Merge branch 'x86-eficross-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / drivers / staging / quatech_usb2 / quatech_usb2.c

/*
 * Driver for Quatech Inc USB2.0 to serial adaptors. Largely unrelated to the
 * serqt_usb driver, based on a re-write of the vendor supplied serqt_usb2 code,
 * which is unrelated to the serqt_usb2 in the staging kernel
 */

#include <linux/errno.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/tty_flip.h>
#include <linux/module.h>
#include <linux/serial.h>
#include <linux/usb.h>
#include <linux/usb/serial.h>
#include <linux/uaccess.h>

static bool debug;

/* Version Information */
#define DRIVER_VERSION "v2.00"
#define DRIVER_AUTHOR "Tim Gobeli, Quatech, Inc"
#define DRIVER_DESC "Quatech USB 2.0 to Serial Driver"

/* vendor and device IDs */
#define USB_VENDOR_ID_QUATECH 0x061d    /* Quatech VID */
#define QUATECH_SSU2_100 0xC120         /* RS232 single port */
#define QUATECH_DSU2_100 0xC140         /* RS232 dual port */
#define QUATECH_DSU2_400 0xC150         /* RS232/422/485 dual port */
#define QUATECH_QSU2_100 0xC160         /* RS232 four port */
#define QUATECH_QSU2_400 0xC170         /* RS232/422/485 four port */
#define QUATECH_ESU2_100 0xC1A0         /* RS232 eight port */
#define QUATECH_ESU2_400 0xC180         /* RS232/422/485 eight port */

/* magic numbers go here, when we find out which ones are needed */

#define QU2BOXPWRON 0x8000              /* magic number to turn FPGA power on */
#define QU2BOX232 0x40                  /* RS232 mode on MEI devices */
#define QU2BOXSPD9600 0x60              /* set speed to 9600 baud */
#define QT2_FIFO_DEPTH 1024                     /* size of hardware fifos */
#define QT2_TX_HEADER_LENGTH    5
/* length of the header sent to the box with each write URB */

/* directions for USB transfers */
#define USBD_TRANSFER_DIRECTION_IN    0xc0
#define USBD_TRANSFER_DIRECTION_OUT   0x40

/* special Quatech command IDs. These are pushed down the
 USB control pipe to get the box on the end to do things */
#define QT_SET_GET_DEVICE               0xc2
#define QT_OPEN_CLOSE_CHANNEL           0xca
/*#define QT_GET_SET_PREBUF_TRIG_LVL    0xcc
#define QT_SET_ATF                      0xcd*/
#define QT2_GET_SET_REGISTER                    0xc0
#define QT2_GET_SET_UART                        0xc1
#define QT2_HW_FLOW_CONTROL_MASK                0xc5
#define QT2_SW_FLOW_CONTROL_MASK                0xc6
#define QT2_SW_FLOW_CONTROL_DISABLE             0xc7
#define QT2_BREAK_CONTROL                       0xc8
#define QT2_STOP_RECEIVE                        0xe0
#define QT2_FLUSH_DEVICE                        0xc4
#define QT2_GET_SET_QMCR                        0xe1

/* sorts of flush we can do on */
#define QT2_FLUSH_RX                    0x00
#define QT2_FLUSH_TX                    0x01

/* port setting constants, used to set up serial port speeds, flow
 * control and so on */
#define QT2_SERIAL_MCR_DTR      0x01
#define QT2_SERIAL_MCR_RTS      0x02
#define QT2_SERIAL_MCR_LOOP     0x10

#define QT2_SERIAL_MSR_CTS      0x10
#define QT2_SERIAL_MSR_CD       0x80
#define QT2_SERIAL_MSR_RI       0x40
#define QT2_SERIAL_MSR_DSR      0x20
#define QT2_SERIAL_MSR_MASK     0xf0

#define QT2_SERIAL_8_DATA       0x03
#define QT2_SERIAL_7_DATA       0x02
#define QT2_SERIAL_6_DATA       0x01
#define QT2_SERIAL_5_DATA       0x00

#define QT2_SERIAL_ODD_PARITY   0x08
#define QT2_SERIAL_EVEN_PARITY  0x18
#define QT2_SERIAL_TWO_STOPB    0x04
#define QT2_SERIAL_ONE_STOPB    0x00

#define QT2_MAX_BAUD_RATE       921600
#define QT2_MAX_BAUD_REMAINDER  4608

#define QT2_SERIAL_LSR_OE       0x02
#define QT2_SERIAL_LSR_PE       0x04
#define QT2_SERIAL_LSR_FE       0x08
#define QT2_SERIAL_LSR_BI       0x10

/* value of Line Status Register when UART has completed
 * emptying data out on the line */
#define QT2_LSR_TEMT     0x40

/* register numbers on each UART, for use with  qt2_box_[get|set]_register*/
#define  QT2_XMT_HOLD_REGISTER          0x00
#define  QT2_XVR_BUFFER_REGISTER        0x00
#define  QT2_FIFO_CONTROL_REGISTER      0x02
#define  QT2_LINE_CONTROL_REGISTER      0x03
#define  QT2_MODEM_CONTROL_REGISTER     0x04
#define  QT2_LINE_STATUS_REGISTER       0x05
#define  QT2_MODEM_STATUS_REGISTER      0x06

/* handy macros for doing escape sequence parsing on data reads */
#define THISCHAR        ((unsigned char *)(urb->transfer_buffer))[i]
#define NEXTCHAR        ((unsigned char *)(urb->transfer_buffer))[i + 1]
#define THIRDCHAR       ((unsigned char *)(urb->transfer_buffer))[i + 2]
#define FOURTHCHAR      ((unsigned char *)(urb->transfer_buffer))[i + 3]
#define FIFTHCHAR       ((unsigned char *)(urb->transfer_buffer))[i + 4]

static const struct usb_device_id quausb2_id_table[] = {
        {USB_DEVICE(USB_VENDOR_ID_QUATECH, QUATECH_SSU2_100)},
        {USB_DEVICE(USB_VENDOR_ID_QUATECH, QUATECH_DSU2_100)},
        {USB_DEVICE(USB_VENDOR_ID_QUATECH, QUATECH_DSU2_400)},
        {USB_DEVICE(USB_VENDOR_ID_QUATECH, QUATECH_QSU2_100)},
        {USB_DEVICE(USB_VENDOR_ID_QUATECH, QUATECH_QSU2_400)},
        {USB_DEVICE(USB_VENDOR_ID_QUATECH, QUATECH_ESU2_100)},
        {USB_DEVICE(USB_VENDOR_ID_QUATECH, QUATECH_ESU2_400)},
        {}      /* Terminating entry */
};

MODULE_DEVICE_TABLE(usb, quausb2_id_table);

/* custom structures we need go here */
static struct usb_driver quausb2_usb_driver = {
        .name = "quatech-usb2-serial",
        .probe = usb_serial_probe,
        .disconnect = usb_serial_disconnect,
        .id_table = quausb2_id_table,
};

/**
 * quatech2_port: Structure in which to keep all the messy stuff that this
 * driver needs alongside the usb_serial_port structure
 * @read_urb_busy: Flag indicating that port->read_urb is in use
 * @close_pending: flag indicating that this port is in the process of
 * being closed (and so no new reads / writes should be started).
 * @shadowLSR: Last received state of the line status register, holds the
 * value of the line status flags from the port
 * @shadowMSR: Last received state of the modem status register, holds
 * the value of the modem status received from the port
 * @rcv_flush: Flag indicating that a receive flush has occurred on
 * the hardware.
 * @xmit_flush: Flag indicating that a transmit flush has been processed by
 * the hardware.
 * @tx_pending_bytes: Number of bytes waiting to be sent. This total
 * includes the size (excluding header) of URBs that have been submitted but
 * have not yet been sent to to the device, and bytes that have been sent out
 * of the port but not yet reported sent by the "xmit_empty" messages (which
 * indicate the number of bytes sent each time they are received, despite the
 * misleading name).
 * - Starts at zero when port is initialised.
 * - is incremented by the size of the data to be written (no headers)
 * each time a write urb is dispatched.
 * - is decremented each time a "transmit empty" message is received
 * by the driver in the data stream.
 * @lock: Mutex to lock access to this structure when we need to ensure that
 * races don't occur to access bits of it.
 * @open_count: The number of uses of the port currently having
 * it open, i.e. the reference count.
 */
struct quatech2_port {
        int     magic;
        bool    read_urb_busy;
        bool    close_pending;
        __u8    shadowLSR;
        __u8    shadowMSR;
        bool    rcv_flush;
        bool    xmit_flush;
        int     tx_pending_bytes;
        struct mutex modelock;
        int     open_count;

        char    active;         /* someone has this device open */
        unsigned char           *xfer_to_tty_buffer;
        wait_queue_head_t       wait;
        __u8    shadowLCR;      /* last LCR value received */
        __u8    shadowMCR;      /* last MCR value received */
        char    RxHolding;
        struct semaphore        pend_xmit_sem;  /* locks this structure */
        spinlock_t lock;
};

/**
 * Structure to hold device-wide internal status information
 * @param ReadBulkStopped The last bulk read attempt ended in tears
 * @param open_ports The number of serial ports currently in use on the box
 * @param current_port Pointer to the serial port structure of the port which
 * the read stream is currently directed to. Escape sequences in the read
 * stream will change this around as data arrives from different ports on the
 * box
 * @buffer_size: The max size buffer each URB can take, used to set the size of
 * the buffers allocated for writing to each port on the device (we need to
 * store this because it is known only to the endpoint, but used each time a
 * port is opened and a new buffer is allocated.
 */
struct quatech2_dev {
        bool    ReadBulkStopped;
        char    open_ports;
        struct usb_serial_port *current_port;
        int     buffer_size;
};

