dz.c

讲述linux的初始化过程

  dz_out (info, DZ_LPR, info->cflags);

  if (info->xmit_buf) {               /* free Tx buffer */
    free_page ((unsigned long)info->xmit_buf);
    info->xmit_buf = 0;
  }

  if (!info->tty || (info->tty->termios->c_cflag & HUPCL)) {
    tmp = dz_in (info, DZ_TCR);
    if (tmp & DZ_MODEM_DTR) {
      tmp &= ~DZ_MODEM_DTR;
      dz_out (info, DZ_TCR, tmp);
    }
  }

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

  info->is_initialized = 0;
  restore_flags (flags);
}

/* 
 * -------------------------------------------------------------------
 * change_speed ()
 *
 * set the baud rate.
 * ------------------------------------------------------------------- 
 */
static void change_speed (struct dz_serial *info)
{
  unsigned long flags;
  unsigned cflag;
  int baud;

  if (!info->tty || !info->tty->termios) return;
  
  save_flags (flags);
  cli ();
  
  info->cflags = info->line;

  cflag = info->tty->termios->c_cflag;

  switch (cflag & CSIZE) {
  case CS5: info->cflags |= DZ_CS5; break;
  case CS6: info->cflags |= DZ_CS6; break;
  case CS7: info->cflags |= DZ_CS7; break;
  case CS8: 
  default:  info->cflags |= DZ_CS8;
  }

  if (cflag & CSTOPB) info->cflags |= DZ_CSTOPB;
  if (cflag & PARENB) info->cflags |= DZ_PARENB;
  if (cflag & PARODD) info->cflags |= DZ_PARODD;
  
  baud = tty_get_baud_rate (info->tty);
  switch (baud) {
  case 50  :  info->cflags |= DZ_B50;   break;
  case 75  :  info->cflags |= DZ_B75;   break;
  case 110 :  info->cflags |= DZ_B110;  break;
  case 134 :  info->cflags |= DZ_B134;  break; 
  case 150 :  info->cflags |= DZ_B150;  break;
  case 300 :  info->cflags |= DZ_B300;  break; 
  case 600 :  info->cflags |= DZ_B600;  break;
  case 1200:  info->cflags |= DZ_B1200; break; 
  case 1800:  info->cflags |= DZ_B1800; break;
  case 2000:  info->cflags |= DZ_B2000; break;
  case 2400:  info->cflags |= DZ_B2400; break;
  case 3600:  info->cflags |= DZ_B3600; break; 
  case 4800:  info->cflags |= DZ_B4800; break;
  case 7200:  info->cflags |= DZ_B7200; break; 
  case 9600: 
  default  :  info->cflags |= DZ_B9600; 
  }

  info->cflags |= DZ_RXENAB;
  dz_out (info, DZ_LPR, info->cflags);

  /* setup accept flag */
  info->read_status_mask = DZ_OERR;
  if (I_INPCK(info->tty))
   info->read_status_mask |= (DZ_FERR | DZ_PERR); 
  
  /* characters to ignore */
  info->ignore_status_mask = 0;
  if (I_IGNPAR(info->tty))
    info->ignore_status_mask |= (DZ_FERR | DZ_PERR);

  restore_flags (flags);
}

/* 
 * -------------------------------------------------------------------
 * dz_flush_char ()
 *
 * Flush the buffer.
 * ------------------------------------------------------------------- 
 */
static void dz_flush_chars (struct tty_struct *tty)
{
  struct dz_serial *info = (struct dz_serial *)tty->driver_data;
  unsigned long flags;

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

 save_flags (flags);
 cli ();  

 dz_start (info->tty);

 restore_flags (flags);
}


/* 
 * -------------------------------------------------------------------
 * dz_write ()
 *
 * main output routine.
 * ------------------------------------------------------------------- 
 */
static int dz_write (struct tty_struct *tty, int from_user, const unsigned char *buf, int count)
{
  struct dz_serial *info = (struct dz_serial *)tty->driver_data;
  unsigned long flags;
  int c, ret = 0;

  if (!tty ) return ret;
  if (!info->xmit_buf) return ret;
  if (!tmp_buf) tmp_buf = tmp_buffer;



  if (from_user) {

    down (&tmp_buf_sem);
    while (1) {
      c = MIN(count, MIN(DZ_XMIT_SIZE - info->xmit_cnt - 1, DZ_XMIT_SIZE - info->xmit_head));
      if (c <= 0) break;

      c -= copy_from_user (tmp_buf, buf, c);
      if (!c) {
        if (!ret) ret = -EFAULT;
        break;
      }

      save_flags (flags);
      cli ();

      c = MIN(c, MIN(DZ_XMIT_SIZE - info->xmit_cnt - 1, DZ_XMIT_SIZE - info->xmit_head));
      memcpy(info->xmit_buf + info->xmit_head, tmp_buf, c);
      info->xmit_head = ((info->xmit_head + c) & (DZ_XMIT_SIZE-1));
      info->xmit_cnt += c;

      restore_flags(flags);

