// SPDX-License-Identifier: GPL-1.0+
/*
 * Device driver for Microgate SyncLink GT serial adapters.
 *
 * written by Paul Fulghum for Microgate Corporation
 * paulkf@microgate.com
 *
 * Microgate and SyncLink are trademarks of Microgate Corporation
 *
 * 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.
 */

/*
 * DEBUG OUTPUT DEFINITIONS
 *
 * uncomment lines below to enable specific types of debug output
 *
 * DBGINFO   information - most verbose output
 * DBGERR    serious errors
 * DBGBH     bottom half service routine debugging
 * DBGISR    interrupt service routine debugging
 * DBGDATA   output receive and transmit data
 * DBGTBUF   output transmit DMA buffers and registers
 * DBGRBUF   output receive DMA buffers and registers
 */

#define DBGINFO(fmt) if (debug_level >= DEBUG_LEVEL_INFO) printk fmt
#define DBGERR(fmt) if (debug_level >= DEBUG_LEVEL_ERROR) printk fmt
#define DBGBH(fmt) if (debug_level >= DEBUG_LEVEL_BH) printk fmt
#define DBGISR(fmt) if (debug_level >= DEBUG_LEVEL_ISR) printk fmt
#define DBGDATA(info, buf, size, label) if (debug_level >= DEBUG_LEVEL_DATA) trace_block((info), (buf), (size), (label))
/*#define DBGTBUF(info) dump_tbufs(info)*/
/*#define DBGRBUF(info) dump_rbufs(info)*/


#include <linux/module.h>
#include <linux/errno.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/interrupt.h>
#include <linux/pci.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/termios.h>
#include <linux/bitops.h>
#include <linux/workqueue.h>
#include <linux/hdlc.h>
#include <linux/synclink.h>

#include <asm/io.h>
#include <asm/irq.h>
#include <asm/dma.h>
#include <asm/types.h>
#include <linux/uaccess.h>

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

/*
 * module identification
 */
static char *driver_name     = "SyncLink GT";
static char *slgt_driver_name = "synclink_gt";
static char *tty_dev_prefix  = "ttySLG";
MODULE_LICENSE("GPL");
#define MGSL_MAGIC 0x5401
#define MAX_DEVICES 32

static const struct pci_device_id pci_table[] = {
        {PCI_VENDOR_ID_MICROGATE, SYNCLINK_GT_DEVICE_ID, PCI_ANY_ID, PCI_ANY_ID,},
        {PCI_VENDOR_ID_MICROGATE, SYNCLINK_GT2_DEVICE_ID, PCI_ANY_ID, PCI_ANY_ID,},
        {PCI_VENDOR_ID_MICROGATE, SYNCLINK_GT4_DEVICE_ID, PCI_ANY_ID, PCI_ANY_ID,},
        {PCI_VENDOR_ID_MICROGATE, SYNCLINK_AC_DEVICE_ID, PCI_ANY_ID, PCI_ANY_ID,},
        {0,}, /* terminate list */
};
MODULE_DEVICE_TABLE(pci, pci_table);

static int  init_one(struct pci_dev *dev,const struct pci_device_id *ent);
static void remove_one(struct pci_dev *dev);
static struct pci_driver pci_driver = {
        .name           = "synclink_gt",
        .id_table       = pci_table,
        .probe          = init_one,
        .remove         = remove_one,
};

static bool pci_registered;

/*
 * module configuration and status
 */
static struct slgt_info *slgt_device_list;
static int slgt_device_count;

static int ttymajor;
static int debug_level;
static int maxframe[MAX_DEVICES];

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

MODULE_PARM_DESC(ttymajor, "TTY major device number override: 0=auto assigned");
MODULE_PARM_DESC(debug_level, "Debug syslog output: 0=disabled, 1 to 5=increasing detail");
MODULE_PARM_DESC(maxframe, "Maximum frame size used by device (4096 to 65535)");

/*
 * tty support and callbacks
 */
static struct tty_driver *serial_driver;

static void wait_until_sent(struct tty_struct *tty, int timeout);
static void flush_buffer(struct tty_struct *tty);
static void tx_release(struct tty_struct *tty);

/*
 * generic HDLC support
 */
#define dev_to_port(D) (dev_to_hdlc(D)->priv)


/*
 * device specific structures, macros and functions
 */

#define SLGT_MAX_PORTS 4
#define SLGT_REG_SIZE  256

/*
 * conditional wait facility
 */
struct cond_wait {
        struct cond_wait *next;
        wait_queue_head_t q;
        wait_queue_entry_t wait;
        unsigned int data;
};
static void flush_cond_wait(struct cond_wait **head);

/*
 * DMA buffer descriptor and access macros
 */
struct slgt_desc
{
        __le16 count;
        __le16 status;
        __le32 pbuf;  /* physical address of data buffer */
        __le32 next;  /* physical address of next descriptor */

        /* driver book keeping */
        char *buf;          /* virtual  address of data buffer */
        unsigned int pdesc; /* physical address of this descriptor */
        dma_addr_t buf_dma_addr;
        unsigned short buf_count;
};

#define set_desc_buffer(a,b) (a).pbuf = cpu_to_le32((unsigned int)(b))
#define set_desc_next(a,b) (a).next   = cpu_to_le32((unsigned int)(b))
#define set_desc_count(a,b)(a).count  = cpu_to_le16((unsigned short)(b))
#define set_desc_eof(a,b)  (a).status = cpu_to_le16((b) ? (le16_to_cpu((a).status) | BIT0) : (le16_to_cpu((a).status) & ~BIT0))
#define set_desc_status(a, b) (a).status = cpu_to_le16((unsigned short)(b))
#define desc_count(a)      (le16_to_cpu((a).count))
#define desc_status(a)     (le16_to_cpu((a).status))
#define desc_complete(a)   (le16_to_cpu((a).status) & BIT15)
#define desc_eof(a)        (le16_to_cpu((a).status) & BIT2)
#define desc_crc_error(a)  (le16_to_cpu((a).status) & BIT1)
#define desc_abort(a)      (le16_to_cpu((a).status) & BIT0)
#define desc_residue(a)    ((le16_to_cpu((a).status) & 0x38) >> 3)

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
 */
struct slgt_info {
        void *if_ptr;           /* General purpose pointer (used by SPPP) */
        struct tty_port port;

        struct slgt_info *next_device;  /* device list link */

        int magic;

        char device_name[25];
        struct pci_dev *pdev;

        int port_count;  /* count of ports on adapter */
        int adapter_num; /* adapter instance number */
        int port_num;    /* port instance number */

        /* array of pointers to port contexts on this adapter */
        struct slgt_info *port_array[SLGT_MAX_PORTS];

        int                     line;           /* tty line instance number */

        struct mgsl_icount      icount;

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

        wait_queue_head_t       status_event_wait_q;
        wait_queue_head_t       event_wait_q;
        struct timer_list       tx_timer;
        struct timer_list       rx_timer;

        unsigned int            gpio_present;
        struct cond_wait        *gpio_wait_q;

        spinlock_t lock;        /* spinlock for synchronizing with ISR */

        struct work_struct task;
        u32 pending_bh;
        bool bh_requested;
        bool bh_running;

        int isr_overflow;
        bool irq_requested;     /* true if IRQ requested */
        bool irq_occurred;      /* for diagnostics use */

        /* device configuration */

        unsigned int bus_type;
        unsigned int irq_level;
        unsigned long irq_flags;

        unsigned char __iomem * reg_addr;  /* memory mapped registers address */
        u32 phys_reg_addr;
        bool reg_addr_requested;

        MGSL_PARAMS params;       /* communications parameters */
        u32 idle_mode;
        u32 max_frame_size;       /* as set by device config */

        unsigned int rbuf_fill_level;
        unsigned int rx_pio;
        unsigned int if_mode;
        unsigned int base_clock;
        unsigned int xsync;
        unsigned int xctrl;

