/*
 * linux/drivers/char/pcmcia/synclink_cs.c
 *
 * $Id: synclink_cs.c,v 4.34 2005/09/08 13:20:54 paulkf Exp $
 *
 * Device driver for Microgate SyncLink PC Card
 * multiprotocol serial adapter.
 *
 * written by Paul Fulghum for Microgate Corporation
 * paulkf@microgate.com
 *
 * Microgate and SyncLink are trademarks of Microgate Corporation
 *
 * This code is released under the GNU General Public License (GPL)
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#define VERSION(ver,rel,seq) (((ver)<<16) | ((rel)<<8) | (seq))
#if defined(__i386__)
#  define BREAKPOINT() asm("   int $3");
#else
#  define BREAKPOINT() { }
#endif

#define MAX_DEVICE_COUNT 4

#include <linux/module.h>
#include <linux/errno.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/time.h>
#include <linux/interrupt.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/serial.h>
#include <linux/major.h>
#include <linux/string.h>
#include <linux/fcntl.h>
#include <linux/ptrace.h>
#include <linux/ioport.h>
#include <linux/mm.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/netdevice.h>
#include <linux/vmalloc.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/ioctl.h>
#include <linux/synclink.h>

#include <asm/io.h>
#include <asm/irq.h>
#include <asm/dma.h>
#include <linux/bitops.h>
#include <asm/types.h>
#include <linux/termios.h>
#include <linux/workqueue.h>
#include <linux/hdlc.h>

#include <pcmcia/cistpl.h>
#include <pcmcia/cisreg.h>
#include <pcmcia/ds.h>

#if defined(CONFIG_HDLC) || (defined(CONFIG_HDLC_MODULE) && defined(CONFIG_SYNCLINK_CS_MODULE))
#define SYNCLINK_GENERIC_HDLC 1
#else
#define SYNCLINK_GENERIC_HDLC 0
#endif

#define GET_USER(error,value,addr) error = get_user(value,addr)
#define COPY_FROM_USER(error,dest,src,size) error = copy_from_user(dest,src,size) ? -EFAULT : 0
#define PUT_USER(error,value,addr) error = put_user(value,addr)
#define COPY_TO_USER(error,dest,src,size) error = copy_to_user(dest,src,size) ? -EFAULT : 0

#include <linux/uaccess.h>

static MGSL_PARAMS default_params = {
        MGSL_MODE_HDLC,                 /* unsigned long mode */
        0,                              /* unsigned char loopback; */
        HDLC_FLAG_UNDERRUN_ABORT15,     /* unsigned short flags; */
        HDLC_ENCODING_NRZI_SPACE,       /* unsigned char encoding; */
        0,                              /* unsigned long clock_speed; */
        0xff,                           /* unsigned char addr_filter; */
        HDLC_CRC_16_CCITT,              /* unsigned short crc_type; */
        HDLC_PREAMBLE_LENGTH_8BITS,     /* unsigned char preamble_length; */
        HDLC_PREAMBLE_PATTERN_NONE,     /* unsigned char preamble; */
        9600,                           /* unsigned long data_rate; */
        8,                              /* unsigned char data_bits; */
        1,                              /* unsigned char stop_bits; */
        ASYNC_PARITY_NONE               /* unsigned char parity; */
};

typedef struct {
        int count;
        unsigned char status;
        char data[1];
} RXBUF;

/* The queue of BH actions to be performed */

#define BH_RECEIVE  1
#define BH_TRANSMIT 2
#define BH_STATUS   4

#define IO_PIN_SHUTDOWN_LIMIT 100

#define RELEVANT_IFLAG(iflag) (iflag & (IGNBRK|BRKINT|IGNPAR|PARMRK|INPCK))

struct _input_signal_events {
        int     ri_up;
        int     ri_down;
        int     dsr_up;
        int     dsr_down;
        int     dcd_up;
        int     dcd_down;
        int     cts_up;
        int     cts_down;
};


/*
 * Device instance data structure
 */

typedef struct _mgslpc_info {
        struct tty_port         port;
        void *if_ptr;   /* General purpose pointer (used by SPPP) */
        int                     magic;
        int                     line;

        struct mgsl_icount      icount;

        int                     timeout;
        int                     x_char;         /* xon/xoff character */
        unsigned char           read_status_mask;
        unsigned char           ignore_status_mask;

        unsigned char *tx_buf;
        int            tx_put;
        int            tx_get;
        int            tx_count;

        /* circular list of fixed length rx buffers */

        unsigned char  *rx_buf;        /* memory allocated for all rx buffers */
        int            rx_buf_total_size; /* size of memory allocated for rx buffers */
        int            rx_put;         /* index of next empty rx buffer */
        int            rx_get;         /* index of next full rx buffer */
        int            rx_buf_size;    /* size in bytes of single rx buffer */
        int            rx_buf_count;   /* total number of rx buffers */
        int            rx_frame_count; /* number of full rx buffers */

        wait_queue_head_t       status_event_wait_q;
        wait_queue_head_t       event_wait_q;
        struct timer_list       tx_timer;       /* HDLC transmit timeout timer */
        struct _mgslpc_info     *next_device;   /* device list link */

        unsigned short imra_value;
        unsigned short imrb_value;
        unsigned char  pim_value;

        spinlock_t lock;
        struct work_struct task;                /* task structure for scheduling bh */

        u32 max_frame_size;

        u32 pending_bh;

        bool bh_running;
        bool bh_requested;

        int dcd_chkcount; /* check counts to prevent */
        int cts_chkcount; /* too many IRQs if a signal */
        int dsr_chkcount; /* is floating */
        int ri_chkcount;

        bool rx_enabled;
        bool rx_overflow;

        bool tx_enabled;
        bool tx_active;
        bool tx_aborting;
        u32 idle_mode;

        int if_mode; /* serial interface selection (RS-232, v.35 etc) */

        char device_name[25];           /* device instance name */

        unsigned int io_base;   /* base I/O address of adapter */
        unsigned int irq_level;

        MGSL_PARAMS params;             /* communications parameters */

        unsigned char serial_signals;   /* current serial signal states */

        bool irq_occurred;              /* for diagnostics use */
        char testing_irq;
        unsigned int init_error;        /* startup error (DIAGS)        */

        char *flag_buf;
        bool drop_rts_on_tx_done;

        struct  _input_signal_events    input_signal_events;

        /* PCMCIA support */
        struct pcmcia_device    *p_dev;
        int                   stop;

        /* SPPP/Cisco HDLC device parts */
        int netcount;
        spinlock_t netlock;

#if SYNCLINK_GENERIC_HDLC
        struct net_device *netdev;
#endif

} MGSLPC_INFO;

#define MGSLPC_MAGIC 0x5402

/*
 * The size of the serial xmit buffer is 1 page, or 4096 bytes
 */
#define TXBUFSIZE 4096


#define CHA     0x00   /* channel A offset */
#define CHB     0x40   /* channel B offset */

/*
 *  FIXME: PPC has PVR defined in asm/reg.h.  For now we just undef it.
 */
#undef PVR

#define RXFIFO  0
#define TXFIFO  0
#define STAR    0x20
#define CMDR    0x20
#define RSTA    0x21
#define PRE     0x21
#define MODE    0x22
#define TIMR    0x23
#define XAD1    0x24
#define XAD2    0x25
#define RAH1    0x26
#define RAH2    0x27
#define DAFO    0x27
#define RAL1    0x28
#define RFC     0x28
#define RHCR    0x29
#define RAL2    0x29
#define RBCL    0x2a
#define XBCL    0x2a
#define RBCH    0x2b
#define XBCH    0x2b
#define CCR0    0x2c
#define CCR1    0x2d
#define CCR2    0x2e
#define CCR3    0x2f
#define VSTR    0x34
#define BGR     0x34
#define RLCR    0x35
#define AML     0x36
#define AMH     0x37
#define GIS     0x38
#define IVA     0x38
#define IPC     0x39
#define ISR     0x3a
#define IMR     0x3a
#define PVR     0x3c
#define PIS     0x3d
#define PIM     0x3d
#define PCR     0x3e
#define CCR4    0x3f

