[minix.git] / drivers / tty / tty.c

/* This file contains the terminal driver, both for the IBM console and regular
 * ASCII terminals.  It handles only the device-independent part of a TTY, the
 * device dependent parts are in console.c, rs232.c, etc.  This file contains
 * two main entry points, tty_task() and tty_wakeup(), and several minor entry
 * points for use by the device-dependent code.
 *
 * The device-independent part accepts "keyboard" input from the device-
 * dependent part, performs input processing (special key interpretation),
 * and sends the input to a process reading from the TTY.  Output to a TTY
 * is sent to the device-dependent code for output processing and "screen"
 * display.  Input processing is done by the device by calling 'in_process'
 * on the input characters, output processing may be done by the device itself
 * or by calling 'out_process'.  The TTY takes care of input queuing, the
 * device does the output queuing.  If a device receives an external signal,
 * like an interrupt, then it causes tty_wakeup() to be run by the CLOCK task
 * to, you guessed it, wake up the TTY to check if input or output can
 * continue.
 *
 * The valid messages and their parameters are:
 *
 *   notify from HARDWARE:       output has been completed or input has arrived
 *   notify from SYSTEM  :      e.g., MINIX wants to shutdown; run code to 
 *                              cleanly stop
 *   DEV_READ:       a process wants to read from a terminal
 *   DEV_WRITE:      a process wants to write on a terminal
 *   DEV_IOCTL:      a process wants to change a terminal's parameters
 *   DEV_OPEN:       a tty line has been opened
 *   DEV_CLOSE:      a tty line has been closed
 *   DEV_SELECT:     start select notification request
 *   CANCEL:         terminate a previous incomplete system call immediately
 *
 *    m_type       DEVICE  USER_ENDPT  COUNT    POSITION  IO_GRANT
 * -----------------------------------------------------------------
 * | HARD_INT    |         |         |         |         |         |
 * |-------------+---------+---------+---------+---------+---------|
 * | DEV_READ    |minor dev| proc nr |  count  |         |  grant  |
 * |-------------+---------+---------+---------+---------+---------|
 * | DEV_WRITE   |minor dev| proc nr |  count  |         |  grant  |
 * |-------------+---------+---------+---------+---------+---------|
 * | DEV_IOCTL   |minor dev| proc nr |func code|user proc|         |
 * |-------------+---------+---------+---------+---------+---------|
 * | DEV_OPEN    |minor dev| proc nr | O_NOCTTY|         |         |
 * |-------------+---------+---------+---------+---------+---------|
 * | DEV_CLOSE   |minor dev| proc nr |         |         |         |
 * |-------------+---------+---------+---------+---------+---------|
 * | CANCEL      |minor dev| proc nr |         |         |         |
 * |-------------+---------+---------+---------+---------+---------|
 * | DEV_SELECT  |minor dev| sel ops |         |         |         |
 * -----------------------------------------------------------------
 *
 * Changes:
 *   Jan 20, 2004   moved TTY driver to user-space  (Jorrit N. Herder)
 *   Sep 20, 2004   local timer management/ sync alarms  (Jorrit N. Herder)
 *   Jul 13, 2004   support for function key observers  (Jorrit N. Herder)  
 */

#include <assert.h>
#include <minix/drivers.h>
#include <minix/driver.h>
#include <termios.h>
#include <sys/ioc_tty.h>
#include <signal.h>
#include <minix/keymap.h>
#include "tty.h"

#include <sys/time.h>
#include <sys/select.h>

unsigned long kbd_irq_set = 0;
unsigned long rs_irq_set = 0;

/* Address of a tty structure. */
#define tty_addr(line)  (&tty_table[line])

/* Macros for magic tty types. */
#define isconsole(tp)   ((tp) < tty_addr(NR_CONS))
#define ispty(tp)       ((tp) != NULL && (tp)->tty_minor >= TTYPX_MINOR)

/* Macros for magic tty structure pointers. */
#define FIRST_TTY       tty_addr(0)
#define END_TTY         tty_addr(sizeof(tty_table) / sizeof(tty_table[0]))

/* A device exists if at least its 'devread' function is defined. */
#define tty_active(tp)  ((tp)->tty_devread != NULL)

/* RS232 lines or pseudo terminals can be completely configured out. */
#if NR_RS_LINES == 0
#define rs_init(tp)     ((void) 0)
#endif

#if NR_PTYS == 0
#define pty_init(tp)    ((void) 0)
#define do_pty(tp, mp)  ((void) 0)
#endif

struct kmessages kmess;

static void tty_timed_out(timer_t *tp);
static void settimer(tty_t *tty_ptr, int enable);
static void in_transfer(tty_t *tp);
static int tty_echo(tty_t *tp, int ch);
static void rawecho(tty_t *tp, int ch);
static int back_over(tty_t *tp);
static void reprint(tty_t *tp);
static void dev_ioctl(tty_t *tp);
static void setattr(tty_t *tp);
static void tty_icancel(tty_t *tp);
static void tty_init(void);
static void do_new_kmess(void);
static void set_console_line(char term[CONS_ARG]);
static void set_kernel_color(char color[CONS_ARG]);
static void set_color(tty_t *tp, int color);
static void reset_color(tty_t *tp);

static int do_open(devminor_t minor, int access, endpoint_t user_endpt);
static int do_close(devminor_t minor);
static ssize_t do_read(devminor_t minor, u64_t position, endpoint_t endpt,
        cp_grant_id_t grant, size_t size, int flags, cdev_id_t id);
static ssize_t do_write(devminor_t minor, u64_t position, endpoint_t endpt,
        cp_grant_id_t grant, size_t size, int flags, cdev_id_t id);
static int do_ioctl(devminor_t minor, unsigned long request, endpoint_t endpt,
        cp_grant_id_t grant, int flags, endpoint_t user_endpt, cdev_id_t id);
static int do_cancel(devminor_t minor, endpoint_t endpt, cdev_id_t id);
static int do_select(devminor_t minor, unsigned int ops, endpoint_t endpt);

static struct chardriver tty_tab = {
        .cdr_open       = do_open,
        .cdr_close      = do_close,
        .cdr_read       = do_read,
        .cdr_write      = do_write,
        .cdr_ioctl      = do_ioctl,
        .cdr_cancel     = do_cancel,
        .cdr_select     = do_select
};

/* Default attributes. */
static struct termios termios_defaults = {
  TINPUT_DEF, TOUTPUT_DEF, TCTRL_DEF, TLOCAL_DEF,
  {
        TEOF_DEF, TEOL_DEF, TERASE_DEF, TINTR_DEF, TKILL_DEF, TMIN_DEF,
        TQUIT_DEF, TTIME_DEF, TSUSP_DEF, TSTART_DEF, TSTOP_DEF,
        TREPRINT_DEF, TLNEXT_DEF, TDISCARD_DEF,
  }, TSPEED_DEF, TSPEED_DEF,
};
static struct winsize winsize_defaults; /* = all zeroes */

/* Global variables for the TTY task (declared extern in tty.h). */
tty_t tty_table[NR_CONS+NR_RS_LINES+NR_PTYS];
int ccurrent;                   /* currently active console */
struct machine machine;         /* kernel environment variables */
u32_t system_hz;
u32_t consoleline = CONS_MINOR;
u32_t kernel_msg_color = 0;

