zs.c

讲述linux的初始化过程

		transmit_chars(info);
	}
#endif
	restore_flags(flags);
}

/*
 * This routine is used to handle the "bottom half" processing for the
 * serial driver, known also the "software interrupt" processing.
 * This processing is done at the kernel interrupt level, after the
 * rs_interrupt() has returned, BUT WITH INTERRUPTS TURNED ON.  This
 * is where time-consuming activities which can not be done in the
 * interrupt driver proper are done; the interrupt driver schedules
 * them using rs_sched_event(), and they get done here.
 */
static void do_serial_bh(void)
{
	run_task_queue(&tq_zs_serial);
}

static void do_softint(void *private_)
{
	struct dec_serial	*info = (struct dec_serial *) private_;
	struct tty_struct	*tty;
	
	tty = info->tty;
	if (!tty)
		return;

	if (test_and_clear_bit(RS_EVENT_WRITE_WAKEUP, &info->event)) {
		if ((tty->flags & (1 << TTY_DO_WRITE_WAKEUP)) &&
		    tty->ldisc.write_wakeup)
			(tty->ldisc.write_wakeup)(tty);
		wake_up_interruptible(&tty->write_wait);
	}
}

static int startup(struct dec_serial * info)
{
	unsigned long flags;

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

	if (!info->xmit_buf) {
		info->xmit_buf = (unsigned char *) get_free_page(GFP_KERNEL);
		if (!info->xmit_buf)
			return -ENOMEM;
	}

	save_flags(flags); cli();

#ifdef SERIAL_DEBUG_OPEN
	printk("starting up ttyS%d (irq %d)...", info->line, info->irq);
#endif

	/*
	 * Clear the receive FIFO.
	 */
	ZS_CLEARFIFO(info->zs_channel);
	info->xmit_fifo_size = 1;

	/*
	 * Clear the interrupt registers.
	 */
	write_zsreg(info->zs_channel, 0, ERR_RES);
	write_zsreg(info->zs_channel, 0, RES_H_IUS);

	/*
	 * Turn on RTS and DTR.
	 */
	zs_rtsdtr(info, 1);

	/*
	 * Finally, enable sequencing and interrupts
	 */
	info->zs_channel->curregs[1] = (info->zs_channel->curregs[1] & ~0x18) | (EXT_INT_ENAB | INT_ALL_Rx | TxINT_ENAB);
	info->zs_channel->curregs[3] |= (RxENABLE | Rx8);
	info->zs_channel->curregs[5] |= (TxENAB | Tx8);
	info->zs_channel->curregs[15] |= (DCDIE | CTSIE | TxUIE | BRKIE);
	info->zs_channel->curregs[9] |= (VIS | MIE);
	write_zsreg(info->zs_channel, 1, info->zs_channel->curregs[1]);
	write_zsreg(info->zs_channel, 3, info->zs_channel->curregs[3]);
	write_zsreg(info->zs_channel, 5, info->zs_channel->curregs[5]);
	write_zsreg(info->zs_channel, 15, info->zs_channel->curregs[15]);
	write_zsreg(info->zs_channel, 9, info->zs_channel->curregs[9]);

	/*
	 * And clear the interrupt registers again for luck.
	 */
	write_zsreg(info->zs_channel, 0, ERR_RES);
	write_zsreg(info->zs_channel, 0, RES_H_IUS);

	if (info->tty)
		clear_bit(TTY_IO_ERROR, &info->tty->flags);
	info->xmit_cnt = info->xmit_head = info->xmit_tail = 0;

	/*
	 * Set the speed of the serial port
	 */
	change_speed(info);

	/* Save the current value of RR0 */
	info->read_reg_zero = read_zsreg(info->zs_channel, 0);

	info->flags |= ZILOG_INITIALIZED;
	restore_flags(flags);
	return 0;
}

/*
 * This routine will shutdown a serial port; interrupts are disabled, and
 * DTR is dropped if the hangup on close termio flag is on.
 */
static void shutdown(struct dec_serial * info)
{
	unsigned long	flags;

	if (!(info->flags & ZILOG_INITIALIZED))
		return;