        /* device status */

        bool rx_enabled;
        bool rx_restart;

        bool tx_enabled;
        bool tx_active;

        unsigned char signals;    /* serial signal states */
        int init_error;  /* initialization error */

        unsigned char *tx_buf;
        int tx_count;

        char *flag_buf;
        bool drop_rts_on_tx_done;
        struct  _input_signal_events    input_signal_events;

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

        char *bufs;             /* virtual address of DMA buffer lists */
        dma_addr_t bufs_dma_addr; /* physical address of buffer descriptors */

        unsigned int rbuf_count;
        struct slgt_desc *rbufs;
        unsigned int rbuf_current;
        unsigned int rbuf_index;
        unsigned int rbuf_fill_index;
        unsigned short rbuf_fill_count;

        unsigned int tbuf_count;
        struct slgt_desc *tbufs;
        unsigned int tbuf_current;
        unsigned int tbuf_start;

        unsigned char *tmp_rbuf;
        unsigned int tmp_rbuf_count;

        /* SPPP/Cisco HDLC device parts */

        int netcount;
        spinlock_t netlock;
#if SYNCLINK_GENERIC_HDLC
        struct net_device *netdev;
#endif

};

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


#define BH_RECEIVE  1
#define BH_TRANSMIT 2
#define BH_STATUS   4
#define IO_PIN_SHUTDOWN_LIMIT 100

#define DMABUFSIZE 256
#define DESC_LIST_SIZE 4096

#define MASK_PARITY  BIT1
#define MASK_FRAMING BIT0
#define MASK_BREAK   BIT14
#define MASK_OVERRUN BIT4

#define GSR   0x00 /* global status */
#define JCR   0x04 /* JTAG control */
#define IODR  0x08 /* GPIO direction */
#define IOER  0x0c /* GPIO interrupt enable */
#define IOVR  0x10 /* GPIO value */
#define IOSR  0x14 /* GPIO interrupt status */
#define TDR   0x80 /* tx data */
#define RDR   0x80 /* rx data */
#define TCR   0x82 /* tx control */
#define TIR   0x84 /* tx idle */
#define TPR   0x85 /* tx preamble */
#define RCR   0x86 /* rx control */
#define VCR   0x88 /* V.24 control */
#define CCR   0x89 /* clock control */
#define BDR   0x8a /* baud divisor */
#define SCR   0x8c /* serial control */
#define SSR   0x8e /* serial status */
#define RDCSR 0x90 /* rx DMA control/status */
#define TDCSR 0x94 /* tx DMA control/status */
#define RDDAR 0x98 /* rx DMA descriptor address */
#define TDDAR 0x9c /* tx DMA descriptor address */
#define XSR   0x40 /* extended sync pattern */
#define XCR   0x44 /* extended control */

#define RXIDLE      BIT14
#define RXBREAK     BIT14
#define IRQ_TXDATA  BIT13
#define IRQ_TXIDLE  BIT12
#define IRQ_TXUNDER BIT11 /* HDLC */
#define IRQ_RXDATA  BIT10
#define IRQ_RXIDLE  BIT9  /* HDLC */
#define IRQ_RXBREAK BIT9  /* async */
#define IRQ_RXOVER  BIT8
#define IRQ_DSR     BIT7
#define IRQ_CTS     BIT6
#define IRQ_DCD     BIT5
#define IRQ_RI      BIT4
#define IRQ_ALL     0x3ff0
#define IRQ_MASTER  BIT0

#define slgt_irq_on(info, mask) \
        wr_reg16((info), SCR, (unsigned short)(rd_reg16((info), SCR) | (mask)))
#define slgt_irq_off(info, mask) \
        wr_reg16((info), SCR, (unsigned short)(rd_reg16((info), SCR) & ~(mask)))

static __u8  rd_reg8(struct slgt_info *info, unsigned int addr);
static void  wr_reg8(struct slgt_info *info, unsigned int addr, __u8 value);
static __u16 rd_reg16(struct slgt_info *info, unsigned int addr);
static void  wr_reg16(struct slgt_info *info, unsigned int addr, __u16 value);
static __u32 rd_reg32(struct slgt_info *info, unsigned int addr);
static void  wr_reg32(struct slgt_info *info, unsigned int addr, __u32 value);

static void  msc_set_vcr(struct slgt_info *info);

static int  startup(struct slgt_info *info);
static int  block_til_ready(struct tty_struct *tty, struct file * filp,struct slgt_info *info);
static void shutdown(struct slgt_info *info);
static void program_hw(struct slgt_info *info);
static void change_params(struct slgt_info *info);

static int  adapter_test(struct slgt_info *info);

static void reset_port(struct slgt_info *info);
static void async_mode(struct slgt_info *info);
static void sync_mode(struct slgt_info *info);

static void rx_stop(struct slgt_info *info);
static void rx_start(struct slgt_info *info);
static void reset_rbufs(struct slgt_info *info);
static void free_rbufs(struct slgt_info *info, unsigned int first, unsigned int last);
static bool rx_get_frame(struct slgt_info *info);
static bool rx_get_buf(struct slgt_info *info);

static void tx_start(struct slgt_info *info);
static void tx_stop(struct slgt_info *info);
static void tx_set_idle(struct slgt_info *info);
static unsigned int tbuf_bytes(struct slgt_info *info);
static void reset_tbufs(struct slgt_info *info);
static void tdma_reset(struct slgt_info *info);
static bool tx_load(struct slgt_info *info, const char *buf, unsigned int count);

static void get_signals(struct slgt_info *info);
static void set_signals(struct slgt_info *info);
static void set_rate(struct slgt_info *info, u32 data_rate);

static void bh_transmit(struct slgt_info *info);
static void isr_txeom(struct slgt_info *info, unsigned short status);

static void tx_timeout(struct timer_list *t);
static void rx_timeout(struct timer_list *t);

/*
 * ioctl handlers
 */
static int  get_stats(struct slgt_info *info, struct mgsl_icount __user *user_icount);
static int  get_params(struct slgt_info *info, MGSL_PARAMS __user *params);
static int  set_params(struct slgt_info *info, MGSL_PARAMS __user *params);
static int  get_txidle(struct slgt_info *info, int __user *idle_mode);
static int  set_txidle(struct slgt_info *info, int idle_mode);
static int  tx_enable(struct slgt_info *info, int enable);
static int  tx_abort(struct slgt_info *info);
static int  rx_enable(struct slgt_info *info, int enable);
static int  modem_input_wait(struct slgt_info *info,int arg);
static int  wait_mgsl_event(struct slgt_info *info, int __user *mask_ptr);
static int  get_interface(struct slgt_info *info, int __user *if_mode);
static int  set_interface(struct slgt_info *info, int if_mode);
static int  set_gpio(struct slgt_info *info, struct gpio_desc __user *gpio);
static int  get_gpio(struct slgt_info *info, struct gpio_desc __user *gpio);
static int  wait_gpio(struct slgt_info *info, struct gpio_desc __user *gpio);
static int  get_xsync(struct slgt_info *info, int __user *if_mode);
static int  set_xsync(struct slgt_info *info, int if_mode);
static int  get_xctrl(struct slgt_info *info, int __user *if_mode);
static int  set_xctrl(struct slgt_info *info, int if_mode);

/*
 * driver functions
 */
static void release_resources(struct slgt_info *info);

/*
 * DEBUG OUTPUT CODE
 */
#ifndef DBGINFO
#define DBGINFO(fmt)
#endif
#ifndef DBGERR
#define DBGERR(fmt)
#endif
#ifndef DBGBH
#define DBGBH(fmt)
#endif
#ifndef DBGISR
#define DBGISR(fmt)
#endif