/* SEF functions and variables. */
static void sef_local_startup(void);
static int sef_cb_init_fresh(int type, sef_init_info_t *info);
static void sef_cb_signal_handler(int signo);

extern struct minix_kerninfo *_minix_kerninfo;

/*===========================================================================*
 *                              tty_task                                     *
 *===========================================================================*/
int main(void)
{
/* Main routine of the terminal task. */

  message tty_mess;             /* buffer for all incoming messages */
  int ipc_status;
  unsigned line;
  int r;
  register tty_t *tp;

  /* SEF local startup. */
  sef_local_startup();
  while (TRUE) {
        /* Check for and handle any events on any of the ttys. */
        for (tp = FIRST_TTY; tp < END_TTY; tp++) {
                if (tp->tty_events) handle_events(tp);
        }

        /* Get a request message. */
        r= driver_receive(ANY, &tty_mess, &ipc_status);
        if (r != 0)
                panic("driver_receive failed with: %d", r);

        /* First handle all kernel notification types that the TTY supports. 
         *  - An alarm went off, expire all timers and handle the events. 
         *  - A hardware interrupt also is an invitation to check for events. 
         *  - A new kernel message is available for printing.
         *  - Reset the console on system shutdown. 
         * Then see if this message is different from a normal device driver
         * request and should be handled separately. These extra functions
         * do not operate on a device, in constrast to the driver requests. 
         */

        if (is_ipc_notify(ipc_status)) {
                switch (_ENDPOINT_P(tty_mess.m_source)) {
                        case CLOCK:
                                /* run watchdogs of expired timers */
                                expire_timers(tty_mess.NOTIFY_TIMESTAMP);
                                break;
                        case HARDWARE: 
                                /* hardware interrupt notification */
                                
                                /* fetch chars from keyboard */
                                if (tty_mess.NOTIFY_ARG & kbd_irq_set)
                                        kbd_interrupt(&tty_mess);
#if NR_RS_LINES > 0
                                /* serial I/O */
                                if (tty_mess.NOTIFY_ARG & rs_irq_set)
                                        rs_interrupt(&tty_mess);
#endif
                                /* run watchdogs of expired timers */
                                expire_timers(tty_mess.NOTIFY_TIMESTAMP);
                                break;
                        default:
                                /* do nothing */
                                break;
                }

                /* done, get new message */
                continue;
        }

        switch (tty_mess.m_type) { 
        case TTY_FKEY_CONTROL:          /* (un)register a fkey observer */
                do_fkey_ctl(&tty_mess);
                continue;
        case INPUT_EVENT:
                do_kb_inject(&tty_mess);
                continue;
        default:                        /* should be a driver request */
                ;                       /* do nothing; end switch */
        }

        if (!IS_DEV_RQ(tty_mess.m_type)) {
                chardriver_process(&tty_tab, &tty_mess, ipc_status);
                continue;
        }

        /* Only device requests should get to this point.
         * All requests have a minor device number.
         */
        line = tty_mess.DEVICE;
        if (line == KBD_MINOR || line == KBDAUX_MINOR) {
                do_kbd(&tty_mess, ipc_status);
                continue;
        } else if (line == VIDEO_MINOR) {
                do_video(&tty_mess, ipc_status);
                continue;
        } else if (line - PTYPX_MINOR < NR_PTYS &&
                        tty_mess.m_type != DEV_IOCTL_S) {
                /* Terminals and pseudo terminals belong together. We can only
                 * make a distinction between the two based on position in the
                 * tty_table and not on minor number (i.e., use ispty macro).
                 * Hence this special case.
                 */
                do_pty(&tty_mess, ipc_status);
                continue;
        }

        /* Execute the requested device driver function. */
        chardriver_process(&tty_tab, &tty_mess, ipc_status);
  }

  return 0;
}

static void
set_color(tty_t *tp, int color)
{
        char buf[8];

        buf[0] = '\033';
        snprintf(&buf[1], sizeof(buf) - 1, "[1;%dm", color);
        do_write(tp->tty_minor, 0, KERNEL, (cp_grant_id_t) buf, sizeof(buf),
                FLG_OP_NONBLOCK, 0);
}

static void
reset_color(tty_t *tp)
{
        char buf[8];

#define SGR_COLOR_RESET 39
        buf[0] = '\033';
        snprintf(&buf[1], sizeof(buf) - 1, "[0;%dm", SGR_COLOR_RESET);
        do_write(tp->tty_minor, 0, KERNEL, (cp_grant_id_t) buf, sizeof(buf),
                FLG_OP_NONBLOCK, 0);
}

tty_t *
line2tty(devminor_t line)
{
/* Convert a terminal line to tty_table pointer */

        tty_t* tp;

        /* /dev/log goes to /dev/console, and both may be redirected. */
        if (line == CONS_MINOR || line == LOG_MINOR)
                line = consoleline;

        if (line == KBD_MINOR || line == KBDAUX_MINOR || line == VIDEO_MINOR) {
                return(NULL);
        } else if ((line - CONS_MINOR) < NR_CONS) {
                tp = tty_addr(line - CONS_MINOR);
        } else if ((line - RS232_MINOR) < NR_RS_LINES) {
                tp = tty_addr(line - RS232_MINOR + NR_CONS);
        } else if ((line - TTYPX_MINOR) < NR_PTYS) {
                tp = tty_addr(line - TTYPX_MINOR + NR_CONS + NR_RS_LINES);
        } else if ((line - PTYPX_MINOR) < NR_PTYS) {
                tp = tty_addr(line - PTYPX_MINOR + NR_CONS + NR_RS_LINES);
        } else {
                tp = NULL;
        }

        if (tp != NULL && !tty_active(tp))
                tp = NULL;

        return(tp);
}

/*===========================================================================*
 *                             sef_local_startup                             *
 *===========================================================================*/
static void sef_local_startup()
{
  /* Register init callbacks. */
  sef_setcb_init_fresh(sef_cb_init_fresh);
  sef_setcb_init_restart(sef_cb_init_fresh);

  /* No live update support for now. */

  /* Register signal callbacks. */
  sef_setcb_signal_handler(sef_cb_signal_handler);

  /* Let SEF perform startup. */
  sef_startup();
}

/*===========================================================================*
 *                          sef_cb_init_fresh                                *
 *===========================================================================*/
static int sef_cb_init_fresh(int UNUSED(type), sef_init_info_t *UNUSED(info))
{
/* Initialize the tty driver. */
  int r;
  char val[CONS_ARG];

  /* Get kernel environment (protected_mode, pc_at and ega are needed). */ 
  if (OK != (r=sys_getmachine(&machine))) {
    panic("Couldn't obtain kernel environment: %d", r);
  }

  if (env_get_param("console", val, sizeof(val)) == OK) {
        set_console_line(val);
  }

  if ((r = env_get_param("kernelclr", val, sizeof(val))) == OK) {
        set_kernel_color(val);
  }

  /* Initialize the TTY driver. */
  tty_init();

  /* Final one-time keyboard initialization. */
  kb_init_once();

  return(OK);
}

static void
set_console_line(char term[CONS_ARG])
{
/* Parse 'term' and redirect console output there. */
        int i;

        /* Console */
        if (!strncmp(term, "console", CONS_ARG - 1)) {
                consoleline = CONS_MINOR+0;
        }

