// SPDX-License-Identifier: GPL-2.0+
/*
 * drivers/usb/class/usbtmc.c - USB Test & Measurement class driver
 *
 * Copyright (C) 2007 Stefan Kopp, Gechingen, Germany
 * Copyright (C) 2008 Novell, Inc.
 * Copyright (C) 2008 Greg Kroah-Hartman <gregkh@suse.de>
 * Copyright (C) 2018 IVI Foundation, Inc.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <linux/kref.h>
#include <linux/slab.h>
#include <linux/poll.h>
#include <linux/mutex.h>
#include <linux/usb.h>
#include <linux/compat.h>
#include <linux/usb/tmc.h>

/* Increment API VERSION when changing tmc.h with new flags or ioctls
 * or when changing a significant behavior of the driver.
 */
#define USBTMC_API_VERSION (3)

#define USBTMC_HEADER_SIZE      12
#define USBTMC_MINOR_BASE       176

/* Minimum USB timeout (in milliseconds) */
#define USBTMC_MIN_TIMEOUT      100
/* Default USB timeout (in milliseconds) */
#define USBTMC_TIMEOUT          5000

/* Max number of urbs used in write transfers */
#define MAX_URBS_IN_FLIGHT      16
/* I/O buffer size used in generic read/write functions */
#define USBTMC_BUFSIZE          (4096)

/*
 * Maximum number of read cycles to empty bulk in endpoint during CLEAR and
 * ABORT_BULK_IN requests. Ends the loop if (for whatever reason) a short
 * packet is never read.
 */
#define USBTMC_MAX_READS_TO_CLEAR_BULK_IN       100

static const struct usb_device_id usbtmc_devices[] = {
        { USB_INTERFACE_INFO(USB_CLASS_APP_SPEC, 3, 0), },
        { USB_INTERFACE_INFO(USB_CLASS_APP_SPEC, 3, 1), },
        { 0, } /* terminating entry */
};
MODULE_DEVICE_TABLE(usb, usbtmc_devices);

/*
 * This structure is the capabilities for the device
 * See section 4.2.1.8 of the USBTMC specification,
 * and section 4.2.2 of the USBTMC usb488 subclass
 * specification for details.
 */
struct usbtmc_dev_capabilities {
        __u8 interface_capabilities;
        __u8 device_capabilities;
        __u8 usb488_interface_capabilities;
        __u8 usb488_device_capabilities;
};

/* This structure holds private data for each USBTMC device. One copy is
 * allocated for each USBTMC device in the driver's probe function.
 */
struct usbtmc_device_data {
        const struct usb_device_id *id;
        struct usb_device *usb_dev;
        struct usb_interface *intf;
        struct list_head file_list;

        unsigned int bulk_in;
        unsigned int bulk_out;

        u8 bTag;
        u8 bTag_last_write;     /* needed for abort */
        u8 bTag_last_read;      /* needed for abort */

        /* packet size of IN bulk */
        u16            wMaxPacketSize;

        /* data for interrupt in endpoint handling */
        u8             bNotify1;
        u8             bNotify2;
        u16            ifnum;
        u8             iin_bTag;
        u8            *iin_buffer;
        atomic_t       iin_data_valid;
        unsigned int   iin_ep;
        int            iin_ep_present;
        int            iin_interval;
        struct urb    *iin_urb;
        u16            iin_wMaxPacketSize;

        /* coalesced usb488_caps from usbtmc_dev_capabilities */
        __u8 usb488_caps;

        bool zombie; /* fd of disconnected device */

        struct usbtmc_dev_capabilities  capabilities;
        struct kref kref;
        struct mutex io_mutex;  /* only one i/o function running at a time */
        wait_queue_head_t waitq;
        struct fasync_struct *fasync;
        spinlock_t dev_lock; /* lock for file_list */
};
#define to_usbtmc_data(d) container_of(d, struct usbtmc_device_data, kref)

/*
 * This structure holds private data for each USBTMC file handle.
 */
struct usbtmc_file_data {
        struct usbtmc_device_data *data;
        struct list_head file_elem;

        u32            timeout;
        u8             srq_byte;
        atomic_t       srq_asserted;
        atomic_t       closing;
        u8             bmTransferAttributes; /* member of DEV_DEP_MSG_IN */

        u8             eom_val;
        u8             term_char;
        bool           term_char_enabled;
        bool           auto_abort;

        spinlock_t     err_lock; /* lock for errors */

        struct usb_anchor submitted;

        /* data for generic_write */
        struct semaphore limit_write_sem;
        u32 out_transfer_size;
        int out_status;

        /* data for generic_read */
        u32 in_transfer_size;
        int in_status;
        int in_urbs_used;
        struct usb_anchor in_anchor;
        wait_queue_head_t wait_bulk_in;
};

/* Forward declarations */
static struct usb_driver usbtmc_driver;
static void usbtmc_draw_down(struct usbtmc_file_data *file_data);

static void usbtmc_delete(struct kref *kref)
{
        struct usbtmc_device_data *data = to_usbtmc_data(kref);

        usb_put_dev(data->usb_dev);
        kfree(data);
}

static int usbtmc_open(struct inode *inode, struct file *filp)
{
        struct usb_interface *intf;
        struct usbtmc_device_data *data;
        struct usbtmc_file_data *file_data;

        intf = usb_find_interface(&usbtmc_driver, iminor(inode));
        if (!intf) {
                pr_err("can not find device for minor %d", iminor(inode));
                return -ENODEV;
        }

        file_data = kzalloc_obj(*file_data);
        if (!file_data)
                return -ENOMEM;

        spin_lock_init(&file_data->err_lock);
        sema_init(&file_data->limit_write_sem, MAX_URBS_IN_FLIGHT);
        init_usb_anchor(&file_data->submitted);
        init_usb_anchor(&file_data->in_anchor);
        init_waitqueue_head(&file_data->wait_bulk_in);

        data = usb_get_intfdata(intf);
        /* Protect reference to data from file structure until release */
        kref_get(&data->kref);

        mutex_lock(&data->io_mutex);
        file_data->data = data;

        atomic_set(&file_data->closing, 0);

        file_data->timeout = USBTMC_TIMEOUT;
        file_data->term_char = '\n';
        file_data->term_char_enabled = 0;
        file_data->auto_abort = 0;
        file_data->eom_val = 1;

        INIT_LIST_HEAD(&file_data->file_elem);
        spin_lock_irq(&data->dev_lock);
        list_add_tail(&file_data->file_elem, &data->file_list);
        spin_unlock_irq(&data->dev_lock);
        mutex_unlock(&data->io_mutex);

        /* Store pointer in file structure's private data field */
        filp->private_data = file_data;

        return 0;
}

/*
 * usbtmc_flush - called before file handle is closed
 */
static int usbtmc_flush(struct file *file, fl_owner_t id)
{
        struct usbtmc_file_data *file_data;
        struct usbtmc_device_data *data;

        file_data = file->private_data;
        if (file_data == NULL)
                return -ENODEV;

        atomic_set(&file_data->closing, 1);
        data = file_data->data;

        /* wait for io to stop */
        mutex_lock(&data->io_mutex);

        usbtmc_draw_down(file_data);

        spin_lock_irq(&file_data->err_lock);
        file_data->in_status = 0;
        file_data->in_transfer_size = 0;
        file_data->in_urbs_used = 0;
        file_data->out_status = 0;
        file_data->out_transfer_size = 0;
        spin_unlock_irq(&file_data->err_lock);

        wake_up_interruptible_all(&data->waitq);
        mutex_unlock(&data->io_mutex);

        return 0;
}

static int usbtmc_release(struct inode *inode, struct file *file)
{
        struct usbtmc_file_data *file_data = file->private_data;

        /* prevent IO _AND_ usbtmc_interrupt */
        mutex_lock(&file_data->data->io_mutex);
        spin_lock_irq(&file_data->data->dev_lock);

        list_del(&file_data->file_elem);

        spin_unlock_irq(&file_data->data->dev_lock);

        /* flush anchored URBs */
        usbtmc_draw_down(file_data);
        mutex_unlock(&file_data->data->io_mutex);

        kref_put(&file_data->data->kref, usbtmc_delete);
        file_data->data = NULL;
        kfree(file_data);
        return 0;
}

static int usbtmc_ioctl_abort_bulk_in_tag(struct usbtmc_device_data *data,
                                          u8 tag)
{
        u8 *buffer;
        struct device *dev;
        int rv;
        int n;
        int actual;

        dev = &data->intf->dev;
        buffer = kmalloc(USBTMC_BUFSIZE, GFP_KERNEL);
        if (!buffer)
                return -ENOMEM;

        rv = usb_control_msg(data->usb_dev,
                             usb_rcvctrlpipe(data->usb_dev, 0),
                             USBTMC_REQUEST_INITIATE_ABORT_BULK_IN,
                             USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_ENDPOINT,
                             tag, data->bulk_in,
                             buffer, 2, USB_CTRL_GET_TIMEOUT);

        if (rv < 0) {
                dev_err(dev, "usb_control_msg returned %d\n", rv);
                goto exit;
        }

        dev_dbg(dev, "INITIATE_ABORT_BULK_IN returned %x with tag %02x\n",
                buffer[0], buffer[1]);

        if (buffer[0] == USBTMC_STATUS_FAILED) {
                /* No transfer in progress and the Bulk-OUT FIFO is empty. */
                rv = 0;
                goto exit;
        }

        if (buffer[0] == USBTMC_STATUS_TRANSFER_NOT_IN_PROGRESS) {
                /* The device returns this status if either:
                 * - There is a transfer in progress, but the specified bTag
                 *   does not match.
                 * - There is no transfer in progress, but the Bulk-OUT FIFO
                 *   is not empty.
                 */
                rv = -ENOMSG;
                goto exit;
        }

        if (buffer[0] != USBTMC_STATUS_SUCCESS) {
                dev_err(dev, "INITIATE_ABORT_BULK_IN returned %x\n",
                        buffer[0]);
                rv = -EPERM;
                goto exit;
        }

        n = 0;

usbtmc_abort_bulk_in_status:
        dev_dbg(dev, "Reading from bulk in EP\n");