/* structure which holds line and modem status flags */
struct qt2_status_data {
        __u8 line_status;
        __u8 modem_status;
};

/* Function prototypes */
static int qt2_boxpoweron(struct usb_serial *serial);
static int qt2_boxsetQMCR(struct usb_serial *serial, __u16 Uart_Number,
                        __u8 QMCR_Value);
static int port_paranoia_check(struct usb_serial_port *port,
                        const char *function);
static int serial_paranoia_check(struct usb_serial *serial,
                         const char *function);
static inline struct quatech2_port *qt2_get_port_private(struct usb_serial_port
                        *port);
static inline void qt2_set_port_private(struct usb_serial_port *port,
                        struct quatech2_port *data);
static inline struct quatech2_dev *qt2_get_dev_private(struct usb_serial
                        *serial);
static inline void qt2_set_dev_private(struct usb_serial *serial,
                        struct quatech2_dev *data);
static int qt2_openboxchannel(struct usb_serial *serial, __u16
                        Uart_Number, struct qt2_status_data *pDeviceData);
static int qt2_closeboxchannel(struct usb_serial *serial, __u16
                        Uart_Number);
static int qt2_conf_uart(struct usb_serial *serial,  unsigned short Uart_Number,
                         unsigned short divisor, unsigned char LCR);
static void qt2_read_bulk_callback(struct urb *urb);
static void qt2_write_bulk_callback(struct urb *urb);
static void qt2_process_line_status(struct usb_serial_port *port,
                              unsigned char LineStatus);
static void qt2_process_modem_status(struct usb_serial_port *port,
                               unsigned char ModemStatus);
static void qt2_process_xmit_empty(struct usb_serial_port *port,
        unsigned char fourth_char, unsigned char fifth_char);
static void qt2_process_port_change(struct usb_serial_port *port,
                              unsigned char New_Current_Port);
static void qt2_process_rcv_flush(struct usb_serial_port *port);
static void qt2_process_xmit_flush(struct usb_serial_port *port);
static void qt2_process_rx_char(struct usb_serial_port *port,
                                unsigned char data);
static int qt2_box_get_register(struct usb_serial *serial,
                unsigned char uart_number, unsigned short register_num,
                __u8 *pValue);
static int qt2_box_set_register(struct usb_serial *serial,
                unsigned short Uart_Number, unsigned short Register_Num,
                unsigned short Value);
static int qt2_boxsetuart(struct usb_serial *serial, unsigned short Uart_Number,
                unsigned short default_divisor, unsigned char default_LCR);
static int qt2_boxsethw_flowctl(struct usb_serial *serial,
                unsigned int UartNumber, bool bSet);
static int qt2_boxsetsw_flowctl(struct usb_serial *serial, __u16 UartNumber,
                unsigned char stop_char,  unsigned char start_char);
static int qt2_boxunsetsw_flowctl(struct usb_serial *serial, __u16 UartNumber);
static int qt2_boxstoprx(struct usb_serial *serial, unsigned short uart_number,
                         unsigned short stop);

/* implementation functions, roughly in order of use, are here */
static int qt2_calc_num_ports(struct usb_serial *serial)
{
        int num_ports;
        int flag_as_400;
        switch (serial->dev->descriptor.idProduct) {
        case QUATECH_SSU2_100:
                num_ports = 1;
                break;

        case QUATECH_DSU2_400:
                flag_as_400 = true;
        case QUATECH_DSU2_100:
                num_ports = 2;
        break;

        case QUATECH_QSU2_400:
                flag_as_400 = true;
        case QUATECH_QSU2_100:
                num_ports = 4;
        break;

        case QUATECH_ESU2_400:
                flag_as_400 = true;
        case QUATECH_ESU2_100:
                num_ports = 8;
        break;
        default:
        num_ports = 1;
        break;
        }
        return num_ports;
}

static int qt2_attach(struct usb_serial *serial)
{
        struct usb_serial_port *port;
        struct quatech2_port *qt2_port; /* port-specific private data pointer */
        struct quatech2_dev  *qt2_dev;  /* dev-specific private data pointer */
        int i;
        /* stuff for storing endpoint addresses now */
        struct usb_endpoint_descriptor *endpoint;
        struct usb_host_interface *iface_desc;
        struct usb_serial_port *port0;  /* first port structure on device */

        /* check how many endpoints there are on the device, for
         * sanity's sake */
        dbg("%s(): Endpoints: %d bulk in, %d bulk out, %d interrupt in",
                        __func__, serial->num_bulk_in,
                        serial->num_bulk_out, serial->num_interrupt_in);
        if ((serial->num_bulk_in != 1) || (serial->num_bulk_out != 1)) {
                dbg("Device has wrong number of bulk endpoints!");
                return -ENODEV;
        }
        iface_desc = serial->interface->cur_altsetting;

        /* Set up per-device private data, storing extra data alongside
         * struct usb_serial */
        qt2_dev = kzalloc(sizeof(*qt2_dev), GFP_KERNEL);
        if (!qt2_dev) {
                dbg("%s: kmalloc for quatech2_dev failed!",
                    __func__);
                return -ENOMEM;
        }
        qt2_dev->open_ports = 0;        /* no ports open */
        qt2_set_dev_private(serial, qt2_dev);   /* store private data */

        /* Now setup per port private data, which replaces all the things
         * that quatech added to standard kernel structures in their driver */
        for (i = 0; i < serial->num_ports; i++) {
                port = serial->port[i];
                qt2_port = kzalloc(sizeof(*qt2_port), GFP_KERNEL);
                if (!qt2_port) {
                        dbg("%s: kmalloc for quatech2_port (%d) failed!.",
                            __func__, i);
                        return -ENOMEM;
                }
                /* initialise stuff in the structure */
                qt2_port->open_count = 0;       /* port is not open */
                spin_lock_init(&qt2_port->lock);
                mutex_init(&qt2_port->modelock);
                qt2_set_port_private(port, qt2_port);
        }

        /* gain access to port[0]'s structure because we want to store
         * device-level stuff in it */
        if (serial_paranoia_check(serial, __func__))
                return -ENODEV;
        port0 = serial->port[0]; /* get the first port's device structure */

        /* print endpoint addresses so we can check them later
         * by hand */
        for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {
                endpoint = &iface_desc->endpoint[i].desc;
                if ((endpoint->bEndpointAddress & 0x80) &&
                        ((endpoint->bmAttributes & 3) == 0x02)) {
                        /* we found a bulk in endpoint */
                        dbg("found bulk in at %#.2x",
                                endpoint->bEndpointAddress);
                }

                if (((endpoint->bEndpointAddress & 0x80) == 0x00) &&
                        ((endpoint->bmAttributes & 3) == 0x02)) {
                        /* we found a bulk out endpoint */
                        dbg("found bulk out at %#.2x",
                                endpoint->bEndpointAddress);
                        qt2_dev->buffer_size = endpoint->wMaxPacketSize;
                        /* max size of URB needs recording for the device */
                }
        }       /* end printing endpoint addresses */

        /* switch on power to the hardware */
        if (qt2_boxpoweron(serial) < 0) {
                dbg("qt2_boxpoweron() failed");
                goto startup_error;
        }
        /* set all ports to RS232 mode */
        for (i = 0; i < serial->num_ports; ++i) {
                if (qt2_boxsetQMCR(serial, i, QU2BOX232) < 0) {
                        dbg("qt2_boxsetQMCR() on port %d failed",
                                i);
                        goto startup_error;
                }
        }

        return 0;

startup_error:
        for (i = 0; i < serial->num_ports; i++) {
                port = serial->port[i];
                qt2_port = qt2_get_port_private(port);
                kfree(qt2_port);
                qt2_set_port_private(port, NULL);
        }
        qt2_dev = qt2_get_dev_private(serial);
        kfree(qt2_dev);
        qt2_set_dev_private(serial, NULL);

        dbg("Exit fail %s\n", __func__);
        return -EIO;
}

static void qt2_release(struct usb_serial *serial)
{
        struct usb_serial_port *port;
        struct quatech2_port *qt_port;
        int i;

        dbg("enterting %s", __func__);

        for (i = 0; i < serial->num_ports; i++) {
                port = serial->port[i];
                if (!port)
                        continue;

                qt_port = usb_get_serial_port_data(port);
                kfree(qt_port);
                usb_set_serial_port_data(port, NULL);
        }
}
/* This function is called once per serial port on the device, when
 * that port is opened by a userspace application.
 * The tty_struct and the usb_serial_port belong to this port,
 * i.e. there are multiple ones for a multi-port device.
 * However the usb_serial_port structure has a back-pointer
 * to the parent usb_serial structure which belongs to the device,
 * so we can access either the device-wide information or
 * any other port's information (because there are also forward
 * pointers) via that pointer.
 * This is most helpful if the device shares resources (e.g. end
 * points) between different ports
 */
int qt2_open(struct tty_struct *tty, struct usb_serial_port *port)
{
        struct usb_serial *serial;      /* device structure */
        struct usb_serial_port *port0;  /* first port structure on device */
        struct quatech2_port *port_extra;       /* extra data for this port */
        struct quatech2_port *port0_extra;      /* extra data for first port */
        struct quatech2_dev *dev_extra;         /* extra data for the device */
        struct qt2_status_data ChannelData;
        unsigned short default_divisor = QU2BOXSPD9600;
        unsigned char  default_LCR = QT2_SERIAL_8_DATA;
        int status;
        int result;

        if (port_paranoia_check(port, __func__))
                return -ENODEV;

        dbg("%s(): port %d", __func__, port->number);

        serial = port->serial;  /* get the parent device structure */
        if (serial_paranoia_check(serial, __func__)) {
                dbg("usb_serial struct failed sanity check");
                return -ENODEV;
        }
        dev_extra = qt2_get_dev_private(serial);
        /* get the device private data */
        if (dev_extra == NULL) {
                dbg("device extra data pointer is null");
                return -ENODEV;
        }
        port0 = serial->port[0]; /* get the first port's device structure */
        if (port_paranoia_check(port0, __func__)) {
                dbg("port0 usb_serial_port struct failed sanity check");
                return -ENODEV;
        }

        port_extra = qt2_get_port_private(port);
        port0_extra = qt2_get_port_private(port0);
        if (port_extra == NULL || port0_extra == NULL) {
                dbg("failed to get private data for port or port0");
                return -ENODEV;
        }