#ifdef DBGDATA
static void trace_block(struct slgt_info *info, const char *data, int count, const char *label)
{
        int i;
        int linecount;
        printk("%s %s data:\n",info->device_name, label);
        while(count) {
                linecount = (count > 16) ? 16 : count;
                for(i=0; i < linecount; i++)
                        printk("%02X ",(unsigned char)data[i]);
                for(;i<17;i++)
                        printk("   ");
                for(i=0;i<linecount;i++) {
                        if (data[i]>=040 && data[i]<=0176)
                                printk("%c",data[i]);
                        else
                                printk(".");
                }
                printk("\n");
                data  += linecount;
                count -= linecount;
        }
}
#else
#define DBGDATA(info, buf, size, label)
#endif

#ifdef DBGTBUF
static void dump_tbufs(struct slgt_info *info)
{
        int i;
        printk("tbuf_current=%d\n", info->tbuf_current);
        for (i=0 ; i < info->tbuf_count ; i++) {
                printk("%d: count=%04X status=%04X\n",
                        i, le16_to_cpu(info->tbufs[i].count), le16_to_cpu(info->tbufs[i].status));
        }
}
#else
#define DBGTBUF(info)
#endif

#ifdef DBGRBUF
static void dump_rbufs(struct slgt_info *info)
{
        int i;
        printk("rbuf_current=%d\n", info->rbuf_current);
        for (i=0 ; i < info->rbuf_count ; i++) {
                printk("%d: count=%04X status=%04X\n",
                        i, le16_to_cpu(info->rbufs[i].count), le16_to_cpu(info->rbufs[i].status));
        }
}
#else
#define DBGRBUF(info)
#endif

static inline int sanity_check(struct slgt_info *info, char *devname, const char *name)
{
#ifdef SANITY_CHECK
        if (!info) {
                printk("null struct slgt_info for (%s) in %s\n", devname, name);
                return 1;
        }
        if (info->magic != MGSL_MAGIC) {
                printk("bad magic number struct slgt_info (%s) in %s\n", devname, name);
                return 1;
        }
#else
        if (!info)
                return 1;
#endif
        return 0;
}

/*
 * 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);
        }
}

/* tty callbacks */

static int open(struct tty_struct *tty, struct file *filp)
{
        struct slgt_info *info;
        int retval, line;
        unsigned long flags;

        line = tty->index;
        if (line >= slgt_device_count) {
                DBGERR(("%s: open with invalid line #%d.\n", driver_name, line));
                return -ENODEV;
        }

        info = slgt_device_list;
        while(info && info->line != line)
                info = info->next_device;
        if (sanity_check(info, tty->name, "open"))
                return -ENODEV;
        if (info->init_error) {
                DBGERR(("%s init error=%d\n", info->device_name, info->init_error));
                return -ENODEV;
        }

        tty->driver_data = info;
        info->port.tty = tty;

        DBGINFO(("%s open, old ref count = %d\n", info->device_name, info->port.count));

        mutex_lock(&info->port.mutex);

        spin_lock_irqsave(&info->netlock, flags);
        if (info->netcount) {
                retval = -EBUSY;
                spin_unlock_irqrestore(&info->netlock, flags);
                mutex_unlock(&info->port.mutex);
                goto cleanup;
        }
        info->port.count++;
        spin_unlock_irqrestore(&info->netlock, flags);

        if (info->port.count == 1) {
                /* 1st open on this device, init hardware */
                retval = startup(info);
                if (retval < 0) {
                        mutex_unlock(&info->port.mutex);
                        goto cleanup;
                }
        }
        mutex_unlock(&info->port.mutex);
        retval = block_til_ready(tty, filp, info);
        if (retval) {
                DBGINFO(("%s block_til_ready rc=%d\n", info->device_name, retval));
                goto cleanup;
        }

        retval = 0;

cleanup:
        if (retval) {
                if (tty->count == 1)
                        info->port.tty = NULL; /* tty layer will release tty struct */
                if(info->port.count)
                        info->port.count--;
        }

        DBGINFO(("%s open rc=%d\n", info->device_name, retval));
        return retval;
}

static void close(struct tty_struct *tty, struct file *filp)
{
        struct slgt_info *info = tty->driver_data;

        if (sanity_check(info, tty->name, "close"))
                return;
        DBGINFO(("%s close entry, count=%d\n", info->device_name, info->port.count));

        if (tty_port_close_start(&info->port, tty, filp) == 0)
                goto cleanup;

        mutex_lock(&info->port.mutex);
        if (tty_port_initialized(&info->port))
                wait_until_sent(tty, info->timeout);
        flush_buffer(tty);
        tty_ldisc_flush(tty);

        shutdown(info);
        mutex_unlock(&info->port.mutex);

        tty_port_close_end(&info->port, tty);
        info->port.tty = NULL;
cleanup:
        DBGINFO(("%s close exit, count=%d\n", tty->driver->name, info->port.count));
}

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

        if (sanity_check(info, tty->name, "hangup"))
                return;
        DBGINFO(("%s hangup\n", info->device_name));

        flush_buffer(tty);

        mutex_lock(&info->port.mutex);
        shutdown(info);

        spin_lock_irqsave(&info->port.lock, flags);
        info->port.count = 0;
        info->port.tty = NULL;
        spin_unlock_irqrestore(&info->port.lock, flags);
        tty_port_set_active(&info->port, 0);
        mutex_unlock(&info->port.mutex);

        wake_up_interruptible(&info->port.open_wait);
}

static void set_termios(struct tty_struct *tty, struct ktermios *old_termios)
{
        struct slgt_info *info = tty->driver_data;
        unsigned long flags;

        DBGINFO(("%s set_termios\n", tty->driver->name));

        change_params(info);

        /* Handle transition to B0 status */
        if ((old_termios->c_cflag & CBAUD) && !C_BAUD(tty)) {
                info->signals &= ~(SerialSignal_RTS | SerialSignal_DTR);
                spin_lock_irqsave(&info->lock,flags);
                set_signals(info);
                spin_unlock_irqrestore(&info->lock,flags);
        }

        /* Handle transition away from B0 status */
        if (!(old_termios->c_cflag & CBAUD) && C_BAUD(tty)) {
                info->signals |= SerialSignal_DTR;
                if (!C_CRTSCTS(tty) || !tty_throttled(tty))
                        info->signals |= SerialSignal_RTS;
                spin_lock_irqsave(&info->lock,flags);
                set_signals(info);
                spin_unlock_irqrestore(&info->lock,flags);
        }

        /* Handle turning off CRTSCTS */
        if ((old_termios->c_cflag & CRTSCTS) && !C_CRTSCTS(tty)) {
                tty->hw_stopped = 0;
                tx_release(tty);
        }
}

static void update_tx_timer(struct slgt_info *info)
{
        /*
         * use worst case speed of 1200bps to calculate transmit timeout
         * based on data in buffers (tbuf_bytes) and FIFO (128 bytes)
         */
        if (info->params.mode == MGSL_MODE_HDLC) {
                int timeout  = (tbuf_bytes(info) * 7) + 1000;
                mod_timer(&info->tx_timer, jiffies + msecs_to_jiffies(timeout));
        }
}

static int write(struct tty_struct *tty,
                 const unsigned char *buf, int count)
{
        int ret = 0;
        struct slgt_info *info = tty->driver_data;
        unsigned long flags;

        if (sanity_check(info, tty->name, "write"))
                return -EIO;

