Samsung VDLinux n_tty.c

/*
 * n_tty.c --- implements the N_TTY line discipline.
 *
 * This code used to be in tty_io.c, but things are getting hairy
 * enough that it made sense to split things off.  (The N_TTY
 * processing has changed so much that it's hardly recognizable,
 * anyway...)
 *
 * Note that the open routine for N_TTY is guaranteed never to return
 * an error.  This is because Linux will fall back to setting a line
 * to N_TTY if it can not switch to any other line discipline.
 *
 * Written by Theodore Ts'o, Copyright 1994.
 *
 * This file also contains code originally written by Linus Torvalds,
 * Copyright 1991, 1992, 1993, and by Julian Cowley, Copyright 1994.
 *
 * This file may be redistributed under the terms of the GNU General Public
 * License.
 *
 * Reduced memory usage for older ARM systems  - Russell King.
 *
 * 2000/01/20   Fixed SMP locking on put_tty_queue using bits of
 *      the patch by Andrew J. Kroll <ag784@freenet.buffalo.edu>
 *      who actually finally proved there really was a race.
 *
 * 2002/03/18   Implemented n_tty_wakeup to send SIGIO POLL_OUTs to
 *      waiting writing processes-Sapan Bhatia <sapan@corewars.org>.
 *      Also fixed a bug in BLOCKING mode where n_tty_write returns
 *      EAGAIN
 */

#include <linux/types.h>
#include <linux/major.h>
#include <linux/errno.h>
#include <linux/signal.h>
#include <linux/fcntl.h>
#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/tty.h>
#include <linux/timer.h>
#include <linux/ctype.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/poll.h>
#include <linux/bitops.h>
#include <linux/audit.h>
#include <linux/file.h>
#include <linux/uaccess.h>
#include <linux/module.h>

#include <asm/system.h>

#ifdef CONFIG_KDEBUGD
#include <kdebugd/kdebugd.h>
#endif

/* number of characters left in xmit buffer before select has we have room */
#define WAKEUP_CHARS 256

/*
 * This defines the low- and high-watermarks for throttling and
 * unthrottling the TTY driver.  These watermarks are used for
 * controlling the space in the read buffer.
 */
#define TTY_THRESHOLD_THROTTLE      128 /* now based on remaining room */
#define TTY_THRESHOLD_UNTHROTTLE    128

/*
 * Special byte codes used in the echo buffer to represent operations
 * or special handling of characters.  Bytes in the echo buffer that
 * are not part of such special blocks are treated as normal character
 * codes.
 */
#define ECHO_OP_START 0xff
#define ECHO_OP_MOVE_BACK_COL 0x80
#define ECHO_OP_SET_CANON_COL 0x81
#define ECHO_OP_ERASE_TAB 0x82

/* VDLinux, based SELP.Mstar default patch No.15,
   n_tty serial input disable, SP Team 2010-01-29 */
#ifdef CONFIG_SERIAL_INPUT_MANIPULATION

#define MAX_STRING_SIZE 10
static unsigned char enable_serial[MAX_STRING_SIZE];
static unsigned char disable_serial[MAX_STRING_SIZE];

static int enable_string_size=0;
static int disable_string_size=0;

static int enable_index = 0;
static int disable_index = 0;

#define SERIAL_INPUT_DISABLE 0
#define SERIAL_INPUT_ENABLE 1

#ifdef CONFIG_SERIAL_INPUT_DEFAULT_SETUP_ENABLE
static int serial_enable = SERIAL_INPUT_ENABLE;
#else
static int serial_enable = SERIAL_INPUT_DISABLE;
#endif

struct tty_struct *INPUT_tty;
#endif

#ifdef CONFIG_SERIAL_INPUT_ENABLE_ONLY_NUMBER
#define MAX_ARRAY 19
int allow_char[] = { 48, 49, 50, 51, 52, 53, 54, 55, 56, 57 /* 0~9 */,
                                                65, 66, 67, 68, 69, 70 /* A~F */,
                                                32 /*space*/,
                                                13 /*enter*/,
                                                8  /*backspace*/ };
#endif

static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
                   unsigned char __user *ptr)
{
    tty_audit_add_data(tty, &x, 1);
    return put_user(x, ptr);
}

/**
 *  n_tty_set__room -   receive space
 *  @tty: terminal
 *
 *  Called by the driver to find out how much data it is
 *  permitted to feed to the line discipline without any being lost
 *  and thus to manage flow control. Not serialized. Answers for the
 *  "instant".
 */

static void n_tty_set_room(struct tty_struct *tty)
{
    /* tty->read_cnt is not read locked ? */
    int left = N_TTY_BUF_SIZE - tty->read_cnt - 1;

    /*
     * If we are doing input canonicalization, and there are no
     * pending newlines, let characters through without limit, so
     * that erase characters will be handled.  Other excess
     * characters will be beeped.
     */
    if (left <= 0)
        left = tty->icanon && !tty->canon_data;
    tty->receive_room = left;
}

static void put_tty_queue_nolock(unsigned char c, struct tty_struct *tty)
{
    if (tty->read_cnt < N_TTY_BUF_SIZE) {
        tty->read_buf[tty->read_head] = c;
        tty->read_head = (tty->read_head + 1) & (N_TTY_BUF_SIZE-1);
        tty->read_cnt++;
    }
}

/**
 *  put_tty_queue       -   add character to tty
 *  @c: character
 *  @tty: tty device
 *
 *  Add a character to the tty read_buf queue. This is done under the
 *  read_lock to serialize character addition and also to protect us
 *  against parallel reads or flushes
 */

static void put_tty_queue(unsigned char c, struct tty_struct *tty)
{
    unsigned long flags;
    /*
     *  The problem of stomping on the buffers ends here.
     *  Why didn't anyone see this one coming? --AJK
    */
    spin_lock_irqsave(&tty->read_lock, flags);
    put_tty_queue_nolock(c, tty);
    spin_unlock_irqrestore(&tty->read_lock, flags);
}

/**
 *  check_unthrottle    -   allow new receive data
 *  @tty; tty device
 *
 *  Check whether to call the driver unthrottle functions
 *
 *  Can sleep, may be called under the atomic_read_lock mutex but
 *  this is not guaranteed.
 */
static void check_unthrottle(struct tty_struct *tty)
{
    if (tty->count)
        tty_unthrottle(tty);
}

/**
 *  reset_buffer_flags  -   reset buffer state
 *  @tty: terminal to reset
 *
 *  Reset the read buffer counters, clear the flags,
 *  and make sure the driver is unthrottled. Called
 *  from n_tty_open() and n_tty_flush_buffer().
 *
 *  Locking: tty_read_lock for read fields.
 */

static void reset_buffer_flags(struct tty_struct *tty)
{
    unsigned long flags;

    spin_lock_irqsave(&tty->read_lock, flags);
    tty->read_head = tty->read_tail = tty->read_cnt = 0;
    spin_unlock_irqrestore(&tty->read_lock, flags);

    mutex_lock(&tty->echo_lock);
    tty->echo_pos = tty->echo_cnt = tty->echo_overrun = 0;
    mutex_unlock(&tty->echo_lock);

    tty->canon_head = tty->canon_data = tty->erasing = 0;
    memset(&tty->read_flags, 0, sizeof tty->read_flags);
    n_tty_set_room(tty);
    check_unthrottle(tty);
}

/**
 *  n_tty_flush_buffer  -   clean input queue
 *  @tty:   terminal device
 *
 *  Flush the input buffer. Called when the line discipline is
 *  being closed, when the tty layer wants the buffer flushed (eg
 *  at hangup) or when the N_TTY line discipline internally has to
 *  clean the pending queue (for example some signals).
 *
 *  Locking: ctrl_lock, read_lock.
 */

static void n_tty_flush_buffer(struct tty_struct *tty)
{
    unsigned long flags;
    /* clear everything and unthrottle the driver */
    reset_buffer_flags(tty);

    if (!tty->link)
        return;

    spin_lock_irqsave(&tty->ctrl_lock, flags);
    if (tty->link->packet) {
        tty->ctrl_status |= TIOCPKT_FLUSHREAD;
        wake_up_interruptible(&tty->link->read_wait);
    }
    spin_unlock_irqrestore(&tty->ctrl_lock, flags);
}

/**
 *  n_tty_chars_in_buffer   -   report available bytes
 *  @tty: tty device
 *
 *  Report the number of characters buffered to be delivered to user
 *  at this instant in time.
 *
 *  Locking: read_lock
 */

static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
{
    unsigned long flags;
    ssize_t n = 0;

    spin_lock_irqsave(&tty->read_lock, flags);
    if (!tty->icanon) {
        n = tty->read_cnt;
    } else if (tty->canon_data) {
        n = (tty->canon_head > tty->read_tail) ?
            tty->canon_head - tty->read_tail :
            tty->canon_head + (N_TTY_BUF_SIZE - tty->read_tail);
    }
    spin_unlock_irqrestore(&tty->read_lock, flags);
    return n;
}

