/*
 * Ours Technology Inc. OTi-6858 USB to serial adapter driver.
 *
 * Copyleft  (C) 2007 Kees Lemmens (adapted for kernel 2.6.20)
 * Copyright (C) 2006 Tomasz Michal Lukaszewski (FIXME: add e-mail)
 * Copyright (C) 2001-2004 Greg Kroah-Hartman (greg@kroah.com)
 * Copyright (C) 2003 IBM Corp.
 *
 * Many thanks to the authors of pl2303 driver: all functions in this file
 * are heavily based on pl2303 code, buffering code is a 1-to-1 copy.
 *
 * Warning! You use this driver on your own risk! The only official
 * description of this device I have is datasheet from manufacturer,
 * and it doesn't contain almost any information needed to write a driver.
 * Almost all knowlegde used while writing this driver was gathered by:
 *  - analyzing traffic between device and the M$ Windows 2000 driver,
 *  - trying different bit combinations and checking pin states
 *    with a voltmeter,
 *  - receiving malformed frames and producing buffer overflows
 *    to learn how errors are reported,
 * So, THIS CODE CAN DESTROY OTi-6858 AND ANY OTHER DEVICES, THAT ARE
 * CONNECTED TO IT!
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License.
 *
 * See Documentation/usb/usb-serial.txt for more information on using this driver
 *
 * TODO:
 *  - implement correct flushing for ioctls and oti6858_close()
 *  - check how errors (rx overflow, parity error, framing error) are reported
 *  - implement oti6858_break_ctl()
 *  - implement more ioctls
 *  - test/implement flow control
 *  - allow setting custom baud rates
 */

#include <linux/kernel.h>
#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/serial.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/spinlock.h>
#include <linux/usb.h>
#include <linux/usb/serial.h>
#include <asm/uaccess.h>
#include "oti6858.h"

#define OTI6858_DESCRIPTION \
        "Ours Technology Inc. OTi-6858 USB to serial adapter driver"
#define OTI6858_AUTHOR "Tomasz Michal Lukaszewski <FIXME@FIXME>"
#define OTI6858_VERSION "0.1"

static struct usb_device_id id_table [] = {
        { USB_DEVICE(OTI6858_VENDOR_ID, OTI6858_PRODUCT_ID) },
        { }
};

MODULE_DEVICE_TABLE(usb, id_table);

static struct usb_driver oti6858_driver = {
        .name =         "oti6858",
        .probe =        usb_serial_probe,
        .disconnect =   usb_serial_disconnect,
        .id_table =     id_table,
        .no_dynamic_id =        1,
};

static int debug;


/* buffering code, copied from pl2303 driver */
#define PL2303_BUF_SIZE         1024
#define PL2303_TMP_BUF_SIZE     1024

struct oti6858_buf {
        unsigned int    buf_size;
        char            *buf_buf;
        char            *buf_get;
        char            *buf_put;
};

/* requests */
#define OTI6858_REQ_GET_STATUS          (USB_DIR_IN | USB_TYPE_VENDOR | 0x00)
#define OTI6858_REQ_T_GET_STATUS        0x01

#define OTI6858_REQ_SET_LINE            (USB_DIR_OUT | USB_TYPE_VENDOR | 0x00)
#define OTI6858_REQ_T_SET_LINE          0x00

#define OTI6858_REQ_CHECK_TXBUFF        (USB_DIR_IN | USB_TYPE_VENDOR | 0x01)
#define OTI6858_REQ_T_CHECK_TXBUFF      0x00

/* format of the control packet */
struct oti6858_control_pkt {
        u16     divisor;        /* baud rate = 96000000 / (16 * divisor), LE */
#define OTI6858_MAX_BAUD_RATE   3000000
        u8      frame_fmt;
#define FMT_STOP_BITS_MASK      0xc0
#define FMT_STOP_BITS_1         0x00
#define FMT_STOP_BITS_2         0x40    /* 1.5 stop bits if FMT_DATA_BITS_5 */
#define FMT_PARITY_MASK         0x38
#define FMT_PARITY_NONE         0x00
#define FMT_PARITY_ODD          0x08
#define FMT_PARITY_EVEN         0x18
#define FMT_PARITY_MARK         0x28
#define FMT_PARITY_SPACE        0x38
#define FMT_DATA_BITS_MASK      0x03
#define FMT_DATA_BITS_5         0x00
#define FMT_DATA_BITS_6         0x01
#define FMT_DATA_BITS_7         0x02
#define FMT_DATA_BITS_8         0x03
        u8      something;      /* always equals 0x43 */
        u8      control;        /* settings of flow control lines */
#define CONTROL_MASK            0x0c
#define CONTROL_DTR_HIGH        0x08
#define CONTROL_RTS_HIGH        0x04
        u8      tx_status;
#define TX_BUFFER_EMPTIED       0x09
        u8      pin_state;
#define PIN_MASK                0x3f
#define PIN_RTS                 0x20    /* output pin */
#define PIN_CTS                 0x10    /* input pin, active low */
#define PIN_DSR                 0x08    /* input pin, active low */
#define PIN_DTR                 0x04    /* output pin */
#define PIN_RI                  0x02    /* input pin, active low */
#define PIN_DCD                 0x01    /* input pin, active low */
        u8      rx_bytes_avail;         /* number of bytes in rx buffer */;
};

#define OTI6858_CTRL_PKT_SIZE   sizeof(struct oti6858_control_pkt)
#define OTI6858_CTRL_EQUALS_PENDING(a, priv) \
        (    ((a)->divisor == (priv)->pending_setup.divisor) \
          && ((a)->control == (priv)->pending_setup.control) \
          && ((a)->frame_fmt == (priv)->pending_setup.frame_fmt) )

