cypress_m8.c

Go to the documentation of this file.

/*
 * USB Cypress M8 driver
 *
 *  Copyright (C) 2004
 *      Lonnie Mendez ([email protected])
 *  Copyright (C) 2003,2004
 *      Neil Whelchel ([email protected])
 *
 *  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, or
 *  (at your option) any later version.
 *
 * See Documentation/usb/usb-serial.txt for more information on using this
 * driver
 *
 * See http://geocities.com/i0xox0i for information on this driver and the
 * earthmate usb device.
 */

/* Thanks to Neil Whelchel for writing the first cypress m8 implementation
   for linux. */
/* Thanks to cypress for providing references for the hid reports. */
/* Thanks to Jiang Zhang for providing links and for general help. */
/* Code originates and was built up from ftdi_sio, belkin, pl2303 and others.*/


#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/module.h>
#include <linux/moduleparam.h>
#include <linux/spinlock.h>
#include <linux/usb.h>
#include <linux/usb/serial.h>
#include <linux/serial.h>
#include <linux/kfifo.h>
#include <linux/delay.h>
#include <linux/uaccess.h>
#include <asm/unaligned.h>

#include "cypress_m8.h"


static bool stats;
static int interval;
static bool unstable_bauds;

/*
 * Version Information
 */
#define DRIVER_VERSION "v1.10"
#define DRIVER_AUTHOR "Lonnie Mendez <[email protected]>, Neil Whelchel <[email protected]>"
#define DRIVER_DESC "Cypress USB to Serial Driver"

/* write buffer size defines */
#define CYPRESS_BUF_SIZE    1024

static const struct usb_device_id id_table_earthmate[] = {
    { USB_DEVICE(VENDOR_ID_DELORME, PRODUCT_ID_EARTHMATEUSB) },
    { USB_DEVICE(VENDOR_ID_DELORME, PRODUCT_ID_EARTHMATEUSB_LT20) },
    { }                     /* Terminating entry */
};

static const struct usb_device_id id_table_cyphidcomrs232[] = {
    { USB_DEVICE(VENDOR_ID_CYPRESS, PRODUCT_ID_CYPHIDCOM) },
    { USB_DEVICE(VENDOR_ID_POWERCOM, PRODUCT_ID_UPS) },
    { }                     /* Terminating entry */
};

static const struct usb_device_id id_table_nokiaca42v2[] = {
    { USB_DEVICE(VENDOR_ID_DAZZLE, PRODUCT_ID_CA42) },
    { }                     /* Terminating entry */
};

static const struct usb_device_id id_table_combined[] = {
    { USB_DEVICE(VENDOR_ID_DELORME, PRODUCT_ID_EARTHMATEUSB) },
    { USB_DEVICE(VENDOR_ID_DELORME, PRODUCT_ID_EARTHMATEUSB_LT20) },
    { USB_DEVICE(VENDOR_ID_CYPRESS, PRODUCT_ID_CYPHIDCOM) },
    { USB_DEVICE(VENDOR_ID_POWERCOM, PRODUCT_ID_UPS) },
    { USB_DEVICE(VENDOR_ID_DAZZLE, PRODUCT_ID_CA42) },
    { }                     /* Terminating entry */
};

MODULE_DEVICE_TABLE(usb, id_table_combined);

enum packet_format {
    packet_format_1,  /* b0:status, b1:payload count */
    packet_format_2   /* b0[7:3]:status, b0[2:0]:payload count */
};

struct cypress_private {
    spinlock_t lock;           /* private lock */
    int chiptype;              /* identifier of device, for quirks/etc */
    int bytes_in;              /* used for statistics */
    int bytes_out;             /* used for statistics */
    int cmd_count;             /* used for statistics */
    int cmd_ctrl;              /* always set this to 1 before issuing a command */
    struct kfifo write_fifo;       /* write fifo */
    int write_urb_in_use;          /* write urb in use indicator */
    int write_urb_interval;            /* interval to use for write urb */
    int read_urb_interval;             /* interval to use for read urb */
    int comm_is_ok;                    /* true if communication is (still) ok */
    int termios_initialized;
    __u8 line_control;         /* holds dtr / rts value */
    __u8 current_status;           /* received from last read - info on dsr,cts,cd,ri,etc */
    __u8 current_config;           /* stores the current configuration byte */
    __u8 rx_flags;             /* throttling - used from whiteheat/ftdi_sio */
    enum packet_format pkt_fmt;    /* format to use for packet send / receive */
    int get_cfg_unsafe;        /* If true, the CYPRESS_GET_CONFIG is unsafe */
    int baud_rate;             /* stores current baud rate in
                          integer form */
    int isthrottled;           /* if throttled, discard reads */
    wait_queue_head_t delta_msr_wait;  /* used for TIOCMIWAIT */
    char prev_status, diff_status;     /* used for TIOCMIWAIT */
    /* we pass a pointer to this as the argument sent to
       cypress_set_termios old_termios */
    struct ktermios tmp_termios;       /* stores the old termios settings */
};

