serial_core.c

宋宝华的《Linux设备驱动开发详解》第一版的源代码

			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;

	DPRINTK("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;

	DPRINTK("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());
	DPRINTK("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;

	mutex_lock(&port_mutex);
	state = drv->state + line;
	if (mutex_lock_interruptible(&state->mutex)) {
		state = ERR_PTR(-ERESTARTSYS);
		goto out;
	}

	state->count++;
	if (!state->port) {
		state->count--;
		mutex_unlock(&state->mutex);
		state = ERR_PTR(-ENXIO);
		goto out;
	}

	if (!state->info) {
		state->info = kmalloc(sizeof(struct uart_info), GFP_KERNEL);
		if (state->info) {
			memset(state->info, 0, sizeof(struct uart_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 {
			state->count--;
			mutex_unlock(&state->mutex);
			state = ERR_PTR(-ENOMEM);
		}
	}

 out:
	mutex_unlock(&port_mutex);
	return state;
}

/*
 * 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());
	DPRINTK("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;
	struct uart_port *port = state->port;
	char stat_buf[32];
	unsigned int status;
	int ret;

	if (!port)
		return 0;

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

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

	if(capable(CAP_SYS_ADMIN))
	{
		spin_lock_irq(&port->lock);
		status = port->ops->get_mctrl(port);
		spin_unlock_irq(&port->lock);

		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
/*
 *	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 &&