/* function prototypes */
static int oti6858_open(struct usb_serial_port *port, struct file *filp);
static void oti6858_close(struct usb_serial_port *port, struct file *filp);
static void oti6858_set_termios(struct usb_serial_port *port,
                                struct ktermios *old);
static int oti6858_ioctl(struct usb_serial_port *port, struct file *file,
                        unsigned int cmd, unsigned long arg);
static void oti6858_read_int_callback(struct urb *urb);
static void oti6858_read_bulk_callback(struct urb *urb);
static void oti6858_write_bulk_callback(struct urb *urb);
static int oti6858_write(struct usb_serial_port *port,
                        const unsigned char *buf, int count);
static int oti6858_write_room(struct usb_serial_port *port);
static void oti6858_break_ctl(struct usb_serial_port *port, int break_state);
static int oti6858_chars_in_buffer(struct usb_serial_port *port);
static int oti6858_tiocmget(struct usb_serial_port *port, struct file *file);
static int oti6858_tiocmset(struct usb_serial_port *port, struct file *file,
                                unsigned int set, unsigned int clear);
static int oti6858_startup(struct usb_serial *serial);
static void oti6858_shutdown(struct usb_serial *serial);

/* functions operating on buffers */
static struct oti6858_buf *oti6858_buf_alloc(unsigned int size);
static void oti6858_buf_free(struct oti6858_buf *pb);
static void oti6858_buf_clear(struct oti6858_buf *pb);
static unsigned int oti6858_buf_data_avail(struct oti6858_buf *pb);
static unsigned int oti6858_buf_space_avail(struct oti6858_buf *pb);
static unsigned int oti6858_buf_put(struct oti6858_buf *pb, const char *buf,
                                        unsigned int count);
static unsigned int oti6858_buf_get(struct oti6858_buf *pb, char *buf,
                                        unsigned int count);


/* device info */
static struct usb_serial_driver oti6858_device = {
        .driver = {
                .owner =        THIS_MODULE,
                .name =         "oti6858",
        },
        .id_table =             id_table,
        .num_interrupt_in =     1,
        .num_bulk_in =          1,
        .num_bulk_out =         1,
        .num_ports =            1,
        .open =                 oti6858_open,
        .close =                oti6858_close,
        .write =                oti6858_write,
        .ioctl =                oti6858_ioctl,
        .break_ctl =            oti6858_break_ctl,
        .set_termios =          oti6858_set_termios,
        .tiocmget =             oti6858_tiocmget,
        .tiocmset =             oti6858_tiocmset,
        .read_bulk_callback =   oti6858_read_bulk_callback,
        .read_int_callback =    oti6858_read_int_callback,
        .write_bulk_callback =  oti6858_write_bulk_callback,
        .write_room =           oti6858_write_room,
        .chars_in_buffer =      oti6858_chars_in_buffer,
        .attach =               oti6858_startup,
        .shutdown =             oti6858_shutdown,
};

struct oti6858_private {
        spinlock_t lock;

        struct oti6858_buf *buf;
        struct oti6858_control_pkt status;

        struct {
                u8 read_urb_in_use;
                u8 write_urb_in_use;
                u8 termios_initialized;
        } flags;
        struct delayed_work delayed_write_work;

        struct {
                u16 divisor;
                u8 frame_fmt;
                u8 control;
        } pending_setup;
        u8 transient;
        u8 setup_done;
        struct delayed_work delayed_setup_work;

        wait_queue_head_t intr_wait;
        struct usb_serial_port *port;   /* USB port with which associated */
};

#undef dbg
/* #define dbg(format, arg...) printk(KERN_INFO "%s: " format "\n", __FILE__, ## arg) */
#define dbg(format, arg...) printk(KERN_INFO "" format "\n", ## arg)

static void setup_line(struct work_struct *work)
{
        struct oti6858_private *priv = container_of(work, struct oti6858_private, delayed_setup_work.work);
        struct usb_serial_port *port = priv->port;
        struct oti6858_control_pkt *new_setup;
        unsigned long flags;
        int result;

        dbg("%s(port = %d)", __FUNCTION__, port->number);

        if ((new_setup = kmalloc(OTI6858_CTRL_PKT_SIZE, GFP_KERNEL)) == NULL) {
                dev_err(&port->dev, "%s(): out of memory!\n", __FUNCTION__);
                /* we will try again */
                schedule_delayed_work(&priv->delayed_setup_work, msecs_to_jiffies(2));
                return;
        }

        result = usb_control_msg(port->serial->dev,
                                usb_rcvctrlpipe(port->serial->dev, 0),
                                OTI6858_REQ_T_GET_STATUS,
                                OTI6858_REQ_GET_STATUS,
                                0, 0,
                                new_setup, OTI6858_CTRL_PKT_SIZE,
                                100);

        if (result != OTI6858_CTRL_PKT_SIZE) {
                dev_err(&port->dev, "%s(): error reading status\n", __FUNCTION__);
                kfree(new_setup);
                /* we will try again */
                schedule_delayed_work(&priv->delayed_setup_work, msecs_to_jiffies(2));
                return;
        }

        spin_lock_irqsave(&priv->lock, flags);
        if (!OTI6858_CTRL_EQUALS_PENDING(new_setup, priv)) {
                new_setup->divisor = priv->pending_setup.divisor;
                new_setup->control = priv->pending_setup.control;
                new_setup->frame_fmt = priv->pending_setup.frame_fmt;