/* function prototypes for the Cypress USB to serial device */
static int  cypress_earthmate_port_probe(struct usb_serial_port *port);
static int  cypress_hidcom_port_probe(struct usb_serial_port *port);
static int  cypress_ca42v2_port_probe(struct usb_serial_port *port);
static int  cypress_port_remove(struct usb_serial_port *port);
static int  cypress_open(struct tty_struct *tty, struct usb_serial_port *port);
static void cypress_close(struct usb_serial_port *port);
static void cypress_dtr_rts(struct usb_serial_port *port, int on);
static int  cypress_write(struct tty_struct *tty, struct usb_serial_port *port,
            const unsigned char *buf, int count);
static void cypress_send(struct usb_serial_port *port);
static int  cypress_write_room(struct tty_struct *tty);
static int  cypress_ioctl(struct tty_struct *tty,
            unsigned int cmd, unsigned long arg);
static void cypress_set_termios(struct tty_struct *tty,
            struct usb_serial_port *port, struct ktermios *old);
static int  cypress_tiocmget(struct tty_struct *tty);
static int  cypress_tiocmset(struct tty_struct *tty,
            unsigned int set, unsigned int clear);
static int  cypress_chars_in_buffer(struct tty_struct *tty);
static void cypress_throttle(struct tty_struct *tty);
static void cypress_unthrottle(struct tty_struct *tty);
static void cypress_set_dead(struct usb_serial_port *port);
static void cypress_read_int_callback(struct urb *urb);
static void cypress_write_int_callback(struct urb *urb);

static struct usb_serial_driver cypress_earthmate_device = {
    .driver = {
        .owner =        THIS_MODULE,
        .name =         "earthmate",
    },
    .description =          "DeLorme Earthmate USB",
    .id_table =         id_table_earthmate,
    .num_ports =            1,
    .port_probe =           cypress_earthmate_port_probe,
    .port_remove =          cypress_port_remove,
    .open =             cypress_open,
    .close =            cypress_close,
    .dtr_rts =          cypress_dtr_rts,
    .write =            cypress_write,
    .write_room =           cypress_write_room,
    .ioctl =            cypress_ioctl,
    .set_termios =          cypress_set_termios,
    .tiocmget =         cypress_tiocmget,
    .tiocmset =         cypress_tiocmset,
    .chars_in_buffer =      cypress_chars_in_buffer,
    .throttle =         cypress_throttle,
    .unthrottle =           cypress_unthrottle,
    .read_int_callback =        cypress_read_int_callback,
    .write_int_callback =       cypress_write_int_callback,
};

static struct usb_serial_driver cypress_hidcom_device = {
    .driver = {
        .owner =        THIS_MODULE,
        .name =         "cyphidcom",
    },
    .description =          "HID->COM RS232 Adapter",
    .id_table =         id_table_cyphidcomrs232,
    .num_ports =            1,
    .port_probe =           cypress_hidcom_port_probe,
    .port_remove =          cypress_port_remove,
    .open =             cypress_open,
    .close =            cypress_close,
    .dtr_rts =          cypress_dtr_rts,
    .write =            cypress_write,
    .write_room =           cypress_write_room,
    .ioctl =            cypress_ioctl,
    .set_termios =          cypress_set_termios,
    .tiocmget =         cypress_tiocmget,
    .tiocmset =         cypress_tiocmset,
    .chars_in_buffer =      cypress_chars_in_buffer,
    .throttle =         cypress_throttle,
    .unthrottle =           cypress_unthrottle,
    .read_int_callback =        cypress_read_int_callback,
    .write_int_callback =       cypress_write_int_callback,
};

static struct usb_serial_driver cypress_ca42v2_device = {
    .driver = {
        .owner =        THIS_MODULE,
        .name =         "nokiaca42v2",
    },
    .description =          "Nokia CA-42 V2 Adapter",
    .id_table =         id_table_nokiaca42v2,
    .num_ports =            1,
    .port_probe =           cypress_ca42v2_port_probe,
    .port_remove =          cypress_port_remove,
    .open =             cypress_open,
    .close =            cypress_close,
    .dtr_rts =          cypress_dtr_rts,
    .write =            cypress_write,
    .write_room =           cypress_write_room,
    .ioctl =            cypress_ioctl,
    .set_termios =          cypress_set_termios,
    .tiocmget =         cypress_tiocmget,
    .tiocmset =         cypress_tiocmset,
    .chars_in_buffer =      cypress_chars_in_buffer,
    .throttle =         cypress_throttle,
    .unthrottle =           cypress_unthrottle,
    .read_int_callback =        cypress_read_int_callback,
    .write_int_callback =       cypress_write_int_callback,
};

static struct usb_serial_driver * const serial_drivers[] = {
    &cypress_earthmate_device, &cypress_hidcom_device,
    &cypress_ca42v2_device, NULL
};

/*****************************************************************************
 * Cypress serial helper functions
 *****************************************************************************/


static int analyze_baud_rate(struct usb_serial_port *port, speed_t new_rate)
{
    struct cypress_private *priv;
    priv = usb_get_serial_port_data(port);

    if (unstable_bauds)
        return new_rate;

    /*
     * The general purpose firmware for the Cypress M8 allows for
     * a maximum speed of 57600bps (I have no idea whether DeLorme
     * chose to use the general purpose firmware or not), if you
     * need to modify this speed setting for your own project
     * please add your own chiptype and modify the code likewise.
     * The Cypress HID->COM device will work successfully up to
     * 115200bps (but the actual throughput is around 3kBps).
     */
    if (port->serial->dev->speed == USB_SPEED_LOW) {
        /*
         * Mike Isely <[email protected]> 2-Feb-2008: The
         * Cypress app note that describes this mechanism
         * states the the low-speed part can't handle more
         * than 800 bytes/sec, in which case 4800 baud is the
         * safest speed for a part like that.
         */
        if (new_rate > 4800) {
            dev_dbg(&port->dev,
                "%s - failed setting baud rate, device incapable speed %d\n",
                __func__, new_rate);
            return -1;
        }
    }
    switch (priv->chiptype) {
    case CT_EARTHMATE:
        if (new_rate <= 600) {
            /* 300 and 600 baud rates are supported under
             * the generic firmware, but are not used with
             * NMEA and SiRF protocols */
            dev_dbg(&port->dev,
                "%s - failed setting baud rate, unsupported speed of %d on Earthmate GPS",
                __func__, new_rate);
            return -1;
        }
        break;
    default:
        break;
    }
    return new_rate;
}


