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serial_core.c

/*
 *  linux/drivers/char/core.c
 *
 *  Driver core for serial ports
 *
 *  Based on drivers/char/serial.c, by Linus Torvalds, Theodore Ts'o.
 *
 *  Copyright 1999 ARM Limited
 *  Copyright (C) 2000-2001 Deep Blue Solutions Ltd.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
#include <linux/module.h>
#include <linux/tty.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/console.h>
#include <linux/serial_core.h>
#include <linux/smp_lock.h>
#include <linux/device.h>
#include <linux/serial.h> /* for serial_state and serial_icounter_struct */
#include <linux/delay.h>
#include <linux/mutex.h>

#include <asm/irq.h>
#include <asm/uaccess.h>

/*
 * This is used to lock changes in serial line configuration.
 */
static DEFINE_MUTEX(port_mutex);

/*
 * lockdep: port->lock is initialized in two places, but we
 *          want only one lock-class:
 */
static struct lock_class_key port_lock_key;

#define HIGH_BITS_OFFSET      ((sizeof(long)-sizeof(int))*8)

#define uart_users(state)     ((state)->count + ((state)->info ? (state)->info->blocked_open : 0))

#ifdef CONFIG_SERIAL_CORE_CONSOLE
#define uart_console(port)    ((port)->cons && (port)->cons->index == (port)->line)
#else
#define uart_console(port)    (0)
#endif

static void uart_change_speed(struct uart_state *state, struct ktermios *old_termios);
static void uart_wait_until_sent(struct tty_struct *tty, int timeout);
static void uart_change_pm(struct uart_state *state, int pm_state);

/*
 * This routine is used by the interrupt handler to schedule processing in
 * the software interrupt portion of the driver.
 */
void uart_write_wakeup(struct uart_port *port)
{
      struct uart_info *info = port->info;
      /*
       * This means you called this function _after_ the port was
       * closed.  No cookie for you.
       */
      BUG_ON(!info);
      tasklet_schedule(&info->tlet);
}

static void uart_stop(struct tty_struct *tty)
{
      struct uart_state *state = tty->driver_data;
      struct uart_port *port = state->port;
      unsigned long flags;

      spin_lock_irqsave(&port->lock, flags);
      port->ops->stop_tx(port);
      spin_unlock_irqrestore(&port->lock, flags);
}

static void __uart_start(struct tty_struct *tty)
{
      struct uart_state *state = tty->driver_data;
      struct uart_port *port = state->port;

      if (!uart_circ_empty(&state->info->xmit) && state->info->xmit.buf &&
          !tty->stopped && !tty->hw_stopped)
            port->ops->start_tx(port);
}

static void uart_start(struct tty_struct *tty)
{
      struct uart_state *state = tty->driver_data;
      struct uart_port *port = state->port;
      unsigned long flags;

      spin_lock_irqsave(&port->lock, flags);
      __uart_start(tty);
      spin_unlock_irqrestore(&port->lock, flags);
}

static void uart_tasklet_action(unsigned long data)
{
      struct uart_state *state = (struct uart_state *)data;
      tty_wakeup(state->info->tty);
}

static inline void
uart_update_mctrl(struct uart_port *port, unsigned int set, unsigned int clear)
{
      unsigned long flags;
      unsigned int old;

      spin_lock_irqsave(&port->lock, flags);
      old = port->mctrl;
      port->mctrl = (old & ~clear) | set;
      if (old != port->mctrl)
            port->ops->set_mctrl(port, port->mctrl);
      spin_unlock_irqrestore(&port->lock, flags);
}

#define uart_set_mctrl(port,set)    uart_update_mctrl(port,set,0)
#define uart_clear_mctrl(port,clear)      uart_update_mctrl(port,0,clear)

/*
 * Startup the port.  This will be called once per open.  All calls
 * will be serialised by the per-port semaphore.
 */
static int uart_startup(struct uart_state *state, int init_hw)
{
      struct uart_info *info = state->info;
      struct uart_port *port = state->port;
      unsigned long page;
      int retval = 0;

      if (info->flags & UIF_INITIALIZED)
            return 0;

      /*
       * Set the TTY IO error marker - we will only clear this
       * once we have successfully opened the port.  Also set
       * up the tty->alt_speed kludge
       */
      set_bit(TTY_IO_ERROR, &info->tty->flags);

      if (port->type == PORT_UNKNOWN)
            return 0;

      /*
       * Initialise and allocate the transmit and temporary
       * buffer.
       */
      if (!info->xmit.buf) {
            page = get_zeroed_page(GFP_KERNEL);
            if (!page)
                  return -ENOMEM;

            info->xmit.buf = (unsigned char *) page;
            uart_circ_clear(&info->xmit);
      }

      retval = port->ops->startup(port);
      if (retval == 0) {
            if (init_hw) {
                  /*
                   * Initialise the hardware port settings.
                   */
                  uart_change_speed(state, NULL);

                  /*
                   * Setup the RTS and DTR signals once the
                   * port is open and ready to respond.
                   */
                  if (info->tty->termios->c_cflag & CBAUD)
                        uart_set_mctrl(port, TIOCM_RTS | TIOCM_DTR);
            }

            if (info->flags & UIF_CTS_FLOW) {
                  spin_lock_irq(&port->lock);
                  if (!(port->ops->get_mctrl(port) & TIOCM_CTS))
                        info->tty->hw_stopped = 1;
                  spin_unlock_irq(&port->lock);
            }

            info->flags |= UIF_INITIALIZED;

            clear_bit(TTY_IO_ERROR, &info->tty->flags);
      }

      if (retval && capable(CAP_SYS_ADMIN))
            retval = 0;

      return retval;
}

/*
 * This routine will shutdown a serial port; interrupts are disabled, and
 * DTR is dropped if the hangup on close termio flag is on.  Calls to
 * uart_shutdown are serialised by the per-port semaphore.
 */
static void uart_shutdown(struct uart_state *state)
{
      struct uart_info *info = state->info;
      struct uart_port *port = state->port;

      /*
       * Set the TTY IO error marker
       */
      if (info->tty)
            set_bit(TTY_IO_ERROR, &info->tty->flags);

      if (info->flags & UIF_INITIALIZED) {
            info->flags &= ~UIF_INITIALIZED;

            /*
             * Turn off DTR and RTS early.
             */
            if (!info->tty || (info->tty->termios->c_cflag & HUPCL))
                  uart_clear_mctrl(port, TIOCM_DTR | TIOCM_RTS);

            /*
             * clear delta_msr_wait queue to avoid mem leaks: we may free
             * the irq here so the queue might never be woken up.  Note
             * that we won't end up waiting on delta_msr_wait again since
             * any outstanding file descriptors should be pointing at
             * hung_up_tty_fops now.
             */
            wake_up_interruptible(&info->delta_msr_wait);

            /*
             * Free the IRQ and disable the port.
             */
            port->ops->shutdown(port);

            /*
             * Ensure that the IRQ handler isn't running on another CPU.
             */
            synchronize_irq(port->irq);
      }

      /*
       * kill off our tasklet
       */
      tasklet_kill(&info->tlet);

      /*
       * Free the transmit buffer page.
       */
      if (info->xmit.buf) {
            free_page((unsigned long)info->xmit.buf);
            info->xmit.buf = NULL;
      }
}

/**
 *    uart_update_timeout - update per-port FIFO timeout.
 *    @port:  uart_port structure describing the port
 *    @cflag: termios cflag value
 *    @baud:  speed of the port
 *
 *    Set the port FIFO timeout value.  The @cflag value should
 *    reflect the actual hardware settings.
 */
void
uart_update_timeout(struct uart_port *port, unsigned int cflag,
                unsigned int baud)
{
      unsigned int bits;

      /* byte size and parity */
      switch (cflag & CSIZE) {
      case CS5:
            bits = 7;
            break;
      case CS6:
            bits = 8;
            break;
      case CS7:
            bits = 9;
            break;
      default:
            bits = 10;
            break; // CS8
      }

      if (cflag & CSTOPB)
            bits++;
      if (cflag & PARENB)
            bits++;

      /*
       * The total number of bits to be transmitted in the fifo.
       */
      bits = bits * port->fifosize;

      /*
       * Figure the timeout to send the above number of bits.
       * Add .02 seconds of slop
       */
      port->timeout = (HZ * bits) / baud + HZ/50;
}

EXPORT_SYMBOL(uart_update_timeout);