/**
 *  is_utf8_continuation    -   utf8 multibyte check
 *  @c: byte to check
 *
 *  Returns true if the utf8 character 'c' is a multibyte continuation
 *  character. We use this to correctly compute the on screen size
 *  of the character when printing
 */

static inline int is_utf8_continuation(unsigned char c)
{
    return (c & 0xc0) == 0x80;
}

/**
 *  is_continuation     -   multibyte check
 *  @c: byte to check
 *
 *  Returns true if the utf8 character 'c' is a multibyte continuation
 *  character and the terminal is in unicode mode.
 */

static inline int is_continuation(unsigned char c, struct tty_struct *tty)
{
    return I_IUTF8(tty) && is_utf8_continuation(c);
}

/**
 *  do_output_char          -   output one character
 *  @c: character (or partial unicode symbol)
 *  @tty: terminal device
 *  @space: space available in tty driver write buffer
 *
 *  This is a helper function that handles one output character
 *  (including special characters like TAB, CR, LF, etc.),
 *  doing OPOST processing and putting the results in the
 *  tty driver's write buffer.
 *
 *  Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
 *  and NLDLY.  They simply aren't relevant in the world today.
 *  If you ever need them, add them here.
 *
 *  Returns the number of bytes of buffer space used or -1 if
 *  no space left.
 *
 *  Locking: should be called under the output_lock to protect
 *       the column state and space left in the buffer
 */

static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
{
    int spaces;

    if (!space)
        return -1;

    switch (c) {
    case '\n':
        if (O_ONLRET(tty))
            tty->column = 0;
        if (O_ONLCR(tty)) {
            if (space < 2)
                return -1;
            tty->canon_column = tty->column = 0;
            tty->ops->write(tty, "\r\n", 2);
            return 2;
        }
        tty->canon_column = tty->column;
        break;
    case '\r':
        if (O_ONOCR(tty) && tty->column == 0)
            return 0;
        if (O_OCRNL(tty)) {
            c = '\n';
            if (O_ONLRET(tty))
                tty->canon_column = tty->column = 0;
            break;
        }
        tty->canon_column = tty->column = 0;
        break;
    case '\t':
        spaces = 8 - (tty->column & 7);
        if (O_TABDLY(tty) == XTABS) {
            if (space < spaces)
                return -1;
            tty->column += spaces;
            tty->ops->write(tty, "        ", spaces);
            return spaces;
        }
        tty->column += spaces;
        break;
    case '\b':
        if (tty->column > 0)
            tty->column--;
        break;
    default:
        if (!iscntrl(c)) {
            if (O_OLCUC(tty))
                c = toupper(c);
            if (!is_continuation(c, tty))
                tty->column++;
        }
        break;
    }

    tty_put_char(tty, c);
    return 1;
}

/**
 *  process_output          -   output post processor
 *  @c: character (or partial unicode symbol)
 *  @tty: terminal device
 *
 *  Output one character with OPOST processing.
 *  Returns -1 when the output device is full and the character
 *  must be retried.
 *
 *  Locking: output_lock to protect column state and space left
 *       (also, this is called from n_tty_write under the
 *        tty layer write lock)
 */

static int process_output(unsigned char c, struct tty_struct *tty)
{
    int space, retval;

    mutex_lock(&tty->output_lock);

    space = tty_write_room(tty);
    retval = do_output_char(c, tty, space);

    mutex_unlock(&tty->output_lock);
    if (retval < 0)
        return -1;
    else
        return 0;
}

/**
 *  process_output_block        -   block post processor
 *  @tty: terminal device
 *  @buf: character buffer
 *  @nr: number of bytes to output
 *
 *  Output a block of characters with OPOST processing.
 *  Returns the number of characters output.
 *
 *  This path is used to speed up block console writes, among other
 *  things when processing blocks of output data. It handles only
 *  the simple cases normally found and helps to generate blocks of
 *  symbols for the console driver and thus improve performance.
 *
 *  Locking: output_lock to protect column state and space left
 *       (also, this is called from n_tty_write under the
 *        tty layer write lock)
 */

static ssize_t process_output_block(struct tty_struct *tty,
                    const unsigned char *buf, unsigned int nr)
{
    int space;
    int     i;
    const unsigned char *cp;

    mutex_lock(&tty->output_lock);

    space = tty_write_room(tty);
    if (!space) {
        mutex_unlock(&tty->output_lock);
        return 0;
    }
    if (nr > space)
        nr = space;

    for (i = 0, cp = buf; i < nr; i++, cp++) {
        unsigned char c = *cp;

        switch (c) {
        case '\n':
            if (O_ONLRET(tty))
                tty->column = 0;
            if (O_ONLCR(tty))
                goto break_out;
            tty->canon_column = tty->column;
            break;
        case '\r':
            if (O_ONOCR(tty) && tty->column == 0)
                goto break_out;
            if (O_OCRNL(tty))
                goto break_out;
            tty->canon_column = tty->column = 0;
            break;
        case '\t':
            goto break_out;
        case '\b':
            if (tty->column > 0)
                tty->column--;
            break;
        default:
            if (!iscntrl(c)) {
                if (O_OLCUC(tty))
                    goto break_out;
                if (!is_continuation(c, tty))
                    tty->column++;
            }
            break;
        }
    }
break_out:
    i = tty->ops->write(tty, buf, i);

    mutex_unlock(&tty->output_lock);
    return i;
}

/**
 *  process_echoes  -   write pending echo characters
 *  @tty: terminal device
 *
 *  Write previously buffered echo (and other ldisc-generated)
 *  characters to the tty.
 *
 *  Characters generated by the ldisc (including echoes) need to
 *  be buffered because the driver's write buffer can fill during
 *  heavy program output.  Echoing straight to the driver will
 *  often fail under these conditions, causing lost characters and
 *  resulting mismatches of ldisc state information.
 *
 *  Since the ldisc state must represent the characters actually sent
 *  to the driver at the time of the write, operations like certain
 *  changes in column state are also saved in the buffer and executed
 *  here.
 *
 *  A circular fifo buffer is used so that the most recent characters
 *  are prioritized.  Also, when control characters are echoed with a
 *  prefixed "^", the pair is treated atomically and thus not separated.
 *
 *  Locking: output_lock to protect column state and space left,
 *       echo_lock to protect the echo buffer
 */

static void process_echoes(struct tty_struct *tty)
{
    int space, nr;
    unsigned char c;
    unsigned char *cp, *buf_end;

    if (!tty->echo_cnt)
        return;

    mutex_lock(&tty->output_lock);
    mutex_lock(&tty->echo_lock);

    space = tty_write_room(tty);

    buf_end = tty->echo_buf + N_TTY_BUF_SIZE;
    cp = tty->echo_buf + tty->echo_pos;
    nr = tty->echo_cnt;
    while (nr > 0) {
        c = *cp;
        if (c == ECHO_OP_START) {
            unsigned char op;
            unsigned char *opp;
            int no_space_left = 0;

            /*
             * If the buffer byte is the start of a multi-byte
             * operation, get the next byte, which is either the
             * op code or a control character value.
             */
            opp = cp + 1;
            if (opp == buf_end)
                opp -= N_TTY_BUF_SIZE;
            op = *opp;

            switch (op) {
                unsigned int num_chars, num_bs;

            case ECHO_OP_ERASE_TAB:
                if (++opp == buf_end)
                    opp -= N_TTY_BUF_SIZE;
                num_chars = *opp;

                /*
                 * Determine how many columns to go back
                 * in order to erase the tab.
                 * This depends on the number of columns
                 * used by other characters within the tab
                 * area.  If this (modulo 8) count is from
                 * the start of input rather than from a
                 * previous tab, we offset by canon column.
                 * Otherwise, tab spacing is normal.
                 */
                if (!(num_chars & 0x80))
                    num_chars += tty->canon_column;
                num_bs = 8 - (num_chars & 7);

                if (num_bs > space) {
                    no_space_left = 1;
                    break;
                }
                space -= num_bs;
                while (num_bs--) {
                    tty_put_char(tty, '\b');
                    if (tty->column > 0)
                        tty->column--;
                }
                cp += 3;
                nr -= 3;
                break;

            case ECHO_OP_SET_CANON_COL:
                tty->canon_column = tty->column;
                cp += 2;
                nr -= 2;
                break;

            case ECHO_OP_MOVE_BACK_COL:
                if (tty->column > 0)
                    tty->column--;
                cp += 2;
                nr -= 2;
                break;

            case ECHO_OP_START:
                /* This is an escaped echo op start code */
                if (!space) {
                    no_space_left = 1;
                    break;
                }
                tty_put_char(tty, ECHO_OP_START);
                tty->column++;
                space--;
                cp += 2;
                nr -= 2;
                break;

            default:
                /*
                 * If the op is not a special byte code,
                 * it is a ctrl char tagged to be echoed
                 * as "^X" (where X is the letter
                 * representing the control char).
                 * Note that we must ensure there is
                 * enough space for the whole ctrl pair.
                 *
                 */
                if (space < 2) {
                    no_space_left = 1;
                    break;
                }
                tty_put_char(tty, '^');
                tty_put_char(tty, op ^ 0100);
                tty->column += 2;
                space -= 2;
                cp += 2;
                nr -= 2;
            }

            if (no_space_left)
                break;
        } else {
            if (O_OPOST(tty) &&
                !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
                int retval = do_output_char(c, tty, space);
                if (retval < 0)
                    break;
                space -= retval;
            } else {
                if (!space)
                    break;
                tty_put_char(tty, c);
                space -= 1;
            }
            cp += 1;
            nr -= 1;
        }

