serial.c

LINUX1.0内核源代码,学习LINUX编程的一定要看。

	}
	info->flags &= ~(ASYNC_NORMAL_ACTIVE|ASYNC_CALLOUT_ACTIVE|
			 ASYNC_CLOSING);
	wake_up_interruptible(&info->close_wait);
}

/*
 * rs_hangup() --- called by tty_hangup() when a hangup is signaled.
 */
void rs_hangup(struct tty_struct *tty)
{
	struct async_struct * info;
	int line;

	line = DEV_TO_SL(tty->line);
	if ((line < 0) || (line >= NR_PORTS))
		return;
	info = rs_table + line;
	
	shutdown(info, 1);
	clear_bit(line, rs_event);
	info->event = 0;
	info->count = 0;
	info->flags &= ~(ASYNC_NORMAL_ACTIVE|ASYNC_CALLOUT_ACTIVE);
	info->tty = 0;
	wake_up_interruptible(&info->open_wait);
}

/*
 * ------------------------------------------------------------
 * rs_open() and friends
 * ------------------------------------------------------------
 */
static int block_til_ready(struct tty_struct *tty, struct file * filp,
			   struct async_struct *info)
{
	struct wait_queue wait = { current, NULL };
	int		retval;
	int		do_clocal = C_CLOCAL(tty);

	/*
	 * If the device is in the middle of being closed, then block
	 * until it's done, and then try again.
	 */
	if (info->flags & ASYNC_CLOSING) {
		interruptible_sleep_on(&info->close_wait);
#ifdef SERIAL_DO_RESTART
		if (info->flags & ASYNC_HUP_NOTIFY)
			return -EAGAIN;
		else
			return -ERESTARTSYS;
#else
		return -EAGAIN;
#endif
	}

	/*
	 * If this is a callout device, then just make sure the normal
	 * device isn't being used.
	 */
	if (MAJOR(filp->f_rdev) == TTYAUX_MAJOR) {
		if (info->flags & ASYNC_NORMAL_ACTIVE)
			return -EBUSY;
		if ((info->flags & ASYNC_CALLOUT_ACTIVE) &&
		    (info->flags & ASYNC_SESSION_LOCKOUT) &&
		    (info->session != current->session))
		    return -EBUSY;
		if ((info->flags & ASYNC_CALLOUT_ACTIVE) &&
		    (info->flags & ASYNC_PGRP_LOCKOUT) &&
		    (info->pgrp != current->pgrp))
		    return -EBUSY;
		info->flags |= ASYNC_CALLOUT_ACTIVE;
		return 0;
	}
	
	/*
	 * If non-blocking mode is set, then make the check up front
	 * and then exit.
	 */
	if (filp->f_flags & O_NONBLOCK) {
		if (info->flags & ASYNC_CALLOUT_ACTIVE)
			return -EBUSY;
		info->flags |= ASYNC_NORMAL_ACTIVE;
		return 0;
	}

	/*
	 * Block waiting for the carrier detect and the line to become
	 * free (i.e., not in use by the callout).  While we are in
	 * this loop, info->count is dropped by one, so that
	 * rs_close() knows when to free things.  We restore it upon
	 * exit, either normal or abnormal.
	 */
	retval = 0;
	add_wait_queue(&info->open_wait, &wait);
#ifdef SERIAL_DEBUG_OPEN
	printk("block_til_ready before block: ttys%d, count = %d\n",
	       info->line, info->count);
#endif
	info->count--;
	info->blocked_open++;
	while (1) {
		cli();
		if (!(info->flags & ASYNC_CALLOUT_ACTIVE))
			serial_out(info, UART_MCR,
				   serial_inp(info, UART_MCR) |
				   (UART_MCR_DTR | UART_MCR_RTS));
		sti();
		current->state = TASK_INTERRUPTIBLE;
		if (tty_hung_up_p(filp) ||
		    !(info->flags & ASYNC_INITIALIZED)) {
#ifdef SERIAL_DO_RESTART
			if (info->flags & ASYNC_HUP_NOTIFY)
				retval = -EAGAIN;
			else
				retval = -ERESTARTSYS;
#else
			retval = -EAGAIN;
#endif
			break;
		}
		if (!(info->flags & ASYNC_CALLOUT_ACTIVE) &&
		    !(info->flags & ASYNC_CLOSING) &&
		    (do_clocal || (serial_in(info, UART_MSR) &
				   UART_MSR_DCD)))
			break;
		if (current->signal & ~current->blocked) {
			retval = -ERESTARTSYS;
			break;
		}
#ifdef SERIAL_DEBUG_OPEN
		printk("block_til_ready blocking: ttys%d, count = %d\n",
		       info->line, info->count);
#endif
		schedule();
	}
	current->state = TASK_RUNNING;
	remove_wait_queue(&info->open_wait, &wait);
	if (!tty_hung_up_p(filp))
		info->count++;
	info->blocked_open--;
#ifdef SERIAL_DEBUG_OPEN
	printk("block_til_ready after blocking: ttys%d, count = %d\n",
	       info->line, info->count);
#endif
	if (retval)
		return retval;
	info->flags |= ASYNC_NORMAL_ACTIVE;
	return 0;
}	