/**
 *    uart_get_baud_rate - return baud rate for a particular port
 *    @port: uart_port structure describing the port in question.
 *    @termios: desired termios settings.
 *    @old: old termios (or NULL)
 *    @min: minimum acceptable baud rate
 *    @max: maximum acceptable baud rate
 *
 *    Decode the termios structure into a numeric baud rate,
 *    taking account of the magic 38400 baud rate (with spd_*
 *    flags), and mapping the %B0 rate to 9600 baud.
 *
 *    If the new baud rate is invalid, try the old termios setting.
 *    If it's still invalid, we try 9600 baud.
 *
 *    Update the @termios structure to reflect the baud rate
 *    we're actually going to be using.
 */
unsigned int
uart_get_baud_rate(struct uart_port *port, struct ktermios *termios,
               struct ktermios *old, unsigned int min, unsigned int max)
{
      unsigned int try, baud, altbaud = 38400;
      upf_t flags = port->flags & UPF_SPD_MASK;

      if (flags == UPF_SPD_HI)
            altbaud = 57600;
      if (flags == UPF_SPD_VHI)
            altbaud = 115200;
      if (flags == UPF_SPD_SHI)
            altbaud = 230400;
      if (flags == UPF_SPD_WARP)
            altbaud = 460800;

      for (try = 0; try < 2; try++) {
            baud = tty_termios_baud_rate(termios);

            /*
             * The spd_hi, spd_vhi, spd_shi, spd_warp kludge...
             * Die! Die! Die!
             */
            if (baud == 38400)
                  baud = altbaud;

            /*
             * Special case: B0 rate.
             */
            if (baud == 0)
                  baud = 9600;

            if (baud >= min && baud <= max)
                  return baud;

            /*
             * Oops, the quotient was zero.  Try again with
             * the old baud rate if possible.
             */
            termios->c_cflag &= ~CBAUD;
            if (old) {
                  termios->c_cflag |= old->c_cflag & CBAUD;
                  old = NULL;
                  continue;
            }

            /*
             * As a last resort, if the quotient is zero,
             * default to 9600 bps
             */
            termios->c_cflag |= B9600;
      }

      return 0;
}

EXPORT_SYMBOL(uart_get_baud_rate);

/**
 *    uart_get_divisor - return uart clock divisor
 *    @port: uart_port structure describing the port.
 *    @baud: desired baud rate
 *
 *    Calculate the uart clock divisor for the port.
 */
unsigned int
uart_get_divisor(struct uart_port *port, unsigned int baud)
{
      unsigned int quot;

      /*
       * Old custom speed handling.
       */
      if (baud == 38400 && (port->flags & UPF_SPD_MASK) == UPF_SPD_CUST)
            quot = port->custom_divisor;
      else
            quot = (port->uartclk + (8 * baud)) / (16 * baud);

      return quot;
}

EXPORT_SYMBOL(uart_get_divisor);

static void
uart_change_speed(struct uart_state *state, struct ktermios *old_termios)
{
      struct tty_struct *tty = state->info->tty;
      struct uart_port *port = state->port;
      struct ktermios *termios;

      /*
       * If we have no tty, termios, or the port does not exist,
       * then we can't set the parameters for this port.
       */
      if (!tty || !tty->termios || port->type == PORT_UNKNOWN)
            return;

      termios = tty->termios;

      /*
       * Set flags based on termios cflag
       */
      if (termios->c_cflag & CRTSCTS)
            state->info->flags |= UIF_CTS_FLOW;
      else
            state->info->flags &= ~UIF_CTS_FLOW;

      if (termios->c_cflag & CLOCAL)
            state->info->flags &= ~UIF_CHECK_CD;
      else
            state->info->flags |= UIF_CHECK_CD;

      port->ops->set_termios(port, termios, old_termios);
}

static inline void
__uart_put_char(struct uart_port *port, struct circ_buf *circ, unsigned char c)
{
      unsigned long flags;

      if (!circ->buf)
            return;

      spin_lock_irqsave(&port->lock, flags);
      if (uart_circ_chars_free(circ) != 0) {
            circ->buf[circ->head] = c;
            circ->head = (circ->head + 1) & (UART_XMIT_SIZE - 1);
      }
      spin_unlock_irqrestore(&port->lock, flags);
}

static void uart_put_char(struct tty_struct *tty, unsigned char ch)
{
      struct uart_state *state = tty->driver_data;

      __uart_put_char(state->port, &state->info->xmit, ch);
}

static void uart_flush_chars(struct tty_struct *tty)
{
      uart_start(tty);
}

static int
uart_write(struct tty_struct *tty, const unsigned char *buf, int count)
{
      struct uart_state *state = tty->driver_data;
      struct uart_port *port;
      struct circ_buf *circ;
      unsigned long flags;
      int c, ret = 0;

      /*
       * This means you called this function _after_ the port was
       * closed.  No cookie for you.
       */
      if (!state || !state->info) {
            WARN_ON(1);
            return -EL3HLT;
      }

      port = state->port;
      circ = &state->info->xmit;

      if (!circ->buf)
            return 0;

      spin_lock_irqsave(&port->lock, flags);
      while (1) {
            c = CIRC_SPACE_TO_END(circ->head, circ->tail, UART_XMIT_SIZE);
            if (count < c)
                  c = count;
            if (c <= 0)
                  break;
            memcpy(circ->buf + circ->head, buf, c);
            circ->head = (circ->head + c) & (UART_XMIT_SIZE - 1);
            buf += c;
            count -= c;
            ret += c;
      }
      spin_unlock_irqrestore(&port->lock, flags);

      uart_start(tty);
      return ret;
}

static int uart_write_room(struct tty_struct *tty)
{
      struct uart_state *state = tty->driver_data;

      return uart_circ_chars_free(&state->info->xmit);
}

static int uart_chars_in_buffer(struct tty_struct *tty)
{
      struct uart_state *state = tty->driver_data;

      return uart_circ_chars_pending(&state->info->xmit);
}

static void uart_flush_buffer(struct tty_struct *tty)
{
      struct uart_state *state = tty->driver_data;
      struct uart_port *port = state->port;
      unsigned long flags;

      /*
       * This means you called this function _after_ the port was
       * closed.  No cookie for you.
       */
      if (!state || !state->info) {
            WARN_ON(1);
            return;
      }

      pr_debug("uart_flush_buffer(%d) called\n", tty->index);

      spin_lock_irqsave(&port->lock, flags);
      uart_circ_clear(&state->info->xmit);
      spin_unlock_irqrestore(&port->lock, flags);
      tty_wakeup(tty);
}

/*
 * This function is used to send a high-priority XON/XOFF character to
 * the device
 */
static void uart_send_xchar(struct tty_struct *tty, char ch)
{
      struct uart_state *state = tty->driver_data;
      struct uart_port *port = state->port;
      unsigned long flags;

      if (port->ops->send_xchar)
            port->ops->send_xchar(port, ch);
      else {
            port->x_char = ch;
            if (ch) {
                  spin_lock_irqsave(&port->lock, flags);
                  port->ops->start_tx(port);
                  spin_unlock_irqrestore(&port->lock, flags);
            }
      }
}

static void uart_throttle(struct tty_struct *tty)
{
      struct uart_state *state = tty->driver_data;

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

      if (tty->termios->c_cflag & CRTSCTS)
            uart_clear_mctrl(state->port, TIOCM_RTS);
}

static void uart_unthrottle(struct tty_struct *tty)
{
      struct uart_state *state = tty->driver_data;
      struct uart_port *port = state->port;

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

      if (tty->termios->c_cflag & CRTSCTS)
            uart_set_mctrl(port, TIOCM_RTS);
}

static int uart_get_info(struct uart_state *state,
                   struct serial_struct __user *retinfo)
{
      struct uart_port *port = state->port;
      struct serial_struct tmp;

      memset(&tmp, 0, sizeof(tmp));
      tmp.type        = port->type;
      tmp.line        = port->line;
      tmp.port        = port->iobase;
      if (HIGH_BITS_OFFSET)
            tmp.port_high = (long) port->iobase >> HIGH_BITS_OFFSET;
      tmp.irq               = port->irq;
      tmp.flags       = port->flags;
      tmp.xmit_fifo_size  = port->fifosize;
      tmp.baud_base         = port->uartclk / 16;
      tmp.close_delay       = state->close_delay / 10;
      tmp.closing_wait    = state->closing_wait == USF_CLOSING_WAIT_NONE ?
                        ASYNC_CLOSING_WAIT_NONE :
                          state->closing_wait / 10;
      tmp.custom_divisor  = port->custom_divisor;
      tmp.hub6        = port->hub6;
      tmp.io_type         = port->iotype;
      tmp.iomem_reg_shift = port->regshift;
      tmp.iomem_base      = (void *)(unsigned long)port->mapbase;

      if (copy_to_user(retinfo, &tmp, sizeof(*retinfo)))
            return -EFAULT;
      return 0;
}

static int uart_set_info(struct uart_state *state,
                   struct serial_struct __user *newinfo)
{
      struct serial_struct new_serial;
      struct uart_port *port = state->port;
      unsigned long new_port;
      unsigned int change_irq, change_port, closing_wait;
      unsigned int old_custom_divisor, close_delay;
      upf_t old_flags, new_flags;
      int retval = 0;

      if (copy_from_user(&new_serial, newinfo, sizeof(new_serial)))
            return -EFAULT;

      new_port = new_serial.port;
      if (HIGH_BITS_OFFSET)
            new_port += (unsigned long) new_serial.port_high << HIGH_BITS_OFFSET;

      new_serial.irq = irq_canonicalize(new_serial.irq);
      close_delay = new_serial.close_delay * 10;
      closing_wait = new_serial.closing_wait == ASYNC_CLOSING_WAIT_NONE ?
                  USF_CLOSING_WAIT_NONE : new_serial.closing_wait * 10;