      buf += c;
      count -= c;
      ret += c;
    }
    
    up (&tmp_buf_sem);
  } else {


    while (1) {
      save_flags (flags);
      cli ();     

      c = MIN(count, MIN(DZ_XMIT_SIZE - info->xmit_cnt - 1, DZ_XMIT_SIZE - info->xmit_head));
      if (c <= 0) {
        restore_flags (flags);
        break;
      }
      memcpy (info->xmit_buf + info->xmit_head, buf, c);
      info->xmit_head = ((info->xmit_head + c) & (DZ_XMIT_SIZE-1));
      info->xmit_cnt += c;

      restore_flags (flags);

      buf += c;
      count -= c;
      ret += c;
    }
  }


  if (info->xmit_cnt)
    {
      if (!tty->stopped) 
	{
	  if (!tty->hw_stopped)
	    {
	      dz_start (info->tty);
	    }
	}
    }
  return ret;
}

/* 
 * -------------------------------------------------------------------
 * dz_write_room ()
 *
 * compute the amount of space available for writing.
 * ------------------------------------------------------------------- 
 */
static int dz_write_room (struct tty_struct *tty)
{
  struct dz_serial *info = (struct dz_serial *)tty->driver_data;
  int ret;
                                
  ret = DZ_XMIT_SIZE - info->xmit_cnt - 1;
  if (ret < 0) ret = 0;
  return ret;
}

/* 
 * -------------------------------------------------------------------
 * dz_chars_in_buffer ()
 *
 * compute the amount of char left to be transmitted
 * ------------------------------------------------------------------- 
 */
static int dz_chars_in_buffer (struct tty_struct *tty)
{
  struct dz_serial *info = (struct dz_serial *)tty->driver_data;
  
  return info->xmit_cnt;
}

/* 
 * -------------------------------------------------------------------
 * dz_flush_buffer ()
 *
 * Empty the output buffer
 * ------------------------------------------------------------------- 
 */
static void dz_flush_buffer (struct tty_struct *tty)
{
  struct dz_serial *info = (struct dz_serial *)tty->driver_data;
                                
  cli ();
  info->xmit_cnt = info->xmit_head = info->xmit_tail = 0;
  sti ();

  wake_up_interruptible (&tty->write_wait);

  if ((tty->flags & (1 << TTY_DO_WRITE_WAKEUP)) && tty->ldisc.write_wakeup)
    (tty->ldisc.write_wakeup)(tty);
}

/*
 * ------------------------------------------------------------
 * dz_throttle () and dz_unthrottle ()
 * 
 * This routine is called by the upper-layer tty layer to signal that
 * incoming characters should be throttled (or not).
 * ------------------------------------------------------------
 */
static void dz_throttle (struct tty_struct *tty)
{
  struct dz_serial *info = (struct dz_serial *)tty->driver_data;  

  if (I_IXOFF(tty))
    info->x_char = STOP_CHAR(tty);
}

static void dz_unthrottle (struct tty_struct *tty)
{
  struct dz_serial *info = (struct dz_serial *)tty->driver_data;  

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

static void dz_send_xchar (struct tty_struct *tty, char ch)
{
  struct dz_serial *info = (struct dz_serial *)tty->driver_data;

  info->x_char = ch;

  if (ch) dz_start (info->tty);
}

/*
 * ------------------------------------------------------------
 * rs_ioctl () and friends
 * ------------------------------------------------------------
 */
static int get_serial_info (struct dz_serial *info, struct serial_struct *retinfo)
{
  struct serial_struct tmp;
  
  if (!retinfo)
    return -EFAULT;

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

  tmp.type = info->type;
  tmp.line = info->line;
  tmp.port = info->port;
  tmp.irq = SERIAL;
  tmp.flags = info->flags;
  tmp.baud_base = info->baud_base;
  tmp.close_delay = info->close_delay;
  tmp.closing_wait = info->closing_wait;
  
  return copy_to_user (retinfo, &tmp, sizeof(*retinfo));
}

static int set_serial_info (struct dz_serial *info, struct serial_struct *new_info)
{
  struct serial_struct new_serial;
  struct dz_serial old_info;
  int retval = 0;

  if (!new_info)
    return -EFAULT;

  copy_from_user (&new_serial, new_info, sizeof(new_serial));
  old_info = *info;

  if (!suser())
    return -EPERM;

  if (info->count > 1)
    return -EBUSY;