        DBGINFO(("%s write count=%d\n", info->device_name, count));

        if (!info->tx_buf || (count > info->max_frame_size))
                return -EIO;

        if (!count || tty->flow.stopped || tty->hw_stopped)
                return 0;

        spin_lock_irqsave(&info->lock, flags);

        if (info->tx_count) {
                /* send accumulated data from send_char() */
                if (!tx_load(info, info->tx_buf, info->tx_count))
                        goto cleanup;
                info->tx_count = 0;
        }

        if (tx_load(info, buf, count))
                ret = count;

cleanup:
        spin_unlock_irqrestore(&info->lock, flags);
        DBGINFO(("%s write rc=%d\n", info->device_name, ret));
        return ret;
}

static int put_char(struct tty_struct *tty, unsigned char ch)
{
        struct slgt_info *info = tty->driver_data;
        unsigned long flags;
        int ret = 0;

        if (sanity_check(info, tty->name, "put_char"))
                return 0;
        DBGINFO(("%s put_char(%d)\n", info->device_name, ch));
        if (!info->tx_buf)
                return 0;
        spin_lock_irqsave(&info->lock,flags);
        if (info->tx_count < info->max_frame_size) {
                info->tx_buf[info->tx_count++] = ch;
                ret = 1;
        }
        spin_unlock_irqrestore(&info->lock,flags);
        return ret;
}

static void send_xchar(struct tty_struct *tty, char ch)
{
        struct slgt_info *info = tty->driver_data;
        unsigned long flags;

        if (sanity_check(info, tty->name, "send_xchar"))
                return;
        DBGINFO(("%s send_xchar(%d)\n", info->device_name, ch));
        info->x_char = ch;
        if (ch) {
                spin_lock_irqsave(&info->lock,flags);
                if (!info->tx_enabled)
                        tx_start(info);
                spin_unlock_irqrestore(&info->lock,flags);
        }
}

static void wait_until_sent(struct tty_struct *tty, int timeout)
{
        struct slgt_info *info = tty->driver_data;
        unsigned long orig_jiffies, char_time;

        if (!info )
                return;
        if (sanity_check(info, tty->name, "wait_until_sent"))
                return;
        DBGINFO(("%s wait_until_sent entry\n", info->device_name));
        if (!tty_port_initialized(&info->port))
                goto exit;

        orig_jiffies = jiffies;

        /* Set check interval to 1/5 of estimated time to
         * send a character, and make it at least 1. The check
         * interval should also be less than the timeout.
         * Note: use tight timings here to satisfy the NIST-PCTS.
         */

        if (info->params.data_rate) {
                char_time = info->timeout/(32 * 5);
                if (!char_time)
                        char_time++;
        } else
                char_time = 1;

        if (timeout)
                char_time = min_t(unsigned long, char_time, timeout);

        while (info->tx_active) {
                msleep_interruptible(jiffies_to_msecs(char_time));
                if (signal_pending(current))
                        break;
                if (timeout && time_after(jiffies, orig_jiffies + timeout))
                        break;
        }
exit:
        DBGINFO(("%s wait_until_sent exit\n", info->device_name));
}

static unsigned int write_room(struct tty_struct *tty)
{
        struct slgt_info *info = tty->driver_data;
        unsigned int ret;

        if (sanity_check(info, tty->name, "write_room"))
                return 0;
        ret = (info->tx_active) ? 0 : HDLC_MAX_FRAME_SIZE;
        DBGINFO(("%s write_room=%u\n", info->device_name, ret));
        return ret;
}

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

        if (sanity_check(info, tty->name, "flush_chars"))
                return;
        DBGINFO(("%s flush_chars entry tx_count=%d\n", info->device_name, info->tx_count));

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

        DBGINFO(("%s flush_chars start transmit\n", info->device_name));

        spin_lock_irqsave(&info->lock,flags);
        if (info->tx_count && tx_load(info, info->tx_buf, info->tx_count))
                info->tx_count = 0;
        spin_unlock_irqrestore(&info->lock,flags);
}

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

        if (sanity_check(info, tty->name, "flush_buffer"))
                return;
        DBGINFO(("%s flush_buffer\n", info->device_name));

        spin_lock_irqsave(&info->lock, flags);
        info->tx_count = 0;
        spin_unlock_irqrestore(&info->lock, flags);

        tty_wakeup(tty);
}

/*
 * throttle (stop) transmitter
 */
static void tx_hold(struct tty_struct *tty)
{
        struct slgt_info *info = tty->driver_data;
        unsigned long flags;

        if (sanity_check(info, tty->name, "tx_hold"))
                return;
        DBGINFO(("%s tx_hold\n", info->device_name));
        spin_lock_irqsave(&info->lock,flags);
        if (info->tx_enabled && info->params.mode == MGSL_MODE_ASYNC)
                tx_stop(info);
        spin_unlock_irqrestore(&info->lock,flags);
}

/*
 * release (start) transmitter
 */
static void tx_release(struct tty_struct *tty)
{
        struct slgt_info *info = tty->driver_data;
        unsigned long flags;

        if (sanity_check(info, tty->name, "tx_release"))
                return;
        DBGINFO(("%s tx_release\n", info->device_name));
        spin_lock_irqsave(&info->lock, flags);
        if (info->tx_count && tx_load(info, info->tx_buf, info->tx_count))
                info->tx_count = 0;
        spin_unlock_irqrestore(&info->lock, flags);
}

/*
 * Service an IOCTL request
 *
 * Arguments
 *
 *      tty     pointer to tty instance data
 *      cmd     IOCTL command code
 *      arg     command argument/context
 *
 * Return 0 if success, otherwise error code
 */
static int ioctl(struct tty_struct *tty,
                 unsigned int cmd, unsigned long arg)
{
        struct slgt_info *info = tty->driver_data;
        void __user *argp = (void __user *)arg;
        int ret;

        if (sanity_check(info, tty->name, "ioctl"))
                return -ENODEV;
        DBGINFO(("%s ioctl() cmd=%08X\n", info->device_name, cmd));

        if (cmd != TIOCMIWAIT) {
                if (tty_io_error(tty))
                    return -EIO;
        }

        switch (cmd) {
        case MGSL_IOCWAITEVENT:
                return wait_mgsl_event(info, argp);
        case TIOCMIWAIT:
                return modem_input_wait(info,(int)arg);
        case MGSL_IOCSGPIO:
                return set_gpio(info, argp);
        case MGSL_IOCGGPIO:
                return get_gpio(info, argp);
        case MGSL_IOCWAITGPIO:
                return wait_gpio(info, argp);
        case MGSL_IOCGXSYNC:
                return get_xsync(info, argp);
        case MGSL_IOCSXSYNC:
                return set_xsync(info, (int)arg);
        case MGSL_IOCGXCTRL:
                return get_xctrl(info, argp);
        case MGSL_IOCSXCTRL:
                return set_xctrl(info, (int)arg);
        }

        mutex_lock(&info->port.mutex);
        switch (cmd) {
        case MGSL_IOCGPARAMS:
                ret = get_params(info, argp);
                break;
        case MGSL_IOCSPARAMS:
                ret = set_params(info, argp);
                break;
        case MGSL_IOCGTXIDLE:
                ret = get_txidle(info, argp);
                break;
        case MGSL_IOCSTXIDLE:
                ret = set_txidle(info, (int)arg);
                break;
        case MGSL_IOCTXENABLE:
                ret = tx_enable(info, (int)arg);
                break;
        case MGSL_IOCRXENABLE:
                ret = rx_enable(info, (int)arg);
                break;
        case MGSL_IOCTXABORT:
                ret = tx_abort(info);
                break;
        case MGSL_IOCGSTATS:
                ret = get_stats(info, argp);
                break;
        case MGSL_IOCGIF:
                ret = get_interface(info, argp);
                break;
        case MGSL_IOCSIF:
                ret = set_interface(info,(int)arg);
                break;
        default:
                ret = -ENOIOCTLCMD;
        }
        mutex_unlock(&info->port.mutex);
        return ret;
}

static int get_icount(struct tty_struct *tty,
                                struct serial_icounter_struct *icount)