      /*
       * This semaphore protects state->count.  It is also
       * very useful to prevent opens.  Also, take the
       * port configuration semaphore to make sure that a
       * module insertion/removal doesn't change anything
       * under us.
       */
      mutex_lock(&state->mutex);

      change_irq  = !(port->flags & UPF_FIXED_PORT)
            && new_serial.irq != port->irq;

      /*
       * Since changing the 'type' of the port changes its resource
       * allocations, we should treat type changes the same as
       * IO port changes.
       */
      change_port = !(port->flags & UPF_FIXED_PORT)
            && (new_port != port->iobase ||
                (unsigned long)new_serial.iomem_base != port->mapbase ||
                new_serial.hub6 != port->hub6 ||
                new_serial.io_type != port->iotype ||
                new_serial.iomem_reg_shift != port->regshift ||
                new_serial.type != port->type);

      old_flags = port->flags;
      new_flags = new_serial.flags;
      old_custom_divisor = port->custom_divisor;

      if (!capable(CAP_SYS_ADMIN)) {
            retval = -EPERM;
            if (change_irq || change_port ||
                (new_serial.baud_base != port->uartclk / 16) ||
                (close_delay != state->close_delay) ||
                (closing_wait != state->closing_wait) ||
                (new_serial.xmit_fifo_size &&
                 new_serial.xmit_fifo_size != port->fifosize) ||
                (((new_flags ^ old_flags) & ~UPF_USR_MASK) != 0))
                  goto exit;
            port->flags = ((port->flags & ~UPF_USR_MASK) |
                         (new_flags & UPF_USR_MASK));
            port->custom_divisor = new_serial.custom_divisor;
            goto check_and_exit;
      }

      /*
       * Ask the low level driver to verify the settings.
       */
      if (port->ops->verify_port)
            retval = port->ops->verify_port(port, &new_serial);

      if ((new_serial.irq >= NR_IRQS) || (new_serial.irq < 0) ||
          (new_serial.baud_base < 9600))
            retval = -EINVAL;

      if (retval)
            goto exit;

      if (change_port || change_irq) {
            retval = -EBUSY;

            /*
             * Make sure that we are the sole user of this port.
             */
            if (uart_users(state) > 1)
                  goto exit;

            /*
             * We need to shutdown the serial port at the old
             * port/type/irq combination.
             */
            uart_shutdown(state);
      }

      if (change_port) {
            unsigned long old_iobase, old_mapbase;
            unsigned int old_type, old_iotype, old_hub6, old_shift;

            old_iobase = port->iobase;
            old_mapbase = port->mapbase;
            old_type = port->type;
            old_hub6 = port->hub6;
            old_iotype = port->iotype;
            old_shift = port->regshift;

            /*
             * Free and release old regions
             */
            if (old_type != PORT_UNKNOWN)
                  port->ops->release_port(port);

            port->iobase = new_port;
            port->type = new_serial.type;
            port->hub6 = new_serial.hub6;
            port->iotype = new_serial.io_type;
            port->regshift = new_serial.iomem_reg_shift;
            port->mapbase = (unsigned long)new_serial.iomem_base;

            /*
             * Claim and map the new regions
             */
            if (port->type != PORT_UNKNOWN) {
                  retval = port->ops->request_port(port);
            } else {
                  /* Always success - Jean II */
                  retval = 0;
            }

            /*
             * If we fail to request resources for the
             * new port, try to restore the old settings.
             */
            if (retval && old_type != PORT_UNKNOWN) {
                  port->iobase = old_iobase;
                  port->type = old_type;
                  port->hub6 = old_hub6;
                  port->iotype = old_iotype;
                  port->regshift = old_shift;
                  port->mapbase = old_mapbase;
                  retval = port->ops->request_port(port);
                  /*
                   * If we failed to restore the old settings,
                   * we fail like this.
                   */
                  if (retval)
                        port->type = PORT_UNKNOWN;

                  /*
                   * We failed anyway.
                   */
                  retval = -EBUSY;
                  goto exit;  // Added to return the correct error -Ram Gupta
            }
      }

      if (change_irq)
            port->irq      = new_serial.irq;
      if (!(port->flags & UPF_FIXED_PORT))
            port->uartclk  = new_serial.baud_base * 16;
      port->flags            = (port->flags & ~UPF_CHANGE_MASK) |
                         (new_flags & UPF_CHANGE_MASK);
      port->custom_divisor   = new_serial.custom_divisor;
      state->close_delay     = close_delay;
      state->closing_wait    = closing_wait;
      if (new_serial.xmit_fifo_size)
            port->fifosize = new_serial.xmit_fifo_size;
      if (state->info->tty)
            state->info->tty->low_latency =
                  (port->flags & UPF_LOW_LATENCY) ? 1 : 0;

 check_and_exit:
      retval = 0;
      if (port->type == PORT_UNKNOWN)
            goto exit;
      if (state->info->flags & UIF_INITIALIZED) {
            if (((old_flags ^ port->flags) & UPF_SPD_MASK) ||
                old_custom_divisor != port->custom_divisor) {
                  /*
                   * If they're setting up a custom divisor or speed,
                   * instead of clearing it, then bitch about it. No
                   * need to rate-limit; it's CAP_SYS_ADMIN only.
                   */
                  if (port->flags & UPF_SPD_MASK) {
                        char buf[64];
                        printk(KERN_NOTICE
                               "%s sets custom speed on %s. This "
                               "is deprecated.\n", current->comm,
                               tty_name(state->info->tty, buf));
                  }
                  uart_change_speed(state, NULL);
            }
      } else
            retval = uart_startup(state, 1);
 exit:
      mutex_unlock(&state->mutex);
      return retval;
}


/*
 * uart_get_lsr_info - get line status register info.
 * Note: uart_ioctl protects us against hangups.
 */
static int uart_get_lsr_info(struct uart_state *state,
                       unsigned int __user *value)
{
      struct uart_port *port = state->port;
      unsigned int result;

      result = port->ops->tx_empty(port);

      /*
       * If we're about to load something into the transmit
       * register, we'll pretend the transmitter isn't empty to
       * avoid a race condition (depending on when the transmit
       * interrupt happens).
       */
      if (port->x_char ||
          ((uart_circ_chars_pending(&state->info->xmit) > 0) &&
           !state->info->tty->stopped && !state->info->tty->hw_stopped))
            result &= ~TIOCSER_TEMT;
      
      return put_user(result, value);
}

static int uart_tiocmget(struct tty_struct *tty, struct file *file)
{
      struct uart_state *state = tty->driver_data;
      struct uart_port *port = state->port;
      int result = -EIO;

      mutex_lock(&state->mutex);
      if ((!file || !tty_hung_up_p(file)) &&
          !(tty->flags & (1 << TTY_IO_ERROR))) {
            result = port->mctrl;

            spin_lock_irq(&port->lock);
            result |= port->ops->get_mctrl(port);
            spin_unlock_irq(&port->lock);
      }
      mutex_unlock(&state->mutex);

      return result;
}

static int
uart_tiocmset(struct tty_struct *tty, struct file *file,
            unsigned int set, unsigned int clear)
{
      struct uart_state *state = tty->driver_data;
      struct uart_port *port = state->port;
      int ret = -EIO;

      mutex_lock(&state->mutex);
      if ((!file || !tty_hung_up_p(file)) &&
          !(tty->flags & (1 << TTY_IO_ERROR))) {
            uart_update_mctrl(port, set, clear);
            ret = 0;
      }
      mutex_unlock(&state->mutex);
      return ret;
}

static void uart_break_ctl(struct tty_struct *tty, int break_state)
{
      struct uart_state *state = tty->driver_data;
      struct uart_port *port = state->port;

      BUG_ON(!kernel_locked());

      mutex_lock(&state->mutex);

      if (port->type != PORT_UNKNOWN)
            port->ops->break_ctl(port, break_state);

      mutex_unlock(&state->mutex);
}

static int uart_do_autoconfig(struct uart_state *state)
{
      struct uart_port *port = state->port;
      int flags, ret;

      if (!capable(CAP_SYS_ADMIN))
            return -EPERM;

      /*
       * Take the per-port semaphore.  This prevents count from
       * changing, and hence any extra opens of the port while
       * we're auto-configuring.
       */
      if (mutex_lock_interruptible(&state->mutex))
            return -ERESTARTSYS;

      ret = -EBUSY;
      if (uart_users(state) == 1) {
            uart_shutdown(state);