/* This function can either set or retrieve the current serial line settings */
static int cypress_serial_control(struct tty_struct *tty,
    struct usb_serial_port *port, speed_t baud_rate, int data_bits,
    int stop_bits, int parity_enable, int parity_type, int reset,
    int cypress_request_type)
{
    int new_baudrate = 0, retval = 0, tries = 0;
    struct cypress_private *priv;
    struct device *dev = &port->dev;
    u8 *feature_buffer;
    const unsigned int feature_len = 5;
    unsigned long flags;

    priv = usb_get_serial_port_data(port);

    if (!priv->comm_is_ok)
        return -ENODEV;

    feature_buffer = kcalloc(feature_len, sizeof(u8), GFP_KERNEL);
    if (!feature_buffer)
        return -ENOMEM;

    switch (cypress_request_type) {
    case CYPRESS_SET_CONFIG:
        /* 0 means 'Hang up' so doesn't change the true bit rate */
        new_baudrate = priv->baud_rate;
        if (baud_rate && baud_rate != priv->baud_rate) {
            dev_dbg(dev, "%s - baud rate is changing\n", __func__);
            retval = analyze_baud_rate(port, baud_rate);
            if (retval >= 0) {
                new_baudrate = retval;
                dev_dbg(dev, "%s - New baud rate set to %d\n",
                    __func__, new_baudrate);
            }
        }
        dev_dbg(dev, "%s - baud rate is being sent as %d\n", __func__,
            new_baudrate);

        /* fill the feature_buffer with new configuration */
        put_unaligned_le32(new_baudrate, feature_buffer);
        feature_buffer[4] |= data_bits;   /* assign data bits in 2 bit space ( max 3 ) */
        /* 1 bit gap */
        feature_buffer[4] |= (stop_bits << 3);   /* assign stop bits in 1 bit space */
        feature_buffer[4] |= (parity_enable << 4);   /* assign parity flag in 1 bit space */
        feature_buffer[4] |= (parity_type << 5);   /* assign parity type in 1 bit space */
        /* 1 bit gap */
        feature_buffer[4] |= (reset << 7);   /* assign reset at end of byte, 1 bit space */

        dev_dbg(dev, "%s - device is being sent this feature report:\n", __func__);
        dev_dbg(dev, "%s - %02X - %02X - %02X - %02X - %02X\n", __func__,
            feature_buffer[0], feature_buffer[1],
            feature_buffer[2], feature_buffer[3],
            feature_buffer[4]);

        do {
            retval = usb_control_msg(port->serial->dev,
                    usb_sndctrlpipe(port->serial->dev, 0),
                    HID_REQ_SET_REPORT,
                    USB_DIR_OUT | USB_RECIP_INTERFACE | USB_TYPE_CLASS,
                    0x0300, 0, feature_buffer,
                    feature_len, 500);

            if (tries++ >= 3)
                break;

        } while (retval != feature_len &&
             retval != -ENODEV);

        if (retval != feature_len) {
            dev_err(dev, "%s - failed sending serial line settings - %d\n",
                __func__, retval);
            cypress_set_dead(port);
        } else {
            spin_lock_irqsave(&priv->lock, flags);
            priv->baud_rate = new_baudrate;
            priv->current_config = feature_buffer[4];
            spin_unlock_irqrestore(&priv->lock, flags);
            /* If we asked for a speed change encode it */
            if (baud_rate)
                tty_encode_baud_rate(tty,
                    new_baudrate, new_baudrate);
        }
    break;
    case CYPRESS_GET_CONFIG:
        if (priv->get_cfg_unsafe) {
            /* Not implemented for this device,
               and if we try to do it we're likely
               to crash the hardware. */
            retval = -ENOTTY;
            goto out;
        }
        dev_dbg(dev, "%s - retreiving serial line settings\n", __func__);
        do {
            retval = usb_control_msg(port->serial->dev,
                    usb_rcvctrlpipe(port->serial->dev, 0),
                    HID_REQ_GET_REPORT,
                    USB_DIR_IN | USB_RECIP_INTERFACE | USB_TYPE_CLASS,
                    0x0300, 0, feature_buffer,
                    feature_len, 500);

            if (tries++ >= 3)
                break;
        } while (retval != feature_len
                        && retval != -ENODEV);

        if (retval != feature_len) {
            dev_err(dev, "%s - failed to retrieve serial line settings - %d\n",
                __func__, retval);
            cypress_set_dead(port);
            goto out;
        } else {
            spin_lock_irqsave(&priv->lock, flags);
            /* store the config in one byte, and later
               use bit masks to check values */
            priv->current_config = feature_buffer[4];
            priv->baud_rate = get_unaligned_le32(feature_buffer);
            spin_unlock_irqrestore(&priv->lock, flags);
        }
    }
    spin_lock_irqsave(&priv->lock, flags);
    ++priv->cmd_count;
    spin_unlock_irqrestore(&priv->lock, flags);
out:
    kfree(feature_buffer);
    return retval;
} /* cypress_serial_control */


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

    spin_lock_irqsave(&priv->lock, flags);
    if (!priv->comm_is_ok) {
        spin_unlock_irqrestore(&priv->lock, flags);
        return;
    }
    priv->comm_is_ok = 0;
    spin_unlock_irqrestore(&priv->lock, flags);

    dev_err(&port->dev, "cypress_m8 suspending failing port %d - "
        "interval might be too short\n", port->number);
}