        /* The other console terminals */
        for (i = 1; i < NR_CONS; i++) {
                char cons[6];
                strlcpy(cons, "ttyc0", sizeof(cons));
                cons[4] += i;
                if (!strncmp(term, cons,
                    CONS_ARG < sizeof(cons) ? CONS_ARG-1 : sizeof(cons) - 1))
                        consoleline = CONS_MINOR + i;
        }

        /* Serial lines */
        assert(NR_RS_LINES <= 9);/* below assumes this is the case */
        for (i = 0; i < NR_RS_LINES; i++) {
                char sercons[6];
                strlcpy(sercons, "tty00", sizeof(sercons));
                sercons[4] += i;
                if (!strncmp(term, sercons,
                    CONS_ARG < sizeof(sercons) ? CONS_ARG-1:sizeof(sercons)-1))
                        consoleline = RS232_MINOR + i;
        }
}

static void
set_kernel_color(char color[CONS_ARG])
{
        int def_color;

#define SGR_COLOR_START 30
#define SGR_COLOR_END   37

        def_color = atoi(color);
        if ((SGR_COLOR_START + def_color) >= SGR_COLOR_START &&
            (SGR_COLOR_START + def_color) <= SGR_COLOR_END) {
                kernel_msg_color = def_color + SGR_COLOR_START;
        }
}

static void
do_new_kmess(void)
{
/* Kernel wants to print a new message */
        struct kmessages *kmess_ptr;    /* kmessages structure */
        char kernel_buf_copy[_KMESS_BUF_SIZE];
        static int prev_next = 0;
        int next, bytes, copy, restore = 0;
        tty_t *tp, rtp;

        assert(_minix_kerninfo);
        kmess_ptr = _minix_kerninfo->kmessages;

        /* The kernel buffer is circular; print only the new part. Determine
         * how many new bytes there are with the help of current and
         * previous 'next' index. This works fine if less than _KMESS_BUF_SIZE
         * bytes is new data; else we miss % _KMESS_BUF_SIZE here. Obtain
         * 'next' only once, since we are operating on shared memory here.
         * Check for size being positive; the buffer might as well be emptied!
         */
        next = kmess_ptr->km_next;
        bytes = ((next + _KMESS_BUF_SIZE) - prev_next) % _KMESS_BUF_SIZE;
        if (bytes > 0) {
                /* Copy from current position toward end of buffer */
                copy = MIN(_KMESS_BUF_SIZE - prev_next, bytes);
                memcpy(kernel_buf_copy, &kmess_ptr->km_buf[prev_next], copy);

                /* Copy remainder from start of buffer */
                if (copy < bytes) {
                        memcpy(&kernel_buf_copy[copy], &kmess_ptr->km_buf[0],
                                bytes - copy);
                }

                tp = line2tty(consoleline);
                if (tp == NULL)
                        panic("Don't know where to send kernel messages");
                if (tp->tty_outleft > 0) {
                        /* Terminal is already printing */
                        rtp = *tp;      /* Make backup */
                        tp->tty_outleft = 0; /* So do_write is happy */
                        restore = 1;
                }

                if (kernel_msg_color != 0)
                        set_color(tp, kernel_msg_color);
                do_write(tp->tty_minor, 0, KERNEL,
                        (cp_grant_id_t) kernel_buf_copy, bytes,
                        FLG_OP_NONBLOCK, 0);
                if (kernel_msg_color != 0)
                        reset_color(tp);
                if (restore) {
                        *tp = rtp;
                }
        }

        /* Store 'next' pointer so that we can determine what part of the
         * kernel messages buffer to print next time a notification arrives.
         */
        prev_next = next;
}

/*===========================================================================*
 *                         sef_cb_signal_handler                             *
 *===========================================================================*/
static void sef_cb_signal_handler(int signo)
{
  /* Check for known signals, ignore anything else. */
  switch(signo) {
      /* There is a pending message from the kernel. */
      case SIGKMESS:
          do_new_kmess();
      break;
      /* Switch to primary console on termination. */
      case SIGTERM:
          cons_stop();
      break;
  }
}

/*===========================================================================*
 *                              do_read                                      *
 *===========================================================================*/
static ssize_t do_read(devminor_t minor, u64_t UNUSED(position),
        endpoint_t endpt, cp_grant_id_t grant, size_t size, int flags,
        cdev_id_t id)
{
/* A process wants to read from a terminal. */
  tty_t *tp;
  int r;

  if ((tp = line2tty(minor)) == NULL)
        return ENXIO;

  /* Check if there is already a process hanging in a read, check if the
   * parameters are correct, do I/O.
   */
  if (tp->tty_incaller != NONE || tp->tty_inleft > 0)
        return EIO;
  if (size <= 0)
        return EINVAL;

  /* Copy information from the message to the tty struct. */
  tp->tty_incaller = endpt;
  tp->tty_inid = id;
  tp->tty_ingrant = grant;
  assert(tp->tty_incum == 0);
  tp->tty_inleft = size;

  if (!(tp->tty_termios.c_lflag & ICANON) && tp->tty_termios.c_cc[VTIME] > 0) {
        if (tp->tty_termios.c_cc[VMIN] == 0) {
                /* MIN & TIME specify a read timer that finishes the
                 * read in TIME/10 seconds if no bytes are available.
                 */
                settimer(tp, TRUE);
                tp->tty_min = 1;
        } else {
                /* MIN & TIME specify an inter-byte timer that may
                 * have to be cancelled if there are no bytes yet.
                 */
                if (tp->tty_eotct == 0) {
                        settimer(tp, FALSE);
                        tp->tty_min = tp->tty_termios.c_cc[VMIN];
                }
        }
  }

  /* Anything waiting in the input buffer? Clear it out... */
  in_transfer(tp);
  /* ...then go back for more. */
  handle_events(tp);
  if (tp->tty_inleft == 0)
        return EDONTREPLY;      /* already done */

  /* There were no bytes in the input queue available. */
  if (flags & FLG_OP_NONBLOCK) {
        tty_icancel(tp);
        r = tp->tty_incum > 0 ? tp->tty_incum : EAGAIN;
        tp->tty_inleft = tp->tty_incum = 0;
        tp->tty_incaller = NONE;
        return r;
  }

  if (tp->tty_select_ops)
        select_retry(tp);

  return EDONTREPLY;            /* suspend the caller */
}

/*===========================================================================*
 *                              do_write                                     *
 *===========================================================================*/
static ssize_t do_write(devminor_t minor, u64_t UNUSED(position),
        endpoint_t endpt, cp_grant_id_t grant, size_t size, int flags,
        cdev_id_t id)
{
/* A process wants to write on a terminal. */
  tty_t *tp;
  int r;

  if ((tp = line2tty(minor)) == NULL)
        return ENXIO;

  /* Check if there is already a process hanging in a write, check if the
   * parameters are correct, do I/O.
   */
  if (tp->tty_outcaller != NONE || tp->tty_outleft > 0)
        return EIO;
  if (size <= 0)
        return EINVAL;

  /* Copy message parameters to the tty structure. */
  tp->tty_outcaller = endpt;
  tp->tty_outid = id;
  tp->tty_outgrant = grant;
  assert(tp->tty_outcum == 0);
  tp->tty_outleft = size;