        /* Data must be present. So use low timeout 300 ms */
        actual = 0;
        rv = usb_bulk_msg(data->usb_dev,
                          usb_rcvbulkpipe(data->usb_dev,
                                          data->bulk_in),
                          buffer, USBTMC_BUFSIZE,
                          &actual, 300);

        print_hex_dump_debug("usbtmc ", DUMP_PREFIX_NONE, 16, 1,
                             buffer, actual, true);

        n++;

        if (rv < 0) {
                dev_err(dev, "usb_bulk_msg returned %d\n", rv);
                if (rv != -ETIMEDOUT)
                        goto exit;
        }

        if (actual == USBTMC_BUFSIZE)
                goto usbtmc_abort_bulk_in_status;

        if (n >= USBTMC_MAX_READS_TO_CLEAR_BULK_IN) {
                dev_err(dev, "Couldn't clear device buffer within %d cycles\n",
                        USBTMC_MAX_READS_TO_CLEAR_BULK_IN);
                rv = -EPERM;
                goto exit;
        }

        rv = usb_control_msg(data->usb_dev,
                             usb_rcvctrlpipe(data->usb_dev, 0),
                             USBTMC_REQUEST_CHECK_ABORT_BULK_IN_STATUS,
                             USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_ENDPOINT,
                             0, data->bulk_in, buffer, 0x08,
                             USB_CTRL_GET_TIMEOUT);

        if (rv < 0) {
                dev_err(dev, "usb_control_msg returned %d\n", rv);
                goto exit;
        }

        dev_dbg(dev, "CHECK_ABORT_BULK_IN returned %x\n", buffer[0]);

        if (buffer[0] == USBTMC_STATUS_SUCCESS) {
                rv = 0;
                goto exit;
        }

        if (buffer[0] != USBTMC_STATUS_PENDING) {
                dev_err(dev, "CHECK_ABORT_BULK_IN returned %x\n", buffer[0]);
                rv = -EPERM;
                goto exit;
        }

        if ((buffer[1] & 1) > 0) {
                /* The device has 1 or more queued packets the Host can read */
                goto usbtmc_abort_bulk_in_status;
        }

        /* The Host must send CHECK_ABORT_BULK_IN_STATUS at a later time. */
        rv = -EAGAIN;
exit:
        kfree(buffer);
        return rv;
}

static int usbtmc_ioctl_abort_bulk_in(struct usbtmc_device_data *data)
{
        return usbtmc_ioctl_abort_bulk_in_tag(data, data->bTag_last_read);
}

static int usbtmc_ioctl_abort_bulk_out_tag(struct usbtmc_device_data *data,
                                           u8 tag)
{
        struct device *dev;
        u8 *buffer;
        int rv;
        int n;

        dev = &data->intf->dev;

        buffer = kmalloc(8, GFP_KERNEL);
        if (!buffer)
                return -ENOMEM;

        rv = usb_control_msg(data->usb_dev,
                             usb_rcvctrlpipe(data->usb_dev, 0),
                             USBTMC_REQUEST_INITIATE_ABORT_BULK_OUT,
                             USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_ENDPOINT,
                             tag, data->bulk_out,
                             buffer, 2, USB_CTRL_GET_TIMEOUT);

        if (rv < 0) {
                dev_err(dev, "usb_control_msg returned %d\n", rv);
                goto exit;
        }

        dev_dbg(dev, "INITIATE_ABORT_BULK_OUT returned %x\n", buffer[0]);

        if (buffer[0] != USBTMC_STATUS_SUCCESS) {
                dev_err(dev, "INITIATE_ABORT_BULK_OUT returned %x\n",
                        buffer[0]);
                rv = -EPERM;
                goto exit;
        }

        n = 0;

usbtmc_abort_bulk_out_check_status:
        /* do not stress device with subsequent requests */
        msleep(50);
        rv = usb_control_msg(data->usb_dev,
                             usb_rcvctrlpipe(data->usb_dev, 0),
                             USBTMC_REQUEST_CHECK_ABORT_BULK_OUT_STATUS,
                             USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_ENDPOINT,
                             0, data->bulk_out, buffer, 0x08,
                             USB_CTRL_GET_TIMEOUT);
        n++;
        if (rv < 0) {
                dev_err(dev, "usb_control_msg returned %d\n", rv);
                goto exit;
        }

        dev_dbg(dev, "CHECK_ABORT_BULK_OUT returned %x\n", buffer[0]);

        if (buffer[0] == USBTMC_STATUS_SUCCESS)
                goto usbtmc_abort_bulk_out_clear_halt;

        if ((buffer[0] == USBTMC_STATUS_PENDING) &&
            (n < USBTMC_MAX_READS_TO_CLEAR_BULK_IN))
                goto usbtmc_abort_bulk_out_check_status;

        rv = -EPERM;
        goto exit;

usbtmc_abort_bulk_out_clear_halt:
        rv = usb_clear_halt(data->usb_dev,
                            usb_sndbulkpipe(data->usb_dev, data->bulk_out));

        if (rv < 0) {
                dev_err(dev, "usb_control_msg returned %d\n", rv);
                goto exit;
        }
        rv = 0;

exit:
        kfree(buffer);
        return rv;
}

static int usbtmc_ioctl_abort_bulk_out(struct usbtmc_device_data *data)
{
        return usbtmc_ioctl_abort_bulk_out_tag(data, data->bTag_last_write);
}

static int usbtmc_get_stb(struct usbtmc_file_data *file_data, __u8 *stb)
{
        struct usbtmc_device_data *data = file_data->data;
        struct device *dev = &data->intf->dev;
        u8 *buffer;
        u8 tag;
        int rv;
        long wait_rv;
        unsigned long expire;

        dev_dbg(dev, "Enter ioctl_read_stb iin_ep_present: %d\n",
                data->iin_ep_present);

        buffer = kmalloc(8, GFP_KERNEL);
        if (!buffer)
                return -ENOMEM;

        atomic_set(&data->iin_data_valid, 0);

        rv = usb_control_msg(data->usb_dev,
                        usb_rcvctrlpipe(data->usb_dev, 0),
                        USBTMC488_REQUEST_READ_STATUS_BYTE,
                        USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE,
                        data->iin_bTag,
                        data->ifnum,
                        buffer, 0x03, USB_CTRL_GET_TIMEOUT);
        if (rv < 0) {
                dev_err(dev, "stb usb_control_msg returned %d\n", rv);
                goto exit;
        }

        if (buffer[0] != USBTMC_STATUS_SUCCESS) {
                dev_err(dev, "control status returned %x\n", buffer[0]);
                rv = -EIO;
                goto exit;
        }

        if (data->iin_ep_present) {
                expire = msecs_to_jiffies(file_data->timeout);
                wait_rv = wait_event_interruptible_timeout(
                        data->waitq,
                        atomic_read(&data->iin_data_valid) != 0,
                        expire);
                if (wait_rv < 0) {
                        dev_dbg(dev, "wait interrupted %ld\n", wait_rv);
                        rv = wait_rv;
                        goto exit;
                }

                if (wait_rv == 0) {
                        dev_dbg(dev, "wait timed out\n");
                        rv = -ETIMEDOUT;
                        goto exit;
                }

                tag = data->bNotify1 & 0x7f;
                if (tag != data->iin_bTag) {
                        dev_err(dev, "expected bTag %x got %x\n",
                                data->iin_bTag, tag);
                }

                *stb = data->bNotify2;
        } else {
                *stb = buffer[2];
        }

        dev_dbg(dev, "stb:0x%02x received %d\n", (unsigned int)*stb, rv);

        rv = 0;

 exit:
        /* bump interrupt bTag */
        data->iin_bTag += 1;
        if (data->iin_bTag > 127)
                /* 1 is for SRQ see USBTMC-USB488 subclass spec section 4.3.1 */
                data->iin_bTag = 2;

        kfree(buffer);
        return rv;
}

static int usbtmc488_ioctl_read_stb(struct usbtmc_file_data *file_data,
                                void __user *arg)
{
        int srq_asserted = 0;
        __u8 stb;
        int rv;

        rv = usbtmc_get_stb(file_data, &stb);

        if (rv < 0)
                return rv;

        srq_asserted = atomic_xchg(&file_data->srq_asserted, srq_asserted);
        if (srq_asserted)
                stb |= 0x40; /* Set RQS bit */

        rv = put_user(stb, (__u8 __user *)arg);

        return rv;

}

static int usbtmc_ioctl_get_srq_stb(struct usbtmc_file_data *file_data,
                                void __user *arg)
{
        struct usbtmc_device_data *data = file_data->data;
        struct device *dev = &data->intf->dev;
        int srq_asserted = 0;
        __u8 stb = 0;
        int rv;

        spin_lock_irq(&data->dev_lock);
        srq_asserted  = atomic_xchg(&file_data->srq_asserted, srq_asserted);

        if (srq_asserted) {
                stb = file_data->srq_byte;
                spin_unlock_irq(&data->dev_lock);
                rv = put_user(stb, (__u8 __user *)arg);
        } else {
                spin_unlock_irq(&data->dev_lock);
                rv = -ENOMSG;
        }

        dev_dbg(dev, "stb:0x%02x with srq received %d\n", (unsigned int)stb, rv);

        return rv;
}

static int usbtmc488_ioctl_wait_srq(struct usbtmc_file_data *file_data,
                                    __u32 __user *arg)
{
        struct usbtmc_device_data *data = file_data->data;
        struct device *dev = &data->intf->dev;
        u32 timeout;
        unsigned long expire;
        long wait_rv;

        if (!data->iin_ep_present) {
                dev_dbg(dev, "no interrupt endpoint present\n");
                return -EFAULT;
        }

        if (get_user(timeout, arg))
                return -EFAULT;

        expire = msecs_to_jiffies(timeout);

        mutex_unlock(&data->io_mutex);

        wait_rv = wait_event_interruptible_timeout(
                data->waitq,
                atomic_read(&file_data->srq_asserted) != 0 ||
                atomic_read(&file_data->closing),
                expire);

        mutex_lock(&data->io_mutex);