/*
 * This routine is called whenever a serial port is opened.  It
 * enables interrupts for a serial port, linking in its async structure into
 * the IRQ chain.   It also performs the serial-speicific
 * initalization for the tty structure.
 */
int rs_open(struct tty_struct *tty, struct file * filp)
{
	struct async_struct	*info;
	int 			retval, line;

	line = DEV_TO_SL(tty->line);
	if ((line < 0) || (line >= NR_PORTS))
		return -ENODEV;
	info = rs_table + line;
#ifdef SERIAL_DEBUG_OPEN
	printk("rs_open ttys%d, count = %d\n", info->line, info->count);
#endif
	info->count++;
	info->tty = tty;
	
	tty->write = rs_write;
	tty->close = rs_close;
	tty->ioctl = rs_ioctl;
	tty->throttle = rs_throttle;
	tty->set_termios = rs_set_termios;
	tty->stop = rs_stop;
	tty->start = rs_start;
	tty->hangup = rs_hangup;
	if ((info->count == 1) && (info->flags & ASYNC_SPLIT_TERMIOS)) {
		if (MAJOR(filp->f_rdev) == TTY_MAJOR)
			*tty->termios = info->normal_termios;
		else 
			*tty->termios = info->callout_termios;
	}
	/*
	 * Start up serial port
	 */
	retval = startup(info, 1);
	if (retval)
		return retval;

	retval = block_til_ready(tty, filp, info);
	if (retval) {
#ifdef SERIAL_DEBUG_OPEN
		printk("rs_open returning after block_til_ready with %d\n",
		       retval);
#endif
		return retval;
	}

	info->session = current->session;
	info->pgrp = current->pgrp;

#ifdef SERIAL_DEBUG_OPEN
	printk("rs_open ttys%d successful...", info->line);
#endif
	return 0;
}

/*
 * ---------------------------------------------------------------------
 * rs_init() and friends
 *
 * rs_init() is called at boot-time to initialize the serial driver.
 * ---------------------------------------------------------------------
 */

/*
 * This routine prints out the appropriate serial driver version
 * number, and identifies which options were configured into this
 * driver.
 */
static void show_serial_version(void)
{
	printk("Serial driver version 3.99a with");
#ifdef CONFIG_AST_FOURPORT
	printk(" AST_FOURPORT");
#define SERIAL_OPT
#endif
#ifdef CONFIG_ACCENT_ASYNC
	printk(" ACCENT_ASYNC");
#define SERIAL_OPT
#endif
#ifdef CONFIG_HUB6
	printk(" HUB-6");
#define SERIAL_OPT
#endif
#ifdef CONFIG_AUTO_IRQ
	printk (" AUTO_IRQ");
#define SERIAL_OPT
#endif
#ifdef SERIAL_OPT
	printk(" enabled\n");
#else
	printk(" no serial options enabled\n");
#endif
#undef SERIAL_OPT
}

/*
 * This routine is called by do_auto_irq(); it attempts to determine
 * which interrupt a serial port is configured to use.  It is not
 * fool-proof, but it works a large part of the time.
 */
static int get_auto_irq(struct async_struct *info)
{
	unsigned char save_MCR, save_IER, save_ICP=0;
	unsigned short ICP=0, port = info->port;
	unsigned long timeout;
	