  /* Try to write. */
  handle_events(tp);
  if (tp->tty_outleft == 0)
        return EDONTREPLY;      /* already done */

  /* None or not all the bytes could be written. */
  if (flags & FLG_OP_NONBLOCK) {
        r = tp->tty_outcum > 0 ? tp->tty_outcum : EAGAIN;
        tp->tty_outleft = tp->tty_outcum = 0;
        tp->tty_outcaller = NONE;
        return r;
  }

  if (tp->tty_select_ops)
        select_retry(tp);

  return EDONTREPLY;            /* suspend the caller */
}

/*===========================================================================*
 *                              do_ioctl                                     *
 *===========================================================================*/
static int do_ioctl(devminor_t minor, unsigned long request, endpoint_t endpt,
        cp_grant_id_t grant, int flags, endpoint_t user_endpt, cdev_id_t id)
{
/* Perform an IOCTL on this terminal. POSIX termios calls are handled
 * by the IOCTL system call.
 */
  tty_t *tp;
  int i, r;
  size_t size;

  if ((tp = line2tty(minor)) == NULL)
        return ENXIO;

  /* Size of the ioctl parameter. */
  switch (request) {
    case TCGETS:        /* Posix tcgetattr function */
    case TCSETS:        /* Posix tcsetattr function, TCSANOW option */ 
    case TCSETSW:       /* Posix tcsetattr function, TCSADRAIN option */
    case TCSETSF:       /* Posix tcsetattr function, TCSAFLUSH option */
        size = sizeof(struct termios);
        break;

    case TCSBRK:        /* Posix tcsendbreak function */
    case TCFLOW:        /* Posix tcflow function */
    case TCFLSH:        /* Posix tcflush function */
    case TIOCGPGRP:     /* Posix tcgetpgrp function */
    case TIOCSPGRP:     /* Posix tcsetpgrp function */
        size = sizeof(int);
        break;

    case TIOCGWINSZ:    /* get window size (not Posix) */
    case TIOCSWINSZ:    /* set window size (not Posix) */
        size = sizeof(struct winsize);
        break;

    case KIOCSMAP:      /* load keymap (Minix extension) */
        size = sizeof(keymap_t);
        break;

    case TIOCSFON:      /* load font (Minix extension) */
        size = sizeof(u8_t [8192]);
        break;

    case TCDRAIN:       /* Posix tcdrain function -- no parameter */
    default:            size = 0;
  }

  r = OK;
  switch (request) {
    case TCGETS:
        /* Get the termios attributes. */
        r = sys_safecopyto(endpt, grant, 0, (vir_bytes) &tp->tty_termios,
                size);
        break;

    case TCSETSW:
    case TCSETSF:
    case TCDRAIN:
        if (tp->tty_outleft > 0) {
                if (flags & FLG_OP_NONBLOCK)
                        return EAGAIN;
                /* Wait for all ongoing output processing to finish. */
                tp->tty_iocaller = endpt;
                tp->tty_ioid = id;
                tp->tty_ioreq = request;
                tp->tty_iogrant = grant;
                return EDONTREPLY;      /* suspend the caller */
        }
        if (request == TCDRAIN) break;
        if (request == TCSETSF) tty_icancel(tp);
        /*FALL THROUGH*/
    case TCSETS:
        /* Set the termios attributes. */
        r = sys_safecopyfrom(endpt, grant, 0, (vir_bytes) &tp->tty_termios,
                size);
        if (r != OK) break;
        setattr(tp);
        break;

    case TCFLSH:
        r = sys_safecopyfrom(endpt, grant, 0, (vir_bytes) &i, size);
        if (r != OK) break;
        switch (i) {
        case TCIFLUSH:  tty_icancel(tp);                            break;
        case TCOFLUSH:  (*tp->tty_ocancel)(tp, 0);                  break;
        case TCIOFLUSH: tty_icancel(tp); (*tp->tty_ocancel)(tp, 0); break;
        default:        r = EINVAL;
        }
        break;

    case TCFLOW:
        r = sys_safecopyfrom(endpt, grant, 0, (vir_bytes) &i, size);
        if (r != OK) break;
        switch (i) {
            case TCOOFF:
            case TCOON:
                tp->tty_inhibited = (i == TCOOFF);
                tp->tty_events = 1;
                break;
            case TCIOFF:
                (*tp->tty_echo)(tp, tp->tty_termios.c_cc[VSTOP]);
                break;
            case TCION:
                (*tp->tty_echo)(tp, tp->tty_termios.c_cc[VSTART]);
                break;
            default:
                r = EINVAL;
        }
        break;

    case TCSBRK:
        if (tp->tty_break != NULL) (*tp->tty_break)(tp,0);
        break;

    case TIOCGWINSZ:
        r = sys_safecopyto(endpt, grant, 0, (vir_bytes) &tp->tty_winsize,
                size);
        break;

    case TIOCSWINSZ:
        r = sys_safecopyfrom(endpt, grant, 0, (vir_bytes) &tp->tty_winsize,
                size);
        sigchar(tp, SIGWINCH, 0);
        break;

    case KIOCSMAP:
        /* Load a new keymap (only /dev/console). */
        if (isconsole(tp)) r = kbd_loadmap(endpt, grant);
        break;

    case TIOCSFON:
        /* Load a font into an EGA or VGA card (hs@hck.hr) */
        if (isconsole(tp)) r = con_loadfont(endpt, grant);
        break;

/* These Posix functions are allowed to fail if _POSIX_JOB_CONTROL is 
 * not defined.
 */
    case TIOCGPGRP:     
    case TIOCSPGRP:     
    default:
        r = ENOTTY;
  }

  return r;
}

/*===========================================================================*
 *                              do_open                                      *
 *===========================================================================*/
static int do_open(devminor_t minor, int access, endpoint_t user_endpt)
{
/* A tty line has been opened.  Make it the callers controlling tty if
 * O_NOCTTY is *not* set and it is not the log device.  1 is returned if
 * the tty is made the controlling tty, otherwise OK or an error code.
 */
  tty_t *tp;
  int r = OK;

  if ((tp = line2tty(minor)) == NULL)
        return ENXIO;

  if (minor == LOG_MINOR && isconsole(tp)) {
        /* The log device is a write-only diagnostics device. */
        if (access & R_BIT) return EACCES;
  } else {
        if (!(access & O_NOCTTY)) {
                tp->tty_pgrp = user_endpt;
                r = 1;
        }
        tp->tty_openct++;
        if (tp->tty_openct == 1) {
                /* Tell the device that the tty is opened */
                (*tp->tty_open)(tp, 0);
        }
  }

  return r;
}

/*===========================================================================*
 *                              do_close                                     *
 *===========================================================================*/
static int do_close(devminor_t minor)
{
/* A tty line has been closed.  Clean up the line if it is the last close. */
  tty_t *tp;

  if ((tp = line2tty(minor)) == NULL)
        return ENXIO;

  if ((minor != LOG_MINOR || !isconsole(tp)) && --tp->tty_openct == 0) {
        tp->tty_pgrp = 0;
        tty_icancel(tp);
        (*tp->tty_ocancel)(tp, 0);
        (*tp->tty_close)(tp, 0);
        tp->tty_termios = termios_defaults;
        tp->tty_winsize = winsize_defaults;
        setattr(tp);
  }

  return OK;
}

/*===========================================================================*
 *                              do_cancel                                    *
 *===========================================================================*/
static int do_cancel(devminor_t minor, endpoint_t endpt, cdev_id_t id)
{
/* A signal has been sent to a process that is hanging trying to read or write.
 * The pending read or write must be finished off immediately.
 */
  tty_t *tp;
  int r;

  if ((tp = line2tty(minor)) == NULL)
        return ENXIO;