                spin_unlock_irqrestore(&priv->lock, flags);
                result = usb_control_msg(port->serial->dev,
                                        usb_sndctrlpipe(port->serial->dev, 0),
                                        OTI6858_REQ_T_SET_LINE,
                                        OTI6858_REQ_SET_LINE,
                                        0, 0,
                                        new_setup, OTI6858_CTRL_PKT_SIZE,
                                        100);
        } else {
                spin_unlock_irqrestore(&priv->lock, flags);
                result = 0;
        }
        kfree(new_setup);

        spin_lock_irqsave(&priv->lock, flags);
        if (result != OTI6858_CTRL_PKT_SIZE)
                priv->transient = 0;
        priv->setup_done = 1;
        spin_unlock_irqrestore(&priv->lock, flags);

        dbg("%s(): submitting interrupt urb", __FUNCTION__);
        port->interrupt_in_urb->dev = port->serial->dev;
        result = usb_submit_urb(port->interrupt_in_urb, GFP_ATOMIC);
        if (result != 0) {
                dev_err(&port->dev, "%s(): usb_submit_urb() failed"
                                " with error %d\n", __FUNCTION__, result);
        }
}

void send_data(struct work_struct *work)
{
        struct oti6858_private *priv = container_of(work, struct oti6858_private, delayed_write_work.work);
        struct usb_serial_port *port = priv->port;
        int count = 0, result;
        unsigned long flags;
        unsigned char allow;

        dbg("%s(port = %d)", __FUNCTION__, port->number);

        spin_lock_irqsave(&priv->lock, flags);
        if (priv->flags.write_urb_in_use) {
                spin_unlock_irqrestore(&priv->lock, flags);
                schedule_delayed_work(&priv->delayed_write_work, msecs_to_jiffies(2));
                return;
        }
        priv->flags.write_urb_in_use = 1;

        count = oti6858_buf_data_avail(priv->buf);
        spin_unlock_irqrestore(&priv->lock, flags);
        if (count > port->bulk_out_size)
                count = port->bulk_out_size;

        if (count != 0) {
                result = usb_control_msg(port->serial->dev,
                                usb_rcvctrlpipe(port->serial->dev, 0),
                                OTI6858_REQ_T_CHECK_TXBUFF,
                                OTI6858_REQ_CHECK_TXBUFF,
                                count, 0, &allow, 1, 100);
                if (result != 1 || allow != 0)
                        count = 0;
        }

        if (count == 0) {
                priv->flags.write_urb_in_use = 0;

                dbg("%s(): submitting interrupt urb", __FUNCTION__);
                port->interrupt_in_urb->dev = port->serial->dev;
                result = usb_submit_urb(port->interrupt_in_urb, GFP_ATOMIC);
                if (result != 0) {
                        dev_err(&port->dev, "%s(): usb_submit_urb() failed"
                                " with error %d\n", __FUNCTION__, result);
                }
                return;
        }

        spin_lock_irqsave(&priv->lock, flags);
        oti6858_buf_get(priv->buf, port->write_urb->transfer_buffer, count);
        spin_unlock_irqrestore(&priv->lock, flags);

        port->write_urb->transfer_buffer_length = count;
        port->write_urb->dev = port->serial->dev;
        result = usb_submit_urb(port->write_urb, GFP_ATOMIC);
        if (result != 0) {
                dev_err(&port->dev, "%s(): usb_submit_urb() failed"
                               " with error %d\n", __FUNCTION__, result);
                priv->flags.write_urb_in_use = 0;
        }

        usb_serial_port_softint(port);
}

static int oti6858_startup(struct usb_serial *serial)
{
        struct usb_serial_port *port = serial->port[0];
        struct oti6858_private *priv;
        int i;

        for (i = 0; i < serial->num_ports; ++i) {
                priv = kzalloc(sizeof(struct oti6858_private), GFP_KERNEL);
                if (!priv)
                        break;
                priv->buf = oti6858_buf_alloc(PL2303_BUF_SIZE);
                if (priv->buf == NULL) {
                        kfree(priv);
                        break;
                }

                spin_lock_init(&priv->lock);
                init_waitqueue_head(&priv->intr_wait);
//              INIT_WORK(&priv->setup_work, setup_line, serial->port[i]);
//              INIT_WORK(&priv->write_work, send_data, serial->port[i]);
                priv->port = port;
                INIT_DELAYED_WORK(&priv->delayed_setup_work, setup_line);
                INIT_DELAYED_WORK(&priv->delayed_write_work, send_data);

                usb_set_serial_port_data(serial->port[i], priv);
        }
        if (i == serial->num_ports)
                return 0;

        for (--i; i >= 0; --i) {
                priv = usb_get_serial_port_data(serial->port[i]);
                oti6858_buf_free(priv->buf);
                kfree(priv);
                usb_set_serial_port_data(serial->port[i], NULL);
        }
        return -ENOMEM;
}

static int oti6858_write(struct usb_serial_port *port,
                        const unsigned char *buf, int count)
{
        struct oti6858_private *priv = usb_get_serial_port_data(port);
        unsigned long flags;

        dbg("%s(port = %d, count = %d)", __FUNCTION__, port->number, count);

        if (!count)
                return count;

        spin_lock_irqsave(&priv->lock, flags);
        count = oti6858_buf_put(priv->buf, buf, count);
        spin_unlock_irqrestore(&priv->lock, flags);

        return count;
}

static int oti6858_write_room(struct usb_serial_port *port)
{
        struct oti6858_private *priv = usb_get_serial_port_data(port);
        int room = 0;
        unsigned long flags;

        dbg("%s(port = %d)", __FUNCTION__, port->number);

        spin_lock_irqsave(&priv->lock, flags);
        room = oti6858_buf_space_avail(priv->buf);
        spin_unlock_irqrestore(&priv->lock, flags);