        /* FIXME: are these needed?  Does it even do anything useful? */
        /* get the modem and line status values from the UART */
        status = qt2_openboxchannel(serial, port->number,
                        &ChannelData);
        if (status < 0) {
                dbg("qt2_openboxchannel on channel %d failed",
                    port->number);
                return status;
        }
        port_extra->shadowLSR = ChannelData.line_status &
                        (QT2_SERIAL_LSR_OE | QT2_SERIAL_LSR_PE |
                        QT2_SERIAL_LSR_FE | QT2_SERIAL_LSR_BI);
        port_extra->shadowMSR = ChannelData.modem_status &
                        (QT2_SERIAL_MSR_CTS | QT2_SERIAL_MSR_DSR |
                        QT2_SERIAL_MSR_RI | QT2_SERIAL_MSR_CD);

/*      port_extra->fifo_empty_flag = true;*/
        dbg("qt2_openboxchannel on channel %d completed.",
            port->number);

        /* Set Baud rate to default and turn off flow control here */
        status = qt2_conf_uart(serial, port->number, default_divisor,
                                default_LCR);
        if (status < 0) {
                dbg("qt2_conf_uart() failed on channel %d",
                    port->number);
                return status;
        }
        dbg("qt2_conf_uart() completed on channel %d",
                port->number);

        /*
         * At this point we will need some end points to make further progress.
         * Handlily, the correct endpoint addresses have been filled out into
         * the usb_serial_port structure for us by the driver core, so we
         * already have access to them.
         * As there is only one bulk in and one bulk out end-point, these are in
         * port[0]'s structure, and the rest are uninitialised. Handily,
         * when we do a write to a port, we will use the same endpoint
         * regardless of the port, with a 5-byte header added on to
         * tell the box which port it should eventually come out of, so we only
         * need the one set of endpoints. We will have one URB per port for
         * writing, so that multiple ports can be writing at once.
         * Finally we need a bulk in URB to use for background reads from the
         * device, which will deal with uplink data from the box to host.
         */
        dbg("port0 bulk in endpoint is %#.2x", port0->bulk_in_endpointAddress);
        dbg("port0 bulk out endpoint is %#.2x",
                port0->bulk_out_endpointAddress);

        /* set up write_urb for bulk out transfers on this port. The USB
         * serial framework will have allocated a blank URB, buffer etc for
         * port0 when it put the endpoints there, but not for any of the other
         * ports on the device because there are no more endpoints. Thus we
         * have to allocate our own URBs for ports 1-7
         */
        if (port->write_urb == NULL) {
                dbg("port->write_urb == NULL, allocating one");
                port->write_urb = usb_alloc_urb(0, GFP_KERNEL);
                if (!port->write_urb) {
                        err("Allocating write URB failed");
                        return -ENOMEM;
                }
                /* buffer same size as port0 */
                port->bulk_out_size = dev_extra->buffer_size;
                port->bulk_out_buffer = kmalloc(port->bulk_out_size,
                                                GFP_KERNEL);
                if (!port->bulk_out_buffer) {
                        err("Couldn't allocate bulk_out_buffer");
                        return -ENOMEM;
                }
        }
        if (serial->dev == NULL)
                dbg("serial->dev == NULL");
        dbg("port->bulk_out_size is %d", port->bulk_out_size);

        usb_fill_bulk_urb(port->write_urb, serial->dev,
                        usb_sndbulkpipe(serial->dev,
                        port0->bulk_out_endpointAddress),
                        port->bulk_out_buffer,
                        port->bulk_out_size,
                        qt2_write_bulk_callback,
                        port);
        port_extra->tx_pending_bytes = 0;

        if (dev_extra->open_ports == 0) {
                /* this is first port to be opened, so need the read URB
                 * initialised for bulk in transfers (this is shared amongst
                 * all the ports on the device) */
                usb_fill_bulk_urb(port0->read_urb, serial->dev,
                        usb_rcvbulkpipe(serial->dev,
                        port0->bulk_in_endpointAddress),
                        port0->bulk_in_buffer,
                        port0->bulk_in_size,
                        qt2_read_bulk_callback, serial);
                dbg("port0 bulk in URB initialised");

                /* submit URB, i.e. start reading from device (async) */
                dev_extra->ReadBulkStopped = false;
                port_extra->read_urb_busy = true;
                result = usb_submit_urb(port->read_urb, GFP_KERNEL);
                if (result) {
                        dev_err(&port->dev,
                                 "%s(): Error %d submitting bulk in urb",
                                __func__, result);
                        port_extra->read_urb_busy = false;
                        dev_extra->ReadBulkStopped = true;
                }

                /* When the first port is opened, initialise the value of
                 * current_port in dev_extra to this port, so it is set
                 * to something. Once the box sends data it will send the
                 * relevant escape sequences to get it to the right port anyway
                 */
                dev_extra->current_port = port;
        }

        /* initialize our wait queues */
        init_waitqueue_head(&port_extra->wait);
        /* increment the count of openings of this port by one */
        port_extra->open_count++;

        /* remember to store dev_extra, port_extra and port0_extra back again at
         * end !*/
        qt2_set_port_private(port, port_extra);
        qt2_set_port_private(serial->port[0], port0_extra);
        qt2_set_dev_private(serial, dev_extra);

        dev_extra->open_ports++; /* one more port opened */

        return 0;
}

/* called when a port is closed by userspace. It won't be called, however,
 * until calls to chars_in_buffer() reveal that the port has completed
 * sending buffered data, and there is nothing else to do. Thus we don't have
 * to rely on forcing data through in this function. */
/* Setting close_pending should keep new data from being written out,
 * once all the data in the enpoint buffers is moved out we won't get
 * any more. */
/* BoxStopReceive would keep any more data from coming from a given
 * port, but isn't called by the vendor driver, although their comments
 * mention it. Should it be used here to stop the inbound data
 * flow?
 */
static void qt2_close(struct usb_serial_port *port)
{
        /* time out value for flush loops */
        unsigned long jift;
        struct quatech2_port *port_extra;       /* extra data for this port */
        struct usb_serial *serial;      /* device structure */
        struct quatech2_dev *dev_extra; /* extra data for the device */
        __u8  lsr_value = 0;    /* value of Line Status Register */
        int status;     /* result of last USB comms function */

        dbg("%s(): port %d", __func__, port->number);
        serial = port->serial;  /* get the parent device structure */
        dev_extra = qt2_get_dev_private(serial);
        /* get the device private data */
        port_extra = qt2_get_port_private(port); /* port private data */

        /* we can now (and only now) stop reading data */
        port_extra->close_pending = true;
        dbg("%s(): port_extra->close_pending = true", __func__);
        /* although the USB side is now empty, the UART itself may
         * still be pushing characters out over the line, so we have to
         * wait testing the actual line status until the lines change
         * indicating that the data is done transferring. */
        /* FIXME: slow this polling down so it doesn't run the USB bus flat out
         * if it actually has to spend any time in this loop (which it normally
         * doesn't because the buffer is nearly empty) */
        jift = jiffies + (10 * HZ);     /* 10 sec timeout */
        do {
                status = qt2_box_get_register(serial, port->number,
                        QT2_LINE_STATUS_REGISTER, &lsr_value);
                if (status < 0) {
                        dbg("%s(): qt2_box_get_register failed", __func__);
                        break;
                }
                if ((lsr_value & QT2_LSR_TEMT)) {
                        dbg("UART done sending");
                        break;
                }
                schedule();
        } while (jiffies <= jift);

        status = qt2_closeboxchannel(serial, port->number);
        if (status < 0)
                dbg("%s(): port %d qt2_box_open_close_channel failed",
                        __func__, port->number);
        /* to avoid leaking URBs, we should now free the write_urb for this
         * port and set the pointer to null so that next time the port is opened
         * a new URB is allocated. This avoids leaking URBs when the device is
         * removed */
        usb_free_urb(port->write_urb);
        kfree(port->bulk_out_buffer);
        port->bulk_out_buffer = NULL;
        port->bulk_out_size = 0;

        /* decrement the count of openings of this port by one */
        port_extra->open_count--;
        /* one less overall open as well */
        dev_extra->open_ports--;
        dbg("%s(): Exit, dev_extra->open_ports  = %d", __func__,
                dev_extra->open_ports);
}