/*****************************************************************************
 * Cypress serial driver functions
 *****************************************************************************/


static int cypress_generic_port_probe(struct usb_serial_port *port)
{
    struct usb_serial *serial = port->serial;
    struct cypress_private *priv;

    priv = kzalloc(sizeof(struct cypress_private), GFP_KERNEL);
    if (!priv)
        return -ENOMEM;

    priv->comm_is_ok = !0;
    spin_lock_init(&priv->lock);
    if (kfifo_alloc(&priv->write_fifo, CYPRESS_BUF_SIZE, GFP_KERNEL)) {
        kfree(priv);
        return -ENOMEM;
    }
    init_waitqueue_head(&priv->delta_msr_wait);

    usb_reset_configuration(serial->dev);

    priv->cmd_ctrl = 0;
    priv->line_control = 0;
    priv->termios_initialized = 0;
    priv->rx_flags = 0;
    /* Default packet format setting is determined by packet size.
       Anything with a size larger then 9 must have a separate
       count field since the 3 bit count field is otherwise too
       small.  Otherwise we can use the slightly more compact
       format.  This is in accordance with the cypress_m8 serial
       converter app note. */
    if (port->interrupt_out_size > 9)
        priv->pkt_fmt = packet_format_1;
    else
        priv->pkt_fmt = packet_format_2;

    if (interval > 0) {
        priv->write_urb_interval = interval;
        priv->read_urb_interval = interval;
        dev_dbg(&port->dev, "%s - read & write intervals forced to %d\n",
            __func__, interval);
    } else {
        priv->write_urb_interval = port->interrupt_out_urb->interval;
        priv->read_urb_interval = port->interrupt_in_urb->interval;
        dev_dbg(&port->dev, "%s - intervals: read=%d write=%d\n",
            __func__, priv->read_urb_interval,
            priv->write_urb_interval);
    }
    usb_set_serial_port_data(port, priv);

    return 0;
}


static int cypress_earthmate_port_probe(struct usb_serial_port *port)
{
    struct usb_serial *serial = port->serial;
    struct cypress_private *priv;
    int ret;

    ret = cypress_generic_port_probe(port);
    if (ret) {
        dev_dbg(&port->dev, "%s - Failed setting up port\n", __func__);
        return ret;
    }

    priv = usb_get_serial_port_data(port);
    priv->chiptype = CT_EARTHMATE;
    /* All Earthmate devices use the separated-count packet
       format!  Idiotic. */
    priv->pkt_fmt = packet_format_1;
    if (serial->dev->descriptor.idProduct !=
                cpu_to_le16(PRODUCT_ID_EARTHMATEUSB)) {
        /* The old original USB Earthmate seemed able to
           handle GET_CONFIG requests; everything they've
           produced since that time crashes if this command is
           attempted :-( */
        dev_dbg(&port->dev,
            "%s - Marking this device as unsafe for GET_CONFIG commands\n",
            __func__);
        priv->get_cfg_unsafe = !0;
    }

    return 0;
}

static int cypress_hidcom_port_probe(struct usb_serial_port *port)
{
    struct cypress_private *priv;
    int ret;

    ret = cypress_generic_port_probe(port);
    if (ret) {
        dev_dbg(&port->dev, "%s - Failed setting up port\n", __func__);
        return ret;
    }

    priv = usb_get_serial_port_data(port);
    priv->chiptype = CT_CYPHIDCOM;

    return 0;
}

static int cypress_ca42v2_port_probe(struct usb_serial_port *port)
{
    struct cypress_private *priv;
    int ret;

    ret = cypress_generic_port_probe(port);
    if (ret) {
        dev_dbg(&port->dev, "%s - Failed setting up port\n", __func__);
        return ret;
    }

    priv = usb_get_serial_port_data(port);
    priv->chiptype = CT_CA42V2;

    return 0;
}

static int cypress_port_remove(struct usb_serial_port *port)
{
    struct cypress_private *priv;

    priv = usb_get_serial_port_data(port);

    kfifo_free(&priv->write_fifo);
    kfree(priv);

    return 0;
}

static int cypress_open(struct tty_struct *tty, struct usb_serial_port *port)
{
    struct cypress_private *priv = usb_get_serial_port_data(port);
    struct usb_serial *serial = port->serial;
    unsigned long flags;
    int result = 0;

    if (!priv->comm_is_ok)
        return -EIO;

    /* clear halts before open */
    usb_clear_halt(serial->dev, 0x81);
    usb_clear_halt(serial->dev, 0x02);

    spin_lock_irqsave(&priv->lock, flags);
    /* reset read/write statistics */
    priv->bytes_in = 0;
    priv->bytes_out = 0;
    priv->cmd_count = 0;
    priv->rx_flags = 0;
    spin_unlock_irqrestore(&priv->lock, flags);

    /* Set termios */
    cypress_send(port);

    if (tty)
        cypress_set_termios(tty, port, &priv->tmp_termios);

    /* setup the port and start reading from the device */
    if (!port->interrupt_in_urb) {
        dev_err(&port->dev, "%s - interrupt_in_urb is empty!\n",
            __func__);
        return -1;
    }

    usb_fill_int_urb(port->interrupt_in_urb, serial->dev,
        usb_rcvintpipe(serial->dev, port->interrupt_in_endpointAddress),
        port->interrupt_in_urb->transfer_buffer,
        port->interrupt_in_urb->transfer_buffer_length,
        cypress_read_int_callback, port, priv->read_urb_interval);
    result = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);

    if (result) {
        dev_err(&port->dev,
            "%s - failed submitting read urb, error %d\n",
                            __func__, result);
        cypress_set_dead(port);
    }
    port->port.drain_delay = 256;
    return result;
} /* cypress_open */

static void cypress_dtr_rts(struct usb_serial_port *port, int on)
{
    struct cypress_private *priv = usb_get_serial_port_data(port);
    /* drop dtr and rts */
    spin_lock_irq(&priv->lock);
    if (on == 0)
        priv->line_control = 0;
    else 
        priv->line_control = CONTROL_DTR | CONTROL_RTS;
    priv->cmd_ctrl = 1;
    spin_unlock_irq(&priv->lock);
    cypress_write(NULL, port, NULL, 0);
}

