// SPDX-License-Identifier: GPL-2.0
/*
 * 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!
 *
 * See Documentation/usb/usb-serial.rst 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/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 <linux/uaccess.h>
#include <linux/kfifo.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>"

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

MODULE_DEVICE_TABLE(usb, id_table);

/* 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 {
        __le16  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_MSR_MASK            0x1b
#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 tty_struct *tty, struct usb_serial_port *port);
static void oti6858_close(struct usb_serial_port *port);
static void oti6858_set_termios(struct tty_struct *tty,
                                struct usb_serial_port *port,
                                const struct ktermios *old_termios);
static void oti6858_init_termios(struct tty_struct *tty);
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 tty_struct *tty, struct usb_serial_port *port,
                        const unsigned char *buf, int count);
static unsigned int oti6858_write_room(struct tty_struct *tty);
static unsigned int oti6858_chars_in_buffer(struct tty_struct *tty);
static int oti6858_tiocmget(struct tty_struct *tty);
static int oti6858_tiocmset(struct tty_struct *tty,
                                unsigned int set, unsigned int clear);
static int oti6858_port_probe(struct usb_serial_port *port);
static void oti6858_port_remove(struct usb_serial_port *port);

/* device info */
static struct usb_serial_driver oti6858_device = {
        .driver = {
                .name =         "oti6858",
        },
        .id_table =             id_table,
        .num_ports =            1,
        .num_bulk_in =          1,
        .num_bulk_out =         1,
        .num_interrupt_in =     1,
        .open =                 oti6858_open,
        .close =                oti6858_close,
        .write =                oti6858_write,
        .set_termios =          oti6858_set_termios,
        .init_termios =         oti6858_init_termios,
        .tiocmget =             oti6858_tiocmget,
        .tiocmset =             oti6858_tiocmset,
        .tiocmiwait =           usb_serial_generic_tiocmiwait,
        .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,
        .port_probe =           oti6858_port_probe,
        .port_remove =          oti6858_port_remove,
};

static struct usb_serial_driver * const serial_drivers[] = {
        &oti6858_device, NULL
};

struct oti6858_private {
        spinlock_t lock;

        struct oti6858_control_pkt status;

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

        struct {
                __le16 divisor;
                u8 frame_fmt;
                u8 control;
        } pending_setup;
        u8 transient;
        u8 setup_done;
        struct delayed_work delayed_setup_work;

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

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;

        new_setup = kmalloc(OTI6858_CTRL_PKT_SIZE, GFP_KERNEL);
        if (!new_setup) {
                /* 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", __func__);
                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);

        dev_dbg(&port->dev, "%s(): submitting interrupt urb\n", __func__);
        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",
                        __func__, result);
        }
}

static 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;
        u8 *allow;

        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;
        spin_unlock_irqrestore(&priv->lock, flags);

        spin_lock_irqsave(&port->lock, flags);
        count = kfifo_len(&port->write_fifo);
        spin_unlock_irqrestore(&port->lock, flags);

        if (count > port->bulk_out_size)
                count = port->bulk_out_size;

        if (count != 0) {
                allow = kmalloc(1, GFP_KERNEL);
                if (!allow)
                        return;

                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;
                kfree(allow);
        }

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

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

        count = kfifo_out_locked(&port->write_fifo,
                                        port->write_urb->transfer_buffer,
                                        count, &port->lock);
        port->write_urb->transfer_buffer_length = count;
        result = usb_submit_urb(port->write_urb, GFP_NOIO);
        if (result != 0) {
                dev_err_console(port, "%s(): usb_submit_urb() failed with error %d\n",
                                __func__, result);
                priv->flags.write_urb_in_use = 0;
        }

        usb_serial_port_softint(port);
}

static int oti6858_port_probe(struct usb_serial_port *port)
{
        struct oti6858_private *priv;

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

        spin_lock_init(&priv->lock);
        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(port, priv);

        port->port.drain_delay = 256;   /* FIXME: check the FIFO length */

        return 0;
}

static void oti6858_port_remove(struct usb_serial_port *port)
{
        struct oti6858_private *priv;

        priv = usb_get_serial_port_data(port);
        kfree(priv);
}

static int oti6858_write(struct tty_struct *tty, struct usb_serial_port *port,
                        const unsigned char *buf, int count)
{
        if (!count)
                return count;

        count = kfifo_in_locked(&port->write_fifo, buf, count, &port->lock);

        return count;
}

static unsigned int oti6858_write_room(struct tty_struct *tty)
{
        struct usb_serial_port *port = tty->driver_data;
        unsigned int room;
        unsigned long flags;

        spin_lock_irqsave(&port->lock, flags);
        room = kfifo_avail(&port->write_fifo);
        spin_unlock_irqrestore(&port->lock, flags);

        return room;
}

static unsigned int oti6858_chars_in_buffer(struct tty_struct *tty)
{
        struct usb_serial_port *port = tty->driver_data;
        unsigned int chars;
        unsigned long flags;

        spin_lock_irqsave(&port->lock, flags);
        chars = kfifo_len(&port->write_fifo);
        spin_unlock_irqrestore(&port->lock, flags);

        return chars;
}

static void oti6858_init_termios(struct tty_struct *tty)
{
        tty_encode_baud_rate(tty, 38400, 38400);
}

static void oti6858_set_termios(struct tty_struct *tty,
                                struct usb_serial_port *port,
                                const struct ktermios *old_termios)
{
        struct oti6858_private *priv = usb_get_serial_port_data(port);
        unsigned long flags;
        unsigned int cflag;
        u8 frame_fmt, control;
        __le16 divisor;
        int br;