        /* When end of circular buffer reached, wrap around */
        if (cp >= buf_end)
            cp -= N_TTY_BUF_SIZE;
    }

    if (nr == 0) {
        tty->echo_pos = 0;
        tty->echo_cnt = 0;
        tty->echo_overrun = 0;
    } else {
        int num_processed = tty->echo_cnt - nr;
        tty->echo_pos += num_processed;
        tty->echo_pos &= N_TTY_BUF_SIZE - 1;
        tty->echo_cnt = nr;
        if (num_processed > 0)
            tty->echo_overrun = 0;
    }

    mutex_unlock(&tty->echo_lock);
    mutex_unlock(&tty->output_lock);

    if (tty->ops->flush_chars)
        tty->ops->flush_chars(tty);
}

/**
 *  add_echo_byte   -   add a byte to the echo buffer
 *  @c: unicode byte to echo
 *  @tty: terminal device
 *
 *  Add a character or operation byte to the echo buffer.
 *
 *  Should be called under the echo lock to protect the echo buffer.
 */

static void add_echo_byte(unsigned char c, struct tty_struct *tty)
{
    int new_byte_pos;

    if (tty->echo_cnt == N_TTY_BUF_SIZE) {
        /* Circular buffer is already at capacity */
        new_byte_pos = tty->echo_pos;

        /*
         * Since the buffer start position needs to be advanced,
         * be sure to step by a whole operation byte group.
         */
        if (tty->echo_buf[tty->echo_pos] == ECHO_OP_START) {
            if (tty->echo_buf[(tty->echo_pos + 1) &
                      (N_TTY_BUF_SIZE - 1)] ==
                        ECHO_OP_ERASE_TAB) {
                tty->echo_pos += 3;
                tty->echo_cnt -= 2;
            } else {
                tty->echo_pos += 2;
                tty->echo_cnt -= 1;
            }
        } else {
            tty->echo_pos++;
        }
        tty->echo_pos &= N_TTY_BUF_SIZE - 1;

        tty->echo_overrun = 1;
    } else {
        new_byte_pos = tty->echo_pos + tty->echo_cnt;
        new_byte_pos &= N_TTY_BUF_SIZE - 1;
        tty->echo_cnt++;
    }

    tty->echo_buf[new_byte_pos] = c;
}

/**
 *  echo_move_back_col  -   add operation to move back a column
 *  @tty: terminal device
 *
 *  Add an operation to the echo buffer to move back one column.
 *
 *  Locking: echo_lock to protect the echo buffer
 */

static void echo_move_back_col(struct tty_struct *tty)
{
    mutex_lock(&tty->echo_lock);

    add_echo_byte(ECHO_OP_START, tty);
    add_echo_byte(ECHO_OP_MOVE_BACK_COL, tty);

    mutex_unlock(&tty->echo_lock);
}

/**
 *  echo_set_canon_col  -   add operation to set the canon column
 *  @tty: terminal device
 *
 *  Add an operation to the echo buffer to set the canon column
 *  to the current column.
 *
 *  Locking: echo_lock to protect the echo buffer
 */

static void echo_set_canon_col(struct tty_struct *tty)
{
    mutex_lock(&tty->echo_lock);

    add_echo_byte(ECHO_OP_START, tty);
    add_echo_byte(ECHO_OP_SET_CANON_COL, tty);

    mutex_unlock(&tty->echo_lock);
}

/**
 *  echo_erase_tab  -   add operation to erase a tab
 *  @num_chars: number of character columns already used
 *  @after_tab: true if num_chars starts after a previous tab
 *  @tty: terminal device
 *
 *  Add an operation to the echo buffer to erase a tab.
 *
 *  Called by the eraser function, which knows how many character
 *  columns have been used since either a previous tab or the start
 *  of input.  This information will be used later, along with
 *  canon column (if applicable), to go back the correct number
 *  of columns.
 *
 *  Locking: echo_lock to protect the echo buffer
 */

static void echo_erase_tab(unsigned int num_chars, int after_tab,
               struct tty_struct *tty)
{
    mutex_lock(&tty->echo_lock);

    add_echo_byte(ECHO_OP_START, tty);
    add_echo_byte(ECHO_OP_ERASE_TAB, tty);

    /* We only need to know this modulo 8 (tab spacing) */
    num_chars &= 7;

    /* Set the high bit as a flag if num_chars is after a previous tab */
    if (after_tab)
        num_chars |= 0x80;

    add_echo_byte(num_chars, tty);

    mutex_unlock(&tty->echo_lock);
}

/**
 *  echo_char_raw   -   echo a character raw
 *  @c: unicode byte to echo
 *  @tty: terminal device
 *
 *  Echo user input back onto the screen. This must be called only when
 *  L_ECHO(tty) is true. Called from the driver receive_buf path.
 *
 *  This variant does not treat control characters specially.
 *
 *  Locking: echo_lock to protect the echo buffer
 */

static void echo_char_raw(unsigned char c, struct tty_struct *tty)
{
    mutex_lock(&tty->echo_lock);

    if (c == ECHO_OP_START) {
        add_echo_byte(ECHO_OP_START, tty);
        add_echo_byte(ECHO_OP_START, tty);
    } else {
        add_echo_byte(c, tty);
    }

    mutex_unlock(&tty->echo_lock);
}

/**
 *  echo_char   -   echo a character
 *  @c: unicode byte to echo
 *  @tty: terminal device
 *
 *  Echo user input back onto the screen. This must be called only when
 *  L_ECHO(tty) is true. Called from the driver receive_buf path.
 *
 *  This variant tags control characters to be echoed as "^X"
 *  (where X is the letter representing the control char).
 *
 *  Locking: echo_lock to protect the echo buffer
 */

static void echo_char(unsigned char c, struct tty_struct *tty)
{
    mutex_lock(&tty->echo_lock);

    if (c == ECHO_OP_START) {
        add_echo_byte(ECHO_OP_START, tty);
        add_echo_byte(ECHO_OP_START, tty);
    } else {
        if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
            add_echo_byte(ECHO_OP_START, tty);
        add_echo_byte(c, tty);
    }

    mutex_unlock(&tty->echo_lock);
}

/**
 *  finish_erasing      -   complete erase
 *  @tty: tty doing the erase
 */

static inline void finish_erasing(struct tty_struct *tty)
{
    if (tty->erasing) {
        echo_char_raw('/', tty);
        tty->erasing = 0;
    }
}

/**
 *  eraser      -   handle erase function
 *  @c: character input
 *  @tty: terminal device
 *
 *  Perform erase and necessary output when an erase character is
 *  present in the stream from the driver layer. Handles the complexities
 *  of UTF-8 multibyte symbols.
 *
 *  Locking: read_lock for tty buffers
 */

static void eraser(unsigned char c, struct tty_struct *tty)
{
    enum { ERASE, WERASE, KILL } kill_type;
    int head, seen_alnums, cnt;
    unsigned long flags;

    /* FIXME: locking needed ? */
    if (tty->read_head == tty->canon_head) {
        /* process_output('\a', tty); */ /* what do you think? */
        return;
    }
    if (c == ERASE_CHAR(tty))
        kill_type = ERASE;
    else if (c == WERASE_CHAR(tty))
        kill_type = WERASE;
    else {
        if (!L_ECHO(tty)) {
            spin_lock_irqsave(&tty->read_lock, flags);
            tty->read_cnt -= ((tty->read_head - tty->canon_head) &
                      (N_TTY_BUF_SIZE - 1));
            tty->read_head = tty->canon_head;
            spin_unlock_irqrestore(&tty->read_lock, flags);
            return;
        }
        if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
            spin_lock_irqsave(&tty->read_lock, flags);
            tty->read_cnt -= ((tty->read_head - tty->canon_head) &
                      (N_TTY_BUF_SIZE - 1));
            tty->read_head = tty->canon_head;
            spin_unlock_irqrestore(&tty->read_lock, flags);
            finish_erasing(tty);
            echo_char(KILL_CHAR(tty), tty);
            /* Add a newline if ECHOK is on and ECHOKE is off. */
            if (L_ECHOK(tty))
                echo_char_raw('\n', tty);
            return;
        }
        kill_type = KILL;
    }

    seen_alnums = 0;
    /* FIXME: Locking ?? */
    while (tty->read_head != tty->canon_head) {
        head = tty->read_head;