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

    /* writing is potentially harmful, lock must be taken */
    mutex_lock(&port->serial->disc_mutex);
    if (port->serial->disconnected) {
        mutex_unlock(&port->serial->disc_mutex);
        return;
    }
    spin_lock_irqsave(&priv->lock, flags);
    kfifo_reset_out(&priv->write_fifo);
    spin_unlock_irqrestore(&priv->lock, flags);

    dev_dbg(&port->dev, "%s - stopping urbs\n", __func__);
    usb_kill_urb(port->interrupt_in_urb);
    usb_kill_urb(port->interrupt_out_urb);

    if (stats)
        dev_info(&port->dev, "Statistics: %d Bytes In | %d Bytes Out | %d Commands Issued\n",
            priv->bytes_in, priv->bytes_out, priv->cmd_count);
    mutex_unlock(&port->serial->disc_mutex);
} /* cypress_close */


static int cypress_write(struct tty_struct *tty, struct usb_serial_port *port,
                    const unsigned char *buf, int count)
{
    struct cypress_private *priv = usb_get_serial_port_data(port);

    dev_dbg(&port->dev, "%s - port %d, %d bytes\n", __func__, port->number, count);

    /* line control commands, which need to be executed immediately,
       are not put into the buffer for obvious reasons.
     */
    if (priv->cmd_ctrl) {
        count = 0;
        goto finish;
    }

    if (!count)
        return count;

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

finish:
    cypress_send(port);

    return count;
} /* cypress_write */


static void cypress_send(struct usb_serial_port *port)
{
    int count = 0, result, offset, actual_size;
    struct cypress_private *priv = usb_get_serial_port_data(port);
    struct device *dev = &port->dev;
    unsigned long flags;

    if (!priv->comm_is_ok)
        return;

    dev_dbg(dev, "%s - interrupt out size is %d\n", __func__,
        port->interrupt_out_size);

    spin_lock_irqsave(&priv->lock, flags);
    if (priv->write_urb_in_use) {
        dev_dbg(dev, "%s - can't write, urb in use\n", __func__);
        spin_unlock_irqrestore(&priv->lock, flags);
        return;
    }
    spin_unlock_irqrestore(&priv->lock, flags);

    /* clear buffer */
    memset(port->interrupt_out_urb->transfer_buffer, 0,
                        port->interrupt_out_size);

    spin_lock_irqsave(&priv->lock, flags);
    switch (priv->pkt_fmt) {
    default:
    case packet_format_1:
        /* this is for the CY7C64013... */
        offset = 2;
        port->interrupt_out_buffer[0] = priv->line_control;
        break;
    case packet_format_2:
        /* this is for the CY7C63743... */
        offset = 1;
        port->interrupt_out_buffer[0] = priv->line_control;
        break;
    }

    if (priv->line_control & CONTROL_RESET)
        priv->line_control &= ~CONTROL_RESET;

    if (priv->cmd_ctrl) {
        priv->cmd_count++;
        dev_dbg(dev, "%s - line control command being issued\n", __func__);
        spin_unlock_irqrestore(&priv->lock, flags);
        goto send;
    } else
        spin_unlock_irqrestore(&priv->lock, flags);

    count = kfifo_out_locked(&priv->write_fifo,
                    &port->interrupt_out_buffer[offset],
                    port->interrupt_out_size - offset,
                    &priv->lock);
    if (count == 0)
        return;

    switch (priv->pkt_fmt) {
    default:
    case packet_format_1:
        port->interrupt_out_buffer[1] = count;
        break;
    case packet_format_2:
        port->interrupt_out_buffer[0] |= count;
    }

    dev_dbg(dev, "%s - count is %d\n", __func__, count);

send:
    spin_lock_irqsave(&priv->lock, flags);
    priv->write_urb_in_use = 1;
    spin_unlock_irqrestore(&priv->lock, flags);

    if (priv->cmd_ctrl)
        actual_size = 1;
    else
        actual_size = count +
                  (priv->pkt_fmt == packet_format_1 ? 2 : 1);

    usb_serial_debug_data(dev, __func__, port->interrupt_out_size,
                  port->interrupt_out_urb->transfer_buffer);

    usb_fill_int_urb(port->interrupt_out_urb, port->serial->dev,
        usb_sndintpipe(port->serial->dev, port->interrupt_out_endpointAddress),
        port->interrupt_out_buffer, port->interrupt_out_size,
        cypress_write_int_callback, port, priv->write_urb_interval);
    result = usb_submit_urb(port->interrupt_out_urb, GFP_ATOMIC);
    if (result) {
        dev_err_console(port,
                "%s - failed submitting write urb, error %d\n",
                            __func__, result);
        priv->write_urb_in_use = 0;
        cypress_set_dead(port);
    }

    spin_lock_irqsave(&priv->lock, flags);
    if (priv->cmd_ctrl)
        priv->cmd_ctrl = 0;

    /* do not count the line control and size bytes */
    priv->bytes_out += count;
    spin_unlock_irqrestore(&priv->lock, flags);

    usb_serial_port_softint(port);
} /* cypress_send */


/* returns how much space is available in the soft buffer */
static int cypress_write_room(struct tty_struct *tty)
{
    struct usb_serial_port *port = tty->driver_data;
    struct cypress_private *priv = usb_get_serial_port_data(port);
    int room = 0;
    unsigned long flags;