        /* Note! disconnect or close could be called in the meantime */
        if (atomic_read(&file_data->closing) || data->zombie)
                return -ENODEV;

        if (wait_rv < 0) {
                dev_dbg(dev, "%s - wait interrupted %ld\n", __func__, wait_rv);
                return wait_rv;
        }

        if (wait_rv == 0) {
                dev_dbg(dev, "%s - wait timed out\n", __func__);
                return -ETIMEDOUT;
        }

        dev_dbg(dev, "%s - srq asserted\n", __func__);
        return 0;
}

static int usbtmc488_ioctl_simple(struct usbtmc_device_data *data,
                                void __user *arg, unsigned int cmd)
{
        struct device *dev = &data->intf->dev;
        __u8 val;
        u8 *buffer;
        u16 wValue;
        int rv;

        if (!(data->usb488_caps & USBTMC488_CAPABILITY_SIMPLE))
                return -EINVAL;

        buffer = kmalloc(8, GFP_KERNEL);
        if (!buffer)
                return -ENOMEM;

        if (cmd == USBTMC488_REQUEST_REN_CONTROL) {
                rv = copy_from_user(&val, arg, sizeof(val));
                if (rv) {
                        rv = -EFAULT;
                        goto exit;
                }
                wValue = val ? 1 : 0;
        } else {
                wValue = 0;
        }

        rv = usb_control_msg(data->usb_dev,
                        usb_rcvctrlpipe(data->usb_dev, 0),
                        cmd,
                        USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE,
                        wValue,
                        data->ifnum,
                        buffer, 0x01, USB_CTRL_GET_TIMEOUT);
        if (rv < 0) {
                dev_err(dev, "simple usb_control_msg failed %d\n", rv);
                goto exit;
        } else if (rv != 1) {
                dev_warn(dev, "simple usb_control_msg returned %d\n", rv);
                rv = -EIO;
                goto exit;
        }

        if (buffer[0] != USBTMC_STATUS_SUCCESS) {
                dev_err(dev, "simple control status returned %x\n", buffer[0]);
                rv = -EIO;
                goto exit;
        }
        rv = 0;

 exit:
        kfree(buffer);
        return rv;
}

/*
 * Sends a TRIGGER Bulk-OUT command message
 * See the USBTMC-USB488 specification, Table 2.
 *
 * Also updates bTag_last_write.
 */
static int usbtmc488_ioctl_trigger(struct usbtmc_file_data *file_data)
{
        struct usbtmc_device_data *data = file_data->data;
        int retval;
        u8 *buffer;
        int actual;

        buffer = kzalloc(USBTMC_HEADER_SIZE, GFP_KERNEL);
        if (!buffer)
                return -ENOMEM;

        buffer[0] = 128;
        buffer[1] = data->bTag;
        buffer[2] = ~data->bTag;

        retval = usb_bulk_msg_killable(data->usb_dev,
                              usb_sndbulkpipe(data->usb_dev,
                                              data->bulk_out),
                              buffer, USBTMC_HEADER_SIZE,
                              &actual, file_data->timeout);

        /* Store bTag (in case we need to abort) */
        data->bTag_last_write = data->bTag;

        /* Increment bTag -- and increment again if zero */
        data->bTag++;
        if (!data->bTag)
                data->bTag++;

        kfree(buffer);
        if (retval < 0) {
                dev_err(&data->intf->dev, "%s returned %d\n",
                        __func__, retval);
                return retval;
        }

        return 0;
}

static struct urb *usbtmc_create_urb(void)
{
        const size_t bufsize = USBTMC_BUFSIZE;
        u8 *dmabuf = NULL;
        struct urb *urb = usb_alloc_urb(0, GFP_KERNEL);

        if (!urb)
                return NULL;

        dmabuf = kzalloc(bufsize, GFP_KERNEL);
        if (!dmabuf) {
                usb_free_urb(urb);
                return NULL;
        }

        urb->transfer_buffer = dmabuf;
        urb->transfer_buffer_length = bufsize;
        urb->transfer_flags |= URB_FREE_BUFFER;
        return urb;
}

static void usbtmc_read_bulk_cb(struct urb *urb)
{
        struct usbtmc_file_data *file_data = urb->context;
        int status = urb->status;
        unsigned long flags;

        /* sync/async unlink faults aren't errors */
        if (status) {
                if (!(/* status == -ENOENT || */
                        status == -ECONNRESET ||
                        status == -EREMOTEIO || /* Short packet */
                        status == -ESHUTDOWN))
                        dev_err(&file_data->data->intf->dev,
                        "%s - nonzero read bulk status received: %d\n",
                        __func__, status);

                spin_lock_irqsave(&file_data->err_lock, flags);
                if (!file_data->in_status)
                        file_data->in_status = status;
                spin_unlock_irqrestore(&file_data->err_lock, flags);
        }

        spin_lock_irqsave(&file_data->err_lock, flags);
        file_data->in_transfer_size += urb->actual_length;
        dev_dbg(&file_data->data->intf->dev,
                "%s - total size: %u current: %d status: %d\n",
                __func__, file_data->in_transfer_size,
                urb->actual_length, status);
        spin_unlock_irqrestore(&file_data->err_lock, flags);
        usb_anchor_urb(urb, &file_data->in_anchor);

        wake_up_interruptible(&file_data->wait_bulk_in);
        wake_up_interruptible(&file_data->data->waitq);
}

static inline bool usbtmc_do_transfer(struct usbtmc_file_data *file_data)
{
        bool data_or_error;

        spin_lock_irq(&file_data->err_lock);
        data_or_error = !usb_anchor_empty(&file_data->in_anchor)
                        || file_data->in_status;
        spin_unlock_irq(&file_data->err_lock);
        dev_dbg(&file_data->data->intf->dev, "%s: returns %d\n", __func__,
                data_or_error);
        return data_or_error;
}

static ssize_t usbtmc_generic_read(struct usbtmc_file_data *file_data,
                                   void __user *user_buffer,
                                   u32 transfer_size,
                                   u32 *transferred,
                                   u32 flags)
{
        struct usbtmc_device_data *data = file_data->data;
        struct device *dev = &data->intf->dev;
        u32 done = 0;
        u32 remaining;
        const u32 bufsize = USBTMC_BUFSIZE;
        int retval = 0;
        u32 max_transfer_size;
        unsigned long expire;
        int bufcount = 1;
        int again = 0;
        long wait_rv;

        /* mutex already locked */

        *transferred = done;

        max_transfer_size = transfer_size;

        if (flags & USBTMC_FLAG_IGNORE_TRAILER) {
                /* The device may send extra alignment bytes (up to
                 * wMaxPacketSize – 1) to avoid sending a zero-length
                 * packet
                 */
                remaining = transfer_size;
                if ((max_transfer_size % data->wMaxPacketSize) == 0)
                        max_transfer_size += (data->wMaxPacketSize - 1);
        } else {
                /* round down to bufsize to avoid truncated data left */
                if (max_transfer_size > bufsize) {
                        max_transfer_size =
                                roundup(max_transfer_size + 1 - bufsize,
                                        bufsize);
                }
                remaining = max_transfer_size;
        }

        spin_lock_irq(&file_data->err_lock);

        if (file_data->in_status) {
                /* return the very first error */
                retval = file_data->in_status;
                spin_unlock_irq(&file_data->err_lock);
                goto error;
        }

        if (flags & USBTMC_FLAG_ASYNC) {
                if (usb_anchor_empty(&file_data->in_anchor))
                        again = 1;

                if (file_data->in_urbs_used == 0) {
                        file_data->in_transfer_size = 0;
                        file_data->in_status = 0;
                }
        } else {
                file_data->in_transfer_size = 0;
                file_data->in_status = 0;
        }

        if (max_transfer_size == 0) {
                bufcount = 0;
        } else {
                bufcount = roundup(max_transfer_size, bufsize) / bufsize;
                if (bufcount > file_data->in_urbs_used)
                        bufcount -= file_data->in_urbs_used;
                else
                        bufcount = 0;

                if (bufcount + file_data->in_urbs_used > MAX_URBS_IN_FLIGHT) {
                        bufcount = MAX_URBS_IN_FLIGHT -
                                        file_data->in_urbs_used;
                }
        }
        spin_unlock_irq(&file_data->err_lock);

        dev_dbg(dev, "%s: requested=%u flags=0x%X size=%u bufs=%d used=%d\n",
                __func__, transfer_size, flags,
                max_transfer_size, bufcount, file_data->in_urbs_used);

        while (bufcount > 0) {
                u8 *dmabuf = NULL;
                struct urb *urb = usbtmc_create_urb();

                if (!urb) {
                        retval = -ENOMEM;
                        goto error;
                }

                dmabuf = urb->transfer_buffer;

                usb_fill_bulk_urb(urb, data->usb_dev,
                        usb_rcvbulkpipe(data->usb_dev, data->bulk_in),
                        dmabuf, bufsize,
                        usbtmc_read_bulk_cb, file_data);

                usb_anchor_urb(urb, &file_data->submitted);
                retval = usb_submit_urb(urb, GFP_KERNEL);
                /* urb is anchored. We can release our reference. */
                usb_free_urb(urb);
                if (unlikely(retval)) {
                        usb_unanchor_urb(urb);
                        goto error;
                }
                file_data->in_urbs_used++;
                bufcount--;
        }

        if (again) {
                dev_dbg(dev, "%s: ret=again\n", __func__);
                return -EAGAIN;
        }

        if (user_buffer == NULL)
                return -EINVAL;

        expire = msecs_to_jiffies(file_data->timeout);

        while (max_transfer_size > 0) {
                u32 this_part;
                struct urb *urb = NULL;

                if (!(flags & USBTMC_FLAG_ASYNC)) {
                        dev_dbg(dev, "%s: before wait time %lu\n",
                                __func__, expire);
                        wait_rv = wait_event_interruptible_timeout(
                                file_data->wait_bulk_in,
                                usbtmc_do_transfer(file_data),
                                expire);

                        dev_dbg(dev, "%s: wait returned %ld\n",
                                __func__, wait_rv);

                        if (wait_rv < 0) {
                                retval = wait_rv;
                                goto error;
                        }

                        if (wait_rv == 0) {
                                retval = -ETIMEDOUT;
                                goto error;
                        }

                }

                urb = usb_get_from_anchor(&file_data->in_anchor);
                if (!urb) {
                        if (!(flags & USBTMC_FLAG_ASYNC)) {
                                /* synchronous case: must not happen */
                                retval = -EFAULT;
                                goto error;
                        }