	/*
	 * Enable interrupts and see who answers
	 */
	rs_irq_triggered = 0;
	cli();
	save_IER = serial_inp(info, UART_IER);
	save_MCR = serial_inp(info, UART_MCR);
	if (info->flags & ASYNC_FOURPORT)  {
		serial_outp(info, UART_MCR, UART_MCR_DTR | UART_MCR_RTS);
		serial_outp(info, UART_IER, 0x0f);	/* enable all intrs */
		ICP = (port & 0xFE0) | 0x01F;
		save_ICP = inb_p(ICP);
		outb_p(0x80, ICP);
		(void) inb_p(ICP);
	} else {
		serial_outp(info, UART_MCR,
			    UART_MCR_DTR | UART_MCR_RTS | UART_MCR_OUT2);
		serial_outp(info, UART_IER, 0x0f);	/* enable all intrs */
	}
	sti();
	/*
	 * Next, clear the interrupt registers.
	 */
	(void)serial_inp(info, UART_LSR);
	(void)serial_inp(info, UART_RX);
	(void)serial_inp(info, UART_IIR);
	(void)serial_inp(info, UART_MSR);
	
	timeout = jiffies+2;
	while (timeout >= jiffies) {
		if (rs_irq_triggered)
			break;
	}
	/*
	 * Now check to see if we got any business, and clean up.
	 */
	cli();
	serial_outp(info, UART_IER, save_IER);
	serial_outp(info, UART_MCR, save_MCR);
	if (info->flags & ASYNC_FOURPORT)
		outb_p(save_ICP, ICP);
	sti();
	return(rs_irq_triggered);
}

/*
 * Calls get_auto_irq() multiple times, to make sure we don't get
 * faked out by random interrupts
 */
static int do_auto_irq(struct async_struct * info)
{
	unsigned 		port = info->port;
	int 			irq_lines = 0;
	int			irq_try_1 = 0, irq_try_2 = 0;
	int			retries;
	unsigned long flags;

	if (!port)
		return 0;

	/* Turn on interrupts (they may be off) */
	save_flags(flags); sti();

	irq_lines = grab_all_interrupts(rs_wild_int_mask);
	
	for (retries = 0; retries < 5; retries++) {
		if (!irq_try_1)
			irq_try_1 = get_auto_irq(info);
		if (!irq_try_2)
			irq_try_2 = get_auto_irq(info);
		if (irq_try_1 && irq_try_2) {
			if (irq_try_1 == irq_try_2)
				break;
			irq_try_1 = irq_try_2 = 0;
		}
	}
	restore_flags(flags);
	free_all_interrupts(irq_lines);
	return (irq_try_1 == irq_try_2) ? irq_try_1 : 0;
}

/*
 * This routine is called by rs_init() to initialize a specific serial
 * port.  It determines what type of UART ship this serial port is
 * using: 8250, 16450, 16550, 16550A.  The important question is
 * whether or not this UART is a 16550A or not, since this will
 * determine whether or not we can use its FIFO features or not.
 */
static void autoconfig(struct async_struct * info)
{
	unsigned char status1, status2, scratch, scratch2;
	unsigned port = info->port;
	unsigned long flags;

	info->type = PORT_UNKNOWN;
	
	if (!port)
		return;

	save_flags(flags); cli();
	
	/*
	 * Do a simple existence test first; if we fail this, there's
	 * no point trying anything else.
	 */
	scratch = serial_inp(info, UART_IER);
	serial_outp(info, UART_IER, 0);
	scratch2 = serial_inp(info, UART_IER);
	serial_outp(info, UART_IER, scratch);
	if (scratch2) {
		restore_flags(flags);
		return;		/* We failed; there's nothing here */
	}