        cflag = tty->termios.c_cflag;

        spin_lock_irqsave(&priv->lock, flags);
        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(tty);
        if (br == 0) {
                divisor = 0;
        } else {
                int real_br;
                int new_divisor;
                br = min(br, OTI6858_MAX_BAUD_RATE);

                new_divisor = (96000000 + 8 * br) / (16 * br);
                real_br = 96000000 / (16 * new_divisor);
                divisor = cpu_to_le16(new_divisor);
                tty_encode_baud_rate(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 tty_struct *tty, struct usb_serial_port *port)
{
        struct oti6858_private *priv = usb_get_serial_port_data(port);
        struct usb_serial *serial = port->serial;
        struct oti6858_control_pkt *buf;
        unsigned long flags;
        int result;

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

        buf = kmalloc(OTI6858_CTRL_PKT_SIZE, GFP_KERNEL);
        if (!buf)
                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);

        dev_dbg(&port->dev, "%s(): submitting interrupt urb\n", __func__);
        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",
                        __func__, result);
                oti6858_close(port);
                return result;
        }

        /* setup termios */
        if (tty)
                oti6858_set_termios(tty, port, NULL);

        return 0;
}

static void oti6858_close(struct usb_serial_port *port)
{
        struct oti6858_private *priv = usb_get_serial_port_data(port);
        unsigned long flags;

        spin_lock_irqsave(&port->lock, flags);
        /* clear out any remaining data in the buffer */
        kfifo_reset_out(&port->write_fifo);
        spin_unlock_irqrestore(&port->lock, flags);

        dev_dbg(&port->dev, "%s(): after buf_clear()\n", __func__);

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

        /* shutdown our urbs */
        dev_dbg(&port->dev, "%s(): shutting down urbs\n", __func__);
        usb_kill_urb(port->write_urb);
        usb_kill_urb(port->read_urb);
        usb_kill_urb(port->interrupt_in_urb);
}

static int oti6858_tiocmset(struct tty_struct *tty,
                                unsigned int set, unsigned int clear)
{
        struct usb_serial_port *port = tty->driver_data;
        struct oti6858_private *priv = usb_get_serial_port_data(port);
        unsigned long flags;
        u8 control;

        dev_dbg(&port->dev, "%s(set = 0x%08x, clear = 0x%08x)\n",
                __func__, set, clear);

        /* 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 tty_struct *tty)
{
        struct usb_serial_port *port = tty->driver_data;
        struct oti6858_private *priv = usb_get_serial_port_data(port);
        unsigned long flags;
        unsigned pin_state;
        unsigned result = 0;

        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;

        dev_dbg(&port->dev, "%s() = 0x%08x\n", __func__, result);

        return result;
}

static void oti6858_read_int_callback(struct urb *urb)
{
        struct usb_serial_port *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;

        switch (status) {
        case 0:
                /* success */
                break;
        case -ECONNRESET:
        case -ENOENT:
        case -ESHUTDOWN:
                /* this urb is terminated, clean up */
                dev_dbg(&urb->dev->dev, "%s(): urb shutting down with status: %d\n",
                        __func__, status);
                return;
        default:
                dev_dbg(&urb->dev->dev, "%s(): nonzero urb status received: %d\n",
                        __func__, 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;
                                        dev_dbg(&port->dev, "%s(): scheduling setup_line()\n", __func__);
                                        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;
                                        dev_dbg(&port->dev, "%s(): scheduling setup_line()\n", __func__);
                                        schedule_delayed_work(&priv->delayed_setup_work, 0);
                                }
                        }
                }

                if (!priv->transient) {
                        u8 delta = xs->pin_state ^ priv->status.pin_state;

                        if (delta & PIN_MSR_MASK) {
                                if (delta & PIN_CTS)
                                        port->icount.cts++;
                                if (delta & PIN_DSR)
                                        port->icount.dsr++;
                                if (delta & PIN_RI)
                                        port->icount.rng++;
                                if (delta & PIN_DCD)
                                        port->icount.dcd++;

                                wake_up_interruptible(&port->port.delta_msr_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;

                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", __func__, result);
                } else {
                        resubmit = 0;
                }
        } else if (!transient) {
                unsigned long flags;
                int count;

                spin_lock_irqsave(&port->lock, flags);
                count = kfifo_len(&port->write_fifo);
                spin_unlock_irqrestore(&port->lock, flags);

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

        if (resubmit) {
                int result;

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

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

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

        if (status != 0) {
                dev_dbg(&urb->dev->dev, "%s(): unable to handle the error, exiting\n", __func__);
                return;
        }

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

        /* schedule the interrupt urb */
        result = usb_submit_urb(port->interrupt_in_urb, GFP_ATOMIC);
        if (result != 0 && result != -EPERM) {
                dev_err(&port->dev, "%s(): usb_submit_urb() failed,"
                                " error %d\n", __func__, result);
        }
}

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

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

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

        priv->flags.write_urb_in_use = 0;

        /* schedule the interrupt urb if we are still open */
        dev_dbg(&port->dev, "%s(): submitting interrupt urb\n", __func__);
        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", __func__, result);
        }
}

module_usb_serial_driver(serial_drivers, id_table);

MODULE_DESCRIPTION(OTI6858_DESCRIPTION);
MODULE_AUTHOR(OTI6858_AUTHOR);
MODULE_LICENSE("GPL v2");