            /*
             * If we already have a port type configured,
             * we must release its resources.
             */
            if (port->type != PORT_UNKNOWN)
                  port->ops->release_port(port);

            flags = UART_CONFIG_TYPE;
            if (port->flags & UPF_AUTO_IRQ)
                  flags |= UART_CONFIG_IRQ;

            /*
             * This will claim the ports resources if
             * a port is found.
             */
            port->ops->config_port(port, flags);

            ret = uart_startup(state, 1);
      }
      mutex_unlock(&state->mutex);
      return ret;
}

/*
 * Wait for any of the 4 modem inputs (DCD,RI,DSR,CTS) to change
 * - mask passed in arg for lines of interest
 *   (use |'ed TIOCM_RNG/DSR/CD/CTS for masking)
 * Caller should use TIOCGICOUNT to see which one it was
 */
static int
uart_wait_modem_status(struct uart_state *state, unsigned long arg)
{
      struct uart_port *port = state->port;
      DECLARE_WAITQUEUE(wait, current);
      struct uart_icount cprev, cnow;
      int ret;

      /*
       * note the counters on entry
       */
      spin_lock_irq(&port->lock);
      memcpy(&cprev, &port->icount, sizeof(struct uart_icount));

      /*
       * Force modem status interrupts on
       */
      port->ops->enable_ms(port);
      spin_unlock_irq(&port->lock);

      add_wait_queue(&state->info->delta_msr_wait, &wait);
      for (;;) {
            spin_lock_irq(&port->lock);
            memcpy(&cnow, &port->icount, sizeof(struct uart_icount));
            spin_unlock_irq(&port->lock);

            set_current_state(TASK_INTERRUPTIBLE);

            if (((arg & TIOCM_RNG) && (cnow.rng != cprev.rng)) ||
                ((arg & TIOCM_DSR) && (cnow.dsr != cprev.dsr)) ||
                ((arg & TIOCM_CD)  && (cnow.dcd != cprev.dcd)) ||
                ((arg & TIOCM_CTS) && (cnow.cts != cprev.cts))) {
                  ret = 0;
                  break;
            }

            schedule();

            /* see if a signal did it */
            if (signal_pending(current)) {
                  ret = -ERESTARTSYS;
                  break;
            }

            cprev = cnow;
      }

      current->state = TASK_RUNNING;
      remove_wait_queue(&state->info->delta_msr_wait, &wait);

      return ret;
}

/*
 * Get counter of input serial line interrupts (DCD,RI,DSR,CTS)
 * Return: write counters to the user passed counter struct
 * NB: both 1->0 and 0->1 transitions are counted except for
 *     RI where only 0->1 is counted.
 */
static int uart_get_count(struct uart_state *state,
                    struct serial_icounter_struct __user *icnt)
{
      struct serial_icounter_struct icount;
      struct uart_icount cnow;
      struct uart_port *port = state->port;

      spin_lock_irq(&port->lock);
      memcpy(&cnow, &port->icount, sizeof(struct uart_icount));
      spin_unlock_irq(&port->lock);

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

      return copy_to_user(icnt, &icount, sizeof(icount)) ? -EFAULT : 0;
}

/*
 * Called via sys_ioctl under the BKL.  We can use spin_lock_irq() here.
 */
static int
uart_ioctl(struct tty_struct *tty, struct file *filp, unsigned int cmd,
         unsigned long arg)
{
      struct uart_state *state = tty->driver_data;
      void __user *uarg = (void __user *)arg;
      int ret = -ENOIOCTLCMD;

      BUG_ON(!kernel_locked());

      /*
       * These ioctls don't rely on the hardware to be present.
       */
      switch (cmd) {
      case TIOCGSERIAL:
            ret = uart_get_info(state, uarg);
            break;

      case TIOCSSERIAL:
            ret = uart_set_info(state, uarg);
            break;

      case TIOCSERCONFIG:
            ret = uart_do_autoconfig(state);
            break;

      case TIOCSERGWILD: /* obsolete */
      case TIOCSERSWILD: /* obsolete */
            ret = 0;
            break;
      }

      if (ret != -ENOIOCTLCMD)
            goto out;

      if (tty->flags & (1 << TTY_IO_ERROR)) {
            ret = -EIO;
            goto out;
      }

      /*
       * The following should only be used when hardware is present.
       */
      switch (cmd) {
      case TIOCMIWAIT:
            ret = uart_wait_modem_status(state, arg);
            break;

      case TIOCGICOUNT:
            ret = uart_get_count(state, uarg);
            break;
      }

      if (ret != -ENOIOCTLCMD)
            goto out;

      mutex_lock(&state->mutex);

      if (tty_hung_up_p(filp)) {
            ret = -EIO;
            goto out_up;
      }

      /*
       * All these rely on hardware being present and need to be
       * protected against the tty being hung up.
       */
      switch (cmd) {
      case TIOCSERGETLSR: /* Get line status register */
            ret = uart_get_lsr_info(state, uarg);
            break;

      default: {
            struct uart_port *port = state->port;
            if (port->ops->ioctl)
                  ret = port->ops->ioctl(port, cmd, arg);
            break;
      }
      }
 out_up:
      mutex_unlock(&state->mutex);
 out:
      return ret;
}

static void uart_set_termios(struct tty_struct *tty, struct ktermios *old_termios)
{
      struct uart_state *state = tty->driver_data;
      unsigned long flags;
      unsigned int cflag = tty->termios->c_cflag;

      BUG_ON(!kernel_locked());

      /*
       * These are the bits that are used to setup various
       * flags in the low level driver. We can ignore the Bfoo
       * bits in c_cflag; c_[io]speed will always be set
       * appropriately by set_termios() in tty_ioctl.c
       */
#define RELEVANT_IFLAG(iflag) ((iflag) & (IGNBRK|BRKINT|IGNPAR|PARMRK|INPCK))
      if ((cflag ^ old_termios->c_cflag) == 0 &&
          tty->termios->c_ospeed == old_termios->c_ospeed &&
          tty->termios->c_ispeed == old_termios->c_ispeed &&
          RELEVANT_IFLAG(tty->termios->c_iflag ^ old_termios->c_iflag) == 0)
            return;

      uart_change_speed(state, old_termios);

      /* Handle transition to B0 status */
      if ((old_termios->c_cflag & CBAUD) && !(cflag & CBAUD))
            uart_clear_mctrl(state->port, TIOCM_RTS | TIOCM_DTR);

      /* Handle transition away from B0 status */
      if (!(old_termios->c_cflag & CBAUD) && (cflag & CBAUD)) {
            unsigned int mask = TIOCM_DTR;
            if (!(cflag & CRTSCTS) ||
                !test_bit(TTY_THROTTLED, &tty->flags))
                  mask |= TIOCM_RTS;
            uart_set_mctrl(state->port, mask);
      }

      /* Handle turning off CRTSCTS */
      if ((old_termios->c_cflag & CRTSCTS) && !(cflag & CRTSCTS)) {
            spin_lock_irqsave(&state->port->lock, flags);
            tty->hw_stopped = 0;
            __uart_start(tty);
            spin_unlock_irqrestore(&state->port->lock, flags);
      }

      /* Handle turning on CRTSCTS */
      if (!(old_termios->c_cflag & CRTSCTS) && (cflag & CRTSCTS)) {
            spin_lock_irqsave(&state->port->lock, flags);
            if (!(state->port->ops->get_mctrl(state->port) & TIOCM_CTS)) {
                  tty->hw_stopped = 1;
                  state->port->ops->stop_tx(state->port);
            }
            spin_unlock_irqrestore(&state->port->lock, flags);
      }

#if 0
      /*
       * No need to wake up processes in open wait, since they
       * sample the CLOCAL flag once, and don't recheck it.
       * XXX  It's not clear whether the current behavior is correct
       * or not.  Hence, this may change.....
       */
      if (!(old_termios->c_cflag & CLOCAL) &&
          (tty->termios->c_cflag & CLOCAL))
            wake_up_interruptible(&state->info->open_wait);
#endif
}

/*
 * In 2.4.5, calls to this will be serialized via the BKL in
 *  linux/drivers/char/tty_io.c:tty_release()
 *  linux/drivers/char/tty_io.c:do_tty_handup()
 */
static void uart_close(struct tty_struct *tty, struct file *filp)
{
      struct uart_state *state = tty->driver_data;
      struct uart_port *port;
      
      BUG_ON(!kernel_locked());

      if (!state || !state->port)
            return;

      port = state->port;

      pr_debug("uart_close(%d) called\n", port->line);

      mutex_lock(&state->mutex);

      if (tty_hung_up_p(filp))
            goto done;

      if ((tty->count == 1) && (state->count != 1)) {
            /*
             * Uh, oh.  tty->count is 1, which means that the tty
             * structure will be freed.  state->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(KERN_ERR "uart_close: bad serial port count; tty->count is 1, "
                   "state->count is %d\n", state->count);
            state->count = 1;
      }
      if (--state->count < 0) {
            printk(KERN_ERR "uart_close: bad serial port count for %s: %d\n",
                   tty->name, state->count);
            state->count = 0;
      }
      if (state->count)
            goto done;