{
        struct slgt_info *info = tty->driver_data;
        struct mgsl_icount cnow;        /* kernel counter temps */
        unsigned long flags;

        spin_lock_irqsave(&info->lock,flags);
        cnow = info->icount;
        spin_unlock_irqrestore(&info->lock,flags);

        icount->cts = cnow.cts;
        icount->dsr = cnow.dsr;
        icount->rng = cnow.rng;
        icount->dcd = cnow.dcd;
        icount->rx = cnow.rx;
        icount->tx = cnow.tx;
        icount->frame = cnow.frame;
        icount->overrun = cnow.overrun;
        icount->parity = cnow.parity;
        icount->brk = cnow.brk;
        icount->buf_overrun = cnow.buf_overrun;

        return 0;
}

/*
 * support for 32 bit ioctl calls on 64 bit systems
 */
#ifdef CONFIG_COMPAT
static long get_params32(struct slgt_info *info, struct MGSL_PARAMS32 __user *user_params)
{
        struct MGSL_PARAMS32 tmp_params;

        DBGINFO(("%s get_params32\n", info->device_name));
        memset(&tmp_params, 0, sizeof(tmp_params));
        tmp_params.mode            = (compat_ulong_t)info->params.mode;
        tmp_params.loopback        = info->params.loopback;
        tmp_params.flags           = info->params.flags;
        tmp_params.encoding        = info->params.encoding;
        tmp_params.clock_speed     = (compat_ulong_t)info->params.clock_speed;
        tmp_params.addr_filter     = info->params.addr_filter;
        tmp_params.crc_type        = info->params.crc_type;
        tmp_params.preamble_length = info->params.preamble_length;
        tmp_params.preamble        = info->params.preamble;
        tmp_params.data_rate       = (compat_ulong_t)info->params.data_rate;
        tmp_params.data_bits       = info->params.data_bits;
        tmp_params.stop_bits       = info->params.stop_bits;
        tmp_params.parity          = info->params.parity;
        if (copy_to_user(user_params, &tmp_params, sizeof(struct MGSL_PARAMS32)))
                return -EFAULT;
        return 0;
}

static long set_params32(struct slgt_info *info, struct MGSL_PARAMS32 __user *new_params)
{
        struct MGSL_PARAMS32 tmp_params;

        DBGINFO(("%s set_params32\n", info->device_name));
        if (copy_from_user(&tmp_params, new_params, sizeof(struct MGSL_PARAMS32)))
                return -EFAULT;

        spin_lock(&info->lock);
        if (tmp_params.mode == MGSL_MODE_BASE_CLOCK) {
                info->base_clock = tmp_params.clock_speed;
        } else {
                info->params.mode            = tmp_params.mode;
                info->params.loopback        = tmp_params.loopback;
                info->params.flags           = tmp_params.flags;
                info->params.encoding        = tmp_params.encoding;
                info->params.clock_speed     = tmp_params.clock_speed;
                info->params.addr_filter     = tmp_params.addr_filter;
                info->params.crc_type        = tmp_params.crc_type;
                info->params.preamble_length = tmp_params.preamble_length;
                info->params.preamble        = tmp_params.preamble;
                info->params.data_rate       = tmp_params.data_rate;
                info->params.data_bits       = tmp_params.data_bits;
                info->params.stop_bits       = tmp_params.stop_bits;
                info->params.parity          = tmp_params.parity;
        }
        spin_unlock(&info->lock);

        program_hw(info);

        return 0;
}

static long slgt_compat_ioctl(struct tty_struct *tty,
                         unsigned int cmd, unsigned long arg)
{
        struct slgt_info *info = tty->driver_data;
        int rc;

        if (sanity_check(info, tty->name, "compat_ioctl"))
                return -ENODEV;
        DBGINFO(("%s compat_ioctl() cmd=%08X\n", info->device_name, cmd));

        switch (cmd) {
        case MGSL_IOCSPARAMS32:
                rc = set_params32(info, compat_ptr(arg));
                break;

        case MGSL_IOCGPARAMS32:
                rc = get_params32(info, compat_ptr(arg));
                break;

        case MGSL_IOCGPARAMS:
        case MGSL_IOCSPARAMS:
        case MGSL_IOCGTXIDLE:
        case MGSL_IOCGSTATS:
        case MGSL_IOCWAITEVENT:
        case MGSL_IOCGIF:
        case MGSL_IOCSGPIO:
        case MGSL_IOCGGPIO:
        case MGSL_IOCWAITGPIO:
        case MGSL_IOCGXSYNC:
        case MGSL_IOCGXCTRL:
                rc = ioctl(tty, cmd, (unsigned long)compat_ptr(arg));
                break;
        default:
                rc = ioctl(tty, cmd, arg);
        }
        DBGINFO(("%s compat_ioctl() cmd=%08X rc=%d\n", info->device_name, cmd, rc));
        return rc;
}
#else
#define slgt_compat_ioctl NULL
#endif /* ifdef CONFIG_COMPAT */

/*
 * proc fs support
 */
static inline void line_info(struct seq_file *m, struct slgt_info *info)
{
        char stat_buf[30];
        unsigned long flags;

        seq_printf(m, "%s: IO=%08X IRQ=%d MaxFrameSize=%u\n",
                      info->device_name, info->phys_reg_addr,
                      info->irq_level, info->max_frame_size);

        /* output current serial signal states */
        spin_lock_irqsave(&info->lock,flags);
        get_signals(info);
        spin_unlock_irqrestore(&info->lock,flags);

        stat_buf[0] = 0;
        stat_buf[1] = 0;
        if (info->signals & SerialSignal_RTS)
                strcat(stat_buf, "|RTS");
        if (info->signals & SerialSignal_CTS)
                strcat(stat_buf, "|CTS");
        if (info->signals & SerialSignal_DTR)
                strcat(stat_buf, "|DTR");
        if (info->signals & SerialSignal_DSR)
                strcat(stat_buf, "|DSR");
        if (info->signals & SerialSignal_DCD)
                strcat(stat_buf, "|CD");
        if (info->signals & SerialSignal_RI)
                strcat(stat_buf, "|RI");

        if (info->params.mode != MGSL_MODE_ASYNC) {
                seq_printf(m, "\tHDLC txok:%d rxok:%d",
                               info->icount.txok, info->icount.rxok);
                if (info->icount.txunder)
                        seq_printf(m, " txunder:%d", info->icount.txunder);
                if (info->icount.txabort)
                        seq_printf(m, " txabort:%d", info->icount.txabort);
                if (info->icount.rxshort)
                        seq_printf(m, " rxshort:%d", info->icount.rxshort);
                if (info->icount.rxlong)
                        seq_printf(m, " rxlong:%d", info->icount.rxlong);
                if (info->icount.rxover)
                        seq_printf(m, " rxover:%d", info->icount.rxover);
                if (info->icount.rxcrc)
                        seq_printf(m, " rxcrc:%d", info->icount.rxcrc);
        } else {
                seq_printf(m, "\tASYNC tx:%d rx:%d",
                               info->icount.tx, info->icount.rx);
                if (info->icount.frame)
                        seq_printf(m, " fe:%d", info->icount.frame);
                if (info->icount.parity)
                        seq_printf(m, " pe:%d", info->icount.parity);
                if (info->icount.brk)
                        seq_printf(m, " brk:%d", info->icount.brk);
                if (info->icount.overrun)
                        seq_printf(m, " oe:%d", info->icount.overrun);
        }

        /* Append serial signal status to end */
        seq_printf(m, " %s\n", stat_buf+1);

        seq_printf(m, "\ttxactive=%d bh_req=%d bh_run=%d pending_bh=%x\n",
                       info->tx_active,info->bh_requested,info->bh_running,
                       info->pending_bh);
}

/* Called to print information about devices
 */
static int synclink_gt_proc_show(struct seq_file *m, void *v)
{
        struct slgt_info *info;

        seq_puts(m, "synclink_gt driver\n");

        info = slgt_device_list;
        while( info ) {
                line_info(m, info);
                info = info->next_device;
        }
        return 0;
}