        return room;
}

static int oti6858_chars_in_buffer(struct usb_serial_port *port)
{
        struct oti6858_private *priv = usb_get_serial_port_data(port);
        int chars = 0;
        unsigned long flags;

        dbg("%s(port = %d)", __FUNCTION__, port->number);

        spin_lock_irqsave(&priv->lock, flags);
        chars = oti6858_buf_data_avail(priv->buf);
        spin_unlock_irqrestore(&priv->lock, flags);

        return chars;
}

static void oti6858_set_termios(struct usb_serial_port *port,
                                struct ktermios *old_termios)
{
        struct oti6858_private *priv = usb_get_serial_port_data(port);
        unsigned long flags;
        unsigned int cflag;
        u8 frame_fmt, control;
        u16 divisor;
        int br;

        dbg("%s(port = %d)", __FUNCTION__, port->number);

        if (!port->tty || !port->tty->termios) {
                dbg("%s(): no tty structures", __FUNCTION__);
                return;
        }

        spin_lock_irqsave(&priv->lock, flags);
        if (!priv->flags.termios_initialized) {
                *(port->tty->termios) = tty_std_termios;
                port->tty->termios->c_cflag = B38400 | CS8 | CREAD | HUPCL | CLOCAL;
                priv->flags.termios_initialized = 1;
                port->tty->termios->c_ispeed = 38400;
                port->tty->termios->c_ospeed = 38400;
        }
        spin_unlock_irqrestore(&priv->lock, flags);

        cflag = port->tty->termios->c_cflag;

        spin_lock_irqsave(&priv->lock, flags);
        divisor = priv->pending_setup.divisor;
        frame_fmt = priv->pending_setup.frame_fmt;
        control = priv->pending_setup.control;
        spin_unlock_irqrestore(&priv->lock, flags);

        frame_fmt &= ~FMT_DATA_BITS_MASK;
        switch (cflag & CSIZE) {
                case CS5:
                        frame_fmt |= FMT_DATA_BITS_5;
                        break;
                case CS6:
                        frame_fmt |= FMT_DATA_BITS_6;
                        break;
                case CS7:
                        frame_fmt |= FMT_DATA_BITS_7;
                        break;
                default:
                case CS8:
                        frame_fmt |= FMT_DATA_BITS_8;
                        break;
        }

        /* manufacturer claims that this device can work with baud rates
         * up to 3 Mbps; I've tested it only on 115200 bps, so I can't
         * guarantee that any other baud rate will work (especially
         * the higher ones)
         */
        br = tty_get_baud_rate(port->tty);
        if (br == 0) {
                divisor = 0;
        } else {
                int real_br;
                br = min(br, OTI6858_MAX_BAUD_RATE);

                divisor = (96000000 + 8 * br) / (16 * br);
                real_br = 96000000 / (16 * divisor);
                divisor = cpu_to_le16(divisor);
                tty_encode_baud_rate(port->tty, real_br, real_br);
        }

        frame_fmt &= ~FMT_STOP_BITS_MASK;
        if ((cflag & CSTOPB) != 0) {
                frame_fmt |= FMT_STOP_BITS_2;
        } else {
                frame_fmt |= FMT_STOP_BITS_1;
        }

        frame_fmt &= ~FMT_PARITY_MASK;
        if ((cflag & PARENB) != 0) {
                if ((cflag & PARODD) != 0) {
                        frame_fmt |= FMT_PARITY_ODD;
                } else {
                        frame_fmt |= FMT_PARITY_EVEN;
                }
        } else {
                frame_fmt |= FMT_PARITY_NONE;
        }

        control &= ~CONTROL_MASK;
        if ((cflag & CRTSCTS) != 0)
                control |= (CONTROL_DTR_HIGH | CONTROL_RTS_HIGH);

        /* change control lines if we are switching to or from B0 */
        /* FIXME:
        spin_lock_irqsave(&priv->lock, flags);
        control = priv->line_control;
        if ((cflag & CBAUD) == B0)
                priv->line_control &= ~(CONTROL_DTR | CONTROL_RTS);
        else
                priv->line_control |= (CONTROL_DTR | CONTROL_RTS);
        if (control != priv->line_control) {
                control = priv->line_control;
                spin_unlock_irqrestore(&priv->lock, flags);
                set_control_lines(serial->dev, control);
        } else {
                spin_unlock_irqrestore(&priv->lock, flags);
        }
        */

        spin_lock_irqsave(&priv->lock, flags);
        if (divisor != priv->pending_setup.divisor
                        || control != priv->pending_setup.control
                        || frame_fmt != priv->pending_setup.frame_fmt) {
                priv->pending_setup.divisor = divisor;
                priv->pending_setup.control = control;
                priv->pending_setup.frame_fmt = frame_fmt;
        }
        spin_unlock_irqrestore(&priv->lock, flags);
}

static int oti6858_open(struct usb_serial_port *port, struct file *filp)
{
        struct oti6858_private *priv = usb_get_serial_port_data(port);
        struct ktermios tmp_termios;
        struct usb_serial *serial = port->serial;
        struct oti6858_control_pkt *buf;
        unsigned long flags;
        int result;

        dbg("%s(port = %d)", __FUNCTION__, port->number);

        usb_clear_halt(serial->dev, port->write_urb->pipe);
        usb_clear_halt(serial->dev, port->read_urb->pipe);

        if (port->open_count != 1)
                return 0;

        if ((buf = kmalloc(OTI6858_CTRL_PKT_SIZE, GFP_KERNEL)) == NULL) {
                dev_err(&port->dev, "%s(): out of memory!\n", __FUNCTION__);
                return -ENOMEM;
        }