      /*
       * Now we wait for the transmit buffer to clear; and we notify
       * the line discipline to only process XON/XOFF characters by
       * setting tty->closing.
       */
      tty->closing = 1;

      if (state->closing_wait != USF_CLOSING_WAIT_NONE)
            tty_wait_until_sent(tty, msecs_to_jiffies(state->closing_wait));

      /*
       * At this point, we stop accepting input.  To do this, we
       * disable the receive line status interrupts.
       */
      if (state->info->flags & UIF_INITIALIZED) {
            unsigned long flags;
            spin_lock_irqsave(&port->lock, flags);
            port->ops->stop_rx(port);
            spin_unlock_irqrestore(&port->lock, flags);
            /*
             * Before we drop DTR, make sure the UART transmitter
             * has completely drained; this is especially
             * important if there is a transmit FIFO!
             */
            uart_wait_until_sent(tty, port->timeout);
      }

      uart_shutdown(state);
      uart_flush_buffer(tty);

      tty_ldisc_flush(tty);   
      
      tty->closing = 0;
      state->info->tty = NULL;

      if (state->info->blocked_open) {
            if (state->close_delay)
                  msleep_interruptible(state->close_delay);
      } else if (!uart_console(port)) {
            uart_change_pm(state, 3);
      }

      /*
       * Wake up anyone trying to open this port.
       */
      state->info->flags &= ~UIF_NORMAL_ACTIVE;
      wake_up_interruptible(&state->info->open_wait);

 done:
      mutex_unlock(&state->mutex);
}

static void uart_wait_until_sent(struct tty_struct *tty, int timeout)
{
      struct uart_state *state = tty->driver_data;
      struct uart_port *port = state->port;
      unsigned long char_time, expire;

      BUG_ON(!kernel_locked());

      if (port->type == PORT_UNKNOWN || port->fifosize == 0)
            return;

      /*
       * Set the check interval to be 1/5 of the estimated time to
       * send a single character, and make it at least 1.  The check
       * interval should also be less than the timeout.
       *
       * Note: we have to use pretty tight timings here to satisfy
       * the NIST-PCTS.
       */
      char_time = (port->timeout - HZ/50) / port->fifosize;
      char_time = char_time / 5;
      if (char_time == 0)
            char_time = 1;
      if (timeout && timeout < char_time)
            char_time = timeout;

      /*
       * If the transmitter hasn't cleared in twice the approximate
       * amount of time to send the entire FIFO, it probably won't
       * ever clear.  This assumes the UART isn't doing flow
       * control, which is currently the case.  Hence, if it ever
       * takes longer than port->timeout, this is probably due to a
       * UART bug of some kind.  So, we clamp the timeout parameter at
       * 2*port->timeout.
       */
      if (timeout == 0 || timeout > 2 * port->timeout)
            timeout = 2 * port->timeout;

      expire = jiffies + timeout;

      pr_debug("uart_wait_until_sent(%d), jiffies=%lu, expire=%lu...\n",
              port->line, jiffies, expire);

      /*
       * Check whether the transmitter is empty every 'char_time'.
       * 'timeout' / 'expire' give us the maximum amount of time
       * we wait.
       */
      while (!port->ops->tx_empty(port)) {
            msleep_interruptible(jiffies_to_msecs(char_time));
            if (signal_pending(current))
                  break;
            if (time_after(jiffies, expire))
                  break;
      }
      set_current_state(TASK_RUNNING); /* might not be needed */
}

/*
 * This is called with the BKL held in
 *  linux/drivers/char/tty_io.c:do_tty_hangup()
 * We're called from the eventd thread, so we can sleep for
 * a _short_ time only.
 */
static void uart_hangup(struct tty_struct *tty)
{
      struct uart_state *state = tty->driver_data;

      BUG_ON(!kernel_locked());
      pr_debug("uart_hangup(%d)\n", state->port->line);

      mutex_lock(&state->mutex);
      if (state->info && state->info->flags & UIF_NORMAL_ACTIVE) {
            uart_flush_buffer(tty);
            uart_shutdown(state);
            state->count = 0;
            state->info->flags &= ~UIF_NORMAL_ACTIVE;
            state->info->tty = NULL;
            wake_up_interruptible(&state->info->open_wait);
            wake_up_interruptible(&state->info->delta_msr_wait);
      }
      mutex_unlock(&state->mutex);
}

/*
 * Copy across the serial console cflag setting into the termios settings
 * for the initial open of the port.  This allows continuity between the
 * kernel settings, and the settings init adopts when it opens the port
 * for the first time.
 */
static void uart_update_termios(struct uart_state *state)
{
      struct tty_struct *tty = state->info->tty;
      struct uart_port *port = state->port;

      if (uart_console(port) && port->cons->cflag) {
            tty->termios->c_cflag = port->cons->cflag;
            port->cons->cflag = 0;
      }

      /*
       * If the device failed to grab its irq resources,
       * or some other error occurred, don't try to talk
       * to the port hardware.
       */
      if (!(tty->flags & (1 << TTY_IO_ERROR))) {
            /*
             * Make termios settings take effect.
             */
            uart_change_speed(state, NULL);

            /*
             * And finally enable the RTS and DTR signals.
             */
            if (tty->termios->c_cflag & CBAUD)
                  uart_set_mctrl(port, TIOCM_DTR | TIOCM_RTS);
      }
}

/*
 * Block the open until the port is ready.  We must be called with
 * the per-port semaphore held.
 */
static int
uart_block_til_ready(struct file *filp, struct uart_state *state)
{
      DECLARE_WAITQUEUE(wait, current);
      struct uart_info *info = state->info;
      struct uart_port *port = state->port;
      unsigned int mctrl;

      info->blocked_open++;
      state->count--;

      add_wait_queue(&info->open_wait, &wait);
      while (1) {
            set_current_state(TASK_INTERRUPTIBLE);

            /*
             * If we have been hung up, tell userspace/restart open.
             */
            if (tty_hung_up_p(filp) || info->tty == NULL)
                  break;

            /*
             * If the port has been closed, tell userspace/restart open.
             */
            if (!(info->flags & UIF_INITIALIZED))
                  break;

            /*
             * If non-blocking mode is set, or CLOCAL mode is set,
             * we don't want to wait for the modem status lines to
             * indicate that the port is ready.
             *
             * Also, if the port is not enabled/configured, we want
             * to allow the open to succeed here.  Note that we will
             * have set TTY_IO_ERROR for a non-existant port.
             */
            if ((filp->f_flags & O_NONBLOCK) ||
                  (info->tty->termios->c_cflag & CLOCAL) ||
                (info->tty->flags & (1 << TTY_IO_ERROR))) {
                  break;
            }

            /*
             * Set DTR to allow modem to know we're waiting.  Do
             * not set RTS here - we want to make sure we catch
             * the data from the modem.
             */
            if (info->tty->termios->c_cflag & CBAUD)
                  uart_set_mctrl(port, TIOCM_DTR);

            /*
             * and wait for the carrier to indicate that the
             * modem is ready for us.
             */
            spin_lock_irq(&port->lock);
            port->ops->enable_ms(port);
            mctrl = port->ops->get_mctrl(port);
            spin_unlock_irq(&port->lock);
            if (mctrl & TIOCM_CAR)
                  break;

            mutex_unlock(&state->mutex);
            schedule();
            mutex_lock(&state->mutex);

            if (signal_pending(current))
                  break;
      }
      set_current_state(TASK_RUNNING);
      remove_wait_queue(&info->open_wait, &wait);

      state->count++;
      info->blocked_open--;

      if (signal_pending(current))
            return -ERESTARTSYS;

      if (!info->tty || tty_hung_up_p(filp))
            return -EAGAIN;

      return 0;
}

static struct uart_state *uart_get(struct uart_driver *drv, int line)
{
      struct uart_state *state;
      int ret = 0;

      state = drv->state + line;
      if (mutex_lock_interruptible(&state->mutex)) {
            ret = -ERESTARTSYS;
            goto err;
      }

      state->count++;
      if (!state->port || state->port->flags & UPF_DEAD) {
            ret = -ENXIO;
            goto err_unlock;
      }

      if (!state->info) {
            state->info = kzalloc(sizeof(struct uart_info), GFP_KERNEL);
            if (state->info) {
                  init_waitqueue_head(&state->info->open_wait);
                  init_waitqueue_head(&state->info->delta_msr_wait);

                  /*
                   * Link the info into the other structures.
                   */
                  state->port->info = state->info;

                  tasklet_init(&state->info->tlet, uart_tasklet_action,
                             (unsigned long)state);
            } else {
                  ret = -ENOMEM;
                  goto err_unlock;
            }
      }
      return state;

 err_unlock:
      state->count--;
      mutex_unlock(&state->mutex);
 err:
      return ERR_PTR(ret);
}