        /* erase a single possibly multibyte character */
        do {
            head = (head - 1) & (N_TTY_BUF_SIZE-1);
            c = tty->read_buf[head];
        } while (is_continuation(c, tty) && head != tty->canon_head);

        /* do not partially erase */
        if (is_continuation(c, tty))
            break;

        if (kill_type == WERASE) {
            /* Equivalent to BSD's ALTWERASE. */
            if (isalnum(c) || c == '_')
                seen_alnums++;
            else if (seen_alnums)
                break;
        }
        cnt = (tty->read_head - head) & (N_TTY_BUF_SIZE-1);
        spin_lock_irqsave(&tty->read_lock, flags);
        tty->read_head = head;
        tty->read_cnt -= cnt;
        spin_unlock_irqrestore(&tty->read_lock, flags);
        if (L_ECHO(tty)) {
            if (L_ECHOPRT(tty)) {
                if (!tty->erasing) {
                    echo_char_raw('\\', tty);
                    tty->erasing = 1;
                }
                /* if cnt > 1, output a multi-byte character */
                echo_char(c, tty);
                while (--cnt > 0) {
                    head = (head+1) & (N_TTY_BUF_SIZE-1);
                    echo_char_raw(tty->read_buf[head], tty);
                    echo_move_back_col(tty);
                }
            } else if (kill_type == ERASE && !L_ECHOE(tty)) {
                echo_char(ERASE_CHAR(tty), tty);
            } else if (c == '\t') {
                unsigned int num_chars = 0;
                int after_tab = 0;
                unsigned long tail = tty->read_head;

                /*
                 * Count the columns used for characters
                 * since the start of input or after a
                 * previous tab.
                 * This info is used to go back the correct
                 * number of columns.
                 */
                while (tail != tty->canon_head) {
                    tail = (tail-1) & (N_TTY_BUF_SIZE-1);
                    c = tty->read_buf[tail];
                    if (c == '\t') {
                        after_tab = 1;
                        break;
                    } else if (iscntrl(c)) {
                        if (L_ECHOCTL(tty))
                            num_chars += 2;
                    } else if (!is_continuation(c, tty)) {
                        num_chars++;
                    }
                }
                echo_erase_tab(num_chars, after_tab, tty);
            } else {
                if (iscntrl(c) && L_ECHOCTL(tty)) {
                    echo_char_raw('\b', tty);
                    echo_char_raw(' ', tty);
                    echo_char_raw('\b', tty);
                }
                if (!iscntrl(c) || L_ECHOCTL(tty)) {
                    echo_char_raw('\b', tty);
                    echo_char_raw(' ', tty);
                    echo_char_raw('\b', tty);
                }
            }
        }
        if (kill_type == ERASE)
            break;
    }
    if (tty->read_head == tty->canon_head && L_ECHO(tty))
        finish_erasing(tty);
}

/**
 *  isig        -   handle the ISIG optio
 *  @sig: signal
 *  @tty: terminal
 *  @flush: force flush
 *
 *  Called when a signal is being sent due to terminal input. This
 *  may caus terminal flushing to take place according to the termios
 *  settings and character used. Called from the driver receive_buf
 *  path so serialized.
 *
 *  Locking: ctrl_lock, read_lock (both via flush buffer)
 */

static inline void isig(int sig, struct tty_struct *tty, int flush)
{
    if (tty->pgrp)
        kill_pgrp(tty->pgrp, sig, 1);
    if (flush || !L_NOFLSH(tty)) {
        n_tty_flush_buffer(tty);
        tty_driver_flush_buffer(tty);
    }
}

/**
 *  n_tty_receive_break -   handle break
 *  @tty: terminal
 *
 *  An RS232 break event has been hit in the incoming bitstream. This
 *  can cause a variety of events depending upon the termios settings.
 *
 *  Called from the receive_buf path so single threaded.
 */

static inline void n_tty_receive_break(struct tty_struct *tty)
{
    if (I_IGNBRK(tty))
        return;
    if (I_BRKINT(tty)) {
        isig(SIGINT, tty, 1);
        return;
    }
    if (I_PARMRK(tty)) {
        put_tty_queue('\377', tty);
        put_tty_queue('\0', tty);
    }
    put_tty_queue('\0', tty);
    wake_up_interruptible(&tty->read_wait);
}

/**
 *  n_tty_receive_overrun   -   handle overrun reporting
 *  @tty: terminal
 *
 *  Data arrived faster than we could process it. While the tty
 *  driver has flagged this the bits that were missed are gone
 *  forever.
 *
 *  Called from the receive_buf path so single threaded. Does not
 *  need locking as num_overrun and overrun_time are function
 *  private.
 */

static inline void n_tty_receive_overrun(struct tty_struct *tty)
{
    char buf[64];

    tty->num_overrun++;
    if (time_before(tty->overrun_time, jiffies - HZ) ||
            time_after(tty->overrun_time, jiffies)) {
        printk(KERN_WARNING "%s: %d input overrun(s)\n",
            tty_name(tty, buf),
            tty->num_overrun);
        tty->overrun_time = jiffies;
        tty->num_overrun = 0;
    }
}

/**
 *  n_tty_receive_parity_error  -   error notifier
 *  @tty: terminal device
 *  @c: character
 *
 *  Process a parity error and queue the right data to indicate
 *  the error case if necessary. Locking as per n_tty_receive_buf.
 */
static inline void n_tty_receive_parity_error(struct tty_struct *tty,
                          unsigned char c)
{
    if (I_IGNPAR(tty))
        return;
    if (I_PARMRK(tty)) {
        put_tty_queue('\377', tty);
        put_tty_queue('\0', tty);
        put_tty_queue(c, tty);
    } else  if (I_INPCK(tty))
        put_tty_queue('\0', tty);
    else
        put_tty_queue(c, tty);
    wake_up_interruptible(&tty->read_wait);
}

#ifdef CONFIG_KDEBUGD
/* kdebugd handling code */

char kdbg_buf[DEBUG_MAX_RAW_CHARS]="";
char input_buf[2]={'\0',};

char sched_serial[10] = "";
int  sched_serial_idx = 0;

static inline int check_debug_mode(struct tty_struct *tty, unsigned char c)
{
    debugd_event_t event;
    int ret = 0;
    static unsigned char prev_ch = 0;
    static unsigned int history_idx = 0;
    char * ptr = NULL;


    if( tty != INPUT_tty)
        return ret;

    if(!kdebugd_running)
    {
        if( c == sched_serial[sched_serial_idx]){

            sched_serial_idx ++;
            //printk(KERN_EMERG "[SP Kernel Debugger] ");
            //printk("%d-th ENABLE Magic serial input match!\n"
            //         ,sched_serial_idx);
            if(sched_serial_idx == strlen(sched_serial))
            {
                printk(KERN_EMERG "[SP Kernel Debugger] ");
                printk("Enable Debug Mode!\n");
                kdebugd_start();
                kdebugd_running = 1;
            }

        }else
            sched_serial_idx = 0;

        return ret;
    }

    /* Now, kdebugd is running */

    ret = 1;

    switch (c)
    {
        case 0xd : /* \n */

            /* remove leading and trailing whitespaces */
            ptr = strstrip(kdbg_buf);

            /* copy kdbg_buf to event */
            strncpy(event.input_string, ptr, sizeof(event.input_string) - 1);
            event.input_string[sizeof(event.input_string) - 1] = '\0';

            queue_add_event(&kdebugd_queue, &event);

            /* Fix Me:
               Actually, history_idx need to be set at everyevent_tail modifying code.
               Now, We just set history_idx as event_tail plus 2..
             */
            history_idx = kdebugd_queue.event_tail + 2;

            kdbg_buf[0]='\0';

            break;