  /* Check the parameters carefully, to avoid cancelling twice. */
  r = EDONTREPLY;
  if (tp->tty_inleft != 0 && endpt == tp->tty_incaller && id == tp->tty_inid) {
        /* Process was reading when killed.  Clean up input. */
        tty_icancel(tp); 
        r = tp->tty_incum > 0 ? tp->tty_incum : EAGAIN;
        tp->tty_inleft = tp->tty_incum = 0;
        tp->tty_incaller = NONE;
  } else if (tp->tty_outleft != 0 && endpt == tp->tty_outcaller &&
        id == tp->tty_outid) {
        /* Process was writing when killed.  Clean up output. */
        r = tp->tty_outcum > 0 ? tp->tty_outcum : EAGAIN;
        tp->tty_outleft = tp->tty_outcum = 0;
        tp->tty_outcaller = NONE;
  } else if (tp->tty_ioreq != 0 && endpt == tp->tty_iocaller &&
        id == tp->tty_ioid) {
        /* Process was waiting for output to drain. */
        r = EINTR;
        tp->tty_ioreq = 0;
        tp->tty_iocaller = NONE;
  }
  if (r != EDONTREPLY)
        tp->tty_events = 1;
  /* Only reply if we found a matching request. */
  return r;
}

int select_try(struct tty *tp, int ops)
{
        int ready_ops = 0;

        /* Special case. If line is hung up, no operations will block.
         * (and it can be seen as an exceptional condition.)
         */
        if (tp->tty_termios.c_ospeed == B0) {
                ready_ops |= ops;
        }

        if (ops & SEL_RD) {
                /* will i/o not block on read? */
                if (tp->tty_inleft > 0) {
                        ready_ops |= SEL_RD;    /* EIO - no blocking */
                } else if (tp->tty_incount > 0) {
                        /* Is a regular read possible? tty_incount
                         * says there is data. But a read will only succeed
                         * in canonical mode if a newline has been seen.
                         */
                        if (!(tp->tty_termios.c_lflag & ICANON) ||
                                tp->tty_eotct > 0) {
                                ready_ops |= SEL_RD;
                        }
                }
        }

        if (ops & SEL_WR)  {
                if (tp->tty_outleft > 0)  ready_ops |= SEL_WR;
                else if ((*tp->tty_devwrite)(tp, 1)) ready_ops |= SEL_WR;
        }
        return ready_ops;
}

int select_retry(struct tty *tp)
{
        int ops;

        if (tp->tty_select_ops && (ops = select_try(tp, tp->tty_select_ops))) {
                chardriver_reply_select(tp->tty_select_proc, tp->tty_minor,
                        ops);
                tp->tty_select_ops &= ~ops;
        }
        return OK;
}

/*===========================================================================*
 *                              do_select                                    *
 *===========================================================================*/
static int do_select(devminor_t minor, unsigned int ops, endpoint_t endpt)
{
  tty_t *tp;
  int ready_ops, watch;

  if ((tp = line2tty(minor)) == NULL)
        return ENXIO;

  /* Translated minor numbers are a problem when sending late replies. */
  if (tp->tty_minor != minor)
        return EBADF;

  watch = (ops & SEL_NOTIFY);
  ops &= (SEL_RD | SEL_WR | SEL_ERR);

  ready_ops = select_try(tp, ops);

  ops &= ~ready_ops;
  if (ops && watch) {
        tp->tty_select_ops |= ops;
        tp->tty_select_proc = endpt;
  }

  assert(tp->tty_minor == minor);
  return ready_ops;
}

/*===========================================================================*
 *                              handle_events                                *
 *===========================================================================*/
void handle_events(tp)
tty_t *tp;                      /* TTY to check for events. */
{
/* Handle any events pending on a TTY.  These events are usually device
 * interrupts.
 *
 * Two kinds of events are prominent:
 *      - a character has been received from the console or an RS232 line.
 *      - an RS232 line has completed a write request (on behalf of a user).
 * The interrupt handler may delay the interrupt message at its discretion
 * to avoid swamping the TTY task.  Messages may be overwritten when the
 * lines are fast or when there are races between different lines, input
 * and output, because MINIX only provides single buffering for interrupt
 * messages.  This is handled by explicitly checking each line for fresh input
 * and completed output on each interrupt.
 */

  do {
        tp->tty_events = 0;

        /* Read input and perform input processing. */
        (*tp->tty_devread)(tp, 0);

        /* Perform output processing and write output. */
        (*tp->tty_devwrite)(tp, 0);

        /* Ioctl waiting for some event? */
        if (tp->tty_ioreq != 0) dev_ioctl(tp);
  } while (tp->tty_events);

  /* Transfer characters from the input queue to a waiting process. */
  in_transfer(tp);

  /* Reply if enough bytes are available. */
  if (tp->tty_incum >= tp->tty_min && tp->tty_inleft > 0) {
        chardriver_reply_task(tp->tty_incaller, tp->tty_inid, tp->tty_incum);
        tp->tty_inleft = tp->tty_incum = 0;
        tp->tty_incaller = NONE;
  }
  if (tp->tty_select_ops)
  {
        select_retry(tp);
  }
#if NR_PTYS > 0
  if (ispty(tp))
        select_retry_pty(tp);
#endif
}

/*===========================================================================*
 *                              in_transfer                                  *
 *===========================================================================*/
static void in_transfer(tp)
register tty_t *tp;             /* pointer to terminal to read from */
{
/* Transfer bytes from the input queue to a process reading from a terminal. */

  int ch;
  int count;
  char buf[64], *bp;

  /* Force read to succeed if the line is hung up, looks like EOF to reader. */
  if (tp->tty_termios.c_ospeed == B0) tp->tty_min = 0;

  /* Anything to do? */
  if (tp->tty_inleft == 0 || tp->tty_eotct < tp->tty_min) return;

  bp = buf;
  while (tp->tty_inleft > 0 && tp->tty_eotct > 0) {
        ch = *tp->tty_intail;

        if (!(ch & IN_EOF)) {
                /* One character to be delivered to the user. */
                *bp = ch & IN_CHAR;
                tp->tty_inleft--;
                if (++bp == bufend(buf)) {
                        /* Temp buffer full, copy to user space. */
                        sys_safecopyto(tp->tty_incaller,
                                tp->tty_ingrant, tp->tty_incum,
                                (vir_bytes) buf, (vir_bytes) buflen(buf));
                        tp->tty_incum += buflen(buf);
                        bp = buf;
                }
        }

        /* Remove the character from the input queue. */
        if (++tp->tty_intail == bufend(tp->tty_inbuf))
                tp->tty_intail = tp->tty_inbuf;
        tp->tty_incount--;
        if (ch & IN_EOT) {
                tp->tty_eotct--;
                /* Don't read past a line break in canonical mode. */
                if (tp->tty_termios.c_lflag & ICANON) tp->tty_inleft = 0;
        }
  }

  if (bp > buf) {
        /* Leftover characters in the buffer. */
        count = bp - buf;
        sys_safecopyto(tp->tty_incaller, tp->tty_ingrant, tp->tty_incum,
                (vir_bytes) buf, (vir_bytes) count);
        tp->tty_incum += count;
  }