// IMR/ISR

#define IRQ_BREAK_ON    BIT15   // rx break detected
#define IRQ_DATAOVERRUN BIT14   // receive data overflow
#define IRQ_ALLSENT     BIT13   // all sent
#define IRQ_UNDERRUN    BIT12   // transmit data underrun
#define IRQ_TIMER       BIT11   // timer interrupt
#define IRQ_CTS         BIT10   // CTS status change
#define IRQ_TXREPEAT    BIT9    // tx message repeat
#define IRQ_TXFIFO      BIT8    // transmit pool ready
#define IRQ_RXEOM       BIT7    // receive message end
#define IRQ_EXITHUNT    BIT6    // receive frame start
#define IRQ_RXTIME      BIT6    // rx char timeout
#define IRQ_DCD         BIT2    // carrier detect status change
#define IRQ_OVERRUN     BIT1    // receive frame overflow
#define IRQ_RXFIFO      BIT0    // receive pool full

// STAR

#define XFW   BIT6              // transmit FIFO write enable
#define CEC   BIT2              // command executing
#define CTS   BIT1              // CTS state

#define PVR_DTR      BIT0
#define PVR_DSR      BIT1
#define PVR_RI       BIT2
#define PVR_AUTOCTS  BIT3
#define PVR_RS232    0x20   /* 0010b */
#define PVR_V35      0xe0   /* 1110b */
#define PVR_RS422    0x40   /* 0100b */

/* Register access functions */

#define write_reg(info, reg, val) outb((val),(info)->io_base + (reg))
#define read_reg(info, reg) inb((info)->io_base + (reg))

#define read_reg16(info, reg) inw((info)->io_base + (reg))
#define write_reg16(info, reg, val) outw((val), (info)->io_base + (reg))

#define set_reg_bits(info, reg, mask) \
        write_reg(info, (reg), \
                 (unsigned char) (read_reg(info, (reg)) | (mask)))
#define clear_reg_bits(info, reg, mask) \
        write_reg(info, (reg), \
                 (unsigned char) (read_reg(info, (reg)) & ~(mask)))
/*
 * interrupt enable/disable routines
 */
static void irq_disable(MGSLPC_INFO *info, unsigned char channel, unsigned short mask)
{
        if (channel == CHA) {
                info->imra_value |= mask;
                write_reg16(info, CHA + IMR, info->imra_value);
        } else {
                info->imrb_value |= mask;
                write_reg16(info, CHB + IMR, info->imrb_value);
        }
}
static void irq_enable(MGSLPC_INFO *info, unsigned char channel, unsigned short mask)
{
        if (channel == CHA) {
                info->imra_value &= ~mask;
                write_reg16(info, CHA + IMR, info->imra_value);
        } else {
                info->imrb_value &= ~mask;
                write_reg16(info, CHB + IMR, info->imrb_value);
        }
}

#define port_irq_disable(info, mask) \
        { info->pim_value |= (mask); write_reg(info, PIM, info->pim_value); }

#define port_irq_enable(info, mask) \
        { info->pim_value &= ~(mask); write_reg(info, PIM, info->pim_value); }

static void rx_start(MGSLPC_INFO *info);
static void rx_stop(MGSLPC_INFO *info);

static void tx_start(MGSLPC_INFO *info, struct tty_struct *tty);
static void tx_stop(MGSLPC_INFO *info);
static void tx_set_idle(MGSLPC_INFO *info);

static void get_signals(MGSLPC_INFO *info);
static void set_signals(MGSLPC_INFO *info);

static void reset_device(MGSLPC_INFO *info);

static void hdlc_mode(MGSLPC_INFO *info);
static void async_mode(MGSLPC_INFO *info);

static void tx_timeout(struct timer_list *t);

static int carrier_raised(struct tty_port *port);
static void dtr_rts(struct tty_port *port, int onoff);

#if SYNCLINK_GENERIC_HDLC
#define dev_to_port(D) (dev_to_hdlc(D)->priv)
static void hdlcdev_tx_done(MGSLPC_INFO *info);
static void hdlcdev_rx(MGSLPC_INFO *info, char *buf, int size);
static int  hdlcdev_init(MGSLPC_INFO *info);
static void hdlcdev_exit(MGSLPC_INFO *info);
#endif

static void trace_block(MGSLPC_INFO *info,const char* data, int count, int xmit);

static bool register_test(MGSLPC_INFO *info);
static bool irq_test(MGSLPC_INFO *info);
static int adapter_test(MGSLPC_INFO *info);

static int claim_resources(MGSLPC_INFO *info);
static void release_resources(MGSLPC_INFO *info);
static int mgslpc_add_device(MGSLPC_INFO *info);
static void mgslpc_remove_device(MGSLPC_INFO *info);

static bool rx_get_frame(MGSLPC_INFO *info, struct tty_struct *tty);
static void rx_reset_buffers(MGSLPC_INFO *info);
static int  rx_alloc_buffers(MGSLPC_INFO *info);
static void rx_free_buffers(MGSLPC_INFO *info);

static irqreturn_t mgslpc_isr(int irq, void *dev_id);

/*
 * Bottom half interrupt handlers
 */
static void bh_handler(struct work_struct *work);
static void bh_transmit(MGSLPC_INFO *info, struct tty_struct *tty);
static void bh_status(MGSLPC_INFO *info);

/*
 * ioctl handlers
 */
static int tiocmget(struct tty_struct *tty);
static int tiocmset(struct tty_struct *tty,
                                        unsigned int set, unsigned int clear);
static int get_stats(MGSLPC_INFO *info, struct mgsl_icount __user *user_icount);
static int get_params(MGSLPC_INFO *info, MGSL_PARAMS __user *user_params);
static int set_params(MGSLPC_INFO *info, MGSL_PARAMS __user *new_params, struct tty_struct *tty);
static int get_txidle(MGSLPC_INFO *info, int __user *idle_mode);
static int set_txidle(MGSLPC_INFO *info, int idle_mode);
static int set_txenable(MGSLPC_INFO *info, int enable, struct tty_struct *tty);
static int tx_abort(MGSLPC_INFO *info);
static int set_rxenable(MGSLPC_INFO *info, int enable);
static int wait_events(MGSLPC_INFO *info, int __user *mask);

static MGSLPC_INFO *mgslpc_device_list = NULL;
static int mgslpc_device_count = 0;

/*
 * Set this param to non-zero to load eax with the
 * .text section address and breakpoint on module load.
 * This is useful for use with gdb and add-symbol-file command.
 */
static bool break_on_load;

/*
 * Driver major number, defaults to zero to get auto
 * assigned major number. May be forced as module parameter.
 */
static int ttymajor=0;

static int debug_level = 0;
static int maxframe[MAX_DEVICE_COUNT] = {0,};

module_param(break_on_load, bool, 0);
module_param(ttymajor, int, 0);
module_param(debug_level, int, 0);
module_param_array(maxframe, int, NULL, 0);

MODULE_LICENSE("GPL");

static char *driver_name = "SyncLink PC Card driver";
static char *driver_version = "$Revision: 4.34 $";

static struct tty_driver *serial_driver;

/* number of characters left in xmit buffer before we ask for more */
#define WAKEUP_CHARS 256

static void mgslpc_change_params(MGSLPC_INFO *info, struct tty_struct *tty);
static void mgslpc_wait_until_sent(struct tty_struct *tty, int timeout);

/* PCMCIA prototypes */

static int mgslpc_config(struct pcmcia_device *link);
static void mgslpc_release(u_long arg);
static void mgslpc_detach(struct pcmcia_device *p_dev);