        result = usb_control_msg(serial->dev, usb_rcvctrlpipe(serial->dev, 0),
                                OTI6858_REQ_T_GET_STATUS,
                                OTI6858_REQ_GET_STATUS,
                                0, 0,
                                buf, OTI6858_CTRL_PKT_SIZE,
                                100);
        if (result != OTI6858_CTRL_PKT_SIZE) {
                /* assume default (after power-on reset) values */
                buf->divisor = cpu_to_le16(0x009c);     /* 38400 bps */
                buf->frame_fmt = 0x03;  /* 8N1 */
                buf->something = 0x43;
                buf->control = 0x4c;    /* DTR, RTS */
                buf->tx_status = 0x00;
                buf->pin_state = 0x5b;  /* RTS, CTS, DSR, DTR, RI, DCD */
                buf->rx_bytes_avail = 0x00;
        }

        spin_lock_irqsave(&priv->lock, flags);
        memcpy(&priv->status, buf, OTI6858_CTRL_PKT_SIZE);
        priv->pending_setup.divisor = buf->divisor;
        priv->pending_setup.frame_fmt = buf->frame_fmt;
        priv->pending_setup.control = buf->control;
        spin_unlock_irqrestore(&priv->lock, flags);
        kfree(buf);

        dbg("%s(): submitting interrupt urb", __FUNCTION__);
        port->interrupt_in_urb->dev = serial->dev;
        result = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
        if (result != 0) {
                dev_err(&port->dev, "%s(): usb_submit_urb() failed"
                               " with error %d\n", __FUNCTION__, result);
                oti6858_close(port, NULL);
                return -EPROTO;
        }

        /* setup termios */
        if (port->tty)
                oti6858_set_termios(port, &tmp_termios);

        return 0;
}

static void oti6858_close(struct usb_serial_port *port, struct file *filp)
{
        struct oti6858_private *priv = usb_get_serial_port_data(port);
        unsigned long flags;
        long timeout;
        wait_queue_t wait;

        dbg("%s(port = %d)", __FUNCTION__, port->number);

        /* wait for data to drain from the buffer */
        spin_lock_irqsave(&priv->lock, flags);
        timeout = 30 * HZ;      /* PL2303_CLOSING_WAIT */
        init_waitqueue_entry(&wait, current);
        add_wait_queue(&port->tty->write_wait, &wait);
        dbg("%s(): entering wait loop", __FUNCTION__);
        for (;;) {
                set_current_state(TASK_INTERRUPTIBLE);
                if (oti6858_buf_data_avail(priv->buf) == 0
                || timeout == 0 || signal_pending(current)
                || port->serial->disconnected)
                        break;
                spin_unlock_irqrestore(&priv->lock, flags);
                timeout = schedule_timeout(timeout);
                spin_lock_irqsave(&priv->lock, flags);
        }
        set_current_state(TASK_RUNNING);
        remove_wait_queue(&port->tty->write_wait, &wait);
        dbg("%s(): after wait loop", __FUNCTION__);

        /* clear out any remaining data in the buffer */
        oti6858_buf_clear(priv->buf);
        spin_unlock_irqrestore(&priv->lock, flags);

        /* wait for characters to drain from the device */
        /* (this is long enough for the entire 256 byte */
        /* pl2303 hardware buffer to drain with no flow */
        /* control for data rates of 1200 bps or more, */
        /* for lower rates we should really know how much */
        /* data is in the buffer to compute a delay */
        /* that is not unnecessarily long) */
        /* FIXME
        bps = tty_get_baud_rate(port->tty);
        if (bps > 1200)
                timeout = max((HZ*2560)/bps,HZ/10);
        else
        */
                timeout = 2*HZ;
        schedule_timeout_interruptible(timeout);
        dbg("%s(): after schedule_timeout_interruptible()", __FUNCTION__);

        /* cancel scheduled setup */
        cancel_delayed_work(&priv->delayed_setup_work);
        cancel_delayed_work(&priv->delayed_write_work);
        flush_scheduled_work();

        /* shutdown our urbs */
        dbg("%s(): shutting down urbs", __FUNCTION__);
        usb_kill_urb(port->write_urb);
        usb_kill_urb(port->read_urb);
        usb_kill_urb(port->interrupt_in_urb);

        /*
        if (port->tty && (port->tty->termios->c_cflag) & HUPCL) {
                // drop DTR and RTS
                spin_lock_irqsave(&priv->lock, flags);
                priv->pending_setup.control &= ~CONTROL_MASK;
                spin_unlock_irqrestore(&priv->lock, flags);
        }
        */
}

static int oti6858_tiocmset(struct usb_serial_port *port, struct file *file,
                                unsigned int set, unsigned int clear)
{
        struct oti6858_private *priv = usb_get_serial_port_data(port);
        unsigned long flags;
        u8 control;

        dbg("%s(port = %d, set = 0x%08x, clear = 0x%08x)",
                                __FUNCTION__, port->number, set, clear);

        if (!usb_get_intfdata(port->serial->interface))
                return -ENODEV;

        /* FIXME: check if this is correct (active high/low) */
        spin_lock_irqsave(&priv->lock, flags);
        control = priv->pending_setup.control;
        if ((set & TIOCM_RTS) != 0)
                control |= CONTROL_RTS_HIGH;
        if ((set & TIOCM_DTR) != 0)
                control |= CONTROL_DTR_HIGH;
        if ((clear & TIOCM_RTS) != 0)
                control &= ~CONTROL_RTS_HIGH;
        if ((clear & TIOCM_DTR) != 0)
                control &= ~CONTROL_DTR_HIGH;

        if (control != priv->pending_setup.control) {
                priv->pending_setup.control = control;
        }
        spin_unlock_irqrestore(&priv->lock, flags);

        return 0;
}

static int oti6858_tiocmget(struct usb_serial_port *port, struct file *file)
{
        struct oti6858_private *priv = usb_get_serial_port_data(port);
        unsigned long flags;
        unsigned pin_state;
        unsigned result = 0;

        dbg("%s(port = %d)", __FUNCTION__, port->number);

        if (!usb_get_intfdata(port->serial->interface))
                return -ENODEV;

        spin_lock_irqsave(&priv->lock, flags);
        pin_state = priv->status.pin_state & PIN_MASK;
        spin_unlock_irqrestore(&priv->lock, flags);