	/* 
	 * Check to see if a UART is really there.  Certain broken
	 * internal modems based on the Rockwell chipset fail this
	 * test, because they apparently don't implement the loopback
	 * test mode.  So this test is skipped on the COM 1 through
	 * COM 4 ports.  This *should* be safe, since no board
	 * manufactucturer would be stupid enough to design a board
	 * that conflicts with COM 1-4 --- we hope!
	 */
	if (!(info->flags & ASYNC_SKIP_TEST)) {
		scratch = serial_inp(info, UART_MCR);
		serial_outp(info, UART_MCR, UART_MCR_LOOP | scratch);
		scratch2 = serial_inp(info, UART_MSR);
		serial_outp(info, UART_MCR, UART_MCR_LOOP | 0x0A);
		status1 = serial_inp(info, UART_MSR) & 0xF0;
		serial_outp(info, UART_MCR, scratch);
		serial_outp(info, UART_MSR, scratch2);
		if (status1 != 0x90) {
			restore_flags(flags);
			return;
		}
	} 
	
	/*
	 * If the AUTO_IRQ flag is set, try to do the automatic IRQ
	 * detection.
	 */
	if (info->flags & ASYNC_AUTO_IRQ)
		info->irq = do_auto_irq(info);
		
	serial_outp(info, UART_FCR, UART_FCR_ENABLE_FIFO);
	scratch = serial_in(info, UART_IIR) >> 6;
	info->xmit_fifo_size = 1;
	switch (scratch) {
		case 0:
			info->type = PORT_16450;
			break;
		case 1:
			info->type = PORT_UNKNOWN;
			break;
		case 2:
			info->type = PORT_16550;
			break;
		case 3:
			info->type = PORT_16550A;
			info->xmit_fifo_size = 16;
			break;
	}
	if (info->type == PORT_16450) {
		scratch = serial_in(info, UART_SCR);
		serial_outp(info, UART_SCR, 0xa5);
		status1 = serial_in(info, UART_SCR);
		serial_outp(info, UART_SCR, 0x5a);
		status2 = serial_in(info, UART_SCR);
		serial_outp(info, UART_SCR, scratch);

		if ((status1 != 0xa5) || (status2 != 0x5a))
			info->type = PORT_8250;
	}

	/*
	 * Reset the UART.
	 */
	serial_outp(info, UART_MCR, 0x00);
	serial_outp(info, UART_FCR, (UART_FCR_CLEAR_RCVR |
				     UART_FCR_CLEAR_XMIT));
	(void)serial_in(info, UART_RX);
	
	restore_flags(flags);
}

/*
 * The serial driver boot-time initialization code!
 */
long rs_init(long kmem_start)
{
	int i;
	struct async_struct * info;
	
	memset(&rs_event, 0, sizeof(rs_event));
	bh_base[SERIAL_BH].routine = do_softint;
	timer_table[RS_TIMER].fn = rs_timer;
	timer_table[RS_TIMER].expires = 0;
	IRQ_active = 0;
#ifdef CONFIG_AUTO_IRQ
	rs_wild_int_mask = check_wild_interrupts(1);
#endif

	for (i = 0; i < 16; i++) {
		IRQ_ports[i] = 0;
		IRQ_timeout[i] = 0;
	}
	
	show_serial_version();
	for (i = 0, info = rs_table; i < NR_PORTS; i++,info++) {
		info->line = i;
		info->tty = 0;
		info->type = PORT_UNKNOWN;
		info->custom_divisor = 0;
		info->close_delay = 50;
		info->x_char = 0;
		info->event = 0;
		info->count = 0;
		info->blocked_open = 0;
		memset(&info->callout_termios, 0, sizeof(struct termios));
		memset(&info->normal_termios, 0, sizeof(struct termios));
		info->open_wait = 0;
		info->xmit_wait = 0;
		info->close_wait = 0;
		info->next_port = 0;
		info->prev_port = 0;
		if (info->irq == 2)
			info->irq = 9;
		if (!(info->flags & ASYNC_BOOT_AUTOCONF))
			continue;
		autoconfig(info);
		if (info->type == PORT_UNKNOWN)
			continue;
		printk("tty%02d%s at 0x%04x (irq = %d)", info->line, 
		       (info->flags & ASYNC_FOURPORT) ? " FourPort" : "",
		       info->port, info->irq);
		switch (info->type) {
			case PORT_8250:
				printk(" is a 8250\n");
				break;
			case PORT_16450:
				printk(" is a 16450\n");
				break;
			case PORT_16550:
				printk(" is a 16550\n");
				break;
			case PORT_16550A:
				printk(" is a 16550A\n");
				break;
			default:
				printk("\n");
				break;
		}
	}
	return kmem_start;
}