/*
 * 1st function defined in .text section. Calling this function in
 * init_module() followed by a breakpoint allows a remote debugger
 * (gdb) to get the .text address for the add-symbol-file command.
 * This allows remote debugging of dynamically loadable modules.
 */
static void* mgslpc_get_text_ptr(void)
{
        return mgslpc_get_text_ptr;
}

/**
 * line discipline callback wrappers
 *
 * The wrappers maintain line discipline references
 * while calling into the line discipline.
 *
 * ldisc_receive_buf  - pass receive data to line discipline
 */

static void ldisc_receive_buf(struct tty_struct *tty,
                              const __u8 *data, char *flags, int count)
{
        struct tty_ldisc *ld;
        if (!tty)
                return;
        ld = tty_ldisc_ref(tty);
        if (ld) {
                if (ld->ops->receive_buf)
                        ld->ops->receive_buf(tty, data, flags, count);
                tty_ldisc_deref(ld);
        }
}

static const struct tty_port_operations mgslpc_port_ops = {
        .carrier_raised = carrier_raised,
        .dtr_rts = dtr_rts
};

static int mgslpc_probe(struct pcmcia_device *link)
{
        MGSLPC_INFO *info;
        int ret;

        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("mgslpc_attach\n");

        info = kzalloc(sizeof(MGSLPC_INFO), GFP_KERNEL);
        if (!info) {
                printk("Error can't allocate device instance data\n");
                return -ENOMEM;
        }

        info->magic = MGSLPC_MAGIC;
        tty_port_init(&info->port);
        info->port.ops = &mgslpc_port_ops;
        INIT_WORK(&info->task, bh_handler);
        info->max_frame_size = 4096;
        init_waitqueue_head(&info->status_event_wait_q);
        init_waitqueue_head(&info->event_wait_q);
        spin_lock_init(&info->lock);
        spin_lock_init(&info->netlock);
        memcpy(&info->params,&default_params,sizeof(MGSL_PARAMS));
        info->idle_mode = HDLC_TXIDLE_FLAGS;
        info->imra_value = 0xffff;
        info->imrb_value = 0xffff;
        info->pim_value = 0xff;

        info->p_dev = link;
        link->priv = info;

        /* Initialize the struct pcmcia_device structure */

        ret = mgslpc_config(link);
        if (ret != 0)
                goto failed;

        ret = mgslpc_add_device(info);
        if (ret != 0)
                goto failed_release;

        return 0;

failed_release:
        mgslpc_release((u_long)link);
failed:
        tty_port_destroy(&info->port);
        kfree(info);
        return ret;
}

/* Card has been inserted.
 */

static int mgslpc_ioprobe(struct pcmcia_device *p_dev, void *priv_data)
{
        return pcmcia_request_io(p_dev);
}

static int mgslpc_config(struct pcmcia_device *link)
{
        MGSLPC_INFO *info = link->priv;
        int ret;

        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("mgslpc_config(0x%p)\n", link);

        link->config_flags |= CONF_ENABLE_IRQ | CONF_AUTO_SET_IO;

        ret = pcmcia_loop_config(link, mgslpc_ioprobe, NULL);
        if (ret != 0)
                goto failed;

        link->config_index = 8;
        link->config_regs = PRESENT_OPTION;

        ret = pcmcia_request_irq(link, mgslpc_isr);
        if (ret)
                goto failed;
        ret = pcmcia_enable_device(link);
        if (ret)
                goto failed;

        info->io_base = link->resource[0]->start;
        info->irq_level = link->irq;
        return 0;

failed:
        mgslpc_release((u_long)link);
        return -ENODEV;
}

/* Card has been removed.
 * Unregister device and release PCMCIA configuration.
 * If device is open, postpone until it is closed.
 */
static void mgslpc_release(u_long arg)
{
        struct pcmcia_device *link = (struct pcmcia_device *)arg;

        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("mgslpc_release(0x%p)\n", link);

        pcmcia_disable_device(link);
}

static void mgslpc_detach(struct pcmcia_device *link)
{
        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("mgslpc_detach(0x%p)\n", link);

        ((MGSLPC_INFO *)link->priv)->stop = 1;
        mgslpc_release((u_long)link);

        mgslpc_remove_device((MGSLPC_INFO *)link->priv);
}

static int mgslpc_suspend(struct pcmcia_device *link)
{
        MGSLPC_INFO *info = link->priv;

        info->stop = 1;

        return 0;
}

static int mgslpc_resume(struct pcmcia_device *link)
{
        MGSLPC_INFO *info = link->priv;

        info->stop = 0;

        return 0;
}


static inline bool mgslpc_paranoia_check(MGSLPC_INFO *info,
                                        char *name, const char *routine)
{
#ifdef MGSLPC_PARANOIA_CHECK
        static const char *badmagic =
                "Warning: bad magic number for mgsl struct (%s) in %s\n";
        static const char *badinfo =
                "Warning: null mgslpc_info for (%s) in %s\n";

        if (!info) {
                printk(badinfo, name, routine);
                return true;
        }
        if (info->magic != MGSLPC_MAGIC) {
                printk(badmagic, name, routine);
                return true;
        }
#else
        if (!info)
                return true;
#endif
        return false;
}


#define CMD_RXFIFO      BIT7    // release current rx FIFO
#define CMD_RXRESET     BIT6    // receiver reset
#define CMD_RXFIFO_READ BIT5
#define CMD_START_TIMER BIT4
#define CMD_TXFIFO      BIT3    // release current tx FIFO
#define CMD_TXEOM       BIT1    // transmit end message
#define CMD_TXRESET     BIT0    // transmit reset

static bool wait_command_complete(MGSLPC_INFO *info, unsigned char channel)
{
        int i = 0;
        /* wait for command completion */
        while (read_reg(info, (unsigned char)(channel+STAR)) & BIT2) {
                udelay(1);
                if (i++ == 1000)
                        return false;
        }
        return true;
}

static void issue_command(MGSLPC_INFO *info, unsigned char channel, unsigned char cmd)
{
        wait_command_complete(info, channel);
        write_reg(info, (unsigned char) (channel + CMDR), cmd);
}

static void tx_pause(struct tty_struct *tty)
{
        MGSLPC_INFO *info = (MGSLPC_INFO *)tty->driver_data;
        unsigned long flags;

        if (mgslpc_paranoia_check(info, tty->name, "tx_pause"))
                return;
        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("tx_pause(%s)\n", info->device_name);

        spin_lock_irqsave(&info->lock, flags);
        if (info->tx_enabled)
                tx_stop(info);
        spin_unlock_irqrestore(&info->lock, flags);
}

static void tx_release(struct tty_struct *tty)
{
        MGSLPC_INFO *info = (MGSLPC_INFO *)tty->driver_data;
        unsigned long flags;

        if (mgslpc_paranoia_check(info, tty->name, "tx_release"))
                return;
        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("tx_release(%s)\n", info->device_name);

        spin_lock_irqsave(&info->lock, flags);
        if (!info->tx_enabled)
                tx_start(info, tty);
        spin_unlock_irqrestore(&info->lock, flags);
}