        /* FIXME: check if this is correct (active high/low) */
        if ((pin_state & PIN_RTS) != 0)
                result |= TIOCM_RTS;
        if ((pin_state & PIN_CTS) != 0)
                result |= TIOCM_CTS;
        if ((pin_state & PIN_DSR) != 0)
                result |= TIOCM_DSR;
        if ((pin_state & PIN_DTR) != 0)
                result |= TIOCM_DTR;
        if ((pin_state & PIN_RI) != 0)
                result |= TIOCM_RI;
        if ((pin_state & PIN_DCD) != 0)
                result |= TIOCM_CD;

        dbg("%s() = 0x%08x", __FUNCTION__, result);

        return result;
}

static int wait_modem_info(struct usb_serial_port *port, unsigned int arg)
{
        struct oti6858_private *priv = usb_get_serial_port_data(port);
        unsigned long flags;
        unsigned int prev, status;
        unsigned int changed;

        spin_lock_irqsave(&priv->lock, flags);
        prev = priv->status.pin_state;
        spin_unlock_irqrestore(&priv->lock, flags);

        while (1) {
                wait_event_interruptible(priv->intr_wait, priv->status.pin_state != prev);
                if (signal_pending(current))
                        return -ERESTARTSYS;

                spin_lock_irqsave(&priv->lock, flags);
                status = priv->status.pin_state & PIN_MASK;
                spin_unlock_irqrestore(&priv->lock, flags);

                changed = prev ^ status;
                /* FIXME: check if this is correct (active high/low) */
                if (    ((arg & TIOCM_RNG) && (changed & PIN_RI)) ||
                        ((arg & TIOCM_DSR) && (changed & PIN_DSR)) ||
                        ((arg & TIOCM_CD)  && (changed & PIN_DCD)) ||
                        ((arg & TIOCM_CTS) && (changed & PIN_CTS))) {
                                return 0;
                }
                prev = status;
        }

        /* NOTREACHED */
        return 0;
}

static int oti6858_ioctl(struct usb_serial_port *port, struct file *file,
                        unsigned int cmd, unsigned long arg)
{
        void __user *user_arg = (void __user *) arg;
        unsigned int x;

        dbg("%s(port = %d, cmd = 0x%04x, arg = 0x%08lx)",
                                __FUNCTION__, port->number, cmd, arg);

        switch (cmd) {
                case TCFLSH:
                        /* FIXME */
                        return 0;

                case TIOCMBIS:
                        if (copy_from_user(&x, user_arg, sizeof(x)))
                                return -EFAULT;
                        return oti6858_tiocmset(port, NULL, x, 0);

                case TIOCMBIC:
                        if (copy_from_user(&x, user_arg, sizeof(x)))
                                return -EFAULT;
                        return oti6858_tiocmset(port, NULL, 0, x);

                case TIOCMIWAIT:
                        dbg("%s(): TIOCMIWAIT", __FUNCTION__);
                        return wait_modem_info(port, arg);

                default:
                        dbg("%s(): 0x%04x not supported", __FUNCTION__, cmd);
                        break;
        }

        return -ENOIOCTLCMD;
}

static void oti6858_break_ctl(struct usb_serial_port *port, int break_state)
{
        int state;

        dbg("%s(port = %d)", __FUNCTION__, port->number);

        state = (break_state == 0) ? 0 : 1;
        dbg("%s(): turning break %s", __FUNCTION__, state ? "on" : "off");

        /* FIXME */
/*
        result = usb_control_msg (serial->dev, usb_sndctrlpipe (serial->dev, 0),
                                  BREAK_REQUEST, BREAK_REQUEST_TYPE, state,
                                  0, NULL, 0, 100);
        if (result != 0)
                dbg("%s(): error sending break", __FUNCTION__);
 */
}

static void oti6858_shutdown(struct usb_serial *serial)
{
        struct oti6858_private *priv;
        int i;

        dbg("%s()", __FUNCTION__);

        for (i = 0; i < serial->num_ports; ++i) {
                priv = usb_get_serial_port_data(serial->port[i]);
                if (priv) {
                        oti6858_buf_free(priv->buf);
                        kfree(priv);
                        usb_set_serial_port_data(serial->port[i], NULL);
                }
        }
}

static void oti6858_read_int_callback(struct urb *urb)
{
        struct usb_serial_port *port = (struct usb_serial_port *) urb->context;
        struct oti6858_private *priv = usb_get_serial_port_data(port);
        int transient = 0, can_recv = 0, resubmit = 1;
        int status = urb->status;

        dbg("%s(port = %d, status = %d)",
                                __FUNCTION__, port->number, status);

        switch (status) {
        case 0:
                /* success */
                break;
        case -ECONNRESET:
        case -ENOENT:
        case -ESHUTDOWN:
                /* this urb is terminated, clean up */
                dbg("%s(): urb shutting down with status: %d",
                                        __FUNCTION__, status);
                return;
        default:
                dbg("%s(): nonzero urb status received: %d",
                                        __FUNCTION__, status);
                break;
        }

        if (status == 0 && urb->actual_length == OTI6858_CTRL_PKT_SIZE) {
                struct oti6858_control_pkt *xs = urb->transfer_buffer;
                unsigned long flags;