  /* Usually reply to the reader, possibly even if incum == 0 (EOF). */
  if (tp->tty_inleft == 0) {
        chardriver_reply_task(tp->tty_incaller, tp->tty_inid, tp->tty_incum);
        tp->tty_inleft = tp->tty_incum = 0;
        tp->tty_incaller = NONE;
  }
}

/*===========================================================================*
 *                              in_process                                   *
 *===========================================================================*/
static void in_process_send_byte(
  tty_t *tp,    /* terminal on which character has arrived */
  int ch        /* input character */
)
{
        /* Save the character in the input queue. */
        *tp->tty_inhead++ = ch;
        if (tp->tty_inhead == bufend(tp->tty_inbuf))
                tp->tty_inhead = tp->tty_inbuf;
        tp->tty_incount++;
        if (ch & IN_EOT) tp->tty_eotct++;

        /* Try to finish input if the queue threatens to overflow. */
        if (tp->tty_incount == buflen(tp->tty_inbuf)) in_transfer(tp);
}
 
int in_process(tp, buf, count, scode)
register tty_t *tp;             /* terminal on which character has arrived */
char *buf;                      /* buffer with input characters */
int count;                      /* number of input characters */
int scode;                      /* scan code */
{
/* Characters have just been typed in.  Process, save, and echo them.  Return
 * the number of characters processed.
 */

  int ch, sig, ct;
  int timeset = FALSE;

  /* Send scancode if requested */
  if (tp->tty_termios.c_iflag & SCANCODES) {
        in_process_send_byte(tp, (scode & BYTE) | IN_EOT);
  }

  for (ct = 0; ct < count; ct++) {
        /* Take one character. */
        ch = *buf++ & BYTE;

        /* Strip to seven bits? */
        if (tp->tty_termios.c_iflag & ISTRIP) ch &= 0x7F;

        /* Input extensions? */
        if (tp->tty_termios.c_lflag & IEXTEN) {

                /* Previous character was a character escape? */
                if (tp->tty_escaped) {
                        tp->tty_escaped = NOT_ESCAPED;
                        ch |= IN_ESC;   /* protect character */
                }

                /* LNEXT (^V) to escape the next character? */
                if (ch == tp->tty_termios.c_cc[VLNEXT]) {
                        tp->tty_escaped = ESCAPED;
                        rawecho(tp, '^');
                        rawecho(tp, '\b');
                        continue;       /* do not store the escape */
                }

                /* REPRINT (^R) to reprint echoed characters? */
                if (ch == tp->tty_termios.c_cc[VREPRINT]) {
                        reprint(tp);
                        continue;
                }
        }

        /* _POSIX_VDISABLE is a normal character value, so better escape it. */
        if (ch == _POSIX_VDISABLE) ch |= IN_ESC;

        /* Map CR to LF, ignore CR, or map LF to CR. */
        if (ch == '\r') {
                if (tp->tty_termios.c_iflag & IGNCR) continue;
                if (tp->tty_termios.c_iflag & ICRNL) ch = '\n';
        } else
        if (ch == '\n') {
                if (tp->tty_termios.c_iflag & INLCR) ch = '\r';
        }

        /* Canonical mode? */
        if (tp->tty_termios.c_lflag & ICANON) {

                /* Erase processing (rub out of last character). */
                if (ch == tp->tty_termios.c_cc[VERASE]) {
                        (void) back_over(tp);
                        if (!(tp->tty_termios.c_lflag & ECHOE)) {
                                (void) tty_echo(tp, ch);
                        }
                        continue;
                }

                /* Kill processing (remove current line). */
                if (ch == tp->tty_termios.c_cc[VKILL]) {
                        while (back_over(tp)) {}
                        if (!(tp->tty_termios.c_lflag & ECHOE)) {
                                (void) tty_echo(tp, ch);
                                if (tp->tty_termios.c_lflag & ECHOK)
                                        rawecho(tp, '\n');
                        }
                        continue;
                }

                /* EOF (^D) means end-of-file, an invisible "line break". */
                if (ch == tp->tty_termios.c_cc[VEOF]) ch |= IN_EOT | IN_EOF;

                /* The line may be returned to the user after an LF. */
                if (ch == '\n') ch |= IN_EOT;

                /* Same thing with EOL, whatever it may be. */
                if (ch == tp->tty_termios.c_cc[VEOL]) ch |= IN_EOT;
        }

        /* Start/stop input control? */
        if (tp->tty_termios.c_iflag & IXON) {

                /* Output stops on STOP (^S). */
                if (ch == tp->tty_termios.c_cc[VSTOP]) {
                        tp->tty_inhibited = STOPPED;
                        tp->tty_events = 1;
                        continue;
                }

                /* Output restarts on START (^Q) or any character if IXANY. */
                if (tp->tty_inhibited) {
                        if (ch == tp->tty_termios.c_cc[VSTART]
                                        || (tp->tty_termios.c_iflag & IXANY)) {
                                tp->tty_inhibited = RUNNING;
                                tp->tty_events = 1;
                                if (ch == tp->tty_termios.c_cc[VSTART])
                                        continue;
                        }
                }
        }

        if (tp->tty_termios.c_lflag & ISIG) {
                /* Check for INTR (^?) and QUIT (^\) characters. */
                if (ch == tp->tty_termios.c_cc[VINTR]
                                        || ch == tp->tty_termios.c_cc[VQUIT]) {
                        sig = SIGINT;
                        if (ch == tp->tty_termios.c_cc[VQUIT]) sig = SIGQUIT;
                        sigchar(tp, sig, 1);
                        (void) tty_echo(tp, ch);
                        continue;
                }
        }

        /* Is there space in the input buffer? */
        if (tp->tty_incount == buflen(tp->tty_inbuf)) {
                /* No space; discard in canonical mode, keep in raw mode. */
                if (tp->tty_termios.c_lflag & ICANON) continue;
                break;
        }

        if (!(tp->tty_termios.c_lflag & ICANON)) {
                /* In raw mode all characters are "line breaks". */
                ch |= IN_EOT;

                /* Start an inter-byte timer? */
                if (!timeset && tp->tty_termios.c_cc[VMIN] > 0
                                && tp->tty_termios.c_cc[VTIME] > 0) {
                        settimer(tp, TRUE);
                        timeset = TRUE;
                }
        }

        /* Perform the intricate function of echoing. */
        if (tp->tty_termios.c_lflag & (ECHO|ECHONL)) ch = tty_echo(tp, ch);

        /* Send processed byte of input unless scancodes sent instead */
        if (!(tp->tty_termios.c_iflag & SCANCODES)) {
                in_process_send_byte(tp, ch);
        }
  }
  return ct;
}