            /* When arrow key is pressed, the serial driver sends below character sequently. */
            /* e.g.
               0x1b  => 0x5b => 0x41(up arrow)
               0x1b  => 0x5b => 0x42(down arrow)
             */
        case 0x1b: /* Special Key */
        case 0x5b: /* Special Key */
            prev_ch = c;
            break;

        case 0x41: /* Up arrow */
            if( prev_ch == 0x5b && history_idx > 0) { /* Special Key */
                history_idx--;
                printk("\n%s #%d> %s",sched_serial,history_idx,kdebugd_queue.events[history_idx].input_string);
                snprintf(kdbg_buf, DEBUG_MAX_RAW_CHARS, "%s",kdebugd_queue.events[history_idx].input_string);
                prev_ch =c;
            }
            break;

        case 0x42: /* Down arrow */
            if( prev_ch == 0x5b && history_idx <= kdebugd_queue.event_tail) { /* Special Key */
                printk("\n%s #%d> %s",sched_serial,history_idx,kdebugd_queue.events[history_idx].input_string);
                snprintf(kdbg_buf, DEBUG_MAX_RAW_CHARS, "%s",kdebugd_queue.events[history_idx].input_string);
                history_idx++;
                prev_ch =c;
            }
            break;

        case 0x8: /* Backspace */
        case 0x7F: /* Backspace */
            if( strlen(kdbg_buf) > 0) {
                kdbg_buf[strlen(kdbg_buf) - 1]='\0';
                /* print backspace, space, backspace to remove current character */
                printk("%c %c",c,c);
            }
            break;

        default:
            input_buf[0] = c;
            if(strlen(kdbg_buf) + 1 < DEBUG_MAX_RAW_CHARS ){
                strncat(kdbg_buf,input_buf,1);
            }
            else
            {
                printk("\n[ALERT]Can't enter more input than %d size..", DEBUG_MAX_RAW_CHARS - 1);
            }
            printk("%c",c);
            break;

    }
    return ret;
}
#endif

/**
 *  n_tty_receive_char  -   perform processing
 *  @tty: terminal device
 *  @c: character
 *
 *  Process an individual character of input received from the driver.
 *  This is serialized with respect to itself by the rules for the
 *  driver above.
 */

static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
{
    unsigned long flags;
    int parmrk;

#ifdef CONFIG_SERIAL_INPUT_ENABLE_ONLY_NUMBER
        int check, i;
#endif

#ifdef CONFIG_KDEBUGD
    if(check_debug_mode(tty,c))
        return;
#endif

#ifdef CONFIG_SERIAL_INPUT_MANIPULATION
        if( tty == INPUT_tty )
        {
                /* skip enable check if serial_enable == 1 */
                if( serial_enable == SERIAL_INPUT_ENABLE )
                        goto enable_check_skip;

                /* for debug enable */
                if( c == enable_serial[enable_index] )
                {
                        enable_index++;

#ifdef CONFIG_SERIAL_INPUT_ENABLE_HELP_MSG
                        printk(KERN_ALERT "\n" );
                        printk(KERN_ALERT "[SERIAL INPUT MANAGE] %d-th ENABLE Magic serial input match!\n",
                                                                enable_index );
#endif
                        if( enable_index == enable_string_size )
                        {
                                serial_enable = SERIAL_INPUT_ENABLE;
                                disable_index = 0;

#ifdef CONFIG_SERIAL_INPUT_ENABLE_HELP_MSG
                                printk(KERN_ALERT "\n" );
                                printk(KERN_ALERT "[SERIAL INPUT MANAGE] serial input ENABLE!!!!!\n");
#endif
                        }
                        return;
                }
                else
                        enable_index = 0;

enable_check_skip:
                /* skip disable check if serial_enable == 0 */
                if( serial_enable == SERIAL_INPUT_DISABLE )
                        return;

                /* for debug disable */
                if( c == disable_serial[disable_index] )
                {
                        disable_index++;

#ifdef CONFIG_SERIAL_INPUT_ENABLE_HELP_MSG
                        printk(KERN_ALERT "\n" );
                        printk(KERN_ALERT "[SERIAL INPUT MANAGE] %d-th DISABLE Magic serial input match!\n",
                                                                disable_index );
#endif
                        if( disable_index == disable_string_size )
                        {
                                serial_enable = SERIAL_INPUT_DISABLE;
                                enable_index = 0;

#ifdef CONFIG_SERIAL_INPUT_ENABLE_HELP_MSG
                                printk(KERN_ALERT "\n" );
                                printk(KERN_ALERT "[SERIAL INPUT MANAGE] serial input DISABLE!!!!!\n");
#endif
                                return;
                        }
                }
                else
                        disable_index = 0;
#ifdef CONFIG_SERIAL_INPUT_ENABLE_ONLY_NUMBER
                // additional checking 0~9, space, enter, backspace, SPTEAM 2010-02-07
                check = i = 0;
                while(i < MAX_ARRAY )
                {
                        if( allow_char[i] == c )
                        {
                                check = 1;
                                break;
                        }
                        i++;
                }

                if( !check )
                        return;
#endif
        }
#endif

    if (tty->raw) {
        put_tty_queue(c, tty);
        return;
    }

    if (I_ISTRIP(tty))
        c &= 0x7f;
    if (I_IUCLC(tty) && L_IEXTEN(tty))
        c = tolower(c);

    if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&
        I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty) &&
        c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) && c != SUSP_CHAR(tty)) {
        start_tty(tty);
        process_echoes(tty);
    }

    if (tty->closing) {
        if (I_IXON(tty)) {
            if (c == START_CHAR(tty)) {
                start_tty(tty);
                process_echoes(tty);
            } else if (c == STOP_CHAR(tty))
                stop_tty(tty);
        }
        return;
    }

    /*
     * If the previous character was LNEXT, or we know that this
     * character is not one of the characters that we'll have to
     * handle specially, do shortcut processing to speed things
     * up.
     */
    if (!test_bit(c, tty->process_char_map) || tty->lnext) {
        tty->lnext = 0;
        parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
        if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) {
            /* beep if no space */
            if (L_ECHO(tty))
                process_output('\a', tty);
            return;
        }
        if (L_ECHO(tty)) {
            finish_erasing(tty);
            /* Record the column of first canon char. */
            if (tty->canon_head == tty->read_head)
                echo_set_canon_col(tty);
            echo_char(c, tty);
            process_echoes(tty);
        }
        if (parmrk)
            put_tty_queue(c, tty);
        put_tty_queue(c, tty);
        return;
    }

    if (I_IXON(tty)) {
        if (c == START_CHAR(tty)) {
            start_tty(tty);
            process_echoes(tty);
            return;
        }
        if (c == STOP_CHAR(tty)) {
            stop_tty(tty);
            return;
        }
    }

    if (L_ISIG(tty)) {
        int signal;
        signal = SIGINT;
        if (c == INTR_CHAR(tty))
            goto send_signal;
        signal = SIGQUIT;
        if (c == QUIT_CHAR(tty))
            goto send_signal;
        signal = SIGTSTP;
        if (c == SUSP_CHAR(tty)) {
send_signal:
            /*
             * Note that we do not use isig() here because we want
             * the order to be:
             * 1) flush, 2) echo, 3) signal
             */
            if (!L_NOFLSH(tty)) {
                n_tty_flush_buffer(tty);
                tty_driver_flush_buffer(tty);
            }
            if (I_IXON(tty))
                start_tty(tty);
            if (L_ECHO(tty)) {
                echo_char(c, tty);
                process_echoes(tty);
            }
            if (tty->pgrp)
                kill_pgrp(tty->pgrp, signal, 1);
            return;
        }
    }

    if (c == '\r') {
        if (I_IGNCR(tty))
            return;
        if (I_ICRNL(tty))
            c = '\n';
    } else if (c == '\n' && I_INLCR(tty))
        c = '\r';

    if (tty->icanon) {
        if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
            (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
            eraser(c, tty);
            process_echoes(tty);
            return;
        }
        if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
            tty->lnext = 1;
            if (L_ECHO(tty)) {
                finish_erasing(tty);
                if (L_ECHOCTL(tty)) {
                    echo_char_raw('^', tty);
                    echo_char_raw('\b', tty);
                    process_echoes(tty);
                }
            }
            return;
        }
        if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
            L_IEXTEN(tty)) {
            unsigned long tail = tty->canon_head;

            finish_erasing(tty);
            echo_char(c, tty);
            echo_char_raw('\n', tty);
            while (tail != tty->read_head) {
                echo_char(tty->read_buf[tail], tty);
                tail = (tail+1) & (N_TTY_BUF_SIZE-1);
            }
            process_echoes(tty);
            return;
        }
        if (c == '\n') {
            if (tty->read_cnt >= N_TTY_BUF_SIZE) {
                if (L_ECHO(tty))
                    process_output('\a', tty);
                return;
            }
            if (L_ECHO(tty) || L_ECHONL(tty)) {
                echo_char_raw('\n', tty);
                process_echoes(tty);
            }
            goto handle_newline;
        }
        if (c == EOF_CHAR(tty)) {
            if (tty->read_cnt >= N_TTY_BUF_SIZE)
                return;
            if (tty->canon_head != tty->read_head)
                set_bit(TTY_PUSH, &tty->flags);
            c = __DISABLED_CHAR;
            goto handle_newline;
        }
        if ((c == EOL_CHAR(tty)) ||
            (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
            parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty))
                 ? 1 : 0;
            if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk)) {
                if (L_ECHO(tty))
                    process_output('\a', tty);
                return;
            }
            /*
             * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
             */
            if (L_ECHO(tty)) {
                /* Record the column of first canon char. */
                if (tty->canon_head == tty->read_head)
                    echo_set_canon_col(tty);
                echo_char(c, tty);
                process_echoes(tty);
            }
            /*
             * XXX does PARMRK doubling happen for
             * EOL_CHAR and EOL2_CHAR?
             */
            if (parmrk)
                put_tty_queue(c, tty);