/* Return next bottom half action to perform.
 * or 0 if nothing to do.
 */
static int bh_action(MGSLPC_INFO *info)
{
        unsigned long flags;
        int rc = 0;

        spin_lock_irqsave(&info->lock, flags);

        if (info->pending_bh & BH_RECEIVE) {
                info->pending_bh &= ~BH_RECEIVE;
                rc = BH_RECEIVE;
        } else if (info->pending_bh & BH_TRANSMIT) {
                info->pending_bh &= ~BH_TRANSMIT;
                rc = BH_TRANSMIT;
        } else if (info->pending_bh & BH_STATUS) {
                info->pending_bh &= ~BH_STATUS;
                rc = BH_STATUS;
        }

        if (!rc) {
                /* Mark BH routine as complete */
                info->bh_running = false;
                info->bh_requested = false;
        }

        spin_unlock_irqrestore(&info->lock, flags);

        return rc;
}

static void bh_handler(struct work_struct *work)
{
        MGSLPC_INFO *info = container_of(work, MGSLPC_INFO, task);
        struct tty_struct *tty;
        int action;

        if (debug_level >= DEBUG_LEVEL_BH)
                printk("%s(%d):bh_handler(%s) entry\n",
                        __FILE__,__LINE__,info->device_name);

        info->bh_running = true;
        tty = tty_port_tty_get(&info->port);

        while((action = bh_action(info)) != 0) {

                /* Process work item */
                if (debug_level >= DEBUG_LEVEL_BH)
                        printk("%s(%d):bh_handler() work item action=%d\n",
                                __FILE__,__LINE__,action);

                switch (action) {

                case BH_RECEIVE:
                        while(rx_get_frame(info, tty));
                        break;
                case BH_TRANSMIT:
                        bh_transmit(info, tty);
                        break;
                case BH_STATUS:
                        bh_status(info);
                        break;
                default:
                        /* unknown work item ID */
                        printk("Unknown work item ID=%08X!\n", action);
                        break;
                }
        }

        tty_kref_put(tty);
        if (debug_level >= DEBUG_LEVEL_BH)
                printk("%s(%d):bh_handler(%s) exit\n",
                        __FILE__,__LINE__,info->device_name);
}

static void bh_transmit(MGSLPC_INFO *info, struct tty_struct *tty)
{
        if (debug_level >= DEBUG_LEVEL_BH)
                printk("bh_transmit() entry on %s\n", info->device_name);

        if (tty)
                tty_wakeup(tty);
}

static void bh_status(MGSLPC_INFO *info)
{
        info->ri_chkcount = 0;
        info->dsr_chkcount = 0;
        info->dcd_chkcount = 0;
        info->cts_chkcount = 0;
}

/* eom: non-zero = end of frame */
static void rx_ready_hdlc(MGSLPC_INFO *info, int eom)
{
        unsigned char data[2];
        unsigned char fifo_count, read_count, i;
        RXBUF *buf = (RXBUF*)(info->rx_buf + (info->rx_put * info->rx_buf_size));

        if (debug_level >= DEBUG_LEVEL_ISR)
                printk("%s(%d):rx_ready_hdlc(eom=%d)\n", __FILE__, __LINE__, eom);

        if (!info->rx_enabled)
                return;

        if (info->rx_frame_count >= info->rx_buf_count) {
                /* no more free buffers */
                issue_command(info, CHA, CMD_RXRESET);
                info->pending_bh |= BH_RECEIVE;
                info->rx_overflow = true;
                info->icount.buf_overrun++;
                return;
        }

        if (eom) {
                /* end of frame, get FIFO count from RBCL register */
                fifo_count = (unsigned char)(read_reg(info, CHA+RBCL) & 0x1f);
                if (fifo_count == 0)
                        fifo_count = 32;
        } else
                fifo_count = 32;

        do {
                if (fifo_count == 1) {
                        read_count = 1;
                        data[0] = read_reg(info, CHA + RXFIFO);
                } else {
                        read_count = 2;
                        *((unsigned short *) data) = read_reg16(info, CHA + RXFIFO);
                }
                fifo_count -= read_count;
                if (!fifo_count && eom)
                        buf->status = data[--read_count];

                for (i = 0; i < read_count; i++) {
                        if (buf->count >= info->max_frame_size) {
                                /* frame too large, reset receiver and reset current buffer */
                                issue_command(info, CHA, CMD_RXRESET);
                                buf->count = 0;
                                return;
                        }
                        *(buf->data + buf->count) = data[i];
                        buf->count++;
                }
        } while (fifo_count);

        if (eom) {
                info->pending_bh |= BH_RECEIVE;
                info->rx_frame_count++;
                info->rx_put++;
                if (info->rx_put >= info->rx_buf_count)
                        info->rx_put = 0;
        }
        issue_command(info, CHA, CMD_RXFIFO);
}

static void rx_ready_async(MGSLPC_INFO *info, int tcd)
{
        struct tty_port *port = &info->port;
        unsigned char data, status, flag;
        int fifo_count;
        int work = 0;
        struct mgsl_icount *icount = &info->icount;

        if (tcd) {
                /* early termination, get FIFO count from RBCL register */
                fifo_count = (unsigned char)(read_reg(info, CHA+RBCL) & 0x1f);

                /* Zero fifo count could mean 0 or 32 bytes available.
                 * If BIT5 of STAR is set then at least 1 byte is available.
                 */
                if (!fifo_count && (read_reg(info,CHA+STAR) & BIT5))
                        fifo_count = 32;
        } else
                fifo_count = 32;

        tty_buffer_request_room(port, fifo_count);
        /* Flush received async data to receive data buffer. */
        while (fifo_count) {
                data   = read_reg(info, CHA + RXFIFO);
                status = read_reg(info, CHA + RXFIFO);
                fifo_count -= 2;

                icount->rx++;
                flag = TTY_NORMAL;

                // if no frameing/crc error then save data
                // BIT7:parity error
                // BIT6:framing error

                if (status & (BIT7 + BIT6)) {
                        if (status & BIT7)
                                icount->parity++;
                        else
                                icount->frame++;

                        /* discard char if tty control flags say so */
                        if (status & info->ignore_status_mask)
                                continue;

                        status &= info->read_status_mask;

                        if (status & BIT7)
                                flag = TTY_PARITY;
                        else if (status & BIT6)
                                flag = TTY_FRAME;
                }
                work += tty_insert_flip_char(port, data, flag);
        }
        issue_command(info, CHA, CMD_RXFIFO);

        if (debug_level >= DEBUG_LEVEL_ISR) {
                printk("%s(%d):rx_ready_async",
                        __FILE__,__LINE__);
                printk("%s(%d):rx=%d brk=%d parity=%d frame=%d overrun=%d\n",
                        __FILE__,__LINE__,icount->rx,icount->brk,
                        icount->parity,icount->frame,icount->overrun);
        }

        if (work)
                tty_flip_buffer_push(port);
}


static void tx_done(MGSLPC_INFO *info, struct tty_struct *tty)
{
        if (!info->tx_active)
                return;

        info->tx_active = false;
        info->tx_aborting = false;

        if (info->params.mode == MGSL_MODE_ASYNC)
                return;

        info->tx_count = info->tx_put = info->tx_get = 0;
        del_timer(&info->tx_timer);

        if (info->drop_rts_on_tx_done) {
                get_signals(info);
                if (info->serial_signals & SerialSignal_RTS) {
                        info->serial_signals &= ~SerialSignal_RTS;
                        set_signals(info);
                }
                info->drop_rts_on_tx_done = false;
        }