/**
 * qt2_write - write bytes from the tty layer out to the USB device.
 * @buf: The data to be written, size at least count.
 * @count: The number of bytes requested for transmission.
 * @return The number of bytes actually accepted for transmission to the device.
 */
static int qt2_write(struct tty_struct *tty, struct usb_serial_port *port,
                const unsigned char *buf, int count)
{
        struct usb_serial *serial;      /* parent device struct */
        __u8 header_array[5];   /* header used to direct writes to the correct
        port on the device */
        struct quatech2_port *port_extra;       /* extra data for this port */
        int result;

        serial = port->serial; /* get the parent device of the port */
        port_extra = qt2_get_port_private(port); /* port extra info */
        if (serial == NULL)
                return -ENODEV;
        dbg("%s(): port %d, requested to write %d bytes, %d already pending",
                __func__, port->number, count, port_extra->tx_pending_bytes);

        if (count <= 0) {
                dbg("%s(): write request of <= 0 bytes", __func__);
                return 0;       /* no bytes written */
        }

        /* check if the write urb is already in use, i.e. data already being
         * sent to this port */
        if ((port->write_urb->status == -EINPROGRESS)) {
                /* Fifo hasn't been emptied since last write to this port */
                dbg("%s(): already writing, port->write_urb->status == "
                        "-EINPROGRESS", __func__);
                /* schedule_work(&port->work); commented in vendor driver */
                return 0;
        } else if (port_extra->tx_pending_bytes >= QT2_FIFO_DEPTH) {
                /* buffer is full (==). > should not occur, but would indicate
                 * that an overflow had occurred */
                dbg("%s(): port transmit buffer is full!", __func__);
                /* schedule_work(&port->work); commented in vendor driver */
                return 0;
        }

        /* We must fill the first 5 bytes of anything we sent with a transmit
         * header which directes the data to the correct port. The maximum
         * size we can send out in one URB is port->bulk_out_size, which caps
         * the number of bytes of real data we can send in each write. As the
         * semantics of write allow us to write less than we were give, we cap
         * the maximum we will ever write to the device as 5 bytes less than
         * one URB's worth, by reducing the value of the count argument
         * appropriately*/
        if (count > port->bulk_out_size - QT2_TX_HEADER_LENGTH) {
                count = port->bulk_out_size - QT2_TX_HEADER_LENGTH;
                dbg("%s(): write request bigger than urb, only accepting "
                        "%d bytes", __func__, count);
        }
        /* we must also ensure that the FIFO at the other end can cope with the
         * URB we send it, otherwise it will have problems. As above, we can
         * restrict the write size by just shrinking count.*/
        if (count > (QT2_FIFO_DEPTH - port_extra->tx_pending_bytes)) {
                count = QT2_FIFO_DEPTH - port_extra->tx_pending_bytes;
                dbg("%s(): not enough room in buffer, only accepting %d bytes",
                        __func__, count);
        }
        /* now build the header for transmission */
        header_array[0] = 0x1b;
        header_array[1] = 0x1b;
        header_array[2] = (__u8)port->number;
        header_array[3] = (__u8)count;
        header_array[4] = (__u8)count >> 8;
        /* copy header into URB */
        memcpy(port->write_urb->transfer_buffer, header_array,
                QT2_TX_HEADER_LENGTH);
        /* and actual data to write */
        memcpy(port->write_urb->transfer_buffer + 5, buf, count);

        dbg("%s(): first data byte to send = %#.2x", __func__, *buf);

        /* set up our urb */
        usb_fill_bulk_urb(port->write_urb, serial->dev,
                        usb_sndbulkpipe(serial->dev,
                        port->bulk_out_endpointAddress),
                        port->write_urb->transfer_buffer, count + 5,
                        (qt2_write_bulk_callback), port);
        /* send the data out the bulk port */
        result = usb_submit_urb(port->write_urb, GFP_ATOMIC);
        if (result) {
                /* error couldn't submit urb */
                result = 0;     /* return 0 as nothing got written */
                dbg("%s(): failed submitting write urb, error %d",
                        __func__, result);
        } else {
                port_extra->tx_pending_bytes += count;
                result = count; /* return number of bytes written, i.e. count */
                dbg("%s(): submitted write urb, wrote %d bytes, "
                        "total pending bytes %d",
                        __func__, result, port_extra->tx_pending_bytes);
        }
        return result;
}

/* This is used by the next layer up to know how much space is available
 * in the buffer on the device. It is used on a device closure to avoid
 * calling close() until the buffer is reported to be empty.
 * The returned value must never go down by more than the number of bytes
 * written for correct behaviour further up the driver stack, i.e. if I call
 * it, then write 6 bytes, then call again I should get 6 less, or possibly
 * only 5 less if one was written in the meantime, etc. I should never get 7
 * less (or any bigger number) because I only wrote 6 bytes.
 */
static int qt2_write_room(struct tty_struct *tty)
{
        struct usb_serial_port *port = tty->driver_data;
                /* parent usb_serial_port pointer */
        struct quatech2_port *port_extra;       /* extra data for this port */
        int room = 0;
        port_extra = qt2_get_port_private(port);

        if (port_extra->close_pending == true) {
                dbg("%s(): port_extra->close_pending == true", __func__);
                return -ENODEV;
        }
        /* Q: how many bytes would a write() call actually succeed in writing
         * if it happened now?
         * A: one QT2_FIFO_DEPTH, less the number of bytes waiting to be sent
         * out of the port, unless this is more than the size of the
         * write_urb output buffer less the header, which is the maximum
         * size write we can do.

         * Most of the implementation of this is done when writes to the device
         * are started or terminate. When we send a write to the device, we
         * reduce the free space count by the size of the dispatched write.
         * When a "transmit empty" message comes back up the USB read stream,
         * we decrement the count by the number of bytes reported sent, thus
         * keeping track of the difference between sent and received bytes.
         */

        room = (QT2_FIFO_DEPTH - port_extra->tx_pending_bytes);
        /* space in FIFO */
        if (room > port->bulk_out_size - QT2_TX_HEADER_LENGTH)
                room = port->bulk_out_size - QT2_TX_HEADER_LENGTH;
        /* if more than the URB can hold, then cap to that limit */

        dbg("%s(): port %d: write room is %d", __func__, port->number, room);
        return room;
}

static int qt2_chars_in_buffer(struct tty_struct *tty)
{
        struct usb_serial_port *port = tty->driver_data;
        /* parent usb_serial_port pointer */
        struct quatech2_port *port_extra;       /* extra data for this port */
        port_extra = qt2_get_port_private(port);

        dbg("%s(): port %d: chars_in_buffer = %d", __func__,
                port->number, port_extra->tx_pending_bytes);
        return port_extra->tx_pending_bytes;
}

/* called when userspace does an ioctl() on the device. Note that
 * TIOCMGET and TIOCMSET are filtered off to their own methods before they get
 * here, so we don't have to handle them.
 */
static int qt2_ioctl(struct tty_struct *tty,
                     unsigned int cmd, unsigned long arg)
{
        struct usb_serial_port *port = tty->driver_data;
        struct usb_serial *serial = port->serial;
        __u8 mcr_value; /* Modem Control Register value */
        __u8 msr_value; /* Modem Status Register value */
        unsigned short prev_msr_value; /* Previous value of Modem Status
         * Register used to implement waiting for a line status change to
         * occur */
        struct quatech2_port *port_extra;       /* extra data for this port */
        DECLARE_WAITQUEUE(wait, current);
        /* Declare a wait queue named "wait" */

        unsigned int value;
        unsigned int UartNumber;

        if (serial == NULL)
                return -ENODEV;
        UartNumber = tty->index - serial->minor;
        port_extra = qt2_get_port_private(port);

        dbg("%s(): port %d, UartNumber %d, tty =0x%p", __func__,
            port->number, UartNumber, tty);

        if (cmd == TIOCMBIS || cmd == TIOCMBIC) {
                if (qt2_box_get_register(port->serial, UartNumber,
                        QT2_MODEM_CONTROL_REGISTER, &mcr_value) < 0)
                        return -ESPIPE;
                if (copy_from_user(&value, (unsigned int *)arg,
                        sizeof(value)))
                        return -EFAULT;