#ifdef SERIAL_DEBUG_OPEN
	printk("Shutting down serial port %d (irq %d)....", info->line,
	       info->irq);
#endif
	
	save_flags(flags); cli(); /* Disable interrupts */
	
	if (info->xmit_buf) {
		free_page((unsigned long) info->xmit_buf);
		info->xmit_buf = 0;
	}

	info->zs_channel->curregs[1] = 0;
	write_zsreg(info->zs_channel, 1, info->zs_channel->curregs[1]);	/* no interrupts */

	info->zs_channel->curregs[3] &= ~RxENABLE;
	write_zsreg(info->zs_channel, 3, info->zs_channel->curregs[3]);

	info->zs_channel->curregs[5] &= ~TxENAB;
	write_zsreg(info->zs_channel, 5, info->zs_channel->curregs[5]);
	if (!info->tty || C_HUPCL(info->tty)) {
		info->zs_chan_a->curregs[5] &= ~(DTR | RTS);
		write_zsreg(info->zs_chan_a, 5, info->zs_chan_a->curregs[5]);
	}

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

	info->flags &= ~ZILOG_INITIALIZED;
	restore_flags(flags);
}

/*
 * This routine is called to set the UART divisor registers to match
 * the specified baud rate for a serial port.
 */
static void change_speed(struct dec_serial *info)
{
	unsigned short port;
	unsigned cflag;
	int	i;
	int	brg;
	unsigned long flags;

	if (!info->tty || !info->tty->termios)
		return;
	cflag = info->tty->termios->c_cflag;
	if (!(port = info->port))
		return;
	i = cflag & CBAUD;

	save_flags(flags); cli();
	info->zs_baud = baud_table[i];
	info->clk_divisor = 16;

	switch (info->zs_baud) {
	default:
		info->zs_channel->curregs[4] = X16CLK;
		brg = BPS_TO_BRG(info->zs_baud, ZS_CLOCK/info->clk_divisor);
		info->zs_channel->curregs[12] = (brg & 255);
		info->zs_channel->curregs[13] = ((brg >> 8) & 255);
	}

	/* byte size and parity */
	info->zs_channel->curregs[3] &= ~RxNBITS_MASK;
	info->zs_channel->curregs[5] &= ~TxNBITS_MASK;
	switch (cflag & CSIZE) {
	case CS5:
		info->zs_channel->curregs[3] |= Rx5;
		info->zs_channel->curregs[5] |= Tx5;
		break;
	case CS6:
		info->zs_channel->curregs[3] |= Rx6;
		info->zs_channel->curregs[5] |= Tx6;
		break;
	case CS7:
		info->zs_channel->curregs[3] |= Rx7;
		info->zs_channel->curregs[5] |= Tx7;
		break;
	case CS8:
	default: /* defaults to 8 bits */
		info->zs_channel->curregs[3] |= Rx8;
		info->zs_channel->curregs[5] |= Tx8;
		break;
	}

	info->zs_channel->curregs[4] &= ~(SB_MASK | PAR_ENA | PAR_EVEN);
	if (cflag & CSTOPB) {
		info->zs_channel->curregs[4] |= SB2;
	} else {
		info->zs_channel->curregs[4] |= SB1;
	}
	if (cflag & PARENB) {
		info->zs_channel->curregs[4] |= PAR_ENA;
	}
	if (!(cflag & PARODD)) {
		info->zs_channel->curregs[4] |= PAR_EVEN;
	}

	if (!(cflag & CLOCAL)) {
		if (!(info->zs_channel->curregs[15] & DCDIE))
			info->read_reg_zero = read_zsreg(info->zs_channel, 0);
		info->zs_channel->curregs[15] |= DCDIE;
	} else
		info->zs_channel->curregs[15] &= ~DCDIE;
	if (cflag & CRTSCTS) {
		info->zs_channel->curregs[15] |= CTSIE;
		if ((read_zsreg(info->zs_channel, 0) & CTS) != 0)
			info->tx_stopped = 1;
	} else {
		info->zs_channel->curregs[15] &= ~CTSIE;
		info->tx_stopped = 0;
	}