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

    dev_dbg(&port->dev, "%s - returns %d\n", __func__, room);
    return room;
}


static int cypress_tiocmget(struct tty_struct *tty)
{
    struct usb_serial_port *port = tty->driver_data;
    struct cypress_private *priv = usb_get_serial_port_data(port);
    __u8 status, control;
    unsigned int result = 0;
    unsigned long flags;

    spin_lock_irqsave(&priv->lock, flags);
    control = priv->line_control;
    status = priv->current_status;
    spin_unlock_irqrestore(&priv->lock, flags);

    result = ((control & CONTROL_DTR)        ? TIOCM_DTR : 0)
        | ((control & CONTROL_RTS)       ? TIOCM_RTS : 0)
        | ((status & UART_CTS)        ? TIOCM_CTS : 0)
        | ((status & UART_DSR)        ? TIOCM_DSR : 0)
        | ((status & UART_RI)         ? TIOCM_RI  : 0)
        | ((status & UART_CD)         ? TIOCM_CD  : 0);

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

    return result;
}


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

    spin_lock_irqsave(&priv->lock, flags);
    if (set & TIOCM_RTS)
        priv->line_control |= CONTROL_RTS;
    if (set & TIOCM_DTR)
        priv->line_control |= CONTROL_DTR;
    if (clear & TIOCM_RTS)
        priv->line_control &= ~CONTROL_RTS;
    if (clear & TIOCM_DTR)
        priv->line_control &= ~CONTROL_DTR;
    priv->cmd_ctrl = 1;
    spin_unlock_irqrestore(&priv->lock, flags);

    return cypress_write(tty, port, NULL, 0);
}


static int cypress_ioctl(struct tty_struct *tty,
                    unsigned int cmd, unsigned long arg)
{
    struct usb_serial_port *port = tty->driver_data;
    struct cypress_private *priv = usb_get_serial_port_data(port);

    dev_dbg(&port->dev, "%s - port %d, cmd 0x%.4x\n", __func__, port->number, cmd);

    switch (cmd) {
    /* This code comes from drivers/char/serial.c and ftdi_sio.c */
    case TIOCMIWAIT:
        while (priv != NULL) {
            interruptible_sleep_on(&priv->delta_msr_wait);
            /* see if a signal did it */
            if (signal_pending(current))
                return -ERESTARTSYS;
            else {
                char diff = priv->diff_status;
                if (diff == 0)
                    return -EIO; /* no change => error */

                /* consume all events */
                priv->diff_status = 0;

                /* return 0 if caller wanted to know about
                   these bits */
                if (((arg & TIOCM_RNG) && (diff & UART_RI)) ||
                    ((arg & TIOCM_DSR) && (diff & UART_DSR)) ||
                    ((arg & TIOCM_CD) && (diff & UART_CD)) ||
                    ((arg & TIOCM_CTS) && (diff & UART_CTS)))
                    return 0;
                /* otherwise caller can't care less about what
                 * happened, and so we continue to wait for
                 * more events.
                 */
            }
        }
        return 0;
    default:
        break;
    }
    dev_dbg(&port->dev, "%s - arg not supported - it was 0x%04x - check include/asm/ioctls.h\n", __func__, cmd);
    return -ENOIOCTLCMD;
} /* cypress_ioctl */


static void cypress_set_termios(struct tty_struct *tty,
    struct usb_serial_port *port, struct ktermios *old_termios)
{
    struct cypress_private *priv = usb_get_serial_port_data(port);
    struct device *dev = &port->dev;
    int data_bits, stop_bits, parity_type, parity_enable;
    unsigned cflag, iflag;
    unsigned long flags;
    __u8 oldlines;
    int linechange = 0;

    spin_lock_irqsave(&priv->lock, flags);
    /* We can't clean this one up as we don't know the device type
       early enough */
    if (!priv->termios_initialized) {
        if (priv->chiptype == CT_EARTHMATE) {
            tty->termios = tty_std_termios;
            tty->termios.c_cflag = B4800 | CS8 | CREAD | HUPCL |
                CLOCAL;
            tty->termios.c_ispeed = 4800;
            tty->termios.c_ospeed = 4800;
        } else if (priv->chiptype == CT_CYPHIDCOM) {
            tty->termios = tty_std_termios;
            tty->termios.c_cflag = B9600 | CS8 | CREAD | HUPCL |
                CLOCAL;
            tty->termios.c_ispeed = 9600;
            tty->termios.c_ospeed = 9600;
        } else if (priv->chiptype == CT_CA42V2) {
            tty->termios = tty_std_termios;
            tty->termios.c_cflag = B9600 | CS8 | CREAD | HUPCL |
                CLOCAL;
            tty->termios.c_ispeed = 9600;
            tty->termios.c_ospeed = 9600;
        }
        priv->termios_initialized = 1;
    }
    spin_unlock_irqrestore(&priv->lock, flags);

    /* Unsupported features need clearing */
    tty->termios.c_cflag &= ~(CMSPAR|CRTSCTS);

    cflag = tty->termios.c_cflag;
    iflag = tty->termios.c_iflag;

    /* check if there are new settings */
    if (old_termios) {
        spin_lock_irqsave(&priv->lock, flags);
        priv->tmp_termios = tty->termios;
        spin_unlock_irqrestore(&priv->lock, flags);
    }

    /* set number of data bits, parity, stop bits */
    /* when parity is disabled the parity type bit is ignored */