/*
 * return count of bytes in transmit buffer
 */
static unsigned int chars_in_buffer(struct tty_struct *tty)
{
        struct slgt_info *info = tty->driver_data;
        unsigned int count;
        if (sanity_check(info, tty->name, "chars_in_buffer"))
                return 0;
        count = tbuf_bytes(info);
        DBGINFO(("%s chars_in_buffer()=%u\n", info->device_name, count));
        return count;
}

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

        if (sanity_check(info, tty->name, "throttle"))
                return;
        DBGINFO(("%s throttle\n", info->device_name));
        if (I_IXOFF(tty))
                send_xchar(tty, STOP_CHAR(tty));
        if (C_CRTSCTS(tty)) {
                spin_lock_irqsave(&info->lock,flags);
                info->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 unthrottle(struct tty_struct * tty)
{
        struct slgt_info *info = tty->driver_data;
        unsigned long flags;

        if (sanity_check(info, tty->name, "unthrottle"))
                return;
        DBGINFO(("%s unthrottle\n", info->device_name));
        if (I_IXOFF(tty)) {
                if (info->x_char)
                        info->x_char = 0;
                else
                        send_xchar(tty, START_CHAR(tty));
        }
        if (C_CRTSCTS(tty)) {
                spin_lock_irqsave(&info->lock,flags);
                info->signals |= SerialSignal_RTS;
                set_signals(info);
                spin_unlock_irqrestore(&info->lock,flags);
        }
}

/*
 * set or clear transmit break condition
 * break_state  -1=set break condition, 0=clear
 */
static int set_break(struct tty_struct *tty, int break_state)
{
        struct slgt_info *info = tty->driver_data;
        unsigned short value;
        unsigned long flags;

        if (sanity_check(info, tty->name, "set_break"))
                return -EINVAL;
        DBGINFO(("%s set_break(%d)\n", info->device_name, break_state));

        spin_lock_irqsave(&info->lock,flags);
        value = rd_reg16(info, TCR);
        if (break_state == -1)
                value |= BIT6;
        else
                value &= ~BIT6;
        wr_reg16(info, TCR, value);
        spin_unlock_irqrestore(&info->lock,flags);
        return 0;
}

#if SYNCLINK_GENERIC_HDLC

/**
 * hdlcdev_attach - called by generic HDLC layer when protocol selected (PPP, frame relay, etc.)
 * @dev:      pointer to network device structure
 * @encoding: serial encoding setting
 * @parity:   FCS setting
 *
 * Set encoding and frame check sequence (FCS) options.
 *
 * Return: 0 if success, otherwise error code
 */
static int hdlcdev_attach(struct net_device *dev, unsigned short encoding,
                          unsigned short parity)
{
        struct slgt_info *info = dev_to_port(dev);
        unsigned char  new_encoding;
        unsigned short new_crctype;

        /* return error if TTY interface open */
        if (info->port.count)
                return -EBUSY;

        DBGINFO(("%s hdlcdev_attach\n", info->device_name));

        switch (encoding)
        {
        case ENCODING_NRZ:        new_encoding = HDLC_ENCODING_NRZ; break;
        case ENCODING_NRZI:       new_encoding = HDLC_ENCODING_NRZI_SPACE; break;
        case ENCODING_FM_MARK:    new_encoding = HDLC_ENCODING_BIPHASE_MARK; break;
        case ENCODING_FM_SPACE:   new_encoding = HDLC_ENCODING_BIPHASE_SPACE; break;
        case ENCODING_MANCHESTER: new_encoding = HDLC_ENCODING_BIPHASE_LEVEL; break;
        default: return -EINVAL;
        }

        switch (parity)
        {
        case PARITY_NONE:            new_crctype = HDLC_CRC_NONE; break;
        case PARITY_CRC16_PR1_CCITT: new_crctype = HDLC_CRC_16_CCITT; break;
        case PARITY_CRC32_PR1_CCITT: new_crctype = HDLC_CRC_32_CCITT; break;
        default: return -EINVAL;
        }

        info->params.encoding = new_encoding;
        info->params.crc_type = new_crctype;

        /* if network interface up, reprogram hardware */
        if (info->netcount)
                program_hw(info);

        return 0;
}

/**
 * hdlcdev_xmit - called by generic HDLC layer to send a frame
 * @skb: socket buffer containing HDLC frame
 * @dev: pointer to network device structure
 */
static netdev_tx_t hdlcdev_xmit(struct sk_buff *skb,
                                      struct net_device *dev)
{
        struct slgt_info *info = dev_to_port(dev);
        unsigned long flags;

        DBGINFO(("%s hdlc_xmit\n", dev->name));

        if (!skb->len)
                return NETDEV_TX_OK;

        /* stop sending until this frame completes */
        netif_stop_queue(dev);

        /* update network statistics */
        dev->stats.tx_packets++;
        dev->stats.tx_bytes += skb->len;

        /* save start time for transmit timeout detection */
        netif_trans_update(dev);

        spin_lock_irqsave(&info->lock, flags);
        tx_load(info, skb->data, skb->len);
        spin_unlock_irqrestore(&info->lock, flags);

        /* done with socket buffer, so free it */
        dev_kfree_skb(skb);

        return NETDEV_TX_OK;
}

/**
 * hdlcdev_open - called by network layer when interface enabled
 * @dev: pointer to network device structure
 *
 * Claim resources and initialize hardware.
 *
 * Return: 0 if success, otherwise error code
 */
static int hdlcdev_open(struct net_device *dev)
{
        struct slgt_info *info = dev_to_port(dev);
        int rc;
        unsigned long flags;

        if (!try_module_get(THIS_MODULE))
                return -EBUSY;

        DBGINFO(("%s hdlcdev_open\n", dev->name));

        /* generic HDLC layer open processing */
        rc = hdlc_open(dev);
        if (rc)
                return rc;

        /* arbitrate between network and tty opens */
        spin_lock_irqsave(&info->netlock, flags);
        if (info->port.count != 0 || info->netcount != 0) {
                DBGINFO(("%s hdlc_open busy\n", dev->name));
                spin_unlock_irqrestore(&info->netlock, flags);
                return -EBUSY;
        }
        info->netcount=1;
        spin_unlock_irqrestore(&info->netlock, flags);

        /* claim resources and init adapter */
        if ((rc = startup(info)) != 0) {
                spin_lock_irqsave(&info->netlock, flags);
                info->netcount=0;
                spin_unlock_irqrestore(&info->netlock, flags);
                return rc;
        }

        /* assert RTS and DTR, apply hardware settings */
        info->signals |= SerialSignal_RTS | SerialSignal_DTR;
        program_hw(info);

        /* enable network layer transmit */
        netif_trans_update(dev);
        netif_start_queue(dev);

        /* inform generic HDLC layer of current DCD status */
        spin_lock_irqsave(&info->lock, flags);
        get_signals(info);
        spin_unlock_irqrestore(&info->lock, flags);
        if (info->signals & SerialSignal_DCD)
                netif_carrier_on(dev);
        else
                netif_carrier_off(dev);
        return 0;
}

/**
 * hdlcdev_close - called by network layer when interface is disabled
 * @dev:  pointer to network device structure
 *
 * Shutdown hardware and release resources.
 *
 * Return: 0 if success, otherwise error code
 */
static int hdlcdev_close(struct net_device *dev)
{
        struct slgt_info *info = dev_to_port(dev);
        unsigned long flags;

        DBGINFO(("%s hdlcdev_close\n", dev->name));

        netif_stop_queue(dev);