                spin_lock_irqsave(&priv->lock, flags);

                if (!priv->transient) {
                        if (!OTI6858_CTRL_EQUALS_PENDING(xs, priv)) {
                                if (xs->rx_bytes_avail == 0) {
                                        priv->transient = 4;
                                        priv->setup_done = 0;
                                        resubmit = 0;
                                        dbg("%s(): scheduling setup_line()",
                                            __FUNCTION__);
                                        schedule_delayed_work(&priv->delayed_setup_work, 0);
                                }
                        }
                } else {
                        if (OTI6858_CTRL_EQUALS_PENDING(xs, priv)) {
                                priv->transient = 0;
                        } else if (!priv->setup_done) {
                                resubmit = 0;
                        } else if (--priv->transient == 0) {
                                if (xs->rx_bytes_avail == 0) {
                                        priv->transient = 4;
                                        priv->setup_done = 0;
                                        resubmit = 0;
                                        dbg("%s(): scheduling setup_line()",
                                            __FUNCTION__);
                                        schedule_delayed_work(&priv->delayed_setup_work, 0);
                                }
                        }
                }

                if (!priv->transient) {
                        if (xs->pin_state != priv->status.pin_state)
                                wake_up_interruptible(&priv->intr_wait);
                        memcpy(&priv->status, xs, OTI6858_CTRL_PKT_SIZE);
                }

                if (!priv->transient && xs->rx_bytes_avail != 0) {
                        can_recv = xs->rx_bytes_avail;
                        priv->flags.read_urb_in_use = 1;
                }

                transient = priv->transient;
                spin_unlock_irqrestore(&priv->lock, flags);
        }

        if (can_recv) {
                int result;

                port->read_urb->dev = port->serial->dev;
                result = usb_submit_urb(port->read_urb, GFP_ATOMIC);
                if (result != 0) {
                        priv->flags.read_urb_in_use = 0;
                        dev_err(&port->dev, "%s(): usb_submit_urb() failed,"
                                        " error %d\n", __FUNCTION__, result);
                } else {
                        resubmit = 0;
                }
        } else if (!transient) {
                unsigned long flags;

                spin_lock_irqsave(&priv->lock, flags);
                if (priv->flags.write_urb_in_use == 0
                                && oti6858_buf_data_avail(priv->buf) != 0) {
                        schedule_delayed_work(&priv->delayed_write_work,0);
                        resubmit = 0;
                }
                spin_unlock_irqrestore(&priv->lock, flags);
        }

        if (resubmit) {
                int result;

//              dbg("%s(): submitting interrupt urb", __FUNCTION__);
                urb->dev = port->serial->dev;
                result = usb_submit_urb(urb, GFP_ATOMIC);
                if (result != 0) {
                        dev_err(&urb->dev->dev,
                                        "%s(): usb_submit_urb() failed with"
                                        " error %d\n", __FUNCTION__, result);
                }
        }
}

static void oti6858_read_bulk_callback(struct urb *urb)
{
        struct usb_serial_port *port = (struct usb_serial_port *) urb->context;
        struct oti6858_private *priv = usb_get_serial_port_data(port);
        struct tty_struct *tty;
        unsigned char *data = urb->transfer_buffer;
        unsigned long flags;
        int status = urb->status;

        int result;

        dbg("%s(port = %d, status = %d)",
                                __FUNCTION__, port->number, status);

        spin_lock_irqsave(&priv->lock, flags);
        priv->flags.read_urb_in_use = 0;
        spin_unlock_irqrestore(&priv->lock, flags);

        if (status != 0) {
                if (!port->open_count) {
                        dbg("%s(): port is closed, exiting", __FUNCTION__);
                        return;
                }
                /*
                if (status == -EPROTO) {
                        // PL2303 mysteriously fails with -EPROTO reschedule the read
                        dbg("%s - caught -EPROTO, resubmitting the urb", __FUNCTION__);
                        result = usb_submit_urb(urb, GFP_ATOMIC);
                        if (result)
                                dev_err(&urb->dev->dev, "%s - failed resubmitting read urb, error %d\n", __FUNCTION__, result);
                        return;
                }
                */
                dbg("%s(): unable to handle the error, exiting", __FUNCTION__);
                return;
        }

        tty = port->tty;
        if (tty != NULL && urb->actual_length > 0) {
                tty_insert_flip_string(tty, data, urb->actual_length);
                tty_flip_buffer_push(tty);
        }

        // schedule the interrupt urb if we are still open */
        if (port->open_count != 0) {
                port->interrupt_in_urb->dev = port->serial->dev;
                result = usb_submit_urb(port->interrupt_in_urb, GFP_ATOMIC);
                if (result != 0) {
                        dev_err(&port->dev, "%s(): usb_submit_urb() failed,"
                                        " error %d\n", __FUNCTION__, result);
                }
        }
}

static void oti6858_write_bulk_callback(struct urb *urb)
{
        struct usb_serial_port *port = (struct usb_serial_port *) urb->context;
        struct oti6858_private *priv = usb_get_serial_port_data(port);
        int status = urb->status;
        int result;

        dbg("%s(port = %d, status = %d)",
                                __FUNCTION__, port->number, status);

        switch (status) {
        case 0:
                /* success */
                break;
        case -ECONNRESET:
        case -ENOENT:
        case -ESHUTDOWN:
                /* this urb is terminated, clean up */
                dbg("%s(): urb shutting down with status: %d",
                                        __FUNCTION__, status);
                priv->flags.write_urb_in_use = 0;
                return;
        default:
                /* error in the urb, so we have to resubmit it */
                dbg("%s(): nonzero write bulk status received: %d",
                                        __FUNCTION__, status);
                dbg("%s(): overflow in write", __FUNCTION__);

                port->write_urb->transfer_buffer_length = 1;
                port->write_urb->dev = port->serial->dev;
                result = usb_submit_urb(port->write_urb, GFP_ATOMIC);
                if (result) {
                        dev_err(&port->dev, "%s(): usb_submit_urb() failed,"
                                        " error %d\n", __FUNCTION__, result);
                } else {
                        return;
                }
        }

        priv->flags.write_urb_in_use = 0;