	/* Load up the new values */
	load_zsregs(info->zs_channel, info->zs_channel->curregs);

	restore_flags(flags);
}

static void rs_flush_chars(struct tty_struct *tty)
{
	struct dec_serial *info = (struct dec_serial *)tty->driver_data;
	unsigned long flags;

	if (serial_paranoia_check(info, tty->device, "rs_flush_chars"))
		return;

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

	/* Enable transmitter */
	save_flags(flags); cli();
	transmit_chars(info);
	restore_flags(flags);
}

static int rs_write(struct tty_struct * tty, int from_user,
		    const unsigned char *buf, int count)
{
	int	c, total = 0;
	struct dec_serial *info = (struct dec_serial *)tty->driver_data;
	unsigned long flags;

	if (serial_paranoia_check(info, tty->device, "rs_write"))
		return 0;

	if (!tty || !info->xmit_buf)
		return 0;

	save_flags(flags);
	while (1) {
		cli();		
		c = MIN(count, MIN(SERIAL_XMIT_SIZE - info->xmit_cnt - 1,
				   SERIAL_XMIT_SIZE - info->xmit_head));
		if (c <= 0)
			break;

		if (from_user) {
			down(&tmp_buf_sem);
			copy_from_user(tmp_buf, buf, c);
			c = MIN(c, MIN(SERIAL_XMIT_SIZE - info->xmit_cnt - 1,
				       SERIAL_XMIT_SIZE - info->xmit_head));
			memcpy(info->xmit_buf + info->xmit_head, tmp_buf, c);
			up(&tmp_buf_sem);
		} else
			memcpy(info->xmit_buf + info->xmit_head, buf, c);
		info->xmit_head = (info->xmit_head + c) & (SERIAL_XMIT_SIZE-1);
		info->xmit_cnt += c;
		restore_flags(flags);
		buf += c;
		count -= c;
		total += c;
	}

	if (info->xmit_cnt && !tty->stopped && !info->tx_stopped
	    && !info->tx_active)
		transmit_chars(info);
	restore_flags(flags);
	return total;
}

static int rs_write_room(struct tty_struct *tty)
{
	struct dec_serial *info = (struct dec_serial *)tty->driver_data;
	int	ret;
				
	if (serial_paranoia_check(info, tty->device, "rs_write_room"))
		return 0;
	ret = SERIAL_XMIT_SIZE - info->xmit_cnt - 1;
	if (ret < 0)
		ret = 0;
	return ret;
}

static int rs_chars_in_buffer(struct tty_struct *tty)
{
	struct dec_serial *info = (struct dec_serial *)tty->driver_data;
			
	if (serial_paranoia_check(info, tty->device, "rs_chars_in_buffer"))
		return 0;
	return info->xmit_cnt;
}

static void rs_flush_buffer(struct tty_struct *tty)
{
	struct dec_serial *info = (struct dec_serial *)tty->driver_data;
				
	if (serial_paranoia_check(info, tty->device, "rs_flush_buffer"))
		return;
	cli();
	info->xmit_cnt = info->xmit_head = info->xmit_tail = 0;
	sti();
	wake_up_interruptible(&tty->write_wait);
	if ((tty->flags & (1 << TTY_DO_WRITE_WAKEUP)) &&
	    tty->ldisc.write_wakeup)
		(tty->ldisc.write_wakeup)(tty);
}

/*
 * ------------------------------------------------------------
 * rs_throttle()
 * 
 * This routine is called by the upper-layer tty layer to signal that
 * incoming characters should be throttled.
 * ------------------------------------------------------------
 */
static void rs_throttle(struct tty_struct * tty)
{
	struct dec_serial *info = (struct dec_serial *)tty->driver_data;
	unsigned long flags;