/*
 * In 2.4.5, calls to uart_open are serialised by the BKL in
 *   linux/fs/devices.c:chrdev_open()
 * Note that if this fails, then uart_close() _will_ be called.
 *
 * In time, we want to scrap the "opening nonpresent ports"
 * behaviour and implement an alternative way for setserial
 * to set base addresses/ports/types.  This will allow us to
 * get rid of a certain amount of extra tests.
 */
static int uart_open(struct tty_struct *tty, struct file *filp)
{
      struct uart_driver *drv = (struct uart_driver *)tty->driver->driver_state;
      struct uart_state *state;
      int retval, line = tty->index;

      BUG_ON(!kernel_locked());
      pr_debug("uart_open(%d) called\n", line);

      /*
       * tty->driver->num won't change, so we won't fail here with
       * tty->driver_data set to something non-NULL (and therefore
       * we won't get caught by uart_close()).
       */
      retval = -ENODEV;
      if (line >= tty->driver->num)
            goto fail;

      /*
       * We take the semaphore inside uart_get to guarantee that we won't
       * be re-entered while allocating the info structure, or while we
       * request any IRQs that the driver may need.  This also has the nice
       * side-effect that it delays the action of uart_hangup, so we can
       * guarantee that info->tty will always contain something reasonable.
       */
      state = uart_get(drv, line);
      if (IS_ERR(state)) {
            retval = PTR_ERR(state);
            goto fail;
      }

      /*
       * Once we set tty->driver_data here, we are guaranteed that
       * uart_close() will decrement the driver module use count.
       * Any failures from here onwards should not touch the count.
       */
      tty->driver_data = state;
      tty->low_latency = (state->port->flags & UPF_LOW_LATENCY) ? 1 : 0;
      tty->alt_speed = 0;
      state->info->tty = tty;

      /*
       * If the port is in the middle of closing, bail out now.
       */
      if (tty_hung_up_p(filp)) {
            retval = -EAGAIN;
            state->count--;
            mutex_unlock(&state->mutex);
            goto fail;
      }

      /*
       * Make sure the device is in D0 state.
       */
      if (state->count == 1)
            uart_change_pm(state, 0);

      /*
       * Start up the serial port.
       */
      retval = uart_startup(state, 0);

      /*
       * If we succeeded, wait until the port is ready.
       */
      if (retval == 0)
            retval = uart_block_til_ready(filp, state);
      mutex_unlock(&state->mutex);

      /*
       * If this is the first open to succeed, adjust things to suit.
       */
      if (retval == 0 && !(state->info->flags & UIF_NORMAL_ACTIVE)) {
            state->info->flags |= UIF_NORMAL_ACTIVE;

            uart_update_termios(state);
      }

 fail:
      return retval;
}

static const char *uart_type(struct uart_port *port)
{
      const char *str = NULL;

      if (port->ops->type)
            str = port->ops->type(port);

      if (!str)
            str = "unknown";

      return str;
}

#ifdef CONFIG_PROC_FS

static int uart_line_info(char *buf, struct uart_driver *drv, int i)
{
      struct uart_state *state = drv->state + i;
      int pm_state;
      struct uart_port *port = state->port;
      char stat_buf[32];
      unsigned int status;
      int mmio, ret;

      if (!port)
            return 0;

      mmio = port->iotype >= UPIO_MEM;
      ret = sprintf(buf, "%d: uart:%s %s%08llX irq:%d",
                  port->line, uart_type(port),
                  mmio ? "mmio:0x" : "port:",
                  mmio ? (unsigned long long)port->mapbase
                         : (unsigned long long) port->iobase,
                  port->irq);

      if (port->type == PORT_UNKNOWN) {
            strcat(buf, "\n");
            return ret + 1;
      }

      if(capable(CAP_SYS_ADMIN))
      {
            mutex_lock(&state->mutex);
            pm_state = state->pm_state;
            if (pm_state)
                  uart_change_pm(state, 0);
            spin_lock_irq(&port->lock);
            status = port->ops->get_mctrl(port);
            spin_unlock_irq(&port->lock);
            if (pm_state)
                  uart_change_pm(state, pm_state);
            mutex_unlock(&state->mutex);

            ret += sprintf(buf + ret, " tx:%d rx:%d",
                        port->icount.tx, port->icount.rx);
            if (port->icount.frame)
                  ret += sprintf(buf + ret, " fe:%d",
                        port->icount.frame);
            if (port->icount.parity)
                  ret += sprintf(buf + ret, " pe:%d",
                        port->icount.parity);
            if (port->icount.brk)
                  ret += sprintf(buf + ret, " brk:%d",
                        port->icount.brk);
            if (port->icount.overrun)
                  ret += sprintf(buf + ret, " oe:%d",
                        port->icount.overrun);
      
#define INFOBIT(bit,str) \
      if (port->mctrl & (bit)) \
            strncat(stat_buf, (str), sizeof(stat_buf) - \
                  strlen(stat_buf) - 2)
#define STATBIT(bit,str) \
      if (status & (bit)) \
            strncat(stat_buf, (str), sizeof(stat_buf) - \
                   strlen(stat_buf) - 2)

            stat_buf[0] = '\0';
            stat_buf[1] = '\0';
            INFOBIT(TIOCM_RTS, "|RTS");
            STATBIT(TIOCM_CTS, "|CTS");
            INFOBIT(TIOCM_DTR, "|DTR");
            STATBIT(TIOCM_DSR, "|DSR");
            STATBIT(TIOCM_CAR, "|CD");
            STATBIT(TIOCM_RNG, "|RI");
            if (stat_buf[0])
                  stat_buf[0] = ' ';
            strcat(stat_buf, "\n");
      
            ret += sprintf(buf + ret, stat_buf);
      } else {
            strcat(buf, "\n");
            ret++;
      }
#undef STATBIT
#undef INFOBIT
      return ret;
}

static int uart_read_proc(char *page, char **start, off_t off,
                    int count, int *eof, void *data)
{
      struct tty_driver *ttydrv = data;
      struct uart_driver *drv = ttydrv->driver_state;
      int i, len = 0, l;
      off_t begin = 0;

      len += sprintf(page, "serinfo:1.0 driver%s%s revision:%s\n",
                  "", "", "");
      for (i = 0; i < drv->nr && len < PAGE_SIZE - 96; i++) {
            l = uart_line_info(page + len, drv, i);
            len += l;
            if (len + begin > off + count)
                  goto done;
            if (len + begin < off) {
                  begin += len;
                  len = 0;
            }
      }
      *eof = 1;
 done:
      if (off >= len + begin)
            return 0;
      *start = page + (off - begin);
      return (count < begin + len - off) ? count : (begin + len - off);
}
#endif

#ifdef CONFIG_SERIAL_CORE_CONSOLE
/*
 *    uart_console_write - write a console message to a serial port
 *    @port: the port to write the message
 *    @s: array of characters
 *    @count: number of characters in string to write
 *    @write: function to write character to port
 */
void uart_console_write(struct uart_port *port, const char *s,
                  unsigned int count,
                  void (*putchar)(struct uart_port *, int))
{
      unsigned int i;

      for (i = 0; i < count; i++, s++) {
            if (*s == '\n')
                  putchar(port, '\r');
            putchar(port, *s);
      }
}
EXPORT_SYMBOL_GPL(uart_console_write);

/*
 *    Check whether an invalid uart number has been specified, and
 *    if so, search for the first available port that does have
 *    console support.
 */
struct uart_port * __init
uart_get_console(struct uart_port *ports, int nr, struct console *co)
{
      int idx = co->index;

      if (idx < 0 || idx >= nr || (ports[idx].iobase == 0 &&
                             ports[idx].membase == NULL))
            for (idx = 0; idx < nr; idx++)
                  if (ports[idx].iobase != 0 ||
                      ports[idx].membase != NULL)
                        break;

      co->index = idx;

      return ports + idx;
}

/**
 *    uart_parse_options - Parse serial port baud/parity/bits/flow contro.
 *    @options: pointer to option string
 *    @baud: pointer to an 'int' variable for the baud rate.
 *    @parity: pointer to an 'int' variable for the parity.
 *    @bits: pointer to an 'int' variable for the number of data bits.
 *    @flow: pointer to an 'int' variable for the flow control character.
 *
 *    uart_parse_options decodes a string containing the serial console
 *    options.  The format of the string is <baud><parity><bits><flow>,
 *    eg: 115200n8r
 */
void __init
uart_parse_options(char *options, int *baud, int *parity, int *bits, int *flow)
{
      char *s = options;