                        /* asynchronous case: ready, do not block or wait */
                        *transferred = done;
                        dev_dbg(dev, "%s: (async) done=%u ret=0\n",
                                __func__, done);
                        return 0;
                }

                file_data->in_urbs_used--;

                if (max_transfer_size > urb->actual_length)
                        max_transfer_size -= urb->actual_length;
                else
                        max_transfer_size = 0;

                if (remaining > urb->actual_length)
                        this_part = urb->actual_length;
                else
                        this_part = remaining;

                print_hex_dump_debug("usbtmc ", DUMP_PREFIX_NONE, 16, 1,
                        urb->transfer_buffer, urb->actual_length, true);

                if (copy_to_user(user_buffer + done,
                                 urb->transfer_buffer, this_part)) {
                        usb_free_urb(urb);
                        retval = -EFAULT;
                        goto error;
                }

                remaining -= this_part;
                done += this_part;

                spin_lock_irq(&file_data->err_lock);
                if (urb->status) {
                        /* return the very first error */
                        retval = file_data->in_status;
                        spin_unlock_irq(&file_data->err_lock);
                        usb_free_urb(urb);
                        goto error;
                }
                spin_unlock_irq(&file_data->err_lock);

                if (urb->actual_length < bufsize) {
                        /* short packet or ZLP received => ready */
                        usb_free_urb(urb);
                        retval = 1;
                        break;
                }

                if (!(flags & USBTMC_FLAG_ASYNC) &&
                    max_transfer_size > (bufsize * file_data->in_urbs_used)) {
                        /* resubmit, since other buffers still not enough */
                        usb_anchor_urb(urb, &file_data->submitted);
                        retval = usb_submit_urb(urb, GFP_KERNEL);
                        if (unlikely(retval)) {
                                usb_unanchor_urb(urb);
                                usb_free_urb(urb);
                                goto error;
                        }
                        file_data->in_urbs_used++;
                }
                usb_free_urb(urb);
                retval = 0;
        }

error:
        *transferred = done;

        dev_dbg(dev, "%s: before kill\n", __func__);
        /* Attention: killing urbs can take long time (2 ms) */
        usb_kill_anchored_urbs(&file_data->submitted);
        dev_dbg(dev, "%s: after kill\n", __func__);
        usb_scuttle_anchored_urbs(&file_data->in_anchor);
        file_data->in_urbs_used = 0;
        file_data->in_status = 0; /* no spinlock needed here */
        dev_dbg(dev, "%s: done=%u ret=%d\n", __func__, done, retval);

        return retval;
}

static ssize_t usbtmc_ioctl_generic_read(struct usbtmc_file_data *file_data,
                                         void __user *arg)
{
        struct usbtmc_message msg;
        ssize_t retval = 0;

        /* mutex already locked */

        if (copy_from_user(&msg, arg, sizeof(struct usbtmc_message)))
                return -EFAULT;

        retval = usbtmc_generic_read(file_data, msg.message,
                                     msg.transfer_size, &msg.transferred,
                                     msg.flags);

        if (put_user(msg.transferred,
                     &((struct usbtmc_message __user *)arg)->transferred))
                return -EFAULT;

        return retval;
}

static void usbtmc_write_bulk_cb(struct urb *urb)
{
        struct usbtmc_file_data *file_data = urb->context;
        int wakeup = 0;
        unsigned long flags;

        spin_lock_irqsave(&file_data->err_lock, flags);
        file_data->out_transfer_size += urb->actual_length;

        /* sync/async unlink faults aren't errors */
        if (urb->status) {
                if (!(urb->status == -ENOENT ||
                        urb->status == -ECONNRESET ||
                        urb->status == -ESHUTDOWN))
                        dev_err(&file_data->data->intf->dev,
                                "%s - nonzero write bulk status received: %d\n",
                                __func__, urb->status);

                if (!file_data->out_status) {
                        file_data->out_status = urb->status;
                        wakeup = 1;
                }
        }
        spin_unlock_irqrestore(&file_data->err_lock, flags);

        dev_dbg(&file_data->data->intf->dev,
                "%s - write bulk total size: %u\n",
                __func__, file_data->out_transfer_size);

        up(&file_data->limit_write_sem);
        if (usb_anchor_empty(&file_data->submitted) || wakeup)
                wake_up_interruptible(&file_data->data->waitq);
}

static ssize_t usbtmc_generic_write(struct usbtmc_file_data *file_data,
                                    const void __user *user_buffer,
                                    u32 transfer_size,
                                    u32 *transferred,
                                    u32 flags)
{
        struct usbtmc_device_data *data = file_data->data;
        struct device *dev;
        u32 done = 0;
        u32 remaining;
        unsigned long expire;
        const u32 bufsize = USBTMC_BUFSIZE;
        struct urb *urb = NULL;
        int retval = 0;
        u32 timeout;

        *transferred = 0;

        /* Get pointer to private data structure */
        dev = &data->intf->dev;

        dev_dbg(dev, "%s: size=%u flags=0x%X sema=%u\n",
                __func__, transfer_size, flags,
                file_data->limit_write_sem.count);

        if (flags & USBTMC_FLAG_APPEND) {
                spin_lock_irq(&file_data->err_lock);
                retval = file_data->out_status;
                spin_unlock_irq(&file_data->err_lock);
                if (retval < 0)
                        return retval;
        } else {
                spin_lock_irq(&file_data->err_lock);
                file_data->out_transfer_size = 0;
                file_data->out_status = 0;
                spin_unlock_irq(&file_data->err_lock);
        }

        remaining = transfer_size;
        if (remaining > INT_MAX)
                remaining = INT_MAX;

        timeout = file_data->timeout;
        expire = msecs_to_jiffies(timeout);

        while (remaining > 0) {
                u32 this_part, aligned;
                u8 *buffer = NULL;

                if (flags & USBTMC_FLAG_ASYNC) {
                        if (down_trylock(&file_data->limit_write_sem)) {
                                retval = (done)?(0):(-EAGAIN);
                                goto exit;
                        }
                } else {
                        retval = down_timeout(&file_data->limit_write_sem,
                                              expire);
                        if (retval < 0) {
                                retval = -ETIMEDOUT;
                                goto error;
                        }
                }

                spin_lock_irq(&file_data->err_lock);
                retval = file_data->out_status;
                spin_unlock_irq(&file_data->err_lock);
                if (retval < 0) {
                        up(&file_data->limit_write_sem);
                        goto error;
                }

                /* prepare next urb to send */
                urb = usbtmc_create_urb();
                if (!urb) {
                        retval = -ENOMEM;
                        up(&file_data->limit_write_sem);
                        goto error;
                }
                buffer = urb->transfer_buffer;

                if (remaining > bufsize)
                        this_part = bufsize;
                else
                        this_part = remaining;

                if (copy_from_user(buffer, user_buffer + done, this_part)) {
                        retval = -EFAULT;
                        up(&file_data->limit_write_sem);
                        goto error;
                }

                print_hex_dump_debug("usbtmc ", DUMP_PREFIX_NONE,
                        16, 1, buffer, this_part, true);

                /* fill bulk with 32 bit alignment to meet USBTMC specification
                 * (size + 3 & ~3) rounds up and simplifies user code
                 */
                aligned = (this_part + 3) & ~3;
                dev_dbg(dev, "write(size:%u align:%u done:%u)\n",
                        (unsigned int)this_part,
                        (unsigned int)aligned,
                        (unsigned int)done);

                usb_fill_bulk_urb(urb, data->usb_dev,
                        usb_sndbulkpipe(data->usb_dev, data->bulk_out),
                        urb->transfer_buffer, aligned,
                        usbtmc_write_bulk_cb, file_data);

                usb_anchor_urb(urb, &file_data->submitted);
                retval = usb_submit_urb(urb, GFP_KERNEL);
                if (unlikely(retval)) {
                        usb_unanchor_urb(urb);
                        up(&file_data->limit_write_sem);
                        goto error;
                }

                usb_free_urb(urb);
                urb = NULL; /* urb will be finally released by usb driver */

                remaining -= this_part;
                done += this_part;
        }

        /* All urbs are on the fly */
        if (!(flags & USBTMC_FLAG_ASYNC)) {
                if (!usb_wait_anchor_empty_timeout(&file_data->submitted,
                                                   timeout)) {
                        retval = -ETIMEDOUT;
                        goto error;
                }
        }

        retval = 0;
        goto exit;

error:
        usb_kill_anchored_urbs(&file_data->submitted);
exit:
        usb_free_urb(urb);

        spin_lock_irq(&file_data->err_lock);
        if (!(flags & USBTMC_FLAG_ASYNC))
                done = file_data->out_transfer_size;
        if (!retval && file_data->out_status)
                retval = file_data->out_status;
        spin_unlock_irq(&file_data->err_lock);

        *transferred = done;

        dev_dbg(dev, "%s: done=%u, retval=%d, urbstat=%d\n",
                __func__, done, retval, file_data->out_status);

        return retval;
}

static ssize_t usbtmc_ioctl_generic_write(struct usbtmc_file_data *file_data,
                                          void __user *arg)
{
        struct usbtmc_message msg;
        ssize_t retval = 0;

        /* mutex already locked */

        if (copy_from_user(&msg, arg, sizeof(struct usbtmc_message)))
                return -EFAULT;

        retval = usbtmc_generic_write(file_data, msg.message,
                                      msg.transfer_size, &msg.transferred,
                                      msg.flags);

        if (put_user(msg.transferred,
                     &((struct usbtmc_message __user *)arg)->transferred))
                return -EFAULT;

        return retval;
}

/*
 * Get the generic write result
 */
static ssize_t usbtmc_ioctl_write_result(struct usbtmc_file_data *file_data,
                                void __user *arg)
{
        u32 transferred;
        int retval;

        spin_lock_irq(&file_data->err_lock);
        transferred = file_data->out_transfer_size;
        retval = file_data->out_status;
        spin_unlock_irq(&file_data->err_lock);

        if (put_user(transferred, (__u32 __user *)arg))
                return -EFAULT;

        return retval;
}

/*
 * Sends a REQUEST_DEV_DEP_MSG_IN message on the Bulk-OUT endpoint.
 * @transfer_size: number of bytes to request from the device.
 *
 * See the USBTMC specification, Table 4.
 *
 * Also updates bTag_last_write.
 */
static int send_request_dev_dep_msg_in(struct usbtmc_file_data *file_data,
                                       u32 transfer_size)
{
        struct usbtmc_device_data *data = file_data->data;
        int retval;
        u8 *buffer;
        int actual;

        buffer = kmalloc(USBTMC_HEADER_SIZE, GFP_KERNEL);
        if (!buffer)
                return -ENOMEM;
        /* Setup IO buffer for REQUEST_DEV_DEP_MSG_IN message
         * Refer to class specs for details
         */
        buffer[0] = 2;
        buffer[1] = data->bTag;
        buffer[2] = ~data->bTag;
        buffer[3] = 0; /* Reserved */
        buffer[4] = transfer_size >> 0;
        buffer[5] = transfer_size >> 8;
        buffer[6] = transfer_size >> 16;
        buffer[7] = transfer_size >> 24;
        buffer[8] = file_data->term_char_enabled * 2;
        /* Use term character? */
        buffer[9] = file_data->term_char;
        buffer[10] = 0; /* Reserved */
        buffer[11] = 0; /* Reserved */