/*===========================================================================*
 *                              echo                                         *
 *===========================================================================*/
static int tty_echo(tp, ch)
register tty_t *tp;             /* terminal on which to echo */
register int ch;                /* pointer to character to echo */
{
/* Echo the character if echoing is on.  Some control characters are echoed
 * with their normal effect, other control characters are echoed as "^X",
 * normal characters are echoed normally.  EOF (^D) is echoed, but immediately
 * backspaced over.  Return the character with the echoed length added to its
 * attributes.
 */
  int len, rp;

  ch &= ~IN_LEN;
  if (!(tp->tty_termios.c_lflag & ECHO)) {
        if (ch == ('\n' | IN_EOT) && (tp->tty_termios.c_lflag
                                        & (ICANON|ECHONL)) == (ICANON|ECHONL))
                (*tp->tty_echo)(tp, '\n');
        return(ch);
  }

  /* "Reprint" tells if the echo output has been messed up by other output. */
  rp = tp->tty_incount == 0 ? FALSE : tp->tty_reprint;

  if ((ch & IN_CHAR) < ' ') {
        switch (ch & (IN_ESC|IN_EOF|IN_EOT|IN_CHAR)) {
            case '\t':
                len = 0;
                do {
                        (*tp->tty_echo)(tp, ' ');
                        len++;
                } while (len < TAB_SIZE && (tp->tty_position & TAB_MASK) != 0);
                break;
            case '\r' | IN_EOT:
            case '\n' | IN_EOT:
                (*tp->tty_echo)(tp, ch & IN_CHAR);
                len = 0;
                break;
            default:
                (*tp->tty_echo)(tp, '^');
                (*tp->tty_echo)(tp, '@' + (ch & IN_CHAR));
                len = 2;
        }
  } else
  if ((ch & IN_CHAR) == '\177') {
        /* A DEL prints as "^?". */
        (*tp->tty_echo)(tp, '^');
        (*tp->tty_echo)(tp, '?');
        len = 2;
  } else {
        (*tp->tty_echo)(tp, ch & IN_CHAR);
        len = 1;
  }
  if (ch & IN_EOF) while (len > 0) { (*tp->tty_echo)(tp, '\b'); len--; }

  tp->tty_reprint = rp;
  return(ch | (len << IN_LSHIFT));
}

/*===========================================================================*
 *                              rawecho                                      *
 *===========================================================================*/
static void rawecho(tp, ch)
register tty_t *tp;
int ch;
{
/* Echo without interpretation if ECHO is set. */
  int rp = tp->tty_reprint;
  if (tp->tty_termios.c_lflag & ECHO) (*tp->tty_echo)(tp, ch);
  tp->tty_reprint = rp;
}

/*===========================================================================*
 *                              back_over                                    *
 *===========================================================================*/
static int back_over(tp)
register tty_t *tp;
{
/* Backspace to previous character on screen and erase it. */
  u16_t *head;
  int len;

  if (tp->tty_incount == 0) return(0);  /* queue empty */
  head = tp->tty_inhead;
  if (head == tp->tty_inbuf) head = bufend(tp->tty_inbuf);
  if (*--head & IN_EOT) return(0);              /* can't erase "line breaks" */
  if (tp->tty_reprint) reprint(tp);             /* reprint if messed up */
  tp->tty_inhead = head;
  tp->tty_incount--;
  if (tp->tty_termios.c_lflag & ECHOE) {
        len = (*head & IN_LEN) >> IN_LSHIFT;
        while (len > 0) {
                rawecho(tp, '\b');
                rawecho(tp, ' ');
                rawecho(tp, '\b');
                len--;
        }
  }
  return(1);                            /* one character erased */
}

/*===========================================================================*
 *                              reprint                                      *
 *===========================================================================*/
static void reprint(tp)
register tty_t *tp;             /* pointer to tty struct */
{
/* Restore what has been echoed to screen before if the user input has been
 * messed up by output, or if REPRINT (^R) is typed.
 */
  int count;
  u16_t *head;

  tp->tty_reprint = FALSE;

  /* Find the last line break in the input. */
  head = tp->tty_inhead;
  count = tp->tty_incount;
  while (count > 0) {
        if (head == tp->tty_inbuf) head = bufend(tp->tty_inbuf);
        if (head[-1] & IN_EOT) break;
        head--;
        count--;
  }
  if (count == tp->tty_incount) return;         /* no reason to reprint */

  /* Show REPRINT (^R) and move to a new line. */
  (void) tty_echo(tp, tp->tty_termios.c_cc[VREPRINT] | IN_ESC);
  rawecho(tp, '\r');
  rawecho(tp, '\n');

  /* Reprint from the last break onwards. */
  do {
        if (head == bufend(tp->tty_inbuf)) head = tp->tty_inbuf;
        *head = tty_echo(tp, *head);
        head++;
        count++;
  } while (count < tp->tty_incount);
}

/*===========================================================================*
 *                              out_process                                  *
 *===========================================================================*/
void out_process(tp, bstart, bpos, bend, icount, ocount)
tty_t *tp;
char *bstart, *bpos, *bend;     /* start/pos/end of circular buffer */
int *icount;                    /* # input chars / input chars used */
int *ocount;                    /* max output chars / output chars used */
{
/* Perform output processing on a circular buffer.  *icount is the number of
 * bytes to process, and the number of bytes actually processed on return.
 * *ocount is the space available on input and the space used on output.
 * (Naturally *icount < *ocount.)  The column position is updated modulo
 * the TAB size, because we really only need it for tabs.
 */

  int tablen;
  int ict = *icount;
  int oct = *ocount;
  int pos = tp->tty_position;

  while (ict > 0) {
        switch (*bpos) {
        case '\7':
                break;
        case '\b':
                pos--;
                break;
        case '\r':
                pos = 0;
                break;
        case '\n':
                if ((tp->tty_termios.c_oflag & (OPOST|ONLCR))
                                                        == (OPOST|ONLCR)) {
                        /* Map LF to CR+LF if there is space.  Note that the
                         * next character in the buffer is overwritten, so
                         * we stop at this point.
                         */
                        if (oct >= 2) {
                                *bpos = '\r';
                                if (++bpos == bend) bpos = bstart;
                                *bpos = '\n';
                                pos = 0;
                                ict--;
                                oct -= 2;
                        }
                        goto out_done;  /* no space or buffer got changed */
                }
                break;
        case '\t':
                /* Best guess for the tab length. */
                tablen = TAB_SIZE - (pos & TAB_MASK);

                if ((tp->tty_termios.c_oflag & (OPOST|XTABS))
                                                        == (OPOST|XTABS)) {
                        /* Tabs must be expanded. */
                        if (oct >= tablen) {
                                pos += tablen;
                                ict--;
                                oct -= tablen;
                                do {
                                        *bpos = ' ';
                                        if (++bpos == bend) bpos = bstart;
                                } while (--tablen != 0);
                        }
                        goto out_done;
                }
                /* Tabs are output directly. */
                pos += tablen;
                break;
        default:
                /* Assume any other character prints as one character. */
                pos++;
        }
        if (++bpos == bend) bpos = bstart;
        ict--;
        oct--;
  }
out_done:
  tp->tty_position = pos & TAB_MASK;

  *icount -= ict;       /* [io]ct are the number of chars not used */
  *ocount -= oct;       /* *[io]count are the number of chars that are used */
}