handle_newline:
            spin_lock_irqsave(&tty->read_lock, flags);
            set_bit(tty->read_head, tty->read_flags);
            put_tty_queue_nolock(c, tty);
            tty->canon_head = tty->read_head;
            tty->canon_data++;
            spin_unlock_irqrestore(&tty->read_lock, flags);
            kill_fasync(&tty->fasync, SIGIO, POLL_IN);
            if (waitqueue_active(&tty->read_wait))
                wake_up_interruptible(&tty->read_wait);
            return;
        }
    }

    parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
    if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) {
        /* beep if no space */
        if (L_ECHO(tty))
            process_output('\a', tty);
        return;
    }
    if (L_ECHO(tty)) {
        finish_erasing(tty);
        if (c == '\n')
            echo_char_raw('\n', tty);
        else {
            /* Record the column of first canon char. */
            if (tty->canon_head == tty->read_head)
                echo_set_canon_col(tty);
            echo_char(c, tty);
        }
        process_echoes(tty);
    }

    if (parmrk)
        put_tty_queue(c, tty);

    put_tty_queue(c, tty);
}


/**
 *  n_tty_write_wakeup  -   asynchronous I/O notifier
 *  @tty: tty device
 *
 *  Required for the ptys, serial driver etc. since processes
 *  that attach themselves to the master and rely on ASYNC
 *  IO must be woken up
 */

static void n_tty_write_wakeup(struct tty_struct *tty)
{
    if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
        kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
}

/**
 *  n_tty_receive_buf   -   data receive
 *  @tty: terminal device
 *  @cp: buffer
 *  @fp: flag buffer
 *  @count: characters
 *
 *  Called by the terminal driver when a block of characters has
 *  been received. This function must be called from soft contexts
 *  not from interrupt context. The driver is responsible for making
 *  calls one at a time and in order (or using flush_to_ldisc)
 */

static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
                  char *fp, int count)
{
    const unsigned char *p;
    char *f, flags = TTY_NORMAL;
    int i;
    char    buf[64];
    unsigned long cpuflags;

    if (!tty->read_buf)
        return;

    if (tty->real_raw) {
        spin_lock_irqsave(&tty->read_lock, cpuflags);
        i = min(N_TTY_BUF_SIZE - tty->read_cnt,
            N_TTY_BUF_SIZE - tty->read_head);
        i = min(count, i);
        memcpy(tty->read_buf + tty->read_head, cp, i);
        tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
        tty->read_cnt += i;
        cp += i;
        count -= i;

        i = min(N_TTY_BUF_SIZE - tty->read_cnt,
            N_TTY_BUF_SIZE - tty->read_head);
        i = min(count, i);
        memcpy(tty->read_buf + tty->read_head, cp, i);
        tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
        tty->read_cnt += i;
        spin_unlock_irqrestore(&tty->read_lock, cpuflags);
    } else {
        for (i = count, p = cp, f = fp; i; i--, p++) {
            if (f)
                flags = *f++;
            switch (flags) {
            case TTY_NORMAL:
                n_tty_receive_char(tty, *p);
                break;
            case TTY_BREAK:
                n_tty_receive_break(tty);
                break;
            case TTY_PARITY:
            case TTY_FRAME:
                n_tty_receive_parity_error(tty, *p);
                break;
            case TTY_OVERRUN:
                n_tty_receive_overrun(tty);
                break;
            default:
                printk(KERN_ERR "%s: unknown flag %d\n",
                       tty_name(tty, buf), flags);
                break;
            }
        }
        if (tty->ops->flush_chars)
            tty->ops->flush_chars(tty);
    }

    n_tty_set_room(tty);

    if (!tty->icanon && (tty->read_cnt >= tty->minimum_to_wake)) {
        kill_fasync(&tty->fasync, SIGIO, POLL_IN);
        if (waitqueue_active(&tty->read_wait))
            wake_up_interruptible(&tty->read_wait);
    }

    /*
     * Check the remaining room for the input canonicalization
     * mode.  We don't want to throttle the driver if we're in
     * canonical mode and don't have a newline yet!
     */
    if (tty->receive_room < TTY_THRESHOLD_THROTTLE)
        tty_throttle(tty);
}

int is_ignored(int sig)
{
    return (sigismember(&current->blocked, sig) ||
        current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
}

/**
 *  n_tty_set_termios   -   termios data changed
 *  @tty: terminal
 *  @old: previous data
 *
 *  Called by the tty layer when the user changes termios flags so
 *  that the line discipline can plan ahead. This function cannot sleep
 *  and is protected from re-entry by the tty layer. The user is
 *  guaranteed that this function will not be re-entered or in progress
 *  when the ldisc is closed.
 *
 *  Locking: Caller holds tty->termios_mutex
 */

static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
{
    int canon_change = 1;
    BUG_ON(!tty);

    if (old)
        canon_change = (old->c_lflag ^ tty->termios->c_lflag) & ICANON;
    if (canon_change) {
        memset(&tty->read_flags, 0, sizeof tty->read_flags);
        tty->canon_head = tty->read_tail;
        tty->canon_data = 0;
        tty->erasing = 0;
    }

    if (canon_change && !L_ICANON(tty) && tty->read_cnt)
        wake_up_interruptible(&tty->read_wait);

    tty->icanon = (L_ICANON(tty) != 0);
    if (test_bit(TTY_HW_COOK_IN, &tty->flags)) {
        tty->raw = 1;
        tty->real_raw = 1;
        n_tty_set_room(tty);
        return;
    }
    if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
        I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
        I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
        I_PARMRK(tty)) {
        memset(tty->process_char_map, 0, 256/8);

        if (I_IGNCR(tty) || I_ICRNL(tty))
            set_bit('\r', tty->process_char_map);
        if (I_INLCR(tty))
            set_bit('\n', tty->process_char_map);

        if (L_ICANON(tty)) {
            set_bit(ERASE_CHAR(tty), tty->process_char_map);
            set_bit(KILL_CHAR(tty), tty->process_char_map);
            set_bit(EOF_CHAR(tty), tty->process_char_map);
            set_bit('\n', tty->process_char_map);
            set_bit(EOL_CHAR(tty), tty->process_char_map);
            if (L_IEXTEN(tty)) {
                set_bit(WERASE_CHAR(tty),
                    tty->process_char_map);
                set_bit(LNEXT_CHAR(tty),
                    tty->process_char_map);
                set_bit(EOL2_CHAR(tty),
                    tty->process_char_map);
                if (L_ECHO(tty))
                    set_bit(REPRINT_CHAR(tty),
                        tty->process_char_map);
            }
        }
        if (I_IXON(tty)) {
            set_bit(START_CHAR(tty), tty->process_char_map);
            set_bit(STOP_CHAR(tty), tty->process_char_map);
        }
        if (L_ISIG(tty)) {
            set_bit(INTR_CHAR(tty), tty->process_char_map);
            set_bit(QUIT_CHAR(tty), tty->process_char_map);
            set_bit(SUSP_CHAR(tty), tty->process_char_map);
        }
        clear_bit(__DISABLED_CHAR, tty->process_char_map);
        tty->raw = 0;
        tty->real_raw = 0;
    } else {
        tty->raw = 1;
        if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
            (I_IGNPAR(tty) || !I_INPCK(tty)) &&
            (tty->driver->flags & TTY_DRIVER_REAL_RAW))
            tty->real_raw = 1;
        else
            tty->real_raw = 0;
    }
    n_tty_set_room(tty);
    /* The termios change make the tty ready for I/O */
    wake_up_interruptible(&tty->write_wait);
    wake_up_interruptible(&tty->read_wait);
}

/**
 *  n_tty_close     -   close the ldisc for this tty
 *  @tty: device
 *
 *  Called from the terminal layer when this line discipline is
 *  being shut down, either because of a close or becsuse of a
 *  discipline change. The function will not be called while other
 *  ldisc methods are in progress.
 */

static void n_tty_close(struct tty_struct *tty)
{
    n_tty_flush_buffer(tty);
    if (tty->read_buf) {
        kfree(tty->read_buf);
        tty->read_buf = NULL;
    }
    if (tty->echo_buf) {
        kfree(tty->echo_buf);
        tty->echo_buf = NULL;
    }
}