    /* 1 means 2 stop bits, 0 means 1 stop bit */
    stop_bits = cflag & CSTOPB ? 1 : 0;

    if (cflag & PARENB) {
        parity_enable = 1;
        /* 1 means odd parity, 0 means even parity */
        parity_type = cflag & PARODD ? 1 : 0;
    } else
        parity_enable = parity_type = 0;

    switch (cflag & CSIZE) {
    case CS5:
        data_bits = 0;
        break;
    case CS6:
        data_bits = 1;
        break;
    case CS7:
        data_bits = 2;
        break;
    case CS8:
        data_bits = 3;
        break;
    default:
        dev_err(dev, "%s - CSIZE was set, but not CS5-CS8\n", __func__);
        data_bits = 3;
    }
    spin_lock_irqsave(&priv->lock, flags);
    oldlines = priv->line_control;
    if ((cflag & CBAUD) == B0) {
        /* drop dtr and rts */
        dev_dbg(dev, "%s - dropping the lines, baud rate 0bps\n", __func__);
        priv->line_control &= ~(CONTROL_DTR | CONTROL_RTS);
    } else
        priv->line_control = (CONTROL_DTR | CONTROL_RTS);
    spin_unlock_irqrestore(&priv->lock, flags);

    dev_dbg(dev, "%s - sending %d stop_bits, %d parity_enable, %d parity_type, %d data_bits (+5)\n",
        __func__, stop_bits, parity_enable, parity_type, data_bits);

    cypress_serial_control(tty, port, tty_get_baud_rate(tty),
            data_bits, stop_bits,
            parity_enable, parity_type,
            0, CYPRESS_SET_CONFIG);

    /* we perform a CYPRESS_GET_CONFIG so that the current settings are
     * filled into the private structure this should confirm that all is
     * working if it returns what we just set */
    cypress_serial_control(tty, port, 0, 0, 0, 0, 0, 0, CYPRESS_GET_CONFIG);

    /* Here we can define custom tty settings for devices; the main tty
     * termios flag base comes from empeg.c */

    spin_lock_irqsave(&priv->lock, flags);
    if (priv->chiptype == CT_EARTHMATE && priv->baud_rate == 4800) {
        dev_dbg(dev, "Using custom termios settings for a baud rate of 4800bps.\n");
        /* define custom termios settings for NMEA protocol */

        tty->termios.c_iflag /* input modes - */
            &= ~(IGNBRK  /* disable ignore break */
            | BRKINT     /* disable break causes interrupt */
            | PARMRK     /* disable mark parity errors */
            | ISTRIP     /* disable clear high bit of input char */
            | INLCR      /* disable translate NL to CR */
            | IGNCR      /* disable ignore CR */
            | ICRNL      /* disable translate CR to NL */
            | IXON);     /* disable enable XON/XOFF flow control */

        tty->termios.c_oflag /* output modes */
            &= ~OPOST;    /* disable postprocess output char */

        tty->termios.c_lflag /* line discipline modes */
            &= ~(ECHO     /* disable echo input characters */
            | ECHONL      /* disable echo new line */
            | ICANON      /* disable erase, kill, werase, and rprnt
                     special characters */
            | ISIG        /* disable interrupt, quit, and suspend
                     special characters */
            | IEXTEN);    /* disable non-POSIX special characters */
    } /* CT_CYPHIDCOM: Application should handle this for device */

    linechange = (priv->line_control != oldlines);
    spin_unlock_irqrestore(&priv->lock, flags);

    /* if necessary, set lines */
    if (linechange) {
        priv->cmd_ctrl = 1;
        cypress_write(tty, port, NULL, 0);
    }
} /* cypress_set_termios */


/* returns amount of data still left in soft buffer */
static int cypress_chars_in_buffer(struct tty_struct *tty)
{
    struct usb_serial_port *port = tty->driver_data;
    struct cypress_private *priv = usb_get_serial_port_data(port);
    int chars = 0;
    unsigned long flags;

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

    dev_dbg(&port->dev, "%s - returns %d\n", __func__, chars);
    return chars;
}


static void cypress_throttle(struct tty_struct *tty)
{
    struct usb_serial_port *port = tty->driver_data;
    struct cypress_private *priv = usb_get_serial_port_data(port);

    spin_lock_irq(&priv->lock);
    priv->rx_flags = THROTTLED;
    spin_unlock_irq(&priv->lock);
}


static void cypress_unthrottle(struct tty_struct *tty)
{
    struct usb_serial_port *port = tty->driver_data;
    struct cypress_private *priv = usb_get_serial_port_data(port);
    int actually_throttled, result;

    spin_lock_irq(&priv->lock);
    actually_throttled = priv->rx_flags & ACTUALLY_THROTTLED;
    priv->rx_flags = 0;
    spin_unlock_irq(&priv->lock);

    if (!priv->comm_is_ok)
        return;

    if (actually_throttled) {
        result = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
        if (result) {
            dev_err(&port->dev, "%s - failed submitting read urb, "
                    "error %d\n", __func__, result);
            cypress_set_dead(port);
        }
    }
}


static void cypress_read_int_callback(struct urb *urb)
{
    struct usb_serial_port *port = urb->context;
    struct cypress_private *priv = usb_get_serial_port_data(port);
    struct device *dev = &urb->dev->dev;
    struct tty_struct *tty;
    unsigned char *data = urb->transfer_buffer;
    unsigned long flags;
    char tty_flag = TTY_NORMAL;
    int havedata = 0;
    int bytes = 0;
    int result;
    int i = 0;
    int status = urb->status;

    switch (status) {
    case 0: /* success */
        break;
    case -ECONNRESET:
    case -ENOENT:
    case -ESHUTDOWN:
        /* precursor to disconnect so just go away */
        return;
    case -EPIPE:
        /* Can't call usb_clear_halt while in_interrupt */
        /* FALLS THROUGH */
    default:
        /* something ugly is going on... */
        dev_err(dev, "%s - unexpected nonzero read status received: %d\n",
            __func__, status);
        cypress_set_dead(port);
        return;
    }