        /* Send bulk URB */
        retval = usb_bulk_msg_killable(data->usb_dev,
                              usb_sndbulkpipe(data->usb_dev,
                                              data->bulk_out),
                              buffer, USBTMC_HEADER_SIZE,
                              &actual, file_data->timeout);

        /* Store bTag (in case we need to abort) */
        data->bTag_last_write = data->bTag;

        /* Increment bTag -- and increment again if zero */
        data->bTag++;
        if (!data->bTag)
                data->bTag++;

        kfree(buffer);
        if (retval < 0)
                dev_err(&data->intf->dev, "%s returned %d\n",
                        __func__, retval);

        return retval;
}

static ssize_t usbtmc_read(struct file *filp, char __user *buf,
                           size_t count, loff_t *f_pos)
{
        struct usbtmc_file_data *file_data;
        struct usbtmc_device_data *data;
        struct device *dev;
        const u32 bufsize = USBTMC_BUFSIZE;
        u32 n_characters;
        u8 *buffer;
        int actual;
        u32 done = 0;
        u32 remaining;
        int retval;

        /* Get pointer to private data structure */
        file_data = filp->private_data;
        data = file_data->data;
        dev = &data->intf->dev;

        buffer = kmalloc(bufsize, GFP_KERNEL);
        if (!buffer)
                return -ENOMEM;

        retval = mutex_lock_interruptible(&data->io_mutex);
        if (retval < 0)
                goto exit_nolock;

        if (data->zombie) {
                retval = -ENODEV;
                goto exit;
        }

        if (count > INT_MAX)
                count = INT_MAX;

        dev_dbg(dev, "%s(count:%zu)\n", __func__, count);

        retval = send_request_dev_dep_msg_in(file_data, count);

        if (retval < 0) {
                if (file_data->auto_abort)
                        usbtmc_ioctl_abort_bulk_out(data);
                goto exit;
        }

        /* Loop until we have fetched everything we requested */
        remaining = count;
        actual = 0;

        /* Send bulk URB */
        retval = usb_bulk_msg_killable(data->usb_dev,
                              usb_rcvbulkpipe(data->usb_dev,
                                              data->bulk_in),
                              buffer, bufsize, &actual,
                              file_data->timeout);

        dev_dbg(dev, "%s: bulk_msg retval(%u), actual(%d)\n",
                __func__, retval, actual);

        /* Store bTag (in case we need to abort) */
        data->bTag_last_read = data->bTag;

        if (retval < 0) {
                if (file_data->auto_abort)
                        usbtmc_ioctl_abort_bulk_in(data);
                goto exit;
        }

        /* Sanity checks for the header */
        if (actual < USBTMC_HEADER_SIZE) {
                dev_err(dev, "Device sent too small first packet: %u < %u\n",
                        actual, USBTMC_HEADER_SIZE);
                if (file_data->auto_abort)
                        usbtmc_ioctl_abort_bulk_in(data);
                goto exit;
        }

        if (buffer[0] != 2) {
                dev_err(dev, "Device sent reply with wrong MsgID: %u != 2\n",
                        buffer[0]);
                if (file_data->auto_abort)
                        usbtmc_ioctl_abort_bulk_in(data);
                goto exit;
        }

        if (buffer[1] != data->bTag_last_write) {
                dev_err(dev, "Device sent reply with wrong bTag: %u != %u\n",
                buffer[1], data->bTag_last_write);
                if (file_data->auto_abort)
                        usbtmc_ioctl_abort_bulk_in(data);
                goto exit;
        }

        /* How many characters did the instrument send? */
        n_characters = buffer[4] +
                       (buffer[5] << 8) +
                       (buffer[6] << 16) +
                       (buffer[7] << 24);

        file_data->bmTransferAttributes = buffer[8];

        dev_dbg(dev, "Bulk-IN header: N_characters(%u), bTransAttr(%u)\n",
                n_characters, buffer[8]);

        if (n_characters > remaining) {
                dev_err(dev, "Device wants to return more data than requested: %u > %zu\n",
                        n_characters, count);
                if (file_data->auto_abort)
                        usbtmc_ioctl_abort_bulk_in(data);
                goto exit;
        }

        print_hex_dump_debug("usbtmc ", DUMP_PREFIX_NONE,
                             16, 1, buffer, actual, true);

        remaining = n_characters;

        /* Remove the USBTMC header */
        actual -= USBTMC_HEADER_SIZE;

        /* Remove padding if it exists */
        if (actual > remaining)
                actual = remaining;

        remaining -= actual;

        /* Copy buffer to user space */
        if (copy_to_user(buf, &buffer[USBTMC_HEADER_SIZE], actual)) {
                /* There must have been an addressing problem */
                retval = -EFAULT;
                goto exit;
        }

        if ((actual + USBTMC_HEADER_SIZE) == bufsize) {
                retval = usbtmc_generic_read(file_data, buf + actual,
                                             remaining,
                                             &done,
                                             USBTMC_FLAG_IGNORE_TRAILER);
                if (retval < 0)
                        goto exit;
        }
        done += actual;

        /* Update file position value */
        *f_pos = *f_pos + done;
        retval = done;

exit:
        mutex_unlock(&data->io_mutex);
exit_nolock:
        kfree(buffer);
        return retval;
}

static ssize_t usbtmc_write(struct file *filp, const char __user *buf,
                            size_t count, loff_t *f_pos)
{
        struct usbtmc_file_data *file_data;
        struct usbtmc_device_data *data;
        struct urb *urb = NULL;
        ssize_t retval = 0;
        u8 *buffer;
        u32 remaining, done;
        u32 transfersize, aligned, buflen;

        file_data = filp->private_data;
        data = file_data->data;

        mutex_lock(&data->io_mutex);

        if (data->zombie) {
                retval = -ENODEV;
                goto exit;
        }

        done = 0;

        spin_lock_irq(&file_data->err_lock);
        file_data->out_transfer_size = 0;
        file_data->out_status = 0;
        spin_unlock_irq(&file_data->err_lock);

        if (!count)
                goto exit;

        if (down_trylock(&file_data->limit_write_sem)) {
                /* previous calls were async */
                retval = -EBUSY;
                goto exit;
        }

        urb = usbtmc_create_urb();
        if (!urb) {
                retval = -ENOMEM;
                up(&file_data->limit_write_sem);
                goto exit;
        }

        buffer = urb->transfer_buffer;
        buflen = urb->transfer_buffer_length;

        if (count > INT_MAX) {
                transfersize = INT_MAX;
                buffer[8] = 0;
        } else {
                transfersize = count;
                buffer[8] = file_data->eom_val;
        }

        /* Setup IO buffer for DEV_DEP_MSG_OUT message */
        buffer[0] = 1;
        buffer[1] = data->bTag;
        buffer[2] = ~data->bTag;
        buffer[3] = 0; /* Reserved */
        buffer[4] = transfersize >> 0;
        buffer[5] = transfersize >> 8;
        buffer[6] = transfersize >> 16;
        buffer[7] = transfersize >> 24;
        /* buffer[8] is set above... */
        buffer[9] = 0; /* Reserved */
        buffer[10] = 0; /* Reserved */
        buffer[11] = 0; /* Reserved */

        remaining = transfersize;

        if (transfersize + USBTMC_HEADER_SIZE > buflen) {
                transfersize = buflen - USBTMC_HEADER_SIZE;
                aligned = buflen;
        } else {
                aligned = (transfersize + (USBTMC_HEADER_SIZE + 3)) & ~3;
        }

        if (copy_from_user(&buffer[USBTMC_HEADER_SIZE], buf, transfersize)) {
                retval = -EFAULT;
                up(&file_data->limit_write_sem);
                goto exit;
        }

        dev_dbg(&data->intf->dev, "%s(size:%u align:%u)\n", __func__,
                (unsigned int)transfersize, (unsigned int)aligned);

        print_hex_dump_debug("usbtmc ", DUMP_PREFIX_NONE,
                             16, 1, buffer, aligned, true);

        usb_fill_bulk_urb(urb, data->usb_dev,
                usb_sndbulkpipe(data->usb_dev, data->bulk_out),
                urb->transfer_buffer, aligned,
                usbtmc_write_bulk_cb, file_data);

        usb_anchor_urb(urb, &file_data->submitted);
        retval = usb_submit_urb(urb, GFP_KERNEL);
        if (unlikely(retval)) {
                usb_unanchor_urb(urb);
                up(&file_data->limit_write_sem);
                goto exit;
        }

        remaining -= transfersize;

        data->bTag_last_write = data->bTag;
        data->bTag++;

        if (!data->bTag)
                data->bTag++;

        /* call generic_write even when remaining = 0 */
        retval = usbtmc_generic_write(file_data, buf + transfersize, remaining,
                                      &done, USBTMC_FLAG_APPEND);
        /* truncate alignment bytes */
        if (done > remaining)
                done = remaining;