#ifdef SERIAL_DEBUG_THROTTLE
	char	buf[64];
	
	printk("throttle %s: %d....\n", _tty_name(tty, buf),
	       tty->ldisc.chars_in_buffer(tty));
#endif

	if (serial_paranoia_check(info, tty->device, "rs_throttle"))
		return;
	
	if (I_IXOFF(tty)) {
		save_flags(flags); cli();
		info->x_char = STOP_CHAR(tty);
		if (!info->tx_active)
			transmit_chars(info);
		restore_flags(flags);
	}

	if (C_CRTSCTS(tty)) {
		/*
		 * Here we want to turn off the RTS line.  On Macintoshes,
		 * we only get the DTR line, which goes to both DTR and
		 * RTS on the modem.  RTS doesn't go out to the serial
		 * port socket.  So you should make sure your modem is
		 * set to ignore DTR if you're using CRTSCTS.
		 */
		save_flags(flags); cli();
		info->zs_chan_a->curregs[5] &= ~(DTR | RTS);
		write_zsreg(info->zs_chan_a, 5, info->zs_chan_a->curregs[5]);
		restore_flags(flags);
	}
}

static void rs_unthrottle(struct tty_struct * tty)
{
	struct dec_serial *info = (struct dec_serial *)tty->driver_data;
	unsigned long flags;

#ifdef SERIAL_DEBUG_THROTTLE
	char	buf[64];
	
	printk("unthrottle %s: %d....\n", _tty_name(tty, buf),
	       tty->ldisc.chars_in_buffer(tty));
#endif

	if (serial_paranoia_check(info, tty->device, "rs_unthrottle"))
		return;
	
	if (I_IXOFF(tty)) {
		save_flags(flags); cli();
		if (info->x_char)
			info->x_char = 0;
		else {
			info->x_char = START_CHAR(tty);
			if (!info->tx_active)
				transmit_chars(info);
		}
		restore_flags(flags);
	}

	if (C_CRTSCTS(tty)) {
		/* Assert RTS and DTR lines */
		save_flags(flags); cli();
		info->zs_chan_a->curregs[5] |= DTR | RTS;
		write_zsreg(info->zs_chan_a, 5, info->zs_chan_a->curregs[5]);
		restore_flags(flags);
	}
}

/*
 * ------------------------------------------------------------
 * rs_ioctl() and friends
 * ------------------------------------------------------------
 */

static int get_serial_info(struct dec_serial * info,
			   struct serial_struct * retinfo)
{
	struct serial_struct tmp;

	if (!retinfo)
		return -EFAULT;
	memset(&tmp, 0, sizeof(tmp));
	tmp.type = info->type;
	tmp.line = info->line;
	tmp.port = info->port;
	tmp.irq = info->irq;
	tmp.flags = info->flags;
	tmp.baud_base = info->baud_base;
	tmp.close_delay = info->close_delay;
	tmp.closing_wait = info->closing_wait;
	tmp.custom_divisor = info->custom_divisor;
	return copy_to_user(retinfo,&tmp,sizeof(*retinfo));
}

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

	if (!new_info)
		return -EFAULT;
	copy_from_user(&new_serial,new_info,sizeof(new_serial));
	old_info = *info;

	if (!suser()) {
		if ((new_serial.baud_base != info->baud_base) ||
		    (new_serial.type != info->type) ||
		    (new_serial.close_delay != info->close_delay) ||
		    ((new_serial.flags & ~ZILOG_USR_MASK) !=
		     (info->flags & ~ZILOG_USR_MASK)))
			return -EPERM;
		info->flags = ((info->flags & ~ZILOG_USR_MASK) |
			       (new_serial.flags & ZILOG_USR_MASK));
		info->custom_divisor = new_serial.custom_divisor;
		goto check_and_exit;
	}

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

	/*
	 * OK, past this point, all the error checking has been done.
	 * At this point, we start making changes.....
	 */

	info->baud_base = new_serial.baud_base;
	info->flags = ((info->flags & ~ZILOG_FLAGS) |
			(new_serial.flags & ZILOG_FLAGS));
	info->type = new_serial.type;
	info->close_delay = new_serial.close_delay;
	info->closing_wait = new_serial.closing_wait;

check_and_exit:
	retval = startup(info);
	return retval;
}

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

	cli();
	status = read_zsreg(info->zs_channel, 0);
	sti();
	put_user(status,value);
	return 0;
}

static int get_modem_info(struct dec_serial *info, unsigned int *value)
{
	unsigned char control, status;
	unsigned int result;

	cli();
	control = info->zs_chan_a->curregs[5];
	status = read_zsreg(info->zs_channel, 0);
	sti();