                switch (cmd) {
                case TIOCMBIS:
                        if (value & TIOCM_RTS)
                                mcr_value |= QT2_SERIAL_MCR_RTS;
                        if (value & TIOCM_DTR)
                                mcr_value |= QT2_SERIAL_MCR_DTR;
                        if (value & TIOCM_LOOP)
                                mcr_value |= QT2_SERIAL_MCR_LOOP;
                break;
                case TIOCMBIC:
                        if (value & TIOCM_RTS)
                                mcr_value &= ~QT2_SERIAL_MCR_RTS;
                        if (value & TIOCM_DTR)
                                mcr_value &= ~QT2_SERIAL_MCR_DTR;
                        if (value & TIOCM_LOOP)
                                mcr_value &= ~QT2_SERIAL_MCR_LOOP;
                break;
                default:
                break;
                }       /* end of local switch on cmd */
                if (qt2_box_set_register(port->serial,  UartNumber,
                    QT2_MODEM_CONTROL_REGISTER, mcr_value) < 0) {
                        return -ESPIPE;
                } else {
                        port_extra->shadowMCR = mcr_value;
                        return 0;
                }
        } else if (cmd == TIOCMIWAIT) {
                dbg("%s() port %d, cmd == TIOCMIWAIT enter",
                        __func__, port->number);
                prev_msr_value = port_extra->shadowMSR  & QT2_SERIAL_MSR_MASK;
                barrier();
                __set_current_state(TASK_INTERRUPTIBLE);
                while (1) {
                        add_wait_queue(&port_extra->wait, &wait);
                        schedule();
                        dbg("%s(): port %d, cmd == TIOCMIWAIT here\n",
                                __func__, port->number);
                        remove_wait_queue(&port_extra->wait, &wait);
                        /* see if a signal woke us up */
                        if (signal_pending(current))
                                return -ERESTARTSYS;
                        set_current_state(TASK_INTERRUPTIBLE);
                        msr_value = port_extra->shadowMSR & QT2_SERIAL_MSR_MASK;
                        if (msr_value == prev_msr_value) {
                                __set_current_state(TASK_RUNNING);
                                return -EIO;  /* no change - error */
                        }
                        if ((arg & TIOCM_RNG &&
                                ((prev_msr_value & QT2_SERIAL_MSR_RI) ==
                                        (msr_value & QT2_SERIAL_MSR_RI))) ||
                                (arg & TIOCM_DSR &&
                                ((prev_msr_value & QT2_SERIAL_MSR_DSR) ==
                                        (msr_value & QT2_SERIAL_MSR_DSR))) ||
                                (arg & TIOCM_CD &&
                                ((prev_msr_value & QT2_SERIAL_MSR_CD) ==
                                        (msr_value & QT2_SERIAL_MSR_CD))) ||
                                (arg & TIOCM_CTS &&
                                ((prev_msr_value & QT2_SERIAL_MSR_CTS) ==
                                        (msr_value & QT2_SERIAL_MSR_CTS)))) {
                                __set_current_state(TASK_RUNNING);
                                return 0;
                        }
                } /* end inifinite while */
                /* FIXME: This while loop needs a way to break out if the device
                 * is disconnected while a process is waiting for the MSR to
                 * change, because once it's disconnected, it isn't going to
                 * change state ... */
        } else {
                /* any other ioctls we don't know about come here */
                dbg("%s(): No ioctl for that one. port = %d", __func__,
                        port->number);
                return -ENOIOCTLCMD;
        }
}

/* Called when the user wishes to change the port settings using the termios
 * userspace interface */
static void qt2_set_termios(struct tty_struct *tty,
        struct usb_serial_port *port, struct ktermios *old_termios)
{
        struct usb_serial *serial; /* parent serial device */
        int baud, divisor, remainder;
        unsigned char LCR_change_to = 0;
        int status;
        __u16 UartNumber;

        dbg("%s(): port %d", __func__, port->number);

        serial = port->serial;

        UartNumber = port->number;

        if (old_termios && !tty_termios_hw_change(old_termios, tty->termios))
                return;

        switch (tty->termios->c_cflag) {
        case CS5:
                LCR_change_to |= QT2_SERIAL_5_DATA;
                break;
        case CS6:
                LCR_change_to |= QT2_SERIAL_6_DATA;
                break;
        case CS7:
                LCR_change_to |= QT2_SERIAL_7_DATA;
                break;
        default:
        case CS8:
                LCR_change_to |= QT2_SERIAL_8_DATA;
                break;
        }

        /* Parity stuff */
        if (tty->termios->c_cflag & PARENB) {
                if (tty->termios->c_cflag & PARODD)
                        LCR_change_to |= QT2_SERIAL_ODD_PARITY;
                else
                        LCR_change_to |= QT2_SERIAL_EVEN_PARITY;
        }
        /* Because LCR_change_to is initialised to zero, we don't have to worry
         * about the case where PARENB is not set or clearing bits, because by
         * default all of them are cleared, turning parity off.
         * as we don't support mark/space parity, we should clear the
         * mark/space parity bit in c_cflag, so the caller can tell we have
         * ignored the request */
        tty->termios->c_cflag &= ~CMSPAR;

        if (tty->termios->c_cflag & CSTOPB)
                LCR_change_to |= QT2_SERIAL_TWO_STOPB;
        else
                LCR_change_to |= QT2_SERIAL_ONE_STOPB;

        /* Thats the LCR stuff, next we need to work out the divisor as the
         * LCR and the divisor are set together */
        baud = tty_get_baud_rate(tty);
        if (!baud) {
                /* pick a default, any default... */
                baud = 9600;
        }
        dbg("%s(): got baud = %d", __func__, baud);

        divisor = QT2_MAX_BAUD_RATE / baud;
        remainder = QT2_MAX_BAUD_RATE % baud;
        /* Round to nearest divisor */
        if (((remainder * 2) >= baud) && (baud != 110))
                divisor++;
        dbg("%s(): setting divisor = %d, QT2_MAX_BAUD_RATE = %d , LCR = %#.2x",
              __func__, divisor, QT2_MAX_BAUD_RATE, LCR_change_to);

        status = qt2_boxsetuart(serial, UartNumber, (unsigned short) divisor,
                            LCR_change_to);
        if (status < 0) {
                dbg("qt2_boxsetuart() failed");
                return;
        } else {
                /* now encode the baud rate we actually set, which may be
                 * different to the request */
                baud = QT2_MAX_BAUD_RATE / divisor;
                tty_encode_baud_rate(tty, baud, baud);
        }

        /* Now determine flow control */
        if (tty->termios->c_cflag & CRTSCTS) {
                dbg("%s(): Enabling HW flow control port %d", __func__,
                      port->number);
                /* Enable  RTS/CTS flow control */
                status = qt2_boxsethw_flowctl(serial, UartNumber, true);
                if (status < 0) {
                        dbg("qt2_boxsethw_flowctl() failed");
                        return;
                }
        } else {
                /* Disable RTS/CTS flow control */
                dbg("%s(): disabling HW flow control port %d", __func__,
                        port->number);
                status = qt2_boxsethw_flowctl(serial, UartNumber, false);
                if (status < 0) {
                        dbg("qt2_boxsethw_flowctl failed");
                        return;
                }
        }
        /* if we are implementing XON/XOFF, set the start and stop character
         * in the device */
        if (I_IXOFF(tty) || I_IXON(tty)) {
                unsigned char stop_char  = STOP_CHAR(tty);
                unsigned char start_char = START_CHAR(tty);
                status = qt2_boxsetsw_flowctl(serial, UartNumber, stop_char,
                                start_char);
                if (status < 0)
                        dbg("qt2_boxsetsw_flowctl (enabled) failed");
        } else {
                /* disable SW flow control */
                status = qt2_boxunsetsw_flowctl(serial, UartNumber);
                if (status < 0)
                        dbg("qt2_boxunsetsw_flowctl (disabling) failed");
        }
}

static int qt2_tiocmget(struct tty_struct *tty)
{
        struct usb_serial_port *port = tty->driver_data;
        struct usb_serial *serial = port->serial;

        __u8 mcr_value; /* Modem Control Register value */
        __u8 msr_value; /* Modem Status Register value */
        unsigned int result = 0;
        int status;
        unsigned int UartNumber;

        if (serial == NULL)
                return -ENODEV;

        dbg("%s(): port %d, tty =0x%p", __func__, port->number, tty);
        UartNumber = tty->index - serial->minor;
        dbg("UartNumber is %d", UartNumber);

        status = qt2_box_get_register(port->serial, UartNumber,
                        QT2_MODEM_CONTROL_REGISTER,     &mcr_value);
        if (status >= 0) {
                status = qt2_box_get_register(port->serial,  UartNumber,
                                QT2_MODEM_STATUS_REGISTER, &msr_value);
        }
        if (status >= 0) {
                result = ((mcr_value & QT2_SERIAL_MCR_DTR) ? TIOCM_DTR : 0)
                                /*DTR set */
                        | ((mcr_value & QT2_SERIAL_MCR_RTS)  ? TIOCM_RTS : 0)
                                /*RTS set */
                        | ((msr_value & QT2_SERIAL_MSR_CTS)  ? TIOCM_CTS : 0)
                                /* CTS set */
                        | ((msr_value & QT2_SERIAL_MSR_CD)  ? TIOCM_CAR : 0)
                                /*Carrier detect set */
                        | ((msr_value & QT2_SERIAL_MSR_RI)  ? TIOCM_RI : 0)
                                /* Ring indicator set */
                        | ((msr_value & QT2_SERIAL_MSR_DSR)  ? TIOCM_DSR : 0);
                                /* DSR set */
                return result;
        } else {
                return -ESPIPE;
        }
}

static int qt2_tiocmset(struct tty_struct *tty,
                       unsigned int set, unsigned int clear)
{
        struct usb_serial_port *port = tty->driver_data;
        struct usb_serial *serial = port->serial;
        __u8 mcr_value; /* Modem Control Register value */
        int status;
        unsigned int UartNumber;

        if (serial == NULL)
                return -ENODEV;

        UartNumber = tty->index - serial->minor;
        dbg("%s(): port %d, UartNumber %d", __func__, port->number, UartNumber);

        status = qt2_box_get_register(port->serial, UartNumber,
                        QT2_MODEM_CONTROL_REGISTER, &mcr_value);
        if (status < 0)
                return -ESPIPE;

        /* Turn off RTS, DTR and loopback, then only turn on what was asked
         * for */
        mcr_value &= ~(QT2_SERIAL_MCR_RTS | QT2_SERIAL_MCR_DTR |
                        QT2_SERIAL_MCR_LOOP);
        if (set & TIOCM_RTS)
                mcr_value |= QT2_SERIAL_MCR_RTS;
        if (set & TIOCM_DTR)
                mcr_value |= QT2_SERIAL_MCR_DTR;
        if (set & TIOCM_LOOP)
                mcr_value |= QT2_SERIAL_MCR_LOOP;

        status = qt2_box_set_register(port->serial, UartNumber,
                        QT2_MODEM_CONTROL_REGISTER, mcr_value);
        if (status < 0)
                return -ESPIPE;
        else
                return 0;
}