        // schedule the interrupt urb if we are still open */
        port->interrupt_in_urb->dev = port->serial->dev;
        dbg("%s(): submitting interrupt urb", __FUNCTION__);
        result = usb_submit_urb(port->interrupt_in_urb, GFP_ATOMIC);
        if (result != 0) {
                dev_err(&port->dev, "%s(): failed submitting int urb,"
                                        " error %d\n", __FUNCTION__, result);
        }
}


/*
 * oti6858_buf_alloc
 *
 * Allocate a circular buffer and all associated memory.
 */
static struct oti6858_buf *oti6858_buf_alloc(unsigned int size)
{
        struct oti6858_buf *pb;

        if (size == 0)
                return NULL;

        pb = kmalloc(sizeof(struct oti6858_buf), GFP_KERNEL);
        if (pb == NULL)
                return NULL;

        pb->buf_buf = kmalloc(size, GFP_KERNEL);
        if (pb->buf_buf == NULL) {
                kfree(pb);
                return NULL;
        }

        pb->buf_size = size;
        pb->buf_get = pb->buf_put = pb->buf_buf;

        return pb;
}

/*
 * oti6858_buf_free
 *
 * Free the buffer and all associated memory.
 */
static void oti6858_buf_free(struct oti6858_buf *pb)
{
        if (pb) {
                kfree(pb->buf_buf);
                kfree(pb);
        }
}

/*
 * oti6858_buf_clear
 *
 * Clear out all data in the circular buffer.
 */
static void oti6858_buf_clear(struct oti6858_buf *pb)
{
        if (pb != NULL) {
                /* equivalent to a get of all data available */
                pb->buf_get = pb->buf_put;
        }
}

/*
 * oti6858_buf_data_avail
 *
 * Return the number of bytes of data available in the circular
 * buffer.
 */
static unsigned int oti6858_buf_data_avail(struct oti6858_buf *pb)
{
        if (pb == NULL)
                return 0;
        return ((pb->buf_size + pb->buf_put - pb->buf_get) % pb->buf_size);
}

/*
 * oti6858_buf_space_avail
 *
 * Return the number of bytes of space available in the circular
 * buffer.
 */
static unsigned int oti6858_buf_space_avail(struct oti6858_buf *pb)
{
        if (pb == NULL)
                return 0;
        return ((pb->buf_size + pb->buf_get - pb->buf_put - 1) % pb->buf_size);
}

/*
 * oti6858_buf_put
 *
 * Copy data data from a user buffer and put it into the circular buffer.
 * Restrict to the amount of space available.
 *
 * Return the number of bytes copied.
 */
static unsigned int oti6858_buf_put(struct oti6858_buf *pb, const char *buf,
                                        unsigned int count)
{
        unsigned int len;

        if (pb == NULL)
                return 0;

        len  = oti6858_buf_space_avail(pb);
        if (count > len)
                count = len;

        if (count == 0)
                return 0;

        len = pb->buf_buf + pb->buf_size - pb->buf_put;
        if (count > len) {
                memcpy(pb->buf_put, buf, len);
                memcpy(pb->buf_buf, buf+len, count - len);
                pb->buf_put = pb->buf_buf + count - len;
        } else {
                memcpy(pb->buf_put, buf, count);
                if (count < len)
                        pb->buf_put += count;
                else /* count == len */
                        pb->buf_put = pb->buf_buf;
        }

        return count;
}

/*
 * oti6858_buf_get
 *
 * Get data from the circular buffer and copy to the given buffer.
 * Restrict to the amount of data available.
 *
 * Return the number of bytes copied.
 */
static unsigned int oti6858_buf_get(struct oti6858_buf *pb, char *buf,
                                        unsigned int count)
{
        unsigned int len;

        if (pb == NULL)
                return 0;

        len = oti6858_buf_data_avail(pb);
        if (count > len)
                count = len;

        if (count == 0)
                return 0;

        len = pb->buf_buf + pb->buf_size - pb->buf_get;
        if (count > len) {
                memcpy(buf, pb->buf_get, len);
                memcpy(buf+len, pb->buf_buf, count - len);
                pb->buf_get = pb->buf_buf + count - len;
        } else {
                memcpy(buf, pb->buf_get, count);
                if (count < len)
                        pb->buf_get += count;
                else /* count == len */
                        pb->buf_get = pb->buf_buf;
        }

        return count;
}

/* module description and (de)initialization */

static int __init oti6858_init(void)
{
        int retval;

        if ((retval = usb_serial_register(&oti6858_device)) == 0) {
                if ((retval = usb_register(&oti6858_driver)) != 0)
                        usb_serial_deregister(&oti6858_device);
                else
                        return 0;
        }

        return retval;
}

static void __exit oti6858_exit(void)
{
        usb_deregister(&oti6858_driver);
        usb_serial_deregister(&oti6858_device);
}

module_init(oti6858_init);
module_exit(oti6858_exit);

MODULE_DESCRIPTION(OTI6858_DESCRIPTION);
MODULE_AUTHOR(OTI6858_AUTHOR);
MODULE_VERSION(OTI6858_VERSION);
MODULE_LICENSE("GPL");

module_param(debug, bool, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(debug, "enable debug output");