.bInterfaceNumber == 0) {
            usb_control_msg(udev, usb_sndctrlpipe(udev, 0),
                            0x0A,
                            USB_TYPE_CLASS | USB_RECIP_INTERFACE, 0,
                            0, NULL, 0, USB_CTRL_SET_TIMEOUT);
        }
        /* allow device read and ioctl */
        dev->present = 1;

        /* we can register the device now, as it is ready */
        usb_set_intfdata(interface, dev);

        retval = usb_register_dev(interface, &iowarrior_class);
        if (retval) {
                /* something prevented us from registering this driver */
                dev_err(&interface->dev, "Not able to get a minor for this device.\n");
                goto error;
        }

        dev->minor = interface->minor;

        /* let the user know what node this device is now attached to */
        dev_info(&interface->dev, "IOWarrior product=0x%x, serial=%s interface=%d "
                 "now attached to iowarrior%d\n", dev->product_id, dev->chip_serial,
                 iface_desc->desc.bInterfaceNumber, dev->minor - IOWARRIOR_MINOR_BASE);
        return retval;

error:
        iowarrior_delete(dev);
        return retval;
}

/*
 *      iowarrior_disconnect
 *
 *      Called by the usb core when the device is removed from the system.
 */
static void iowarrior_disconnect(struct usb_interface *interface)
{
        struct iowarrior *dev = usb_get_intfdata(interface);
        int minor = dev->minor;

        usb_deregister_dev(interface, &iowarrior_class);

        mutex_lock(&dev->mutex);

        /* prevent device read, write and ioctl */
        dev->present = 0;

        if (dev->opened) {
                /* There is a process that holds a filedescriptor to the device ,
                   so we only shutdown read-/write-ops going on.
                   Deleting the device is postponed until close() was called.
                 */
                usb_kill_urb(dev->int_in_urb);
                usb_kill_anchored_urbs(&dev->submitted);
                wake_up_interruptible(&dev->read_wait);
                wake_up_interruptible(&dev->write_wait);
                mutex_unlock(&dev->mutex);
        } else {
                /* no process is using the device, cleanup now */
                mutex_unlock(&dev->mutex);
                iowarrior_delete(dev);
        }

        dev_info(&interface->dev, "I/O-Warror #%d now disconnected\n",
                 minor - IOWARRIOR_MINOR_BASE);
}

/* usb specific object needed to register this driver with the usb subsystem */
static struct usb_driver iowarrior_driver = {
        .name = "iowarrior",
        .probe = iowarrior_probe,
        .disconnect = iowarrior_disconnect,
        .id_table = iowarrior_ids,
};

module_usb_driver(iowarrior_driver);