#if SYNCLINK_GENERIC_HDLC
        if (info->netcount)
                hdlcdev_tx_done(info);
        else
#endif
        {
                if (tty && (tty->stopped || tty->hw_stopped)) {
                        tx_stop(info);
                        return;
                }
                info->pending_bh |= BH_TRANSMIT;
        }
}

static void tx_ready(MGSLPC_INFO *info, struct tty_struct *tty)
{
        unsigned char fifo_count = 32;
        int c;

        if (debug_level >= DEBUG_LEVEL_ISR)
                printk("%s(%d):tx_ready(%s)\n", __FILE__, __LINE__, info->device_name);

        if (info->params.mode == MGSL_MODE_HDLC) {
                if (!info->tx_active)
                        return;
        } else {
                if (tty && (tty->stopped || tty->hw_stopped)) {
                        tx_stop(info);
                        return;
                }
                if (!info->tx_count)
                        info->tx_active = false;
        }

        if (!info->tx_count)
                return;

        while (info->tx_count && fifo_count) {
                c = min(2, min_t(int, fifo_count, min(info->tx_count, TXBUFSIZE - info->tx_get)));

                if (c == 1) {
                        write_reg(info, CHA + TXFIFO, *(info->tx_buf + info->tx_get));
                } else {
                        write_reg16(info, CHA + TXFIFO,
                                          *((unsigned short*)(info->tx_buf + info->tx_get)));
                }
                info->tx_count -= c;
                info->tx_get = (info->tx_get + c) & (TXBUFSIZE - 1);
                fifo_count -= c;
        }

        if (info->params.mode == MGSL_MODE_ASYNC) {
                if (info->tx_count < WAKEUP_CHARS)
                        info->pending_bh |= BH_TRANSMIT;
                issue_command(info, CHA, CMD_TXFIFO);
        } else {
                if (info->tx_count)
                        issue_command(info, CHA, CMD_TXFIFO);
                else
                        issue_command(info, CHA, CMD_TXFIFO + CMD_TXEOM);
        }
}

static void cts_change(MGSLPC_INFO *info, struct tty_struct *tty)
{
        get_signals(info);
        if ((info->cts_chkcount)++ >= IO_PIN_SHUTDOWN_LIMIT)
                irq_disable(info, CHB, IRQ_CTS);
        info->icount.cts++;
        if (info->serial_signals & SerialSignal_CTS)
                info->input_signal_events.cts_up++;
        else
                info->input_signal_events.cts_down++;
        wake_up_interruptible(&info->status_event_wait_q);
        wake_up_interruptible(&info->event_wait_q);

        if (tty && tty_port_cts_enabled(&info->port)) {
                if (tty->hw_stopped) {
                        if (info->serial_signals & SerialSignal_CTS) {
                                if (debug_level >= DEBUG_LEVEL_ISR)
                                        printk("CTS tx start...");
                                tty->hw_stopped = 0;
                                tx_start(info, tty);
                                info->pending_bh |= BH_TRANSMIT;
                                return;
                        }
                } else {
                        if (!(info->serial_signals & SerialSignal_CTS)) {
                                if (debug_level >= DEBUG_LEVEL_ISR)
                                        printk("CTS tx stop...");
                                tty->hw_stopped = 1;
                                tx_stop(info);
                        }
                }
        }
        info->pending_bh |= BH_STATUS;
}

static void dcd_change(MGSLPC_INFO *info, struct tty_struct *tty)
{
        get_signals(info);
        if ((info->dcd_chkcount)++ >= IO_PIN_SHUTDOWN_LIMIT)
                irq_disable(info, CHB, IRQ_DCD);
        info->icount.dcd++;
        if (info->serial_signals & SerialSignal_DCD) {
                info->input_signal_events.dcd_up++;
        }
        else
                info->input_signal_events.dcd_down++;
#if SYNCLINK_GENERIC_HDLC
        if (info->netcount) {
                if (info->serial_signals & SerialSignal_DCD)
                        netif_carrier_on(info->netdev);
                else
                        netif_carrier_off(info->netdev);
        }
#endif
        wake_up_interruptible(&info->status_event_wait_q);
        wake_up_interruptible(&info->event_wait_q);

        if (tty_port_check_carrier(&info->port)) {
                if (debug_level >= DEBUG_LEVEL_ISR)
                        printk("%s CD now %s...", info->device_name,
                               (info->serial_signals & SerialSignal_DCD) ? "on" : "off");
                if (info->serial_signals & SerialSignal_DCD)
                        wake_up_interruptible(&info->port.open_wait);
                else {
                        if (debug_level >= DEBUG_LEVEL_ISR)
                                printk("doing serial hangup...");
                        if (tty)
                                tty_hangup(tty);
                }
        }
        info->pending_bh |= BH_STATUS;
}

static void dsr_change(MGSLPC_INFO *info)
{
        get_signals(info);
        if ((info->dsr_chkcount)++ >= IO_PIN_SHUTDOWN_LIMIT)
                port_irq_disable(info, PVR_DSR);
        info->icount.dsr++;
        if (info->serial_signals & SerialSignal_DSR)
                info->input_signal_events.dsr_up++;
        else
                info->input_signal_events.dsr_down++;
        wake_up_interruptible(&info->status_event_wait_q);
        wake_up_interruptible(&info->event_wait_q);
        info->pending_bh |= BH_STATUS;
}

static void ri_change(MGSLPC_INFO *info)
{
        get_signals(info);
        if ((info->ri_chkcount)++ >= IO_PIN_SHUTDOWN_LIMIT)
                port_irq_disable(info, PVR_RI);
        info->icount.rng++;
        if (info->serial_signals & SerialSignal_RI)
                info->input_signal_events.ri_up++;
        else
                info->input_signal_events.ri_down++;
        wake_up_interruptible(&info->status_event_wait_q);
        wake_up_interruptible(&info->event_wait_q);
        info->pending_bh |= BH_STATUS;
}

/* Interrupt service routine entry point.
 *
 * Arguments:
 *
 * irq     interrupt number that caused interrupt
 * dev_id  device ID supplied during interrupt registration
 */
static irqreturn_t mgslpc_isr(int dummy, void *dev_id)
{
        MGSLPC_INFO *info = dev_id;
        struct tty_struct *tty;
        unsigned short isr;
        unsigned char gis, pis;
        int count=0;

        if (debug_level >= DEBUG_LEVEL_ISR)
                printk("mgslpc_isr(%d) entry.\n", info->irq_level);

        if (!(info->p_dev->_locked))
                return IRQ_HANDLED;

        tty = tty_port_tty_get(&info->port);

        spin_lock(&info->lock);

        while ((gis = read_reg(info, CHA + GIS))) {
                if (debug_level >= DEBUG_LEVEL_ISR)
                        printk("mgslpc_isr %s gis=%04X\n", info->device_name,gis);

                if ((gis & 0x70) || count > 1000) {
                        printk("synclink_cs:hardware failed or ejected\n");
                        break;
                }
                count++;

                if (gis & (BIT1 | BIT0)) {
                        isr = read_reg16(info, CHB + ISR);
                        if (isr & IRQ_DCD)
                                dcd_change(info, tty);
                        if (isr & IRQ_CTS)
                                cts_change(info, tty);
                }
                if (gis & (BIT3 | BIT2))
                {
                        isr = read_reg16(info, CHA + ISR);
                        if (isr & IRQ_TIMER) {
                                info->irq_occurred = true;
                                irq_disable(info, CHA, IRQ_TIMER);
                        }

                        /* receive IRQs */
                        if (isr & IRQ_EXITHUNT) {
                                info->icount.exithunt++;
                                wake_up_interruptible(&info->event_wait_q);
                        }
                        if (isr & IRQ_BREAK_ON) {
                                info->icount.brk++;
                                if (info->port.flags & ASYNC_SAK)
                                        do_SAK(tty);
                        }
                        if (isr & IRQ_RXTIME) {
                                issue_command(info, CHA, CMD_RXFIFO_READ);
                        }
                        if (isr & (IRQ_RXEOM | IRQ_RXFIFO)) {
                                if (info->params.mode == MGSL_MODE_HDLC)
                                        rx_ready_hdlc(info, isr & IRQ_RXEOM);
                                else
                                        rx_ready_async(info, isr & IRQ_RXEOM);
                        }

                        /* transmit IRQs */
                        if (isr & IRQ_UNDERRUN) {
                                if (info->tx_aborting)
                                        info->icount.txabort++;
                                else
                                        info->icount.txunder++;
                                tx_done(info, tty);
                        }
                        else if (isr & IRQ_ALLSENT) {
                                info->icount.txok++;
                                tx_done(info, tty);
                        }
                        else if (isr & IRQ_TXFIFO)
                                tx_ready(info, tty);
                }
                if (gis & BIT7) {
                        pis = read_reg(info, CHA + PIS);
                        if (pis & BIT1)
                                dsr_change(info);
                        if (pis & BIT2)
                                ri_change(info);
                }
        }