/*===========================================================================*
 *                              dev_ioctl                                    *
 *===========================================================================*/
static void dev_ioctl(tp)
tty_t *tp;
{
/* The ioctl's TCSETSW, TCSETSF and TCDRAIN wait for output to finish to make
 * sure that an attribute change doesn't affect the processing of current
 * output.  Once output finishes the ioctl is executed as in do_ioctl().
 */
  int result = EINVAL;

  if (tp->tty_outleft > 0) return;              /* output not finished */

  if (tp->tty_ioreq != TCDRAIN) {
        if (tp->tty_ioreq == TCSETSF) tty_icancel(tp);
        result = sys_safecopyfrom(tp->tty_iocaller, tp->tty_iogrant, 0,
                (vir_bytes) &tp->tty_termios,
                (vir_bytes) sizeof(tp->tty_termios));
        if (result == OK) setattr(tp);
  }
  tp->tty_ioreq = 0;
  chardriver_reply_task(tp->tty_iocaller, tp->tty_ioid, result);
  tp->tty_iocaller = NONE;
}

/*===========================================================================*
 *                              setattr                                      *
 *===========================================================================*/
static void setattr(tp)
tty_t *tp;
{
/* Apply the new line attributes (raw/canonical, line speed, etc.) */
  u16_t *inp;
  int count;

  if (!(tp->tty_termios.c_lflag & ICANON)) {
        /* Raw mode; put a "line break" on all characters in the input queue.
         * It is undefined what happens to the input queue when ICANON is
         * switched off, a process should use TCSAFLUSH to flush the queue.
         * Keeping the queue to preserve typeahead is the Right Thing, however
         * when a process does use TCSANOW to switch to raw mode.
         */
        count = tp->tty_eotct = tp->tty_incount;
        inp = tp->tty_intail;
        while (count > 0) {
                *inp |= IN_EOT;
                if (++inp == bufend(tp->tty_inbuf)) inp = tp->tty_inbuf;
                --count;
        }
  }

  /* Inspect MIN and TIME. */
  settimer(tp, FALSE);
  if (tp->tty_termios.c_lflag & ICANON) {
        /* No MIN & TIME in canonical mode. */
        tp->tty_min = 1;
  } else {
        /* In raw mode MIN is the number of chars wanted, and TIME how long
         * to wait for them.  With interesting exceptions if either is zero.
         */
        tp->tty_min = tp->tty_termios.c_cc[VMIN];
        if (tp->tty_min == 0 && tp->tty_termios.c_cc[VTIME] > 0)
                tp->tty_min = 1;
  }

  if (!(tp->tty_termios.c_iflag & IXON)) {
        /* No start/stop output control, so don't leave output inhibited. */
        tp->tty_inhibited = RUNNING;
        tp->tty_events = 1;
  }

  /* Setting the output speed to zero hangs up the phone. */
  if (tp->tty_termios.c_ospeed == B0) sigchar(tp, SIGHUP, 1);

  /* SCANCODES is supported only for the console */
  if (!isconsole(tp)) tp->tty_termios.c_iflag &= ~SCANCODES;

  /* Set new line speed, character size, etc at the device level. */
  (*tp->tty_ioctl)(tp, 0);
}

/*===========================================================================*
 *                              sigchar                                      *
 *===========================================================================*/
void sigchar(tp, sig, mayflush)
register tty_t *tp;
int sig;                        /* SIGINT, SIGQUIT, SIGKILL or SIGHUP */
int mayflush;
{
/* Process a SIGINT, SIGQUIT or SIGKILL char from the keyboard or SIGHUP from
 * a tty close, "stty 0", or a real RS-232 hangup.  PM will send the signal to
 * the process group (INT, QUIT), all processes (KILL), or the session leader
 * (HUP).
 */
  int status;

  if (tp->tty_pgrp != 0)  {
      if (OK != (status = sys_kill(tp->tty_pgrp, sig))) {
        panic("Error; call to sys_kill failed: %d", status);
      }
  }

  if (mayflush && !(tp->tty_termios.c_lflag & NOFLSH)) {
        tp->tty_incount = tp->tty_eotct = 0;    /* kill earlier input */
        tp->tty_intail = tp->tty_inhead;
        (*tp->tty_ocancel)(tp, 0);                      /* kill all output */
        tp->tty_inhibited = RUNNING;
        tp->tty_events = 1;
  }
}

/*===========================================================================*
 *                              tty_icancel                                  *
 *===========================================================================*/
static void tty_icancel(tp)
register tty_t *tp;
{
/* Discard all pending input, tty buffer or device. */

  tp->tty_incount = tp->tty_eotct = 0;
  tp->tty_intail = tp->tty_inhead;
  (*tp->tty_icancel)(tp, 0);
}

/*===========================================================================*
 *                              tty_devnop                                   *
 *===========================================================================*/
static int tty_devnop(tty_t *UNUSED(tp), int UNUSED(try))
{
  /* Some functions need not be implemented at the device level. */
  return 0;
}

/*===========================================================================*
 *                              tty_init                                     *
 *===========================================================================*/
static void tty_init()
{
/* Initialize tty structure and call device initialization routines. */

  register tty_t *tp;
  int s;

  system_hz = sys_hz();

  /* Initialize the terminal lines. */
  memset(tty_table, '\0' , sizeof(tty_table));

  for (tp = FIRST_TTY,s=0; tp < END_TTY; tp++,s++) {

        tp->tty_index = s;
        init_timer(&tp->tty_tmr);

        tp->tty_intail = tp->tty_inhead = tp->tty_inbuf;
        tp->tty_min = 1;
        tp->tty_incaller = tp->tty_outcaller = tp->tty_iocaller = NONE;
        tp->tty_termios = termios_defaults;
        tp->tty_icancel = tp->tty_ocancel = tp->tty_ioctl = tp->tty_close =
                          tp->tty_open = tty_devnop;
        if (tp < tty_addr(NR_CONS)) {
                scr_init(tp);

                /* Initialize the keyboard driver. */
                kb_init(tp);

                tp->tty_minor = CONS_MINOR + s;
        } else
        if (tp < tty_addr(NR_CONS+NR_RS_LINES)) {
                rs_init(tp);
                tp->tty_minor = RS232_MINOR + s-NR_CONS;
        } else {
                pty_init(tp);
                tp->tty_minor = s - (NR_CONS+NR_RS_LINES) + TTYPX_MINOR;
        }
  }

}

/*===========================================================================*
 *                              tty_timed_out                                *
 *===========================================================================*/
static void tty_timed_out(timer_t *tp)
{
/* This timer has expired. Set the events flag, to force processing. */
  tty_t *tty_ptr;
  tty_ptr = &tty_table[tmr_arg(tp)->ta_int];
  tty_ptr->tty_min = 0;                 /* force read to succeed */
  tty_ptr->tty_events = 1;              
}

/*===========================================================================*
 *                              settimer                                     *
 *===========================================================================*/
static void settimer(tty_ptr, enable)
tty_t *tty_ptr;                 /* line to set or unset a timer on */
int enable;                     /* set timer if true, otherwise unset */
{
  clock_t ticks;

  if (enable) {
        ticks = tty_ptr->tty_termios.c_cc[VTIME] * (system_hz/10);

        /* Set a new timer for enabling the TTY events flags. */
        set_timer(&tty_ptr->tty_tmr, ticks, tty_timed_out, tty_ptr->tty_index);
  } else {
        /* Remove the timer from the active and expired lists. */
        cancel_timer(&tty_ptr->tty_tmr);
  }
}