        /*add size of first urb*/
        done += transfersize;

        if (retval < 0) {
                usb_kill_anchored_urbs(&file_data->submitted);

                dev_err(&data->intf->dev,
                        "Unable to send data, error %d\n", (int)retval);
                if (file_data->auto_abort)
                        usbtmc_ioctl_abort_bulk_out(data);
                goto exit;
        }

        retval = done;
exit:
        usb_free_urb(urb);
        mutex_unlock(&data->io_mutex);
        return retval;
}

static int usbtmc_ioctl_clear(struct usbtmc_device_data *data)
{
        struct device *dev;
        u8 *buffer;
        int rv;
        int n;
        int actual = 0;

        dev = &data->intf->dev;

        dev_dbg(dev, "Sending INITIATE_CLEAR request\n");

        buffer = kmalloc(USBTMC_BUFSIZE, GFP_KERNEL);
        if (!buffer)
                return -ENOMEM;

        rv = usb_control_msg(data->usb_dev,
                             usb_rcvctrlpipe(data->usb_dev, 0),
                             USBTMC_REQUEST_INITIATE_CLEAR,
                             USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE,
                             0, 0, buffer, 1, USB_CTRL_GET_TIMEOUT);
        if (rv < 0) {
                dev_err(dev, "usb_control_msg returned %d\n", rv);
                goto exit;
        }

        dev_dbg(dev, "INITIATE_CLEAR returned %x\n", buffer[0]);

        if (buffer[0] != USBTMC_STATUS_SUCCESS) {
                dev_err(dev, "INITIATE_CLEAR returned %x\n", buffer[0]);
                rv = -EPERM;
                goto exit;
        }

        n = 0;

usbtmc_clear_check_status:

        dev_dbg(dev, "Sending CHECK_CLEAR_STATUS request\n");

        rv = usb_control_msg(data->usb_dev,
                             usb_rcvctrlpipe(data->usb_dev, 0),
                             USBTMC_REQUEST_CHECK_CLEAR_STATUS,
                             USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE,
                             0, 0, buffer, 2, USB_CTRL_GET_TIMEOUT);
        if (rv < 0) {
                dev_err(dev, "usb_control_msg returned %d\n", rv);
                goto exit;
        }

        dev_dbg(dev, "CHECK_CLEAR_STATUS returned %x\n", buffer[0]);

        if (buffer[0] == USBTMC_STATUS_SUCCESS)
                goto usbtmc_clear_bulk_out_halt;

        if (buffer[0] != USBTMC_STATUS_PENDING) {
                dev_err(dev, "CHECK_CLEAR_STATUS returned %x\n", buffer[0]);
                rv = -EPERM;
                goto exit;
        }

        if ((buffer[1] & 1) != 0) {
                do {
                        dev_dbg(dev, "Reading from bulk in EP\n");

                        actual = 0;
                        rv = usb_bulk_msg(data->usb_dev,
                                          usb_rcvbulkpipe(data->usb_dev,
                                                          data->bulk_in),
                                          buffer, USBTMC_BUFSIZE,
                                          &actual, USB_CTRL_GET_TIMEOUT);

                        print_hex_dump_debug("usbtmc ", DUMP_PREFIX_NONE,
                                             16, 1, buffer, actual, true);

                        n++;

                        if (rv < 0) {
                                dev_err(dev, "usb_control_msg returned %d\n",
                                        rv);
                                goto exit;
                        }
                } while ((actual == USBTMC_BUFSIZE) &&
                          (n < USBTMC_MAX_READS_TO_CLEAR_BULK_IN));
        } else {
                /* do not stress device with subsequent requests */
                msleep(50);
                n++;
        }

        if (n >= USBTMC_MAX_READS_TO_CLEAR_BULK_IN) {
                dev_err(dev, "Couldn't clear device buffer within %d cycles\n",
                        USBTMC_MAX_READS_TO_CLEAR_BULK_IN);
                rv = -EPERM;
                goto exit;
        }

        goto usbtmc_clear_check_status;

usbtmc_clear_bulk_out_halt:

        rv = usb_clear_halt(data->usb_dev,
                            usb_sndbulkpipe(data->usb_dev, data->bulk_out));
        if (rv < 0) {
                dev_err(dev, "usb_clear_halt returned %d\n", rv);
                goto exit;
        }
        rv = 0;

exit:
        kfree(buffer);
        return rv;
}

static int usbtmc_ioctl_clear_out_halt(struct usbtmc_device_data *data)
{
        int rv;

        rv = usb_clear_halt(data->usb_dev,
                            usb_sndbulkpipe(data->usb_dev, data->bulk_out));

        if (rv < 0)
                dev_err(&data->usb_dev->dev, "%s returned %d\n", __func__, rv);
        return rv;
}

static int usbtmc_ioctl_clear_in_halt(struct usbtmc_device_data *data)
{
        int rv;

        rv = usb_clear_halt(data->usb_dev,
                            usb_rcvbulkpipe(data->usb_dev, data->bulk_in));

        if (rv < 0)
                dev_err(&data->usb_dev->dev, "%s returned %d\n", __func__, rv);
        return rv;
}

static int usbtmc_ioctl_cancel_io(struct usbtmc_file_data *file_data)
{
        spin_lock_irq(&file_data->err_lock);
        file_data->in_status = -ECANCELED;
        file_data->out_status = -ECANCELED;
        spin_unlock_irq(&file_data->err_lock);
        usb_kill_anchored_urbs(&file_data->submitted);
        return 0;
}

static int usbtmc_ioctl_cleanup_io(struct usbtmc_file_data *file_data)
{
        usb_kill_anchored_urbs(&file_data->submitted);
        usb_scuttle_anchored_urbs(&file_data->in_anchor);
        spin_lock_irq(&file_data->err_lock);
        file_data->in_status = 0;
        file_data->in_transfer_size = 0;
        file_data->out_status = 0;
        file_data->out_transfer_size = 0;
        spin_unlock_irq(&file_data->err_lock);

        file_data->in_urbs_used = 0;
        return 0;
}

static int get_capabilities(struct usbtmc_device_data *data)
{
        struct device *dev = &data->usb_dev->dev;
        char *buffer;
        int rv = 0;

        buffer = kmalloc(0x18, GFP_KERNEL);
        if (!buffer)
                return -ENOMEM;

        rv = usb_control_msg(data->usb_dev, usb_rcvctrlpipe(data->usb_dev, 0),
                             USBTMC_REQUEST_GET_CAPABILITIES,
                             USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE,
                             0, 0, buffer, 0x18, USB_CTRL_GET_TIMEOUT);
        if (rv < 0) {
                dev_err(dev, "usb_control_msg returned %d\n", rv);
                goto err_out;
        }

        dev_dbg(dev, "GET_CAPABILITIES returned %x\n", buffer[0]);
        if (buffer[0] != USBTMC_STATUS_SUCCESS) {
                dev_err(dev, "GET_CAPABILITIES returned %x\n", buffer[0]);
                rv = -EPERM;
                goto err_out;
        }
        dev_dbg(dev, "Interface capabilities are %x\n", buffer[4]);
        dev_dbg(dev, "Device capabilities are %x\n", buffer[5]);
        dev_dbg(dev, "USB488 interface capabilities are %x\n", buffer[14]);
        dev_dbg(dev, "USB488 device capabilities are %x\n", buffer[15]);

        data->capabilities.interface_capabilities = buffer[4];
        data->capabilities.device_capabilities = buffer[5];
        data->capabilities.usb488_interface_capabilities = buffer[14];
        data->capabilities.usb488_device_capabilities = buffer[15];
        data->usb488_caps = (buffer[14] & 0x07) | ((buffer[15] & 0x0f) << 4);
        rv = 0;

err_out:
        kfree(buffer);
        return rv;
}

#define capability_attribute(name)                                      \
static ssize_t name##_show(struct device *dev,                          \
                           struct device_attribute *attr, char *buf)    \
{                                                                       \
        struct usb_interface *intf = to_usb_interface(dev);             \
        struct usbtmc_device_data *data = usb_get_intfdata(intf);       \
                                                                        \
        return sprintf(buf, "%d\n", data->capabilities.name);           \
}                                                                       \
static DEVICE_ATTR_RO(name)

capability_attribute(interface_capabilities);
capability_attribute(device_capabilities);
capability_attribute(usb488_interface_capabilities);
capability_attribute(usb488_device_capabilities);

static struct attribute *usbtmc_attrs[] = {
        &dev_attr_interface_capabilities.attr,
        &dev_attr_device_capabilities.attr,
        &dev_attr_usb488_interface_capabilities.attr,
        &dev_attr_usb488_device_capabilities.attr,
        NULL,
};
ATTRIBUTE_GROUPS(usbtmc);

static int usbtmc_ioctl_indicator_pulse(struct usbtmc_device_data *data)
{
        struct device *dev;
        u8 *buffer;
        int rv;

        dev = &data->intf->dev;

        buffer = kmalloc(2, GFP_KERNEL);
        if (!buffer)
                return -ENOMEM;

        rv = usb_control_msg(data->usb_dev,
                             usb_rcvctrlpipe(data->usb_dev, 0),
                             USBTMC_REQUEST_INDICATOR_PULSE,
                             USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE,
                             0, 0, buffer, 0x01, USB_CTRL_GET_TIMEOUT);

        if (rv < 0) {
                dev_err(dev, "usb_control_msg returned %d\n", rv);
                goto exit;
        }

        dev_dbg(dev, "INDICATOR_PULSE returned %x\n", buffer[0]);

        if (buffer[0] != USBTMC_STATUS_SUCCESS) {
                dev_err(dev, "INDICATOR_PULSE returned %x\n", buffer[0]);
                rv = -EPERM;
                goto exit;
        }
        rv = 0;

exit:
        kfree(buffer);
        return rv;
}

static int usbtmc_ioctl_request(struct usbtmc_device_data *data,
                                void __user *arg)
{
        struct device *dev = &data->intf->dev;
        struct usbtmc_ctrlrequest request;
        u8 *buffer = NULL;
        int rv;
        unsigned int is_in, pipe;

        if (copy_from_user(&request, arg, sizeof(struct usbtmc_ctrlrequest)))
                return -EFAULT;

        if (request.req.wLength > USBTMC_BUFSIZE)
                return -EMSGSIZE;
        if (request.req.wLength == 0)   /* Length-0 requests are never IN */
                request.req.bRequestType &= ~USB_DIR_IN;

        is_in = request.req.bRequestType & USB_DIR_IN;

        if (request.req.wLength) {
                buffer = kmalloc(request.req.wLength, GFP_KERNEL);
                if (!buffer)
                        return -ENOMEM;

                if (!is_in) {
                        /* Send control data to device */
                        if (copy_from_user(buffer, request.data,
                                           request.req.wLength)) {
                                rv = -EFAULT;
                                goto exit;
                        }
                }
        }

        if (is_in)
                pipe = usb_rcvctrlpipe(data->usb_dev, 0);
        else
                pipe = usb_sndctrlpipe(data->usb_dev, 0);
        rv = usb_control_msg(data->usb_dev,
                        pipe,
                        request.req.bRequest,
                        request.req.bRequestType,
                        request.req.wValue,
                        request.req.wIndex,
                        buffer, request.req.wLength, USB_CTRL_GET_TIMEOUT);

        if (rv < 0) {
                dev_err(dev, "%s failed %d\n", __func__, rv);
                goto exit;
        }

        if (rv && is_in) {
                /* Read control data from device */
                if (copy_to_user(request.data, buffer, rv))
                        rv = -EFAULT;
        }

 exit:
        kfree(buffer);
        return rv;
}

/*
 * Get the usb timeout value
 */
static int usbtmc_ioctl_get_timeout(struct usbtmc_file_data *file_data,
                                void __user *arg)
{
        u32 timeout;

        timeout = file_data->timeout;

        return put_user(timeout, (__u32 __user *)arg);
}

/*
 * Set the usb timeout value
 */
static int usbtmc_ioctl_set_timeout(struct usbtmc_file_data *file_data,
                                void __user *arg)
{
        u32 timeout;

        if (get_user(timeout, (__u32 __user *)arg))
                return -EFAULT;