        /* shutdown adapter and release resources */
        shutdown(info);

        hdlc_close(dev);

        spin_lock_irqsave(&info->netlock, flags);
        info->netcount=0;
        spin_unlock_irqrestore(&info->netlock, flags);

        module_put(THIS_MODULE);
        return 0;
}

/**
 * hdlcdev_ioctl - called by network layer to process IOCTL call to network device
 * @dev: pointer to network device structure
 * @ifr: pointer to network interface request structure
 * @cmd: IOCTL command code
 *
 * Return: 0 if success, otherwise error code
 */
static int hdlcdev_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
{
        const size_t size = sizeof(sync_serial_settings);
        sync_serial_settings new_line;
        sync_serial_settings __user *line = ifr->ifr_settings.ifs_ifsu.sync;
        struct slgt_info *info = dev_to_port(dev);
        unsigned int flags;

        DBGINFO(("%s hdlcdev_ioctl\n", dev->name));

        /* return error if TTY interface open */
        if (info->port.count)
                return -EBUSY;

        if (cmd != SIOCWANDEV)
                return hdlc_ioctl(dev, ifr, cmd);

        memset(&new_line, 0, sizeof(new_line));

        switch(ifr->ifr_settings.type) {
        case IF_GET_IFACE: /* return current sync_serial_settings */

                ifr->ifr_settings.type = IF_IFACE_SYNC_SERIAL;
                if (ifr->ifr_settings.size < size) {
                        ifr->ifr_settings.size = size; /* data size wanted */
                        return -ENOBUFS;
                }

                flags = info->params.flags & (HDLC_FLAG_RXC_RXCPIN | HDLC_FLAG_RXC_DPLL |
                                              HDLC_FLAG_RXC_BRG    | HDLC_FLAG_RXC_TXCPIN |
                                              HDLC_FLAG_TXC_TXCPIN | HDLC_FLAG_TXC_DPLL |
                                              HDLC_FLAG_TXC_BRG    | HDLC_FLAG_TXC_RXCPIN);

                switch (flags){
                case (HDLC_FLAG_RXC_RXCPIN | HDLC_FLAG_TXC_TXCPIN): new_line.clock_type = CLOCK_EXT; break;
                case (HDLC_FLAG_RXC_BRG    | HDLC_FLAG_TXC_BRG):    new_line.clock_type = CLOCK_INT; break;
                case (HDLC_FLAG_RXC_RXCPIN | HDLC_FLAG_TXC_BRG):    new_line.clock_type = CLOCK_TXINT; break;
                case (HDLC_FLAG_RXC_RXCPIN | HDLC_FLAG_TXC_RXCPIN): new_line.clock_type = CLOCK_TXFROMRX; break;
                default: new_line.clock_type = CLOCK_DEFAULT;
                }

                new_line.clock_rate = info->params.clock_speed;
                new_line.loopback   = info->params.loopback ? 1:0;

                if (copy_to_user(line, &new_line, size))
                        return -EFAULT;
                return 0;

        case IF_IFACE_SYNC_SERIAL: /* set sync_serial_settings */

                if(!capable(CAP_NET_ADMIN))
                        return -EPERM;
                if (copy_from_user(&new_line, line, size))
                        return -EFAULT;

                switch (new_line.clock_type)
                {
                case CLOCK_EXT:      flags = HDLC_FLAG_RXC_RXCPIN | HDLC_FLAG_TXC_TXCPIN; break;
                case CLOCK_TXFROMRX: flags = HDLC_FLAG_RXC_RXCPIN | HDLC_FLAG_TXC_RXCPIN; break;
                case CLOCK_INT:      flags = HDLC_FLAG_RXC_BRG    | HDLC_FLAG_TXC_BRG;    break;
                case CLOCK_TXINT:    flags = HDLC_FLAG_RXC_RXCPIN | HDLC_FLAG_TXC_BRG;    break;
                case CLOCK_DEFAULT:  flags = info->params.flags &
                                             (HDLC_FLAG_RXC_RXCPIN | HDLC_FLAG_RXC_DPLL |
                                              HDLC_FLAG_RXC_BRG    | HDLC_FLAG_RXC_TXCPIN |
                                              HDLC_FLAG_TXC_TXCPIN | HDLC_FLAG_TXC_DPLL |
                                              HDLC_FLAG_TXC_BRG    | HDLC_FLAG_TXC_RXCPIN); break;
                default: return -EINVAL;
                }

                if (new_line.loopback != 0 && new_line.loopback != 1)
                        return -EINVAL;

                info->params.flags &= ~(HDLC_FLAG_RXC_RXCPIN | HDLC_FLAG_RXC_DPLL |
                                        HDLC_FLAG_RXC_BRG    | HDLC_FLAG_RXC_TXCPIN |
                                        HDLC_FLAG_TXC_TXCPIN | HDLC_FLAG_TXC_DPLL |
                                        HDLC_FLAG_TXC_BRG    | HDLC_FLAG_TXC_RXCPIN);
                info->params.flags |= flags;

                info->params.loopback = new_line.loopback;

                if (flags & (HDLC_FLAG_RXC_BRG | HDLC_FLAG_TXC_BRG))
                        info->params.clock_speed = new_line.clock_rate;
                else
                        info->params.clock_speed = 0;

                /* if network interface up, reprogram hardware */
                if (info->netcount)
                        program_hw(info);
                return 0;

        default:
                return hdlc_ioctl(dev, ifr, cmd);
        }
}

/**
 * hdlcdev_tx_timeout - called by network layer when transmit timeout is detected
 * @dev: pointer to network device structure
 * @txqueue: unused
 */
static void hdlcdev_tx_timeout(struct net_device *dev, unsigned int txqueue)
{
        struct slgt_info *info = dev_to_port(dev);
        unsigned long flags;

        DBGINFO(("%s hdlcdev_tx_timeout\n", dev->name));

        dev->stats.tx_errors++;
        dev->stats.tx_aborted_errors++;

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

        netif_wake_queue(dev);
}

/**
 * hdlcdev_tx_done - called by device driver when transmit completes
 * @info: pointer to device instance information
 *
 * Reenable network layer transmit if stopped.
 */
static void hdlcdev_tx_done(struct slgt_info *info)
{
        if (netif_queue_stopped(info->netdev))
                netif_wake_queue(info->netdev);
}

/**
 * hdlcdev_rx - called by device driver when frame received
 * @info: pointer to device instance information
 * @buf:  pointer to buffer contianing frame data
 * @size: count of data bytes in buf
 *
 * Pass frame to network layer.
 */
static void hdlcdev_rx(struct slgt_info *info, char *buf, int size)
{
        struct sk_buff *skb = dev_alloc_skb(size);
        struct net_device *dev = info->netdev;

        DBGINFO(("%s hdlcdev_rx\n", dev->name));

        if (skb == NULL) {
                DBGERR(("%s: can't alloc skb, drop packet\n", dev->name));
                dev->stats.rx_dropped++;
                return;
        }

        skb_put_data(skb, buf, size);

        skb->protocol = hdlc_type_trans(skb, dev);

        dev->stats.rx_packets++;
        dev->stats.rx_bytes += size;

        netif_rx(skb);
}

static const struct net_device_ops hdlcdev_ops = {
        .ndo_open       = hdlcdev_open,
        .ndo_stop       = hdlcdev_close,
        .ndo_start_xmit = hdlc_start_xmit,
        .ndo_do_ioctl   = hdlcdev_ioctl,
        .ndo_tx_timeout = hdlcdev_tx_timeout,
};

/**
 * hdlcdev_init - called by device driver when adding device instance
 * @info: pointer to device instance information
 *
 * Do generic HDLC initialization.
 *
 * Return: 0 if success, otherwise error code
 */
static int hdlcdev_init(struct slgt_info *info)
{
        int rc;
        struct net_device *dev;
        hdlc_device *hdlc;

        /* allocate and initialize network and HDLC layer objects */

        dev = alloc_hdlcdev(info);
        if (!dev) {
                printk(KERN_ERR "%s hdlc device alloc failure\n", info->device_name);
                return -ENOMEM;
        }