        /* Request bottom half processing if there's something
         * for it to do and the bh is not already running
         */

        if (info->pending_bh && !info->bh_running && !info->bh_requested) {
                if (debug_level >= DEBUG_LEVEL_ISR)
                        printk("%s(%d):%s queueing bh task.\n",
                                __FILE__,__LINE__,info->device_name);
                schedule_work(&info->task);
                info->bh_requested = true;
        }

        spin_unlock(&info->lock);
        tty_kref_put(tty);

        if (debug_level >= DEBUG_LEVEL_ISR)
                printk("%s(%d):mgslpc_isr(%d)exit.\n",
                       __FILE__, __LINE__, info->irq_level);

        return IRQ_HANDLED;
}

/* Initialize and start device.
 */
static int startup(MGSLPC_INFO * info, struct tty_struct *tty)
{
        int retval = 0;

        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("%s(%d):startup(%s)\n", __FILE__, __LINE__, info->device_name);

        if (tty_port_initialized(&info->port))
                return 0;

        if (!info->tx_buf) {
                /* allocate a page of memory for a transmit buffer */
                info->tx_buf = (unsigned char *)get_zeroed_page(GFP_KERNEL);
                if (!info->tx_buf) {
                        printk(KERN_ERR"%s(%d):%s can't allocate transmit buffer\n",
                                __FILE__, __LINE__, info->device_name);
                        return -ENOMEM;
                }
        }

        info->pending_bh = 0;

        memset(&info->icount, 0, sizeof(info->icount));

        timer_setup(&info->tx_timer, tx_timeout, 0);

        /* Allocate and claim adapter resources */
        retval = claim_resources(info);

        /* perform existence check and diagnostics */
        if (!retval)
                retval = adapter_test(info);

        if (retval) {
                if (capable(CAP_SYS_ADMIN) && tty)
                        set_bit(TTY_IO_ERROR, &tty->flags);
                release_resources(info);
                return retval;
        }

        /* program hardware for current parameters */
        mgslpc_change_params(info, tty);

        if (tty)
                clear_bit(TTY_IO_ERROR, &tty->flags);

        tty_port_set_initialized(&info->port, 1);

        return 0;
}

/* Called by mgslpc_close() and mgslpc_hangup() to shutdown hardware
 */
static void shutdown(MGSLPC_INFO * info, struct tty_struct *tty)
{
        unsigned long flags;

        if (!tty_port_initialized(&info->port))
                return;

        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("%s(%d):mgslpc_shutdown(%s)\n",
                         __FILE__, __LINE__, info->device_name);

        /* clear status wait queue because status changes */
        /* can't happen after shutting down the hardware */
        wake_up_interruptible(&info->status_event_wait_q);
        wake_up_interruptible(&info->event_wait_q);

        del_timer_sync(&info->tx_timer);

        if (info->tx_buf) {
                free_page((unsigned long) info->tx_buf);
                info->tx_buf = NULL;
        }

        spin_lock_irqsave(&info->lock, flags);

        rx_stop(info);
        tx_stop(info);

        /* TODO:disable interrupts instead of reset to preserve signal states */
        reset_device(info);

        if (!tty || C_HUPCL(tty)) {
                info->serial_signals &= ~(SerialSignal_RTS | SerialSignal_DTR);
                set_signals(info);
        }

        spin_unlock_irqrestore(&info->lock, flags);

        release_resources(info);

        if (tty)
                set_bit(TTY_IO_ERROR, &tty->flags);

        tty_port_set_initialized(&info->port, 0);
}

static void mgslpc_program_hw(MGSLPC_INFO *info, struct tty_struct *tty)
{
        unsigned long flags;

        spin_lock_irqsave(&info->lock, flags);

        rx_stop(info);
        tx_stop(info);
        info->tx_count = info->tx_put = info->tx_get = 0;

        if (info->params.mode == MGSL_MODE_HDLC || info->netcount)
                hdlc_mode(info);
        else
                async_mode(info);

        set_signals(info);

        info->dcd_chkcount = 0;
        info->cts_chkcount = 0;
        info->ri_chkcount = 0;
        info->dsr_chkcount = 0;

        irq_enable(info, CHB, IRQ_DCD | IRQ_CTS);
        port_irq_enable(info, (unsigned char) PVR_DSR | PVR_RI);
        get_signals(info);

        if (info->netcount || (tty && C_CREAD(tty)))
                rx_start(info);

        spin_unlock_irqrestore(&info->lock, flags);
}

/* Reconfigure adapter based on new parameters
 */
static void mgslpc_change_params(MGSLPC_INFO *info, struct tty_struct *tty)
{
        unsigned cflag;
        int bits_per_char;

        if (!tty)
                return;

        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("%s(%d):mgslpc_change_params(%s)\n",
                         __FILE__, __LINE__, info->device_name);

        cflag = tty->termios.c_cflag;

        /* if B0 rate (hangup) specified then negate RTS and DTR */
        /* otherwise assert RTS and DTR */
        if (cflag & CBAUD)
                info->serial_signals |= SerialSignal_RTS | SerialSignal_DTR;
        else
                info->serial_signals &= ~(SerialSignal_RTS | SerialSignal_DTR);

        /* byte size and parity */

        switch (cflag & CSIZE) {
        case CS5: info->params.data_bits = 5; break;
        case CS6: info->params.data_bits = 6; break;
        case CS7: info->params.data_bits = 7; break;
        case CS8: info->params.data_bits = 8; break;
        default:  info->params.data_bits = 7; break;
        }

        if (cflag & CSTOPB)
                info->params.stop_bits = 2;
        else
                info->params.stop_bits = 1;

        info->params.parity = ASYNC_PARITY_NONE;
        if (cflag & PARENB) {
                if (cflag & PARODD)
                        info->params.parity = ASYNC_PARITY_ODD;
                else
                        info->params.parity = ASYNC_PARITY_EVEN;
#ifdef CMSPAR
                if (cflag & CMSPAR)
                        info->params.parity = ASYNC_PARITY_SPACE;
#endif
        }

        /* calculate number of jiffies to transmit a full
         * FIFO (32 bytes) at specified data rate
         */
        bits_per_char = info->params.data_bits +
                        info->params.stop_bits + 1;

        /* if port data rate is set to 460800 or less then
         * allow tty settings to override, otherwise keep the
         * current data rate.
         */
        if (info->params.data_rate <= 460800) {
                info->params.data_rate = tty_get_baud_rate(tty);
        }

        if (info->params.data_rate) {
                info->timeout = (32*HZ*bits_per_char) /
                                info->params.data_rate;
        }
        info->timeout += HZ/50;         /* Add .02 seconds of slop */

        tty_port_set_cts_flow(&info->port, cflag & CRTSCTS);
        tty_port_set_check_carrier(&info->port, ~cflag & CLOCAL);

        /* process tty input control flags */

        info->read_status_mask = 0;
        if (I_INPCK(tty))
                info->read_status_mask |= BIT7 | BIT6;
        if (I_IGNPAR(tty))
                info->ignore_status_mask |= BIT7 | BIT6;

        mgslpc_program_hw(info, tty);
}

/* Add a character to the transmit buffer
 */
static int mgslpc_put_char(struct tty_struct *tty, unsigned char ch)
{
        MGSLPC_INFO *info = (MGSLPC_INFO *)tty->driver_data;
        unsigned long flags;

        if (debug_level >= DEBUG_LEVEL_INFO) {
                printk("%s(%d):mgslpc_put_char(%d) on %s\n",
                        __FILE__, __LINE__, ch, info->device_name);
        }

        if (mgslpc_paranoia_check(info, tty->name, "mgslpc_put_char"))
                return 0;

        if (!info->tx_buf)
                return 0;

        spin_lock_irqsave(&info->lock, flags);

        if (info->params.mode == MGSL_MODE_ASYNC || !info->tx_active) {
                if (info->tx_count < TXBUFSIZE - 1) {
                        info->tx_buf[info->tx_put++] = ch;
                        info->tx_put &= TXBUFSIZE-1;
                        info->tx_count++;
                }
        }

        spin_unlock_irqrestore(&info->lock, flags);
        return 1;
}

/* Enable transmitter so remaining characters in the
 * transmit buffer are sent.
 */
static void mgslpc_flush_chars(struct tty_struct *tty)
{
        MGSLPC_INFO *info = (MGSLPC_INFO *)tty->driver_data;
        unsigned long flags;