#ifdef CONFIG_SERIAL_INPUT_MANIPULATION
static int initial_setting = 0;
void set_enable_string(char *val)
{
        if( initial_setting == 0 )
        {
                memset( enable_serial , 0x00, MAX_STRING_SIZE );
                snprintf( enable_serial , MAX_STRING_SIZE, "%s", val);
                initial_setting =  1;
        }
}
#endif

/**
 *  n_tty_open      -   open an ldisc
 *  @tty: terminal to open
 *
 *  Called when this line discipline is being attached to the
 *  terminal device. Can sleep. Called serialized so that no
 *  other events will occur in parallel. No further open will occur
 *  until a close.
 */

static int n_tty_open(struct tty_struct *tty)
{
    if (!tty)
        return -EINVAL;

    /* These are ugly. Currently a malloc failure here can panic */
    if (!tty->read_buf) {
        tty->read_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
        if (!tty->read_buf)
            return -ENOMEM;
    }
    if (!tty->echo_buf) {
        tty->echo_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);

        if (!tty->echo_buf)
            return -ENOMEM;
    }
    reset_buffer_flags(tty);
    tty->column = 0;
    n_tty_set_termios(tty, NULL);
    tty->minimum_to_wake = 1;
    tty->closing = 0;

#ifdef CONFIG_SERIAL_INPUT_MANIPULATION
    if(tty == INPUT_tty )
    {
        memset( disable_serial, 0x00, MAX_STRING_SIZE );

        snprintf( disable_serial, MAX_STRING_SIZE, "%s", CONFIG_SERIAL_INPUT_DISABLE_STRING);

        enable_string_size  = strlen( enable_serial );
        disable_string_size = strlen( disable_serial );

#ifdef CONFIG_SERIAL_INPUT_ENABLE_HELP_MSG
        printk(KERN_ALERT "[SERIAL INPUT MANAGE] disable_serial : %s(len:%d)\n",
                disable_serial, disable_string_size );
        printk(KERN_ALERT "[SERIAL INPUT MANAGE] enable_serial : %s(len: %d)\n",
                enable_serial, enable_string_size );
#endif

#ifdef KDEBUGD_STRING
        sprintf( sched_serial, "%s", KDEBUGD_STRING );
        printk(KERN_ALERT "[KDEBUGD] enter : %s\n\n", KDEBUGD_STRING);
#endif

    }
#endif

    return 0;
}

static inline int input_available_p(struct tty_struct *tty, int amt)
{
    tty_flush_to_ldisc(tty);
    if (tty->icanon) {
        if (tty->canon_data)
            return 1;
    } else if (tty->read_cnt >= (amt ? amt : 1))
        return 1;

    return 0;
}

/**
 *  copy_from_read_buf  -   copy read data directly
 *  @tty: terminal device
 *  @b: user data
 *  @nr: size of data
 *
 *  Helper function to speed up n_tty_read.  It is only called when
 *  ICANON is off; it copies characters straight from the tty queue to
 *  user space directly.  It can be profitably called twice; once to
 *  drain the space from the tail pointer to the (physical) end of the
 *  buffer, and once to drain the space from the (physical) beginning of
 *  the buffer to head pointer.
 *
 *  Called under the tty->atomic_read_lock sem
 *
 */

static int copy_from_read_buf(struct tty_struct *tty,
                      unsigned char __user **b,
                      size_t *nr)

{
    int retval;
    size_t n;
    unsigned long flags;

    retval = 0;
    spin_lock_irqsave(&tty->read_lock, flags);
    n = min(tty->read_cnt, N_TTY_BUF_SIZE - tty->read_tail);
    n = min(*nr, n);
    spin_unlock_irqrestore(&tty->read_lock, flags);
    if (n) {
        retval = copy_to_user(*b, &tty->read_buf[tty->read_tail], n);
        n -= retval;
        tty_audit_add_data(tty, &tty->read_buf[tty->read_tail], n);
        spin_lock_irqsave(&tty->read_lock, flags);
        tty->read_tail = (tty->read_tail + n) & (N_TTY_BUF_SIZE-1);
        tty->read_cnt -= n;
        spin_unlock_irqrestore(&tty->read_lock, flags);
        *b += n;
        *nr -= n;
    }
    return retval;
}

extern ssize_t redirected_tty_write(struct file *, const char __user *,
                            size_t, loff_t *);

/**
 *  job_control     -   check job control
 *  @tty: tty
 *  @file: file handle
 *
 *  Perform job control management checks on this file/tty descriptor
 *  and if appropriate send any needed signals and return a negative
 *  error code if action should be taken.
 *
 *  FIXME:
 *  Locking: None - redirected write test is safe, testing
 *  current->signal should possibly lock current->sighand
 *  pgrp locking ?
 */

static int job_control(struct tty_struct *tty, struct file *file)
{
    /* Job control check -- must be done at start and after
       every sleep (POSIX.1 7.1.1.4). */
    /* NOTE: not yet done after every sleep pending a thorough
       check of the logic of this change. -- jlc */
    /* don't stop on /dev/console */
    if (file->f_op->write != redirected_tty_write &&
        current->signal->tty == tty) {
        if (!tty->pgrp)
            printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
        else if (task_pgrp(current) != tty->pgrp) {
            if (is_ignored(SIGTTIN) ||
                is_current_pgrp_orphaned())
                return -EIO;
            kill_pgrp(task_pgrp(current), SIGTTIN, 1);
            set_thread_flag(TIF_SIGPENDING);
            return -ERESTARTSYS;
        }
    }
    return 0;
}


/**
 *  n_tty_read      -   read function for tty
 *  @tty: tty device
 *  @file: file object
 *  @buf: userspace buffer pointer
 *  @nr: size of I/O
 *
 *  Perform reads for the line discipline. We are guaranteed that the
 *  line discipline will not be closed under us but we may get multiple
 *  parallel readers and must handle this ourselves. We may also get
 *  a hangup. Always called in user context, may sleep.
 *
 *  This code must be sure never to sleep through a hangup.
 */

static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
             unsigned char __user *buf, size_t nr)
{
    unsigned char __user *b = buf;
    DECLARE_WAITQUEUE(wait, current);
    int c;
    int minimum, time;
    ssize_t retval = 0;
    ssize_t size;
    long timeout;
    unsigned long flags;
    int packet;

do_it_again:

    BUG_ON(!tty->read_buf);

    c = job_control(tty, file);
    if (c < 0)
        return c;

    minimum = time = 0;
    timeout = MAX_SCHEDULE_TIMEOUT;
    if (!tty->icanon) {
        time = (HZ / 10) * TIME_CHAR(tty);
        minimum = MIN_CHAR(tty);
        if (minimum) {
            if (time)
                tty->minimum_to_wake = 1;
            else if (!waitqueue_active(&tty->read_wait) ||
                 (tty->minimum_to_wake > minimum))
                tty->minimum_to_wake = minimum;
        } else {
            timeout = 0;
            if (time) {
                timeout = time;
                time = 0;
            }
            tty->minimum_to_wake = minimum = 1;
        }
    }

    /*
     *  Internal serialization of reads.
     */
    if (file->f_flags & O_NONBLOCK) {
        if (!mutex_trylock(&tty->atomic_read_lock))
            return -EAGAIN;
    } else {
        if (mutex_lock_interruptible(&tty->atomic_read_lock))
            return -ERESTARTSYS;
    }
    packet = tty->packet;

    add_wait_queue(&tty->read_wait, &wait);
    while (nr) {
        /* First test for status change. */
        if (packet && tty->link->ctrl_status) {
            unsigned char cs;
            if (b != buf)
                break;
            spin_lock_irqsave(&tty->link->ctrl_lock, flags);
            cs = tty->link->ctrl_status;
            tty->link->ctrl_status = 0;
            spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
            if (tty_put_user(tty, cs, b++)) {
                retval = -EFAULT;
                b--;
                break;
            }
            nr--;
            break;
        }
        /* This statement must be first before checking for input
           so that any interrupt will set the state back to
           TASK_RUNNING. */
        set_current_state(TASK_INTERRUPTIBLE);

        if (((minimum - (b - buf)) < tty->minimum_to_wake) &&
            ((minimum - (b - buf)) >= 1))
            tty->minimum_to_wake = (minimum - (b - buf));

        if (!input_available_p(tty, 0)) {
            if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
                retval = -EIO;
                break;
            }
            if (tty_hung_up_p(file))
                break;
            if (!timeout)
                break;
            if (file->f_flags & O_NONBLOCK) {
                retval = -EAGAIN;
                break;
            }
            if (signal_pending(current)) {
                retval = -ERESTARTSYS;
                break;
            }
            /* FIXME: does n_tty_set_room need locking ? */
            n_tty_set_room(tty);
            timeout = schedule_timeout(timeout);
            continue;
        }
        __set_current_state(TASK_RUNNING);