/** qt2_break - Turn BREAK on and off on the UARTs
 */
static void qt2_break(struct tty_struct *tty, int break_state)
{
        struct usb_serial_port *port = tty->driver_data; /* parent port */
        struct usb_serial *serial = port->serial;       /* parent device */
        struct quatech2_port *port_extra;       /* extra data for this port */
        __u16 break_value;
        unsigned int result;

        port_extra = qt2_get_port_private(port);
        if (!serial) {
                dbg("%s(): port %d: no serial object", __func__, port->number);
                return;
        }

        if (break_state == -1)
                break_value = 1;
        else
                break_value = 0;
        dbg("%s(): port %d, break_value %d", __func__, port->number,
                break_value);

        mutex_lock(&port_extra->modelock);
        if (!port_extra->open_count) {
                dbg("%s(): port not open", __func__);
                goto exit;
        }

        result = usb_control_msg(serial->dev, usb_sndctrlpipe(serial->dev, 0),
                                QT2_BREAK_CONTROL, 0x40, break_value,
                                port->number, NULL, 0, 300);
exit:
        mutex_unlock(&port_extra->modelock);
        dbg("%s(): exit port %d", __func__, port->number);

}
/**
 * qt2_throttle: - stop reading new data from the port
 */
static void qt2_throttle(struct tty_struct *tty)
{
        struct usb_serial_port *port = tty->driver_data;
        struct usb_serial *serial = port->serial;
        struct quatech2_port *port_extra;       /* extra data for this port */
        dbg("%s(): port %d", __func__, port->number);

        port_extra = qt2_get_port_private(port);
        if (!serial) {
                dbg("%s(): enter port %d no serial object", __func__,
                      port->number);
                return;
        }

        mutex_lock(&port_extra->modelock);      /* lock structure */
        if (!port_extra->open_count) {
                dbg("%s(): port not open", __func__);
                goto exit;
        }
        /* Send command to box to stop receiving stuff. This will stop this
         * particular UART from filling the endpoint - in the multiport case the
         * FPGA UART will handle any flow control implemented, but for the single
         * port it's handed differently and we just quit submitting urbs
         */
        if (serial->dev->descriptor.idProduct != QUATECH_SSU2_100)
                qt2_boxstoprx(serial, port->number, 1);

        port->throttled = 1;
exit:
        mutex_unlock(&port_extra->modelock);
        dbg("%s(): port %d: setting port->throttled", __func__, port->number);
        return;
}

/**
 * qt2_unthrottle: - start receiving data through the port again after being
 * throttled
 */
static void qt2_unthrottle(struct tty_struct *tty)
{
        struct usb_serial_port *port = tty->driver_data;
        struct usb_serial *serial = port->serial;
        struct quatech2_port *port_extra;       /* extra data for this port */
        struct usb_serial_port *port0;  /* first port structure on device */
        struct quatech2_dev *dev_extra;         /* extra data for the device */

        if (!serial) {
                dbg("%s() enter port %d no serial object!", __func__,
                        port->number);
                return;
        }
        dbg("%s(): enter port %d", __func__, port->number);
        dev_extra = qt2_get_dev_private(serial);
        port_extra = qt2_get_port_private(port);
        port0 = serial->port[0]; /* get the first port's device structure */

        mutex_lock(&port_extra->modelock);
        if (!port_extra->open_count) {
                dbg("%s(): port %d not open", __func__, port->number);
                goto exit;
        }

        if (port->throttled != 0) {
                dbg("%s(): port %d: unsetting port->throttled", __func__,
                    port->number);
                port->throttled = 0;
                /* Send command to box to start receiving stuff */
                if (serial->dev->descriptor.idProduct != QUATECH_SSU2_100) {
                        qt2_boxstoprx(serial,  port->number, 0);
                } else if (dev_extra->ReadBulkStopped == true) {
                        usb_fill_bulk_urb(port0->read_urb, serial->dev,
                                usb_rcvbulkpipe(serial->dev,
                                port0->bulk_in_endpointAddress),
                                port0->bulk_in_buffer,
                                port0->bulk_in_size,
                                qt2_read_bulk_callback,
                                serial);
                }
        }
exit:
        mutex_unlock(&port_extra->modelock);
        dbg("%s(): exit port %d", __func__, port->number);
        return;
}

/* internal, private helper functions for the driver */

/* Power up the FPGA in the box to get it working */
static int qt2_boxpoweron(struct usb_serial *serial)
{
        int result;
        __u8  Direcion;
        unsigned int pipe;
        Direcion = USBD_TRANSFER_DIRECTION_OUT;
        pipe = usb_rcvctrlpipe(serial->dev, 0);
        result = usb_control_msg(serial->dev, pipe, QT_SET_GET_DEVICE,
                                Direcion, QU2BOXPWRON, 0x00, NULL, 0x00,
                                5000);
        return result;
}

/*
 * qt2_boxsetQMCR Issue a QT2_GET_SET_QMCR vendor-spcific request on the
 * default control pipe. If successful return the number of bytes written,
 * otherwise return a negative error number of the problem.
 */
static int qt2_boxsetQMCR(struct usb_serial *serial, __u16 Uart_Number,
                          __u8 QMCR_Value)
{
        int result;
        __u16 PortSettings;

        PortSettings = (__u16)(QMCR_Value);

        dbg("%s(): Port = %d, PortSettings = 0x%x", __func__,
                        Uart_Number, PortSettings);

        result = usb_control_msg(serial->dev, usb_sndctrlpipe(serial->dev, 0),
                                QT2_GET_SET_QMCR, 0x40, PortSettings,
                                (__u16)Uart_Number, NULL, 0, 5000);
        return result;
}

static int port_paranoia_check(struct usb_serial_port *port,
                               const char *function)
{
        if (!port) {
                dbg("%s - port == NULL", function);
                return -1;
        }
        if (!port->serial) {
                dbg("%s - port->serial == NULL\n", function);
                return -1;
        }
        return 0;
}

static int serial_paranoia_check(struct usb_serial *serial,
                                 const char *function)
{
        if (!serial) {
                dbg("%s - serial == NULL\n", function);
                return -1;
        }

        if (!serial->type) {
                dbg("%s - serial->type == NULL!", function);
                return -1;
        }

        return 0;
}

static inline struct quatech2_port *qt2_get_port_private(struct usb_serial_port
                *port)
{
        return (struct quatech2_port *)usb_get_serial_port_data(port);
}

static inline void qt2_set_port_private(struct usb_serial_port *port,
                struct quatech2_port *data)
{
        usb_set_serial_port_data(port, (void *)data);
}

static inline struct quatech2_dev *qt2_get_dev_private(struct usb_serial
                *serial)
{
        return (struct quatech2_dev *)usb_get_serial_data(serial);
}
static inline void qt2_set_dev_private(struct usb_serial *serial,
                struct quatech2_dev *data)
{
        usb_set_serial_data(serial, (void *)data);
}

static int qt2_openboxchannel(struct usb_serial *serial, __u16
                Uart_Number, struct qt2_status_data *status)
{
        int result;
        __u16 length;
        __u8  Direcion;
        unsigned int pipe;
        length = sizeof(struct qt2_status_data);
        Direcion = USBD_TRANSFER_DIRECTION_IN;
        pipe = usb_rcvctrlpipe(serial->dev, 0);
        result = usb_control_msg(serial->dev, pipe, QT_OPEN_CLOSE_CHANNEL,
                        Direcion, 0x00, Uart_Number, status, length, 5000);
        return result;
}
static int qt2_closeboxchannel(struct usb_serial *serial, __u16 Uart_Number)
{
        int result;
        __u8  direcion;
        unsigned int pipe;
        direcion = USBD_TRANSFER_DIRECTION_OUT;
        pipe = usb_sndctrlpipe(serial->dev, 0);
        result = usb_control_msg(serial->dev, pipe, QT_OPEN_CLOSE_CHANNEL,
                  direcion, 0, Uart_Number, NULL, 0, 5000);
        return result;
}

/* qt2_conf_uart Issue a SET_UART vendor-spcific request on the default
 * control pipe. If successful sets baud rate divisor and LCR value
 */
static int qt2_conf_uart(struct usb_serial *serial,  unsigned short Uart_Number,
                      unsigned short divisor, unsigned char LCR)
{
        int result;
        unsigned short UartNumandLCR;

        UartNumandLCR = (LCR << 8) + Uart_Number;

        result = usb_control_msg(serial->dev, usb_sndctrlpipe(serial->dev, 0),
                                QT2_GET_SET_UART, 0x40, divisor, UartNumandLCR,
                                NULL, 0, 300);
        return result;
}