        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("%s(%d):mgslpc_flush_chars() entry on %s tx_count=%d\n",
                        __FILE__, __LINE__, info->device_name, info->tx_count);

        if (mgslpc_paranoia_check(info, tty->name, "mgslpc_flush_chars"))
                return;

        if (info->tx_count <= 0 || tty->stopped ||
            tty->hw_stopped || !info->tx_buf)
                return;

        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("%s(%d):mgslpc_flush_chars() entry on %s starting transmitter\n",
                        __FILE__, __LINE__, info->device_name);

        spin_lock_irqsave(&info->lock, flags);
        if (!info->tx_active)
                tx_start(info, tty);
        spin_unlock_irqrestore(&info->lock, flags);
}

/* Send a block of data
 *
 * Arguments:
 *
 * tty        pointer to tty information structure
 * buf        pointer to buffer containing send data
 * count      size of send data in bytes
 *
 * Returns: number of characters written
 */
static int mgslpc_write(struct tty_struct * tty,
                        const unsigned char *buf, int count)
{
        int c, ret = 0;
        MGSLPC_INFO *info = (MGSLPC_INFO *)tty->driver_data;
        unsigned long flags;

        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("%s(%d):mgslpc_write(%s) count=%d\n",
                        __FILE__, __LINE__, info->device_name, count);

        if (mgslpc_paranoia_check(info, tty->name, "mgslpc_write") ||
                !info->tx_buf)
                goto cleanup;

        if (info->params.mode == MGSL_MODE_HDLC) {
                if (count > TXBUFSIZE) {
                        ret = -EIO;
                        goto cleanup;
                }
                if (info->tx_active)
                        goto cleanup;
                else if (info->tx_count)
                        goto start;
        }

        for (;;) {
                c = min(count,
                        min(TXBUFSIZE - info->tx_count - 1,
                            TXBUFSIZE - info->tx_put));
                if (c <= 0)
                        break;

                memcpy(info->tx_buf + info->tx_put, buf, c);

                spin_lock_irqsave(&info->lock, flags);
                info->tx_put = (info->tx_put + c) & (TXBUFSIZE-1);
                info->tx_count += c;
                spin_unlock_irqrestore(&info->lock, flags);

                buf += c;
                count -= c;
                ret += c;
        }
start:
        if (info->tx_count && !tty->stopped && !tty->hw_stopped) {
                spin_lock_irqsave(&info->lock, flags);
                if (!info->tx_active)
                        tx_start(info, tty);
                spin_unlock_irqrestore(&info->lock, flags);
        }
cleanup:
        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("%s(%d):mgslpc_write(%s) returning=%d\n",
                        __FILE__, __LINE__, info->device_name, ret);
        return ret;
}

/* Return the count of free bytes in transmit buffer
 */
static int mgslpc_write_room(struct tty_struct *tty)
{
        MGSLPC_INFO *info = (MGSLPC_INFO *)tty->driver_data;
        int ret;

        if (mgslpc_paranoia_check(info, tty->name, "mgslpc_write_room"))
                return 0;

        if (info->params.mode == MGSL_MODE_HDLC) {
                /* HDLC (frame oriented) mode */
                if (info->tx_active)
                        return 0;
                else
                        return HDLC_MAX_FRAME_SIZE;
        } else {
                ret = TXBUFSIZE - info->tx_count - 1;
                if (ret < 0)
                        ret = 0;
        }

        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("%s(%d):mgslpc_write_room(%s)=%d\n",
                         __FILE__, __LINE__, info->device_name, ret);
        return ret;
}

/* Return the count of bytes in transmit buffer
 */
static int mgslpc_chars_in_buffer(struct tty_struct *tty)
{
        MGSLPC_INFO *info = (MGSLPC_INFO *)tty->driver_data;
        int rc;

        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("%s(%d):mgslpc_chars_in_buffer(%s)\n",
                         __FILE__, __LINE__, info->device_name);

        if (mgslpc_paranoia_check(info, tty->name, "mgslpc_chars_in_buffer"))
                return 0;

        if (info->params.mode == MGSL_MODE_HDLC)
                rc = info->tx_active ? info->max_frame_size : 0;
        else
                rc = info->tx_count;

        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("%s(%d):mgslpc_chars_in_buffer(%s)=%d\n",
                         __FILE__, __LINE__, info->device_name, rc);

        return rc;
}

/* Discard all data in the send buffer
 */
static void mgslpc_flush_buffer(struct tty_struct *tty)
{
        MGSLPC_INFO *info = (MGSLPC_INFO *)tty->driver_data;
        unsigned long flags;

        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("%s(%d):mgslpc_flush_buffer(%s) entry\n",
                         __FILE__, __LINE__, info->device_name);

        if (mgslpc_paranoia_check(info, tty->name, "mgslpc_flush_buffer"))
                return;

        spin_lock_irqsave(&info->lock, flags);
        info->tx_count = info->tx_put = info->tx_get = 0;
        del_timer(&info->tx_timer);
        spin_unlock_irqrestore(&info->lock, flags);

        wake_up_interruptible(&tty->write_wait);
        tty_wakeup(tty);
}

/* Send a high-priority XON/XOFF character
 */
static void mgslpc_send_xchar(struct tty_struct *tty, char ch)
{
        MGSLPC_INFO *info = (MGSLPC_INFO *)tty->driver_data;
        unsigned long flags;

        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("%s(%d):mgslpc_send_xchar(%s,%d)\n",
                         __FILE__, __LINE__, info->device_name, ch);

        if (mgslpc_paranoia_check(info, tty->name, "mgslpc_send_xchar"))
                return;

        info->x_char = ch;
        if (ch) {
                spin_lock_irqsave(&info->lock, flags);
                if (!info->tx_enabled)
                        tx_start(info, tty);
                spin_unlock_irqrestore(&info->lock, flags);
        }
}

/* Signal remote device to throttle send data (our receive data)
 */
static void mgslpc_throttle(struct tty_struct * tty)
{
        MGSLPC_INFO *info = (MGSLPC_INFO *)tty->driver_data;
        unsigned long flags;

        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("%s(%d):mgslpc_throttle(%s) entry\n",
                         __FILE__, __LINE__, info->device_name);

        if (mgslpc_paranoia_check(info, tty->name, "mgslpc_throttle"))
                return;

        if (I_IXOFF(tty))
                mgslpc_send_xchar(tty, STOP_CHAR(tty));

        if (C_CRTSCTS(tty)) {
                spin_lock_irqsave(&info->lock, flags);
                info->serial_signals &= ~SerialSignal_RTS;
                set_signals(info);
                spin_unlock_irqrestore(&info->lock, flags);
        }
}

/* Signal remote device to stop throttling send data (our receive data)
 */
static void mgslpc_unthrottle(struct tty_struct * tty)
{
        MGSLPC_INFO *info = (MGSLPC_INFO *)tty->driver_data;
        unsigned long flags;