    spin_lock_irqsave(&priv->lock, flags);
    if (priv->rx_flags & THROTTLED) {
        dev_dbg(dev, "%s - now throttling\n", __func__);
        priv->rx_flags |= ACTUALLY_THROTTLED;
        spin_unlock_irqrestore(&priv->lock, flags);
        return;
    }
    spin_unlock_irqrestore(&priv->lock, flags);

    tty = tty_port_tty_get(&port->port);
    if (!tty) {
        dev_dbg(dev, "%s - bad tty pointer - exiting\n", __func__);
        return;
    }

    spin_lock_irqsave(&priv->lock, flags);
    result = urb->actual_length;
    switch (priv->pkt_fmt) {
    default:
    case packet_format_1:
        /* This is for the CY7C64013... */
        priv->current_status = data[0] & 0xF8;
        bytes = data[1] + 2;
        i = 2;
        if (bytes > 2)
            havedata = 1;
        break;
    case packet_format_2:
        /* This is for the CY7C63743... */
        priv->current_status = data[0] & 0xF8;
        bytes = (data[0] & 0x07) + 1;
        i = 1;
        if (bytes > 1)
            havedata = 1;
        break;
    }
    spin_unlock_irqrestore(&priv->lock, flags);
    if (result < bytes) {
        dev_dbg(dev,
            "%s - wrong packet size - received %d bytes but packet said %d bytes\n",
            __func__, result, bytes);
        goto continue_read;
    }

    usb_serial_debug_data(&port->dev, __func__, urb->actual_length, data);

    spin_lock_irqsave(&priv->lock, flags);
    /* check to see if status has changed */
    if (priv->current_status != priv->prev_status) {
        priv->diff_status |= priv->current_status ^
            priv->prev_status;
        wake_up_interruptible(&priv->delta_msr_wait);
        priv->prev_status = priv->current_status;
    }
    spin_unlock_irqrestore(&priv->lock, flags);

    /* hangup, as defined in acm.c... this might be a bad place for it
     * though */
    if (tty && !(tty->termios.c_cflag & CLOCAL) &&
            !(priv->current_status & UART_CD)) {
        dev_dbg(dev, "%s - calling hangup\n", __func__);
        tty_hangup(tty);
        goto continue_read;
    }

    /* There is one error bit... I'm assuming it is a parity error
     * indicator as the generic firmware will set this bit to 1 if a
     * parity error occurs.
     * I can not find reference to any other error events. */
    spin_lock_irqsave(&priv->lock, flags);
    if (priv->current_status & CYP_ERROR) {
        spin_unlock_irqrestore(&priv->lock, flags);
        tty_flag = TTY_PARITY;
        dev_dbg(dev, "%s - Parity Error detected\n", __func__);
    } else
        spin_unlock_irqrestore(&priv->lock, flags);

    /* process read if there is data other than line status */
    if (tty && bytes > i) {
        tty_insert_flip_string_fixed_flag(tty, data + i,
                tty_flag, bytes - i);
        tty_flip_buffer_push(tty);
    }

    spin_lock_irqsave(&priv->lock, flags);
    /* control and status byte(s) are also counted */
    priv->bytes_in += bytes;
    spin_unlock_irqrestore(&priv->lock, flags);

continue_read:
    tty_kref_put(tty);

    /* Continue trying to always read */

    if (priv->comm_is_ok) {
        usb_fill_int_urb(port->interrupt_in_urb, port->serial->dev,
                usb_rcvintpipe(port->serial->dev,
                    port->interrupt_in_endpointAddress),
                port->interrupt_in_urb->transfer_buffer,
                port->interrupt_in_urb->transfer_buffer_length,
                cypress_read_int_callback, port,
                priv->read_urb_interval);
        result = usb_submit_urb(port->interrupt_in_urb, GFP_ATOMIC);
        if (result && result != -EPERM) {
            dev_err(dev, "%s - failed resubmitting read urb, error %d\n",
                __func__, result);
            cypress_set_dead(port);
        }
    }
} /* cypress_read_int_callback */


static void cypress_write_int_callback(struct urb *urb)
{
    struct usb_serial_port *port = urb->context;
    struct cypress_private *priv = usb_get_serial_port_data(port);
    struct device *dev = &urb->dev->dev;
    int result;
    int status = urb->status;

    switch (status) {
    case 0:
        /* success */
        break;
    case -ECONNRESET:
    case -ENOENT:
    case -ESHUTDOWN:
        /* this urb is terminated, clean up */
        dev_dbg(dev, "%s - urb shutting down with status: %d\n",
            __func__, status);
        priv->write_urb_in_use = 0;
        return;
    case -EPIPE: /* no break needed; clear halt and resubmit */
        if (!priv->comm_is_ok)
            break;
        usb_clear_halt(port->serial->dev, 0x02);
        /* error in the urb, so we have to resubmit it */
        dev_dbg(dev, "%s - nonzero write bulk status received: %d\n",
            __func__, status);
        port->interrupt_out_urb->transfer_buffer_length = 1;
        result = usb_submit_urb(port->interrupt_out_urb, GFP_ATOMIC);
        if (!result)
            return;
        dev_err(dev, "%s - failed resubmitting write urb, error %d\n",
            __func__, result);
        cypress_set_dead(port);
        break;
    default:
        dev_err(dev, "%s - unexpected nonzero write status received: %d\n",
            __func__, status);
        cypress_set_dead(port);
        break;
    }
    priv->write_urb_in_use = 0;

    /* send any buffered data */
    cypress_send(port);
}

module_usb_serial_driver(serial_drivers, id_table_combined);

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

module_param(stats, bool, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(stats, "Enable statistics or not");
module_param(interval, int, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(interval, "Overrides interrupt interval");
module_param(unstable_bauds, bool, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(unstable_bauds, "Allow unstable baud rates");