/** @brief Callback for asynchronous submission of read URBs on bulk in
 * endpoints
 *
 * Registered in qt2_open_port(), used to deal with incomming data
 * from the box.
 */
static void qt2_read_bulk_callback(struct urb *urb)
{
        /* Get the device pointer (struct usb_serial) back out of the URB */
        struct usb_serial *serial = urb->context;
        /* get the extra struct for the device */
        struct quatech2_dev *dev_extra = qt2_get_dev_private(serial);
        /* Get first port structure from the device */
        struct usb_serial_port *port0 = serial->port[0];
        /* Get the currently active port structure from serial struct */
        struct usb_serial_port *active = dev_extra->current_port;
        /* get the extra struct for port 0 */
        struct quatech2_port *port0_extra = qt2_get_port_private(port0);
        /* and for the currently active port */
        struct quatech2_port *active_extra = qt2_get_port_private(active);
        /* When we finally get to doing some tty stuff, we will need this */
        struct tty_struct *tty_st;
        unsigned int RxCount;   /* the length of the data to process */
        unsigned int i; /* loop counter over the data to process */
        int result;     /* return value cache variable */
        bool escapeflag;        /* flag set to true if this loop iteration is
                                 * parsing an escape sequence, rather than
                                 * ordinary data */
        dbg("%s(): callback running, active port is %d", __func__,
                active->number);

        if (urb->status) {
                /* read didn't go well */
                dev_extra->ReadBulkStopped = true;
                dbg("%s(): nonzero bulk read status received: %d",
                        __func__, urb->status);
                return;
        }

        /* inline port_sofrint() here */
        if (port_paranoia_check(port0, __func__) != 0) {
                dbg("%s - port_paranoia_check on port0 failed, exiting\n",
__func__);
                return;
        }
        if (port_paranoia_check(active, __func__) != 0) {
                dbg("%s - port_paranoia_check on current_port "
                        "failed, exiting", __func__);
                return;
        }

/* This single callback function has to do for all the ports on
 * the device. Data being read up the USB can contain certain
 * escape sequences which are used to communicate out-of-band
 * information from the serial port in-band over the USB.
 * These escapes include sending modem and flow control line
 * status, and switching the port. The concept of a "Current Port"
 * is used, which is where data is going until a port change
 * escape seqence is received. This Current Port is kept between
 * callbacks so that when this function enters we know which the
 * currently active port is and can get to work right away without
 * the box having to send repeat escape sequences (anyway, how
 * would it know to do so?).
 */

        if (active_extra->close_pending == true) {
                /* We are closing , stop reading */
                dbg("%s - (active->close_pending == true", __func__);
                if (dev_extra->open_ports <= 0) {
                        /* If this is the only port left open - stop the
                         * bulk read */
                        dev_extra->ReadBulkStopped = true;
                        dbg("%s - (ReadBulkStopped == true;", __func__);
                        return;
                }
        }

        /*
         * RxHolding is asserted by throttle, if we assert it, we're not
         * receiving any more characters and let the box handle the flow
         * control
         */
        if ((port0_extra->RxHolding == true) &&
                    (serial->dev->descriptor.idProduct == QUATECH_SSU2_100)) {
                /* single port device, input is already stopped, so we don't
                 * need any more input data */
                dev_extra->ReadBulkStopped = true;
                return;
        }
        /* finally, we are in a situation where we might consider the data
         * that is contained within the URB, and what to do about it.
         * This is likely to involved communicating up to the TTY layer, so
         * we will need to get hold of the tty for the port we are currently
         * dealing with */

        /* active is a usb_serial_port. It has a member port which is a
         * tty_port. From this we get a tty_struct pointer which is what we
         * actually wanted, and keep it on tty_st */
        tty_st = tty_port_tty_get(&active->port);
        if (!tty_st) {
                dbg("%s - bad tty pointer - exiting", __func__);
                return;
        }
        RxCount = urb->actual_length;   /* grab length of data handy */

        if (RxCount) {
                /* skip all this if no data to process */
                for (i = 0; i < RxCount ; ++i) {
                        /* Look ahead code here -works on several bytes at onc*/
                        if ((i <= (RxCount - 3)) && (THISCHAR == 0x1b)
                                && (NEXTCHAR == 0x1b)) {
                                /* we are in an escape sequence, type
                                 * determined by the 3rd char */
                                escapeflag = false;
                                switch (THIRDCHAR) {
                                case 0x00:
                                        /* Line status change 4th byte must
                                         * follow */
                                        if (i > (RxCount - 4)) {
                                                dbg("Illegal escape sequences "
                                                "in received data");
                                                break;
                                        }
                                        qt2_process_line_status(active,
                                                FOURTHCHAR);
                                        i += 3;
                                        escapeflag = true;
                                        break;
                                case 0x01:
                                        /* Modem status status change 4th byte
                                         * must follow */
                                        if (i > (RxCount - 4)) {
                                                dbg("Illegal escape sequences "
                                                "in received data");
                                                break;
                                        }
                                        qt2_process_modem_status(active,
                                                FOURTHCHAR);
                                        i += 3;
                                        escapeflag = true;
                                        break;
                                case 0x02:
                                        /* xmit hold empty 4th byte
                                         * must follow */
                                        if (i > (RxCount - 4)) {
                                                dbg("Illegal escape sequences "
                                                "in received data");
                                                break;
                                        }
                                        qt2_process_xmit_empty(active,
                                                FOURTHCHAR, FIFTHCHAR);
                                        i += 4;
                                        escapeflag = true;
                                        break;
                                case 0x03:
                                        /* Port number change 4th byte
                                         * must follow */
                                        if (i > (RxCount - 4)) {
                                                dbg("Illegal escape sequences "
                                                "in received data");
                                                break;
                                        }
                                        /* Port change. If port open push
                                         * current data up to tty layer */
                                        if (active_extra->open_count > 0)
                                                tty_flip_buffer_push(tty_st);

                                        dbg("Port Change: new port = %d",
                                                FOURTHCHAR);
                                        qt2_process_port_change(active,
                                                FOURTHCHAR);
                                        i += 3;
                                        escapeflag = true;
                                        /* having changed port, the pointers for
                                         * the currently active port are all out
                                         * of date and need updating */
                                        active = dev_extra->current_port;
                                        active_extra =
                                                qt2_get_port_private(active);
                                        tty_st = tty_port_tty_get(
                                                &active->port);
                                        break;
                                case 0x04:
                                        /* Recv flush 3rd byte must
                                         * follow */
                                        if (i > (RxCount - 3)) {
                                                dbg("Illegal escape sequences "
                                                        "in received data");
                                                break;
                                        }
                                        qt2_process_rcv_flush(active);
                                        i += 2;
                                        escapeflag = true;
                                        break;
                                case 0x05:
                                        /* xmit flush 3rd byte must follow */
                                        if (i > (RxCount - 3)) {
                                                dbg("Illegal escape sequences "
                                                "in received data");
                                                break;
                                        }
                                        qt2_process_xmit_flush(active);
                                        i += 2;
                                        escapeflag = true;
                                        break;
                                case 0xff:
                                        dbg("No status sequence");
                                        qt2_process_rx_char(active, THISCHAR);
                                        qt2_process_rx_char(active, NEXTCHAR);
                                        i += 2;
                                        break;
                                default:
                                        qt2_process_rx_char(active, THISCHAR);
                                        i += 1;
                                        break;
                                } /*end switch*/
                                if (escapeflag == true)
                                        continue;
                                /* if we did an escape char, we don't need
                                 * to mess around pushing data through the
                                 * tty layer, and can go round again */
                        } /*endif*/
                        if (tty_st && urb->actual_length) {
                                tty_buffer_request_room(tty_st, 1);
                                tty_insert_flip_string(tty_st, &(
                                                (unsigned char *)
                                                (urb->transfer_buffer)
                                        )[i], 1);
                        }
                } /*endfor*/
                tty_flip_buffer_push(tty_st);
        } /*endif*/

        /* at this point we have complete dealing with the data for this
         * callback. All we have to do now is to start the async read process
         * back off again. */

        usb_fill_bulk_urb(port0->read_urb, serial->dev,
                usb_rcvbulkpipe(serial->dev, port0->bulk_in_endpointAddress),
                port0->bulk_in_buffer, port0->bulk_in_size,
                qt2_read_bulk_callback, serial);
        result = usb_submit_urb(port0->read_urb, GFP_ATOMIC);
        if (result) {
                dbg("%s(): failed resubmitting read urb, error %d",
                        __func__, result);
        } else {
                dbg("%s() successfully resubmitted read urb", __func__);
                if (tty_st && RxCount) {
                        /* if some inbound data was processed, then
                         * we need to push that through the tty layer
                         */
                        tty_flip_buffer_push(tty_st);
                        tty_schedule_flip(tty_st);
                }
        }

        /* cribbed from serqt_usb2 driver, but not sure which work needs
         * scheduling - port0 or currently active port? */
        /* schedule_work(&port->work); */
        dbg("%s() completed", __func__);
        return;
}