        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("%s(%d):mgslpc_unthrottle(%s) entry\n",
                         __FILE__, __LINE__, info->device_name);

        if (mgslpc_paranoia_check(info, tty->name, "mgslpc_unthrottle"))
                return;

        if (I_IXOFF(tty)) {
                if (info->x_char)
                        info->x_char = 0;
                else
                        mgslpc_send_xchar(tty, START_CHAR(tty));
        }

        if (C_CRTSCTS(tty)) {
                spin_lock_irqsave(&info->lock, flags);
                info->serial_signals |= SerialSignal_RTS;
                set_signals(info);
                spin_unlock_irqrestore(&info->lock, flags);
        }
}

/* get the current serial statistics
 */
static int get_stats(MGSLPC_INFO * info, struct mgsl_icount __user *user_icount)
{
        int err;
        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("get_params(%s)\n", info->device_name);
        if (!user_icount) {
                memset(&info->icount, 0, sizeof(info->icount));
        } else {
                COPY_TO_USER(err, user_icount, &info->icount, sizeof(struct mgsl_icount));
                if (err)
                        return -EFAULT;
        }
        return 0;
}

/* get the current serial parameters
 */
static int get_params(MGSLPC_INFO * info, MGSL_PARAMS __user *user_params)
{
        int err;
        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("get_params(%s)\n", info->device_name);
        COPY_TO_USER(err,user_params, &info->params, sizeof(MGSL_PARAMS));
        if (err)
                return -EFAULT;
        return 0;
}

/* set the serial parameters
 *
 * Arguments:
 *
 *      info            pointer to device instance data
 *      new_params      user buffer containing new serial params
 *
 * Returns:     0 if success, otherwise error code
 */
static int set_params(MGSLPC_INFO * info, MGSL_PARAMS __user *new_params, struct tty_struct *tty)
{
        unsigned long flags;
        MGSL_PARAMS tmp_params;
        int err;

        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("%s(%d):set_params %s\n", __FILE__,__LINE__,
                        info->device_name);
        COPY_FROM_USER(err,&tmp_params, new_params, sizeof(MGSL_PARAMS));
        if (err) {
                if (debug_level >= DEBUG_LEVEL_INFO)
                        printk("%s(%d):set_params(%s) user buffer copy failed\n",
                                __FILE__, __LINE__, info->device_name);
                return -EFAULT;
        }

        spin_lock_irqsave(&info->lock, flags);
        memcpy(&info->params,&tmp_params,sizeof(MGSL_PARAMS));
        spin_unlock_irqrestore(&info->lock, flags);

        mgslpc_change_params(info, tty);

        return 0;
}

static int get_txidle(MGSLPC_INFO * info, int __user *idle_mode)
{
        int err;
        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("get_txidle(%s)=%d\n", info->device_name, info->idle_mode);
        COPY_TO_USER(err,idle_mode, &info->idle_mode, sizeof(int));
        if (err)
                return -EFAULT;
        return 0;
}

static int set_txidle(MGSLPC_INFO * info, int idle_mode)
{
        unsigned long flags;
        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("set_txidle(%s,%d)\n", info->device_name, idle_mode);
        spin_lock_irqsave(&info->lock, flags);
        info->idle_mode = idle_mode;
        tx_set_idle(info);
        spin_unlock_irqrestore(&info->lock, flags);
        return 0;
}

static int get_interface(MGSLPC_INFO * info, int __user *if_mode)
{
        int err;
        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("get_interface(%s)=%d\n", info->device_name, info->if_mode);
        COPY_TO_USER(err,if_mode, &info->if_mode, sizeof(int));
        if (err)
                return -EFAULT;
        return 0;
}

static int set_interface(MGSLPC_INFO * info, int if_mode)
{
        unsigned long flags;
        unsigned char val;
        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("set_interface(%s,%d)\n", info->device_name, if_mode);
        spin_lock_irqsave(&info->lock, flags);
        info->if_mode = if_mode;

        val = read_reg(info, PVR) & 0x0f;
        switch (info->if_mode)
        {
        case MGSL_INTERFACE_RS232: val |= PVR_RS232; break;
        case MGSL_INTERFACE_V35:   val |= PVR_V35;   break;
        case MGSL_INTERFACE_RS422: val |= PVR_RS422; break;
        }
        write_reg(info, PVR, val);

        spin_unlock_irqrestore(&info->lock, flags);
        return 0;
}

static int set_txenable(MGSLPC_INFO * info, int enable, struct tty_struct *tty)
{
        unsigned long flags;

        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("set_txenable(%s,%d)\n", info->device_name, enable);

        spin_lock_irqsave(&info->lock, flags);
        if (enable) {
                if (!info->tx_enabled)
                        tx_start(info, tty);
        } else {
                if (info->tx_enabled)
                        tx_stop(info);
        }
        spin_unlock_irqrestore(&info->lock, flags);
        return 0;
}

static int tx_abort(MGSLPC_INFO * info)
{
        unsigned long flags;

        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("tx_abort(%s)\n", info->device_name);

        spin_lock_irqsave(&info->lock, flags);
        if (info->tx_active && info->tx_count &&
            info->params.mode == MGSL_MODE_HDLC) {
                /* clear data count so FIFO is not filled on next IRQ.
                 * This results in underrun and abort transmission.
                 */
                info->tx_count = info->tx_put = info->tx_get = 0;
                info->tx_aborting = true;
        }
        spin_unlock_irqrestore(&info->lock, flags);
        return 0;
}

static int set_rxenable(MGSLPC_INFO * info, int enable)
{
        unsigned long flags;

        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("set_rxenable(%s,%d)\n", info->device_name, enable);

        spin_lock_irqsave(&info->lock, flags);
        if (enable) {
                if (!info->rx_enabled)
                        rx_start(info);
        } else {
                if (info->rx_enabled)
                        rx_stop(info);
        }
        spin_unlock_irqrestore(&info->lock, flags);
        return 0;
}

/* wait for specified event to occur
 *
 * Arguments:           info    pointer to device instance data
 *                      mask    pointer to bitmask of events to wait for
 * Return Value:        0       if successful and bit mask updated with
 *                              of events triggerred,
 *                      otherwise error code
 */
static int wait_events(MGSLPC_INFO * info, int __user *mask_ptr)
{
        unsigned long flags;
        int s;
        int rc=0;
        struct mgsl_icount cprev, cnow;
        int events;
        int mask;
        struct  _input_signal_events oldsigs, newsigs;
        DECLARE_WAITQUEUE(wait, current);

        COPY_FROM_USER(rc,&mask, mask_ptr, sizeof(int));
        if (rc)
                return  -EFAULT;

        if (debug_level >= DEBUG_LEVEL_INFO)
                printk("wait_events(%s,%d)\n", info->device_name, mask);

        spin_lock_irqsave(&info->lock, flags);

        /* return immediately if state matches requested events */
        get_signals(info);
        s = info->serial_signals;
        events = mask &
                ( ((s & SerialSignal_DSR) ? MgslEvent_DsrActive:MgslEvent_DsrInactive) +
                  ((s & SerialSignal_DCD) ? MgslEvent_DcdActive:MgslEvent_DcdInactive) +
                  ((s & SerialSignal_CTS) ? MgslEvent_CtsActive:MgslEvent_CtsInactive) +
                  ((s & SerialSignal_RI)  ? MgslEvent_RiActive :MgslEvent_RiInactive) );
        if (events) {
                spin_unlock_irqrestore(&info->lock, flags);
                goto exit;
        }

        /* save current irq counts */
        cprev = info->icount;
        oldsigs = info->input_signal_events;

        if ((info->params.mode == MGSL_MODE_HDLC) &&
            (mask & MgslEvent_ExitHuntMode))
                irq_enable(info, CHA, IRQ_EXITHUNT);

        set_current_state(TASK_INTERRUPTIBLE);
        add_wait_queue(&info->event_wait_q, &wait);

        spin_unlock_irqrestore(&info->lock, flags);


        for(;;) {
                schedule();
                if (signal_pending(current)) {