serial.c

linux内核

/*
 *  linux/kernel/serial.c
 *
 *  (C) 1991  Linus Torvalds
 */

/*
 *	serial.c
 *
 * This module implements the rs232 io functions
 *	void rs_write(struct tty_struct * queue);
 *	void rs_init(void);
 * and all interrupts pertaining to serial IO.
 */

#include <linux/tty.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <asm/system.h>
#include <asm/io.h>

#define WAKEUP_CHARS (TTY_BUF_SIZE/4)

extern void rs1_interrupt(void);
extern void rs2_interrupt(void);

static void com1_timer(void)
{
	copy_to_cooked(tty_table+64);
}

static void com2_timer(void)
{
	copy_to_cooked(tty_table+65);
}

static inline void do_rs_write(unsigned int port)
{
	char c;

#define TTY (tty_table[64+port].write_q)
#define TIMER (SER1_TIMEOUT+port)
	cli();
	if (!EMPTY(TTY)) {
		outb_p(inb_p(TTY->data+1)|0x02,TTY->data+1);
		if (inb(TTY->data+5) & 0x20) {
			GETCH(TTY,c);
			outb(c,TTY->data);
		}
		timer_table[TIMER].expires = jiffies + 50;
		timer_active |= 1 << TIMER;
	} else
		timer_active &= ~(1 << TIMER);
	sti();
#undef TIMER
#undef TTY
}

static void com1_timeout(void)
{
	do_rs_write(0);
}

static void com2_timeout(void)
{
	do_rs_write(1);
}

static void init(int port)
{
	outb_p(0x80,port+3);	/* set DLAB of line control reg */
	outb_p(0x30,port);	/* LS of divisor (48 -> 2400 bps */
	outb_p(0x00,port+1);	/* MS of divisor */
	outb_p(0x03,port+3);	/* reset DLAB */
	outb_p(0x0b,port+4);	/* set DTR,RTS, OUT_2 */
	outb_p(0x0d,port+1);	/* enable all intrs but writes */
	(void)inb(port);	/* read data port to reset things (?) */
}

void rs_init(void)
{
/* SERx_TIMER timers are used for receiving: timeout is always 0 (immediate) */
	timer_table[SER1_TIMER].fn = com1_timer;
	timer_table[SER1_TIMER].expires = 0;
	timer_table[SER2_TIMER].fn = com2_timer;
	timer_table[SER2_TIMER].expires = 0;
/* SERx_TIMEOUT timers are used for writing: prevent serial lockups */
	timer_table[SER1_TIMEOUT].fn = com1_timeout;
	timer_table[SER1_TIMEOUT].expires = 0;
	timer_table[SER2_TIMEOUT].fn = com2_timeout;
	timer_table[SER2_TIMEOUT].expires = 0;
	set_intr_gate(0x24,rs1_interrupt);
	set_intr_gate(0x23,rs2_interrupt);
	init(tty_table[64].read_q->data);
	init(tty_table[65].read_q->data);
	outb(inb_p(0x21)&0xE7,0x21);
}

/*
 * This routine gets called when tty_write has put something into
 * the write_queue. It must check wheter the queue is empty, and
 * set the interrupt register accordingly
 *
 *	void _rs_write(struct tty_struct * tty);
 */
void rs_write(struct tty_struct * tty)
{
	cli();
	if (!EMPTY(tty->write_q))
		outb_p(inb_p(tty->write_q->data+1)|0x02,tty->write_q->data+1);
	timer_active |= 3 << SER1_TIMEOUT;
	sti();
}