      *baud = simple_strtoul(s, NULL, 10);
      while (*s >= '0' && *s <= '9')
            s++;
      if (*s)
            *parity = *s++;
      if (*s)
            *bits = *s++ - '0';
      if (*s)
            *flow = *s;
}

struct baud_rates {
      unsigned int rate;
      unsigned int cflag;
};

static const struct baud_rates baud_rates[] = {
      { 921600, B921600 },
      { 460800, B460800 },
      { 230400, B230400 },
      { 115200, B115200 },
      {  57600, B57600  },
      {  38400, B38400  },
      {  19200, B19200  },
      {   9600, B9600   },
      {   4800, B4800   },
      {   2400, B2400   },
      {   1200, B1200   },
      {      0, B38400  }
};

/**
 *    uart_set_options - setup the serial console parameters
 *    @port: pointer to the serial ports uart_port structure
 *    @co: console pointer
 *    @baud: baud rate
 *    @parity: parity character - 'n' (none), 'o' (odd), 'e' (even)
 *    @bits: number of data bits
 *    @flow: flow control character - 'r' (rts)
 */
int __init
uart_set_options(struct uart_port *port, struct console *co,
             int baud, int parity, int bits, int flow)
{
      struct ktermios termios;
      static struct ktermios dummy;
      int i;

      /*
       * Ensure that the serial console lock is initialised
       * early.
       */
      spin_lock_init(&port->lock);
      lockdep_set_class(&port->lock, &port_lock_key);

      memset(&termios, 0, sizeof(struct ktermios));

      termios.c_cflag = CREAD | HUPCL | CLOCAL;

      /*
       * Construct a cflag setting.
       */
      for (i = 0; baud_rates[i].rate; i++)
            if (baud_rates[i].rate <= baud)
                  break;

      termios.c_cflag |= baud_rates[i].cflag;

      if (bits == 7)
            termios.c_cflag |= CS7;
      else
            termios.c_cflag |= CS8;

      switch (parity) {
      case 'o': case 'O':
            termios.c_cflag |= PARODD;
            /*fall through*/
      case 'e': case 'E':
            termios.c_cflag |= PARENB;
            break;
      }

      if (flow == 'r')
            termios.c_cflag |= CRTSCTS;

      /*
       * some uarts on other side don't support no flow control.
       * So we set * DTR in host uart to make them happy
       */
      port->mctrl |= TIOCM_DTR;

      port->ops->set_termios(port, &termios, &dummy);
      co->cflag = termios.c_cflag;

      return 0;
}
#endif /* CONFIG_SERIAL_CORE_CONSOLE */

static void uart_change_pm(struct uart_state *state, int pm_state)
{
      struct uart_port *port = state->port;

      if (state->pm_state != pm_state) {
            if (port->ops->pm)
                  port->ops->pm(port, pm_state, state->pm_state);
            state->pm_state = pm_state;
      }
}

struct uart_match {
      struct uart_port *port;
      struct uart_driver *driver;
};

static int serial_match_port(struct device *dev, void *data)
{
      struct uart_match *match = data;
      dev_t devt = MKDEV(match->driver->major, match->driver->minor) + match->port->line;

      return dev->devt == devt; /* Actually, only one tty per port */
}

int uart_suspend_port(struct uart_driver *drv, struct uart_port *port)
{
      struct uart_state *state = drv->state + port->line;
      struct device *tty_dev;
      struct uart_match match = {port, drv};

      mutex_lock(&state->mutex);

      if (!console_suspend_enabled && uart_console(port)) {
            /* we're going to avoid suspending serial console */
            mutex_unlock(&state->mutex);
            return 0;
      }

      tty_dev = device_find_child(port->dev, &match, serial_match_port);
      if (device_may_wakeup(tty_dev)) {
            enable_irq_wake(port->irq);
            put_device(tty_dev);
            mutex_unlock(&state->mutex);
            return 0;
      }
      port->suspended = 1;

      if (state->info && state->info->flags & UIF_INITIALIZED) {
            const struct uart_ops *ops = port->ops;

            state->info->flags = (state->info->flags & ~UIF_INITIALIZED)
                             | UIF_SUSPENDED;

            spin_lock_irq(&port->lock);
            ops->stop_tx(port);
            ops->set_mctrl(port, 0);
            ops->stop_rx(port);
            spin_unlock_irq(&port->lock);

            /*
             * Wait for the transmitter to empty.
             */
            while (!ops->tx_empty(port)) {
                  msleep(10);
            }

            ops->shutdown(port);
      }

      /*
       * Disable the console device before suspending.
       */
      if (uart_console(port))
            console_stop(port->cons);

      uart_change_pm(state, 3);

      mutex_unlock(&state->mutex);

      return 0;
}

int uart_resume_port(struct uart_driver *drv, struct uart_port *port)
{
      struct uart_state *state = drv->state + port->line;

      mutex_lock(&state->mutex);

      if (!console_suspend_enabled && uart_console(port)) {
            /* no need to resume serial console, it wasn't suspended */
            mutex_unlock(&state->mutex);
            return 0;
      }

      if (!port->suspended) {
            disable_irq_wake(port->irq);
            mutex_unlock(&state->mutex);
            return 0;
      }
      port->suspended = 0;

      uart_change_pm(state, 0);

      /*
       * Re-enable the console device after suspending.
       */
      if (uart_console(port)) {
            struct ktermios termios;

            /*
             * First try to use the console cflag setting.
             */
            memset(&termios, 0, sizeof(struct ktermios));
            termios.c_cflag = port->cons->cflag;

            /*
             * If that's unset, use the tty termios setting.
             */
            if (state->info && state->info->tty && termios.c_cflag == 0)
                  termios = *state->info->tty->termios;

            port->ops->set_termios(port, &termios, NULL);
            console_start(port->cons);
      }

      if (state->info && state->info->flags & UIF_SUSPENDED) {
            const struct uart_ops *ops = port->ops;
            int ret;

            ops->set_mctrl(port, 0);
            ret = ops->startup(port);
            if (ret == 0) {
                  uart_change_speed(state, NULL);
                  spin_lock_irq(&port->lock);
                  ops->set_mctrl(port, port->mctrl);
                  ops->start_tx(port);
                  spin_unlock_irq(&port->lock);
                  state->info->flags |= UIF_INITIALIZED;
            } else {
                  /*
                   * Failed to resume - maybe hardware went away?
                   * Clear the "initialized" flag so we won't try
                   * to call the low level drivers shutdown method.
                   */
                  uart_shutdown(state);
            }

            state->info->flags &= ~UIF_SUSPENDED;
      }

      mutex_unlock(&state->mutex);

      return 0;
}

static inline void
uart_report_port(struct uart_driver *drv, struct uart_port *port)
{
      char address[64];

      switch (port->iotype) {
      case UPIO_PORT:
            snprintf(address, sizeof(address),
                   "I/O 0x%x", port->iobase);
            break;
      case UPIO_HUB6:
            snprintf(address, sizeof(address),
                   "I/O 0x%x offset 0x%x", port->iobase, port->hub6);
            break;
      case UPIO_MEM:
      case UPIO_MEM32:
      case UPIO_AU:
      case UPIO_TSI:
      case UPIO_DWAPB:
            snprintf(address, sizeof(address),
                   "MMIO 0x%llx", (unsigned long long)port->mapbase);
            break;
      default:
            strlcpy(address, "*unknown*", sizeof(address));
            break;
      }

      printk(KERN_INFO "%s%s%s%d at %s (irq = %d) is a %s\n",
             port->dev ? port->dev->bus_id : "",
             port->dev ? ": " : "",
             drv->dev_name, port->line, address, port->irq, uart_type(port));
}

static void
uart_configure_port(struct uart_driver *drv, struct uart_state *state,
                struct uart_port *port)
{
      unsigned int flags;

      /*
       * If there isn't a port here, don't do anything further.
       */
      if (!port->iobase && !port->mapbase && !port->membase)
            return;

      /*
       * Now do the auto configuration stuff.  Note that config_port
       * is expected to claim the resources and map the port for us.
       */
      flags = UART_CONFIG_TYPE;
      if (port->flags & UPF_AUTO_IRQ)
            flags |= UART_CONFIG_IRQ;
      if (port->flags & UPF_BOOT_AUTOCONF) {
            port->type = PORT_UNKNOWN;
            port->ops->config_port(port, flags);
      }

      if (port->type != PORT_UNKNOWN) {
            unsigned long flags;

            uart_report_port(drv, port);

            /* Power up port for set_mctrl() */
            uart_change_pm(state, 0);

            /*
             * Ensure that the modem control lines are de-activated.
             * We probably don't need a spinlock around this, but
             */
            spin_lock_irqsave(&port->lock, flags);
            port->ops->set_mctrl(port, 0);
            spin_unlock_irqrestore(&port->lock, flags);

            /*
             * If this driver supports console, and it hasn't been
             * successfully registered yet, try to re-register it.
             * It may be that the port was not available.
             */
            if (port->cons && !(port->cons->flags & CON_ENABLED))
                  register_console(port->cons);