        /* for network layer reporting purposes only */
        dev->mem_start = info->phys_reg_addr;
        dev->mem_end   = info->phys_reg_addr + SLGT_REG_SIZE - 1;
        dev->irq       = info->irq_level;

        /* network layer callbacks and settings */
        dev->netdev_ops     = &hdlcdev_ops;
        dev->watchdog_timeo = 10 * HZ;
        dev->tx_queue_len   = 50;

        /* generic HDLC layer callbacks and settings */
        hdlc         = dev_to_hdlc(dev);
        hdlc->attach = hdlcdev_attach;
        hdlc->xmit   = hdlcdev_xmit;

        /* register objects with HDLC layer */
        rc = register_hdlc_device(dev);
        if (rc) {
                printk(KERN_WARNING "%s:unable to register hdlc device\n",__FILE__);
                free_netdev(dev);
                return rc;
        }

        info->netdev = dev;
        return 0;
}

/**
 * hdlcdev_exit - called by device driver when removing device instance
 * @info: pointer to device instance information
 *
 * Do generic HDLC cleanup.
 */
static void hdlcdev_exit(struct slgt_info *info)
{
        unregister_hdlc_device(info->netdev);
        free_netdev(info->netdev);
        info->netdev = NULL;
}

#endif /* ifdef CONFIG_HDLC */

/*
 * get async data from rx DMA buffers
 */
static void rx_async(struct slgt_info *info)
{
        struct mgsl_icount *icount = &info->icount;
        unsigned int start, end;
        unsigned char *p;
        unsigned char status;
        struct slgt_desc *bufs = info->rbufs;
        int i, count;
        int chars = 0;
        int stat;
        unsigned char ch;

        start = end = info->rbuf_current;

        while(desc_complete(bufs[end])) {
                count = desc_count(bufs[end]) - info->rbuf_index;
                p     = bufs[end].buf + info->rbuf_index;

                DBGISR(("%s rx_async count=%d\n", info->device_name, count));
                DBGDATA(info, p, count, "rx");

                for(i=0 ; i < count; i+=2, p+=2) {
                        ch = *p;
                        icount->rx++;

                        stat = 0;

                        status = *(p + 1) & (BIT1 + BIT0);
                        if (status) {
                                if (status & BIT1)
                                        icount->parity++;
                                else if (status & BIT0)
                                        icount->frame++;
                                /* discard char if tty control flags say so */
                                if (status & info->ignore_status_mask)
                                        continue;
                                if (status & BIT1)
                                        stat = TTY_PARITY;
                                else if (status & BIT0)
                                        stat = TTY_FRAME;
                        }
                        tty_insert_flip_char(&info->port, ch, stat);
                        chars++;
                }

                if (i < count) {
                        /* receive buffer not completed */
                        info->rbuf_index += i;
                        mod_timer(&info->rx_timer, jiffies + 1);
                        break;
                }

                info->rbuf_index = 0;
                free_rbufs(info, end, end);

                if (++end == info->rbuf_count)
                        end = 0;

                /* if entire list searched then no frame available */
                if (end == start)
                        break;
        }

        if (chars)
                tty_flip_buffer_push(&info->port);
}

/*
 * return next bottom half action to perform
 */
static int bh_action(struct slgt_info *info)
{
        unsigned long flags;
        int rc;

        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;
        } else {
                /* Mark BH routine as complete */
                info->bh_running = false;
                info->bh_requested = false;
                rc = 0;
        }

        spin_unlock_irqrestore(&info->lock,flags);

        return rc;
}

/*
 * perform bottom half processing
 */
static void bh_handler(struct work_struct *work)
{
        struct slgt_info *info = container_of(work, struct slgt_info, task);
        int action;

        info->bh_running = true;

        while((action = bh_action(info))) {
                switch (action) {
                case BH_RECEIVE:
                        DBGBH(("%s bh receive\n", info->device_name));
                        switch(info->params.mode) {
                        case MGSL_MODE_ASYNC:
                                rx_async(info);
                                break;
                        case MGSL_MODE_HDLC:
                                while(rx_get_frame(info));
                                break;
                        case MGSL_MODE_RAW:
                        case MGSL_MODE_MONOSYNC:
                        case MGSL_MODE_BISYNC:
                        case MGSL_MODE_XSYNC:
                                while(rx_get_buf(info));
                                break;
                        }
                        /* restart receiver if rx DMA buffers exhausted */
                        if (info->rx_restart)
                                rx_start(info);
                        break;
                case BH_TRANSMIT:
                        bh_transmit(info);
                        break;
                case BH_STATUS:
                        DBGBH(("%s bh status\n", info->device_name));
                        info->ri_chkcount = 0;
                        info->dsr_chkcount = 0;
                        info->dcd_chkcount = 0;
                        info->cts_chkcount = 0;
                        break;
                default:
                        DBGBH(("%s unknown action\n", info->device_name));
                        break;
                }
        }
        DBGBH(("%s bh_handler exit\n", info->device_name));
}

static void bh_transmit(struct slgt_info *info)
{
        struct tty_struct *tty = info->port.tty;

        DBGBH(("%s bh_transmit\n", info->device_name));
        if (tty)
                tty_wakeup(tty);
}

static void dsr_change(struct slgt_info *info, unsigned short status)
{
        if (status & BIT3) {
                info->signals |= SerialSignal_DSR;
                info->input_signal_events.dsr_up++;
        } else {
                info->signals &= ~SerialSignal_DSR;
                info->input_signal_events.dsr_down++;
        }
        DBGISR(("dsr_change %s signals=%04X\n", info->device_name, info->signals));
        if ((info->dsr_chkcount)++ == IO_PIN_SHUTDOWN_LIMIT) {
                slgt_irq_off(info, IRQ_DSR);
                return;
        }
        info->icount.dsr++;
        wake_up_interruptible(&info->status_event_wait_q);
        wake_up_interruptible(&info->event_wait_q);
        info->pending_bh |= BH_STATUS;
}

static void cts_change(struct slgt_info *info, unsigned short status)
{
        if (status & BIT2) {
                info->signals |= SerialSignal_CTS;
                info->input_signal_events.cts_up++;
        } else {
                info->signals &= ~SerialSignal_CTS;
                info->input_signal_events.cts_down++;
        }
        DBGISR(("cts_change %s signals=%04X\n", info->device_name, info->signals));
        if ((info->cts_chkcount)++ == IO_PIN_SHUTDOWN_LIMIT) {
                slgt_irq_off(info, IRQ_CTS);
                return;
        }
        info->icount.cts++;
        wake_up_interruptible(&info->status_event_wait_q);
        wake_up_interruptible(&info->event_wait_q);
        info->pending_bh |= BH_STATUS;

        if (tty_port_cts_enabled(&info->port)) {
                if (info->port.tty) {
                        if (info->port.tty->hw_stopped) {
                                if (info->signals & SerialSignal_CTS) {
                                        info->port.tty->hw_stopped = 0;
                                        info->pending_bh |= BH_TRANSMIT;
                                        return;
                                }
                        } else {
                                if (!(info->signals & SerialSignal_CTS))
                                        info->port.tty->hw_stopped = 1;
                        }
                }
        }
}

static void dcd_change(struct slgt_info *info, unsigned short status)
{
        if (status & BIT1) {
                info->signals |= SerialSignal_DCD;
                info->input_signal_events.dcd_up++;
        } else {
                info->signals &= ~SerialSignal_DCD;
                info->input_signal_events.dcd_down++;
        }
        DBGISR(("dcd_change %s signals=%04X\n", info->device_name, info->signals));
        if ((info->dcd_chkcount)++ == IO_PIN_SHUTDOWN_LIMIT) {
                slgt_irq_off(info, IRQ_DCD);
                return;
        }
        info->icount.dcd++;
#if SYNCLINK_GENERIC_HDLC
        if (info->netcount) {
                if (info->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);
        info->pending_bh |= BH_STATUS;