        /* Note that timeout = 0 means
         * MAX_SCHEDULE_TIMEOUT in usb_control_msg
         */
        if (timeout < USBTMC_MIN_TIMEOUT)
                return -EINVAL;

        file_data->timeout = timeout;

        return 0;
}

/*
 * enables/disables sending EOM on write
 */
static int usbtmc_ioctl_eom_enable(struct usbtmc_file_data *file_data,
                                void __user *arg)
{
        u8 eom_enable;

        if (copy_from_user(&eom_enable, arg, sizeof(eom_enable)))
                return -EFAULT;

        if (eom_enable > 1)
                return -EINVAL;

        file_data->eom_val = eom_enable;

        return 0;
}

/*
 * Configure termination character for read()
 */
static int usbtmc_ioctl_config_termc(struct usbtmc_file_data *file_data,
                                void __user *arg)
{
        struct usbtmc_termchar termc;

        if (copy_from_user(&termc, arg, sizeof(termc)))
                return -EFAULT;

        if ((termc.term_char_enabled > 1) ||
                (termc.term_char_enabled &&
                !(file_data->data->capabilities.device_capabilities & 1)))
                return -EINVAL;

        file_data->term_char = termc.term_char;
        file_data->term_char_enabled = termc.term_char_enabled;

        return 0;
}

static long usbtmc_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
        struct usbtmc_file_data *file_data;
        struct usbtmc_device_data *data;
        int retval = -EBADRQC;
        __u8 tmp_byte;

        file_data = file->private_data;
        data = file_data->data;

        mutex_lock(&data->io_mutex);
        if (data->zombie) {
                retval = -ENODEV;
                goto skip_io_on_zombie;
        }

        switch (cmd) {
        case USBTMC_IOCTL_CLEAR_OUT_HALT:
                retval = usbtmc_ioctl_clear_out_halt(data);
                break;

        case USBTMC_IOCTL_CLEAR_IN_HALT:
                retval = usbtmc_ioctl_clear_in_halt(data);
                break;

        case USBTMC_IOCTL_INDICATOR_PULSE:
                retval = usbtmc_ioctl_indicator_pulse(data);
                break;

        case USBTMC_IOCTL_CLEAR:
                retval = usbtmc_ioctl_clear(data);
                break;

        case USBTMC_IOCTL_ABORT_BULK_OUT:
                retval = usbtmc_ioctl_abort_bulk_out(data);
                break;

        case USBTMC_IOCTL_ABORT_BULK_IN:
                retval = usbtmc_ioctl_abort_bulk_in(data);
                break;

        case USBTMC_IOCTL_CTRL_REQUEST:
                retval = usbtmc_ioctl_request(data, (void __user *)arg);
                break;

        case USBTMC_IOCTL_GET_TIMEOUT:
                retval = usbtmc_ioctl_get_timeout(file_data,
                                                  (void __user *)arg);
                break;

        case USBTMC_IOCTL_SET_TIMEOUT:
                retval = usbtmc_ioctl_set_timeout(file_data,
                                                  (void __user *)arg);
                break;

        case USBTMC_IOCTL_EOM_ENABLE:
                retval = usbtmc_ioctl_eom_enable(file_data,
                                                 (void __user *)arg);
                break;

        case USBTMC_IOCTL_CONFIG_TERMCHAR:
                retval = usbtmc_ioctl_config_termc(file_data,
                                                   (void __user *)arg);
                break;

        case USBTMC_IOCTL_WRITE:
                retval = usbtmc_ioctl_generic_write(file_data,
                                                    (void __user *)arg);
                break;

        case USBTMC_IOCTL_READ:
                retval = usbtmc_ioctl_generic_read(file_data,
                                                   (void __user *)arg);
                break;

        case USBTMC_IOCTL_WRITE_RESULT:
                retval = usbtmc_ioctl_write_result(file_data,
                                                   (void __user *)arg);
                break;

        case USBTMC_IOCTL_API_VERSION:
                retval = put_user(USBTMC_API_VERSION,
                                  (__u32 __user *)arg);
                break;

        case USBTMC488_IOCTL_GET_CAPS:
                retval = put_user(data->usb488_caps,
                                  (unsigned char __user *)arg);
                break;

        case USBTMC488_IOCTL_READ_STB:
                retval = usbtmc488_ioctl_read_stb(file_data,
                                                  (void __user *)arg);
                break;

        case USBTMC488_IOCTL_REN_CONTROL:
                retval = usbtmc488_ioctl_simple(data, (void __user *)arg,
                                                USBTMC488_REQUEST_REN_CONTROL);
                break;

        case USBTMC488_IOCTL_GOTO_LOCAL:
                retval = usbtmc488_ioctl_simple(data, (void __user *)arg,
                                                USBTMC488_REQUEST_GOTO_LOCAL);
                break;

        case USBTMC488_IOCTL_LOCAL_LOCKOUT:
                retval = usbtmc488_ioctl_simple(data, (void __user *)arg,
                                                USBTMC488_REQUEST_LOCAL_LOCKOUT);
                break;

        case USBTMC488_IOCTL_TRIGGER:
                retval = usbtmc488_ioctl_trigger(file_data);
                break;

        case USBTMC488_IOCTL_WAIT_SRQ:
                retval = usbtmc488_ioctl_wait_srq(file_data,
                                                  (__u32 __user *)arg);
                break;

        case USBTMC_IOCTL_MSG_IN_ATTR:
                retval = put_user(file_data->bmTransferAttributes,
                                  (__u8 __user *)arg);
                break;

        case USBTMC_IOCTL_AUTO_ABORT:
                retval = get_user(tmp_byte, (unsigned char __user *)arg);
                if (retval == 0)
                        file_data->auto_abort = !!tmp_byte;
                break;

        case USBTMC_IOCTL_GET_STB:
                retval = usbtmc_get_stb(file_data, &tmp_byte);
                if (!retval)
                        retval = put_user(tmp_byte, (__u8 __user *)arg);
                break;

        case USBTMC_IOCTL_GET_SRQ_STB:
                retval = usbtmc_ioctl_get_srq_stb(file_data,
                                                  (void __user *)arg);
                break;

        case USBTMC_IOCTL_CANCEL_IO:
                retval = usbtmc_ioctl_cancel_io(file_data);
                break;

        case USBTMC_IOCTL_CLEANUP_IO:
                retval = usbtmc_ioctl_cleanup_io(file_data);
                break;
        }

skip_io_on_zombie:
        mutex_unlock(&data->io_mutex);
        return retval;
}

static int usbtmc_fasync(int fd, struct file *file, int on)
{
        struct usbtmc_file_data *file_data = file->private_data;

        return fasync_helper(fd, file, on, &file_data->data->fasync);
}

static __poll_t usbtmc_poll(struct file *file, poll_table *wait)
{
        struct usbtmc_file_data *file_data = file->private_data;
        struct usbtmc_device_data *data = file_data->data;
        __poll_t mask;

        mutex_lock(&data->io_mutex);

        if (data->zombie) {
                mask = EPOLLHUP | EPOLLERR;
                goto no_poll;
        }

        poll_wait(file, &data->waitq, wait);

        /* Note that EPOLLPRI is now assigned to SRQ, and
         * EPOLLIN|EPOLLRDNORM to normal read data.
         */
        mask = 0;
        if (atomic_read(&file_data->srq_asserted))
                mask |= EPOLLPRI;

        /* Note that the anchor submitted includes all urbs for BULK IN
         * and OUT. So EPOLLOUT is signaled when BULK OUT is empty and
         * all BULK IN urbs are completed and moved to in_anchor.
         */
        if (usb_anchor_empty(&file_data->submitted))
                mask |= (EPOLLOUT | EPOLLWRNORM);
        if (!usb_anchor_empty(&file_data->in_anchor))
                mask |= (EPOLLIN | EPOLLRDNORM);

        spin_lock_irq(&file_data->err_lock);
        if (file_data->in_status || file_data->out_status)
                mask |= EPOLLERR;
        spin_unlock_irq(&file_data->err_lock);

        dev_dbg(&data->intf->dev, "poll mask = %x\n", mask);

no_poll:
        mutex_unlock(&data->io_mutex);
        return mask;
}

static const struct file_operations fops = {
        .owner          = THIS_MODULE,
        .read           = usbtmc_read,
        .write          = usbtmc_write,
        .open           = usbtmc_open,
        .release        = usbtmc_release,
        .flush          = usbtmc_flush,
        .unlocked_ioctl = usbtmc_ioctl,
        .compat_ioctl   = compat_ptr_ioctl,
        .fasync         = usbtmc_fasync,
        .poll           = usbtmc_poll,
        .llseek         = default_llseek,
};

static struct usb_class_driver usbtmc_class = {
        .name =         "usbtmc%d",
        .fops =         &fops,
        .minor_base =   USBTMC_MINOR_BASE,
};

static void usbtmc_interrupt(struct urb *urb)
{
        struct usbtmc_device_data *data = urb->context;
        struct device *dev = &data->intf->dev;
        int status = urb->status;
        int rv;

        dev_dbg(&data->intf->dev, "int status: %d len %d\n",
                status, urb->actual_length);

        switch (status) {
        case 0: /* SUCCESS */
                /* check for valid STB notification */
                if (data->iin_buffer[0] > 0x81) {
                        data->bNotify1 = data->iin_buffer[0];
                        data->bNotify2 = data->iin_buffer[1];
                        atomic_set(&data->iin_data_valid, 1);
                        wake_up_interruptible(&data->waitq);
                        goto exit;
                }
                /* check for SRQ notification */
                if (data->iin_buffer[0] == 0x81) {
                        unsigned long flags;
                        struct list_head *elem;