  /*
   * OK, past this point, all the error checking has been done.
   * At this point, we start making changes.....
   */
  
  info->baud_base = new_serial.baud_base;
  info->type = new_serial.type;
  info->close_delay = new_serial.close_delay;
  info->closing_wait = new_serial.closing_wait;

  retval = startup (info);
  return retval;
}

/*
 * get_lsr_info - get line status register info
 *
 * Purpose: Let user call ioctl() to get info when the UART physically
 *          is emptied.  On bus types like RS485, the transmitter must
 *          release the bus after transmitting. This must be done when
 *          the transmit shift register is empty, not be done when the
 *          transmit holding register is empty.  This functionality
 *          allows an RS485 driver to be written in user space. 
 */
static int get_lsr_info (struct dz_serial *info, unsigned int *value)
{
  unsigned short status = dz_in (info, DZ_LPR);

  return put_user (status, value);
}

/*
 * This routine sends a break character out the serial port.
 */
static void send_break (struct dz_serial *info, int duration)
{
  unsigned long flags;
  unsigned short tmp, mask;

  if (!info->port)
    return;

  mask = 1 << info->line;
  tmp = dz_in (info, DZ_TCR);
  tmp |= mask;

  current->state = TASK_INTERRUPTIBLE;

  save_flags (flags);
  cli();
  
  dz_out (info, DZ_TCR, tmp);
  
  schedule_timeout(duration);
  
  tmp &= ~mask;
  dz_out (info, DZ_TCR, tmp);
  
  restore_flags (flags);
}

static int dz_ioctl (struct tty_struct *tty, struct file *file, unsigned int cmd, unsigned long arg)
{
  int error;
  struct dz_serial * info = (struct dz_serial *)tty->driver_data;
  int retval;

  if ((cmd != TIOCGSERIAL) && (cmd != TIOCSSERIAL) &&
      (cmd != TIOCSERCONFIG) && (cmd != TIOCSERGWILD)  &&
      (cmd != TIOCSERSWILD) && (cmd != TIOCSERGSTRUCT)) {
    if (tty->flags & (1 << TTY_IO_ERROR))
      return -EIO;
  }

  switch (cmd) {
  case TCSBRK:    /* SVID version: non-zero arg --> no break */
    retval = tty_check_change (tty);
    if (retval)
      return retval;
    tty_wait_until_sent (tty, 0);
    if (!arg)
      send_break (info, HZ/4); /* 1/4 second */
    return 0;

  case TCSBRKP:   /* support for POSIX tcsendbreak() */
    retval = tty_check_change (tty);
    if (retval)
      return retval;
    tty_wait_until_sent (tty, 0);
    send_break (info, arg ? arg*(HZ/10) : HZ/4);
    return 0;

  case TIOCGSOFTCAR:
    error = verify_area (VERIFY_WRITE, (void *)arg, sizeof(long));
    if (error)
      return error;
    put_user (C_CLOCAL(tty) ? 1 : 0, (unsigned long *)arg);
    return 0;

  case TIOCSSOFTCAR:
    error = get_user (arg, (unsigned long *)arg);
    if (error)
      return error;
    tty->termios->c_cflag = ((tty->termios->c_cflag & ~CLOCAL) | (arg ? CLOCAL : 0));
    return 0;

  case TIOCGSERIAL:
    error = verify_area (VERIFY_WRITE, (void *)arg, sizeof(struct serial_struct));
    if (error)
      return error;
    return get_serial_info (info, (struct serial_struct *)arg);

  case TIOCSSERIAL:
    return set_serial_info (info, (struct serial_struct *) arg);

  case TIOCSERGETLSR: /* Get line status register */
    error = verify_area (VERIFY_WRITE, (void *)arg, sizeof(unsigned int));
    if (error)
      return error;
    else
      return get_lsr_info (info, (unsigned int *)arg);

  case TIOCSERGSTRUCT:
    error = verify_area (VERIFY_WRITE, (void *)arg, sizeof(struct dz_serial));
    if (error)
      return error;
    copy_to_user((struct dz_serial *)arg, info, sizeof(struct dz_serial));
    return 0;
    
  default:
    return -ENOIOCTLCMD;
  }

  return 0;
}

static void dz_set_termios (struct tty_struct *tty,
			    struct termios *old_termios)
{
  struct dz_serial *info = (struct dz_serial *)tty->driver_data;

  if (tty->termios->c_cflag == old_termios->c_cflag)
    return;

  change_speed (info);

  if ((old_termios->c_cflag & CRTSCTS) &&
      !(tty->termios->c_cflag & CRTSCTS)) {
    tty->hw_stopped = 0;
    dz_start (tty);
  }
}

/*
 * ------------------------------------------------------------
 * dz_close()
 * 
 * This routine is called when the serial port gets closed.  First, we
 * wait for the last remaining data to be sent.  Then, we turn off
 * the transmit enable and receive enable flags.
 * ------------------------------------------------------------
 */
static void dz_close (struct tty_struct *tty, struct file *filp)
{
  struct dz_serial * info = (struct dz_serial *)tty->driver_data;
  unsigned long flags;

  if (!info) return;
        
  save_flags (flags); 
  cli();
        
  if (tty_hung_up_p (filp)) {
    restore_flags (flags);
    return;
  }

  if ((tty->count == 1) && (info->count != 1)) {
    /*
     * Uh, oh.  tty->count is 1, which means that the tty
     * structure will be freed.  Info->count should always
     * be one in these conditions.  If it's greater than
     * one, we've got real problems, since it means the
     * serial port won't be shutdown.
     */
    printk("dz_close: bad serial port count; tty->count is 1, "
                       "info->count is %d\n", info->count);
                info->count = 1;
  }