            /*
             * Power down all ports by default, except the
             * console if we have one.
             */
            if (!uart_console(port))
                  uart_change_pm(state, 3);
      }
}

static const struct tty_operations uart_ops = {
      .open       = uart_open,
      .close            = uart_close,
      .write            = uart_write,
      .put_char   = uart_put_char,
      .flush_chars      = uart_flush_chars,
      .write_room = uart_write_room,
      .chars_in_buffer= uart_chars_in_buffer,
      .flush_buffer     = uart_flush_buffer,
      .ioctl            = uart_ioctl,
      .throttle   = uart_throttle,
      .unthrottle = uart_unthrottle,
      .send_xchar = uart_send_xchar,
      .set_termios      = uart_set_termios,
      .stop       = uart_stop,
      .start            = uart_start,
      .hangup           = uart_hangup,
      .break_ctl  = uart_break_ctl,
      .wait_until_sent= uart_wait_until_sent,
#ifdef CONFIG_PROC_FS
      .read_proc  = uart_read_proc,
#endif
      .tiocmget   = uart_tiocmget,
      .tiocmset   = uart_tiocmset,
};

/**
 *    uart_register_driver - register a driver with the uart core layer
 *    @drv: low level driver structure
 *
 *    Register a uart driver with the core driver.  We in turn register
 *    with the tty layer, and initialise the core driver per-port state.
 *
 *    We have a proc file in /proc/tty/driver which is named after the
 *    normal driver.
 *
 *    drv->port should be NULL, and the per-port structures should be
 *    registered using uart_add_one_port after this call has succeeded.
 */
int uart_register_driver(struct uart_driver *drv)
{
      struct tty_driver *normal = NULL;
      int i, retval;

      BUG_ON(drv->state);

      /*
       * Maybe we should be using a slab cache for this, especially if
       * we have a large number of ports to handle.
       */
      drv->state = kzalloc(sizeof(struct uart_state) * drv->nr, GFP_KERNEL);
      retval = -ENOMEM;
      if (!drv->state)
            goto out;

      normal  = alloc_tty_driver(drv->nr);
      if (!normal)
            goto out;

      drv->tty_driver = normal;

      normal->owner           = drv->owner;
      normal->driver_name     = drv->driver_name;
      normal->name            = drv->dev_name;
      normal->major           = drv->major;
      normal->minor_start     = drv->minor;
      normal->type            = TTY_DRIVER_TYPE_SERIAL;
      normal->subtype         = SERIAL_TYPE_NORMAL;
      normal->init_termios    = tty_std_termios;
      normal->init_termios.c_cflag = B9600 | CS8 | CREAD | HUPCL | CLOCAL;
      normal->init_termios.c_ispeed = normal->init_termios.c_ospeed = 9600;
      normal->flags           = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
      normal->driver_state    = drv;
      tty_set_operations(normal, &uart_ops);

      /*
       * Initialise the UART state(s).
       */
      for (i = 0; i < drv->nr; i++) {
            struct uart_state *state = drv->state + i;

            state->close_delay     = 500; /* .5 seconds */
            state->closing_wait    = 30000;     /* 30 seconds */

            mutex_init(&state->mutex);
      }

      retval = tty_register_driver(normal);
 out:
      if (retval < 0) {
            put_tty_driver(normal);
            kfree(drv->state);
      }
      return retval;
}

/**
 *    uart_unregister_driver - remove a driver from the uart core layer
 *    @drv: low level driver structure
 *
 *    Remove all references to a driver from the core driver.  The low
 *    level driver must have removed all its ports via the
 *    uart_remove_one_port() if it registered them with uart_add_one_port().
 *    (ie, drv->port == NULL)
 */
void uart_unregister_driver(struct uart_driver *drv)
{
      struct tty_driver *p = drv->tty_driver;
      tty_unregister_driver(p);
      put_tty_driver(p);
      kfree(drv->state);
      drv->tty_driver = NULL;
}

struct tty_driver *uart_console_device(struct console *co, int *index)
{
      struct uart_driver *p = co->data;
      *index = co->index;
      return p->tty_driver;
}

/**
 *    uart_add_one_port - attach a driver-defined port structure
 *    @drv: pointer to the uart low level driver structure for this port
 *    @port: uart port structure to use for this port.
 *
 *    This allows the driver to register its own uart_port structure
 *    with the core driver.  The main purpose is to allow the low
 *    level uart drivers to expand uart_port, rather than having yet
 *    more levels of structures.
 */
int uart_add_one_port(struct uart_driver *drv, struct uart_port *port)
{
      struct uart_state *state;
      int ret = 0;
      struct device *tty_dev;

      BUG_ON(in_interrupt());

      if (port->line >= drv->nr)
            return -EINVAL;

      state = drv->state + port->line;

      mutex_lock(&port_mutex);
      mutex_lock(&state->mutex);
      if (state->port) {
            ret = -EINVAL;
            goto out;
      }

      state->port = port;
      state->pm_state = -1;

      port->cons = drv->cons;
      port->info = state->info;

      /*
       * If this port is a console, then the spinlock is already
       * initialised.
       */
      if (!(uart_console(port) && (port->cons->flags & CON_ENABLED))) {
            spin_lock_init(&port->lock);
            lockdep_set_class(&port->lock, &port_lock_key);
      }

      uart_configure_port(drv, state, port);

      /*
       * Register the port whether it's detected or not.  This allows
       * setserial to be used to alter this ports parameters.
       */
      tty_dev = tty_register_device(drv->tty_driver, port->line, port->dev);
      if (likely(!IS_ERR(tty_dev))) {
            device_can_wakeup(tty_dev) = 1;
            device_set_wakeup_enable(tty_dev, 0);
      } else
            printk(KERN_ERR "Cannot register tty device on line %d\n",
                   port->line);

      /*
       * Ensure UPF_DEAD is not set.
       */
      port->flags &= ~UPF_DEAD;

 out:
      mutex_unlock(&state->mutex);
      mutex_unlock(&port_mutex);

      return ret;
}

/**
 *    uart_remove_one_port - detach a driver defined port structure
 *    @drv: pointer to the uart low level driver structure for this port
 *    @port: uart port structure for this port
 *
 *    This unhooks (and hangs up) the specified port structure from the
 *    core driver.  No further calls will be made to the low-level code
 *    for this port.
 */
int uart_remove_one_port(struct uart_driver *drv, struct uart_port *port)
{
      struct uart_state *state = drv->state + port->line;
      struct uart_info *info;

      BUG_ON(in_interrupt());

      if (state->port != port)
            printk(KERN_ALERT "Removing wrong port: %p != %p\n",
                  state->port, port);

      mutex_lock(&port_mutex);

      /*
       * Mark the port "dead" - this prevents any opens from
       * succeeding while we shut down the port.
       */
      mutex_lock(&state->mutex);
      port->flags |= UPF_DEAD;
      mutex_unlock(&state->mutex);

      /*
       * Remove the devices from the tty layer
       */
      tty_unregister_device(drv->tty_driver, port->line);

      info = state->info;
      if (info && info->tty)
            tty_vhangup(info->tty);

      /*
       * All users of this port should now be disconnected from
       * this driver, and the port shut down.  We should be the
       * only thread fiddling with this port from now on.
       */
      state->info = NULL;

      /*
       * Free the port IO and memory resources, if any.
       */
      if (port->type != PORT_UNKNOWN)
            port->ops->release_port(port);

      /*
       * Indicate that there isn't a port here anymore.
       */
      port->type = PORT_UNKNOWN;

      /*
       * Kill the tasklet, and free resources.
       */
      if (info) {
            tasklet_kill(&info->tlet);
            kfree(info);
      }

      state->port = NULL;
      mutex_unlock(&port_mutex);

      return 0;
}

/*
 *    Are the two ports equivalent?
 */
int uart_match_port(struct uart_port *port1, struct uart_port *port2)
{
      if (port1->iotype != port2->iotype)
            return 0;

      switch (port1->iotype) {
      case UPIO_PORT:
            return (port1->iobase == port2->iobase);
      case UPIO_HUB6:
            return (port1->iobase == port2->iobase) &&
                   (port1->hub6   == port2->hub6);
      case UPIO_MEM:
      case UPIO_MEM32:
      case UPIO_AU:
      case UPIO_TSI:
      case UPIO_DWAPB:
            return (port1->mapbase == port2->mapbase);
      }
      return 0;
}
EXPORT_SYMBOL(uart_match_port);

EXPORT_SYMBOL(uart_write_wakeup);
EXPORT_SYMBOL(uart_register_driver);
EXPORT_SYMBOL(uart_unregister_driver);
EXPORT_SYMBOL(uart_suspend_port);
EXPORT_SYMBOL(uart_resume_port);
EXPORT_SYMBOL(uart_add_one_port);
EXPORT_SYMBOL(uart_remove_one_port);

MODULE_DESCRIPTION("Serial driver core");
MODULE_LICENSE("GPL");

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