        /* Deal with packet mode. */
        if (packet && b == buf) {
            if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
                retval = -EFAULT;
                b--;
                break;
            }
            nr--;
        }

        if (tty->icanon) {
            /* N.B. avoid overrun if nr == 0 */
            while (nr && tty->read_cnt) {
                int eol;

                eol = test_and_clear_bit(tty->read_tail,
                        tty->read_flags);
                c = tty->read_buf[tty->read_tail];
                spin_lock_irqsave(&tty->read_lock, flags);
                tty->read_tail = ((tty->read_tail+1) &
                          (N_TTY_BUF_SIZE-1));
                tty->read_cnt--;
                if (eol) {
                    /* this test should be redundant:
                     * we shouldn't be reading data if
                     * canon_data is 0
                     */
                    if (--tty->canon_data < 0)
                        tty->canon_data = 0;
                }
                spin_unlock_irqrestore(&tty->read_lock, flags);

                if (!eol || (c != __DISABLED_CHAR)) {
                    if (tty_put_user(tty, c, b++)) {
                        retval = -EFAULT;
                        b--;
                        break;
                    }
                    nr--;
                }
                if (eol) {
                    tty_audit_push(tty);
                    break;
                }
            }
            if (retval)
                break;
        } else {
            int uncopied;
            /* The copy function takes the read lock and handles
               locking internally for this case */
            uncopied = copy_from_read_buf(tty, &b, &nr);
            uncopied += copy_from_read_buf(tty, &b, &nr);
            if (uncopied) {
                retval = -EFAULT;
                break;
            }
        }

        /* If there is enough space in the read buffer now, let the
         * low-level driver know. We use n_tty_chars_in_buffer() to
         * check the buffer, as it now knows about canonical mode.
         * Otherwise, if the driver is throttled and the line is
         * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
         * we won't get any more characters.
         */
        if (n_tty_chars_in_buffer(tty) <= TTY_THRESHOLD_UNTHROTTLE) {
            n_tty_set_room(tty);
            check_unthrottle(tty);
        }

        if (b - buf >= minimum)
            break;
        if (time)
            timeout = time;
    }
    mutex_unlock(&tty->atomic_read_lock);
    remove_wait_queue(&tty->read_wait, &wait);

    if (!waitqueue_active(&tty->read_wait))
        tty->minimum_to_wake = minimum;

    __set_current_state(TASK_RUNNING);
    size = b - buf;
    if (size) {
        retval = size;
        if (nr)
            clear_bit(TTY_PUSH, &tty->flags);
    } else if (test_and_clear_bit(TTY_PUSH, &tty->flags))
         goto do_it_again;

    n_tty_set_room(tty);
    return retval;
}

/**
 *  n_tty_write     -   write function for tty
 *  @tty: tty device
 *  @file: file object
 *  @buf: userspace buffer pointer
 *  @nr: size of I/O
 *
 *  Write function of the terminal device.  This is serialized with
 *  respect to other write callers but not to termios changes, reads
 *  and other such events.  Since the receive code will echo characters,
 *  thus calling driver write methods, the output_lock is used in
 *  the output processing functions called here as well as in the
 *  echo processing function to protect the column state and space
 *  left in the buffer.
 *
 *  This code must be sure never to sleep through a hangup.
 *
 *  Locking: output_lock to protect column state and space left
 *       (note that the process_output*() functions take this
 *        lock themselves)
 */

static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
               const unsigned char *buf, size_t nr)
{
    const unsigned char *b = buf;
    DECLARE_WAITQUEUE(wait, current);
    int c;
    ssize_t retval = 0;

    /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
    if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
        retval = tty_check_change(tty);
        if (retval)
            return retval;
    }

    /* Write out any echoed characters that are still pending */
    process_echoes(tty);

    add_wait_queue(&tty->write_wait, &wait);
    while (1) {
        set_current_state(TASK_INTERRUPTIBLE);
        if (signal_pending(current)) {
            retval = -ERESTARTSYS;
            break;
        }
        if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
            retval = -EIO;
            break;
        }
        if (O_OPOST(tty) && !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
            while (nr > 0) {
                ssize_t num = process_output_block(tty, b, nr);
                if (num < 0) {
                    if (num == -EAGAIN)
                        break;
                    retval = num;
                    goto break_out;
                }
                b += num;
                nr -= num;
                if (nr == 0)
                    break;
                c = *b;
                if (process_output(c, tty) < 0)
                    break;
                b++; nr--;
            }
            if (tty->ops->flush_chars)
                tty->ops->flush_chars(tty);
        } else {
            while (nr > 0) {
                c = tty->ops->write(tty, b, nr);
                if (c < 0) {
                    retval = c;
                    goto break_out;
                }
                if (!c)
                    break;
                b += c;
                nr -= c;
            }
        }
        if (!nr)
            break;
        if (file->f_flags & O_NONBLOCK) {
            retval = -EAGAIN;
            break;
        }
        schedule();
    }
break_out:
    __set_current_state(TASK_RUNNING);
    remove_wait_queue(&tty->write_wait, &wait);
    if (b - buf != nr && tty->fasync)
        set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
    return (b - buf) ? b - buf : retval;
}

/**
 *  n_tty_poll      -   poll method for N_TTY
 *  @tty: terminal device
 *  @file: file accessing it
 *  @wait: poll table
 *
 *  Called when the line discipline is asked to poll() for data or
 *  for special events. This code is not serialized with respect to
 *  other events save open/close.
 *
 *  This code must be sure never to sleep through a hangup.
 *  Called without the kernel lock held - fine
 */

static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
                            poll_table *wait)
{
    unsigned int mask = 0;

    poll_wait(file, &tty->read_wait, wait);
    poll_wait(file, &tty->write_wait, wait);
    if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
        mask |= POLLIN | POLLRDNORM;
    if (tty->packet && tty->link->ctrl_status)
        mask |= POLLPRI | POLLIN | POLLRDNORM;
    if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
        mask |= POLLHUP;
    if (tty_hung_up_p(file))
        mask |= POLLHUP;
    if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
        if (MIN_CHAR(tty) && !TIME_CHAR(tty))
            tty->minimum_to_wake = MIN_CHAR(tty);
        else
            tty->minimum_to_wake = 1;
    }
    if (tty->ops->write && !tty_is_writelocked(tty) &&
            tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
            tty_write_room(tty) > 0)
        mask |= POLLOUT | POLLWRNORM;
    return mask;
}

static unsigned long inq_canon(struct tty_struct *tty)
{
    int nr, head, tail;

    if (!tty->canon_data)
        return 0;
    head = tty->canon_head;
    tail = tty->read_tail;
    nr = (head - tail) & (N_TTY_BUF_SIZE-1);
    /* Skip EOF-chars.. */
    while (head != tail) {
        if (test_bit(tail, tty->read_flags) &&
            tty->read_buf[tail] == __DISABLED_CHAR)
            nr--;
        tail = (tail+1) & (N_TTY_BUF_SIZE-1);
    }
    return nr;
}

static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
               unsigned int cmd, unsigned long arg)
{
    int retval;

    switch (cmd) {
    case TIOCOUTQ:
        return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
    case TIOCINQ:
        /* FIXME: Locking */
        retval = tty->read_cnt;
        if (L_ICANON(tty))
            retval = inq_canon(tty);
        return put_user(retval, (unsigned int __user *) arg);
    default:
        return n_tty_ioctl_helper(tty, file, cmd, arg);
    }
}

struct tty_ldisc_ops tty_ldisc_N_TTY = {
    .magic           = TTY_LDISC_MAGIC,
    .name            = "n_tty",
    .open            = n_tty_open,
    .close           = n_tty_close,
    .flush_buffer    = n_tty_flush_buffer,
    .chars_in_buffer = n_tty_chars_in_buffer,
    .read            = n_tty_read,
    .write           = n_tty_write,
    .ioctl           = n_tty_ioctl,
    .set_termios     = n_tty_set_termios,
    .poll            = n_tty_poll,
    .receive_buf     = n_tty_receive_buf,
    .write_wakeup    = n_tty_write_wakeup
};

/**
 *  n_tty_inherit_ops   -   inherit N_TTY methods
 *  @ops: struct tty_ldisc_ops where to save N_TTY methods
 *
 *  Used by a generic struct tty_ldisc_ops to easily inherit N_TTY
 *  methods.
 */

void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
{
    *ops = tty_ldisc_N_TTY;
    ops->owner = NULL;
    ops->refcount = ops->flags = 0;
}
EXPORT_SYMBOL_GPL(n_tty_inherit_ops);