                        if (data->fasync)
                                kill_fasync(&data->fasync,
                                        SIGIO, POLL_PRI);

                        spin_lock_irqsave(&data->dev_lock, flags);
                        list_for_each(elem, &data->file_list) {
                                struct usbtmc_file_data *file_data;

                                file_data = list_entry(elem,
                                                       struct usbtmc_file_data,
                                                       file_elem);
                                file_data->srq_byte = data->iin_buffer[1];
                                atomic_set(&file_data->srq_asserted, 1);
                        }
                        spin_unlock_irqrestore(&data->dev_lock, flags);

                        dev_dbg(dev, "srq received bTag %x stb %x\n",
                                (unsigned int)data->iin_buffer[0],
                                (unsigned int)data->iin_buffer[1]);
                        wake_up_interruptible_all(&data->waitq);
                        goto exit;
                }
                dev_warn(dev, "invalid notification: %x\n",
                         data->iin_buffer[0]);
                break;
        case -EOVERFLOW:
                dev_err(dev, "overflow with length %d, actual length is %d\n",
                        data->iin_wMaxPacketSize, urb->actual_length);
                fallthrough;
        default:
                /* urb terminated, clean up */
                dev_dbg(dev, "urb terminated, status: %d\n", status);
                return;
        }
exit:
        rv = usb_submit_urb(urb, GFP_ATOMIC);
        if (rv)
                dev_err(dev, "usb_submit_urb failed: %d\n", rv);
}

static void usbtmc_free_int(struct usbtmc_device_data *data)
{
        if (!data->iin_ep_present || !data->iin_urb)
                return;
        usb_kill_urb(data->iin_urb);
        kfree(data->iin_buffer);
        data->iin_buffer = NULL;
        usb_free_urb(data->iin_urb);
        data->iin_urb = NULL;
        kref_put(&data->kref, usbtmc_delete);
}

static int usbtmc_probe(struct usb_interface *intf,
                        const struct usb_device_id *id)
{
        struct usbtmc_device_data *data;
        struct usb_host_interface *iface_desc;
        struct usb_endpoint_descriptor *bulk_in, *bulk_out, *int_in;
        int retcode;

        dev_dbg(&intf->dev, "%s called\n", __func__);

        data = kzalloc_obj(*data);
        if (!data)
                return -ENOMEM;

        data->intf = intf;
        data->id = id;
        data->usb_dev = usb_get_dev(interface_to_usbdev(intf));
        usb_set_intfdata(intf, data);
        kref_init(&data->kref);
        mutex_init(&data->io_mutex);
        init_waitqueue_head(&data->waitq);
        atomic_set(&data->iin_data_valid, 0);
        INIT_LIST_HEAD(&data->file_list);
        spin_lock_init(&data->dev_lock);

        data->zombie = 0;

        /* Initialize USBTMC bTag and other fields */
        data->bTag      = 1;
        /*  2 <= bTag <= 127   USBTMC-USB488 subclass specification 4.3.1 */
        data->iin_bTag = 2;

        /* USBTMC devices have only one setting, so use that */
        iface_desc = data->intf->cur_altsetting;
        data->ifnum = iface_desc->desc.bInterfaceNumber;

        /* Find bulk endpoints */
        retcode = usb_find_common_endpoints(iface_desc,
                        &bulk_in, &bulk_out, NULL, NULL);
        if (retcode) {
                dev_err(&intf->dev, "bulk endpoints not found\n");
                goto err_put;
        }

        retcode = -EINVAL;
        data->bulk_in = bulk_in->bEndpointAddress;
        data->wMaxPacketSize = usb_endpoint_maxp(bulk_in);
        if (!data->wMaxPacketSize)
                goto err_put;
        dev_dbg(&intf->dev, "Found bulk in endpoint at %u\n", data->bulk_in);

        data->bulk_out = bulk_out->bEndpointAddress;
        dev_dbg(&intf->dev, "Found Bulk out endpoint at %u\n", data->bulk_out);

        /* Find int endpoint */
        retcode = usb_find_int_in_endpoint(iface_desc, &int_in);
        if (!retcode) {
                data->iin_ep_present = 1;
                data->iin_ep = int_in->bEndpointAddress;
                data->iin_wMaxPacketSize = usb_endpoint_maxp(int_in);
                data->iin_interval = int_in->bInterval;
                dev_dbg(&intf->dev, "Found Int in endpoint at %u\n",
                                data->iin_ep);
        }

        retcode = get_capabilities(data);
        if (retcode)
                dev_err(&intf->dev, "can't read capabilities\n");

        if (data->iin_ep_present) {
                /* allocate int urb */
                data->iin_urb = usb_alloc_urb(0, GFP_KERNEL);
                if (!data->iin_urb) {
                        retcode = -ENOMEM;
                        goto error_register;
                }

                /* Protect interrupt in endpoint data until iin_urb is freed */
                kref_get(&data->kref);

                /* allocate buffer for interrupt in */
                data->iin_buffer = kmalloc(data->iin_wMaxPacketSize,
                                        GFP_KERNEL);
                if (!data->iin_buffer) {
                        retcode = -ENOMEM;
                        goto error_register;
                }

                /* fill interrupt urb */
                usb_fill_int_urb(data->iin_urb, data->usb_dev,
                                usb_rcvintpipe(data->usb_dev, data->iin_ep),
                                data->iin_buffer, data->iin_wMaxPacketSize,
                                usbtmc_interrupt,
                                data, data->iin_interval);

                retcode = usb_submit_urb(data->iin_urb, GFP_KERNEL);
                if (retcode) {
                        dev_err(&intf->dev, "Failed to submit iin_urb\n");
                        goto error_register;
                }
        }

        retcode = usb_register_dev(intf, &usbtmc_class);
        if (retcode) {
                dev_err(&intf->dev, "Not able to get a minor (base %u, slice default): %d\n",
                        USBTMC_MINOR_BASE,
                        retcode);
                goto error_register;
        }
        dev_dbg(&intf->dev, "Using minor number %d\n", intf->minor);

        return 0;

error_register:
        usbtmc_free_int(data);
err_put:
        kref_put(&data->kref, usbtmc_delete);
        return retcode;
}

static void usbtmc_disconnect(struct usb_interface *intf)
{
        struct usbtmc_device_data *data  = usb_get_intfdata(intf);
        struct list_head *elem;

        usb_deregister_dev(intf, &usbtmc_class);
        mutex_lock(&data->io_mutex);
        data->zombie = 1;
        wake_up_interruptible_all(&data->waitq);
        list_for_each(elem, &data->file_list) {
                struct usbtmc_file_data *file_data;

                file_data = list_entry(elem,
                                       struct usbtmc_file_data,
                                       file_elem);
                usb_kill_anchored_urbs(&file_data->submitted);
                usb_scuttle_anchored_urbs(&file_data->in_anchor);
        }
        mutex_unlock(&data->io_mutex);
        usbtmc_free_int(data);
        kref_put(&data->kref, usbtmc_delete);
}

static void usbtmc_draw_down(struct usbtmc_file_data *file_data)
{
        int time;

        time = usb_wait_anchor_empty_timeout(&file_data->submitted, 1000);
        if (!time)
                usb_kill_anchored_urbs(&file_data->submitted);
        usb_scuttle_anchored_urbs(&file_data->in_anchor);
}

static int usbtmc_suspend(struct usb_interface *intf, pm_message_t message)
{
        struct usbtmc_device_data *data = usb_get_intfdata(intf);
        struct list_head *elem;

        if (!data)
                return 0;

        mutex_lock(&data->io_mutex);
        list_for_each(elem, &data->file_list) {
                struct usbtmc_file_data *file_data;

                file_data = list_entry(elem,
                                       struct usbtmc_file_data,
                                       file_elem);
                usbtmc_draw_down(file_data);
        }

        if (data->iin_ep_present && data->iin_urb)
                usb_kill_urb(data->iin_urb);

        mutex_unlock(&data->io_mutex);
        return 0;
}

static int usbtmc_resume(struct usb_interface *intf)
{
        struct usbtmc_device_data *data = usb_get_intfdata(intf);
        int retcode = 0;

        if (data->iin_ep_present && data->iin_urb)
                retcode = usb_submit_urb(data->iin_urb, GFP_KERNEL);
        if (retcode)
                dev_err(&intf->dev, "Failed to submit iin_urb\n");

        return retcode;
}

static int usbtmc_pre_reset(struct usb_interface *intf)
{
        struct usbtmc_device_data *data  = usb_get_intfdata(intf);
        struct list_head *elem;

        if (!data)
                return 0;

        mutex_lock(&data->io_mutex);

        list_for_each(elem, &data->file_list) {
                struct usbtmc_file_data *file_data;

                file_data = list_entry(elem,
                                       struct usbtmc_file_data,
                                       file_elem);
                usbtmc_ioctl_cancel_io(file_data);
        }

        return 0;
}

static int usbtmc_post_reset(struct usb_interface *intf)
{
        struct usbtmc_device_data *data  = usb_get_intfdata(intf);

        mutex_unlock(&data->io_mutex);

        return 0;
}

static struct usb_driver usbtmc_driver = {
        .name           = "usbtmc",
        .id_table       = usbtmc_devices,
        .probe          = usbtmc_probe,
        .disconnect     = usbtmc_disconnect,
        .suspend        = usbtmc_suspend,
        .resume         = usbtmc_resume,
        .pre_reset      = usbtmc_pre_reset,
        .post_reset     = usbtmc_post_reset,
        .dev_groups     = usbtmc_groups,
};

module_usb_driver(usbtmc_driver);

MODULE_DESCRIPTION("USB Test & Measurement class driver");
MODULE_LICENSE("GPL");