/** @brief Callback for asynchronous submission of write URBs on bulk in
 * endpoints
 *
 * Registered in qt2_write(), used to deal with outgoing data
 * to the box.
 */
static void qt2_write_bulk_callback(struct urb *urb)
{
        struct usb_serial_port *port = (struct usb_serial_port *)urb->context;
        struct usb_serial *serial = port->serial;
        dbg("%s(): port %d", __func__, port->number);
        if (!serial) {
                dbg("%s(): bad serial pointer, exiting", __func__);
                return;
        }
        if (urb->status) {
                dbg("%s(): nonzero write bulk status received: %d",
                        __func__, urb->status);
                return;
        }
        /* FIXME What is supposed to be going on here?
         * does this actually do anything useful, and should it?
         */
        /*port_softint((void *) serial); commented in vendor driver */
        schedule_work(&port->work);
        dbg("%s(): port %d exit", __func__, port->number);
        return;
}

static void qt2_process_line_status(struct usb_serial_port *port,
        unsigned char LineStatus)
{
        /* obtain the private structure for the port */
        struct quatech2_port *port_extra = qt2_get_port_private(port);
        port_extra->shadowLSR = LineStatus & (QT2_SERIAL_LSR_OE |
                QT2_SERIAL_LSR_PE | QT2_SERIAL_LSR_FE | QT2_SERIAL_LSR_BI);
}
static void qt2_process_modem_status(struct usb_serial_port *port,
        unsigned char ModemStatus)
{
        /* obtain the private structure for the port */
        struct quatech2_port *port_extra = qt2_get_port_private(port);
        port_extra->shadowMSR = ModemStatus;
        wake_up_interruptible(&port_extra->wait);
        /* this wakes up the otherwise indefinitely waiting code for
         * the TIOCMIWAIT ioctl, so that it can notice that
         * port_extra->shadowMSR has changed and the ioctl needs to return.
         */
}

static void qt2_process_xmit_empty(struct usb_serial_port *port,
        unsigned char fourth_char, unsigned char fifth_char)
{
        int byte_count;
        /* obtain the private structure for the port */
        struct quatech2_port *port_extra = qt2_get_port_private(port);

        byte_count = (int)(fifth_char * 16);
        byte_count +=  (int)fourth_char;
        /* byte_count indicates how many bytes the device has written out. This
         * message appears to occur regularly, and is used in the vendor driver
         * to keep track of the fill state of the port transmit buffer */
        port_extra->tx_pending_bytes -= byte_count;
        /* reduce the stored data queue length by the known number of bytes
         * sent */
        dbg("port %d: %d bytes reported sent, %d still pending", port->number,
                        byte_count, port_extra->tx_pending_bytes);

        /*port_extra->xmit_fifo_room_bytes = FIFO_DEPTH; ???*/
}

static void qt2_process_port_change(struct usb_serial_port *port,
        unsigned char New_Current_Port)
{
        /* obtain the parent usb serial device structure */
        struct usb_serial *serial = port->serial;
        /* obtain the private structure for the device */
        struct quatech2_dev *dev_extra = qt2_get_dev_private(serial);
        dev_extra->current_port = serial->port[New_Current_Port];
        /* what should I do with this? commented out in upstream
         * driver */
        /*schedule_work(&port->work);*/
}

static void qt2_process_rcv_flush(struct usb_serial_port *port)
{
        /* obtain the private structure for the port */
        struct quatech2_port *port_extra = qt2_get_port_private(port);
        port_extra->rcv_flush = true;
}
static void qt2_process_xmit_flush(struct usb_serial_port *port)
{
        /* obtain the private structure for the port */
        struct quatech2_port *port_extra = qt2_get_port_private(port);
        port_extra->xmit_flush = true;
}

static void qt2_process_rx_char(struct usb_serial_port *port,
        unsigned char data)
{
        /* get the tty_struct for this port */
        struct tty_struct *tty = tty_port_tty_get(&(port->port));
        /* get the URB with the data in to push */
        struct urb *urb = port->serial->port[0]->read_urb;

        if (tty && urb->actual_length) {
                tty_buffer_request_room(tty, 1);
                tty_insert_flip_string(tty, &data, 1);
                /* should this be commented out here? */
                /*tty_flip_buffer_push(tty);*/
        }
}

/** @brief Retrieve the value of a register from the device
 *
 * Issues a GET_REGISTER vendor-spcific request over the USB control
 * pipe to obtain a value back from a specific register on a specific
 * UART
 * @param serial Serial device handle to access the device through
 * @param uart_number Which UART the value is wanted from
 * @param register_num Which register to read the value from
 * @param pValue Pointer to somewhere to put the retrieved value
 */
static int qt2_box_get_register(struct usb_serial *serial,
                unsigned char uart_number, unsigned short register_num,
                __u8 *pValue)
{
        int result;
        result = usb_control_msg(serial->dev, usb_rcvctrlpipe(serial->dev, 0),
                        QT2_GET_SET_REGISTER, 0xC0, register_num,
                        uart_number, (void *)pValue, sizeof(*pValue), 300);
        return result;
}

/** qt2_box_set_register
 * Issue a SET_REGISTER vendor-specific request on the default control pipe
 */
static int qt2_box_set_register(struct usb_serial *serial,
                unsigned short Uart_Number, unsigned short Register_Num,
                unsigned short Value)
{
        int result;
        unsigned short reg_and_byte;

        reg_and_byte = Value;
        reg_and_byte = reg_and_byte << 8;
        reg_and_byte = reg_and_byte + Register_Num;

        result = usb_control_msg(serial->dev, usb_sndctrlpipe(serial->dev, 0),
                        QT2_GET_SET_REGISTER, 0x40, reg_and_byte,
                        Uart_Number, NULL, 0, 300);
        return result;
}

/** qt2_boxsetuart - Issue a SET_UART vendor-spcific request on the default
 * control pipe. If successful sets baud rate divisor and LCR value.
 */
static int qt2_boxsetuart(struct usb_serial *serial, unsigned short Uart_Number,
                unsigned short default_divisor, unsigned char default_LCR)
{
        unsigned short UartNumandLCR;

        UartNumandLCR = (default_LCR << 8) + Uart_Number;

        return usb_control_msg(serial->dev, usb_sndctrlpipe(serial->dev, 0),
                        QT2_GET_SET_UART, 0x40, default_divisor, UartNumandLCR,
                        NULL, 0, 300);
}

/** qt2_boxsethw_flowctl - Turn hardware (RTS/CTS) flow control on and off for
 * a hardware UART.
 */
static int qt2_boxsethw_flowctl(struct usb_serial *serial,
                unsigned int UartNumber, bool bSet)
{
        __u8 MCR_Value = 0;
        __u8 MSR_Value = 0;
        __u16 MOUT_Value = 0;

        if (bSet == true) {
                MCR_Value =  QT2_SERIAL_MCR_RTS;
                /* flow control, box will clear RTS line to prevent remote
                 * device from transmitting more chars */
        } else {
                /* no flow control to remote device */
                MCR_Value =  0;
        }
        MOUT_Value = MCR_Value << 8;

        if (bSet == true) {
                MSR_Value = QT2_SERIAL_MSR_CTS;
                /* flow control on, box will inhibit tx data if CTS line is
                 * asserted */
        } else {
                /* Box will not inhibit tx data due to CTS line */
                MSR_Value = 0;
        }
        MOUT_Value |= MSR_Value;
        return usb_control_msg(serial->dev, usb_sndctrlpipe(serial->dev, 0),
                        QT2_HW_FLOW_CONTROL_MASK, 0x40, MOUT_Value, UartNumber,
                        NULL, 0, 300);
}

/** qt2_boxsetsw_flowctl - Turn software (XON/XOFF) flow control on for
 * a hardware UART, and set the XON and XOFF characters.
 */
static int qt2_boxsetsw_flowctl(struct usb_serial *serial, __u16 UartNumber,
                        unsigned char stop_char,  unsigned char start_char)
{
        __u16 nSWflowout;

        nSWflowout = start_char << 8;
        nSWflowout = (unsigned short)stop_char;
        return usb_control_msg(serial->dev, usb_sndctrlpipe(serial->dev, 0),
                        QT2_SW_FLOW_CONTROL_MASK, 0x40, nSWflowout, UartNumber,
                        NULL, 0, 300);
}

/** qt2_boxunsetsw_flowctl - Turn software (XON/XOFF) flow control off for
 * a hardware UART.
 */
static int qt2_boxunsetsw_flowctl(struct usb_serial *serial, __u16 UartNumber)
{
        return usb_control_msg(serial->dev, usb_sndctrlpipe(serial->dev, 0),
                        QT2_SW_FLOW_CONTROL_DISABLE, 0x40, 0, UartNumber, NULL,
                        0, 300);
}

/**
 * qt2_boxstoprx - Start and stop reception of data by the FPGA UART in
 * response to requests from the tty layer
 * @serial: pointer to the usb_serial structure for the parent device
 * @uart_number: which UART on the device we are addressing
 * @stop: Whether to start or stop data reception. Set to 1 to stop data being
 * received, and to 0 to start it being received.
 */
static int qt2_boxstoprx(struct usb_serial *serial, unsigned short uart_number,
                unsigned short stop)
{
        return usb_control_msg(serial->dev, usb_sndctrlpipe(serial->dev, 0),
                QT2_STOP_RECEIVE, 0x40, stop, uart_number, NULL, 0, 300);
}


/*
 * last things in file: stuff to register this driver into the generic
 * USB serial framework.
 */

static struct usb_serial_driver quatech2_device = {
        .driver = {
                .owner = THIS_MODULE,
                .name = "quatech_usb2",
        },
        .description = DRIVER_DESC,
        .id_table = quausb2_id_table,
        .num_ports = 8,
        .open = qt2_open,
        .close = qt2_close,
        .write = qt2_write,
        .write_room = qt2_write_room,
        .chars_in_buffer = qt2_chars_in_buffer,
        .throttle = qt2_throttle,
        .unthrottle = qt2_unthrottle,
        .calc_num_ports = qt2_calc_num_ports,
        .ioctl = qt2_ioctl,
        .set_termios = qt2_set_termios,
        .break_ctl = qt2_break,
        .tiocmget = qt2_tiocmget,
        .tiocmset = qt2_tiocmset,
        .attach = qt2_attach,
        .release = qt2_release,
        .read_bulk_callback = qt2_read_bulk_callback,
        .write_bulk_callback = qt2_write_bulk_callback,
};

static struct usb_serial_driver * const serial_drivers[] = {
        &quatech2_device, NULL
};

module_usb_serial_driver(quausb2_usb_driver, serial_drivers);

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

module_param(debug, bool, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(debug, "Debug enabled or not");