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Linux-0.0.1內核閱讀連載筆記-2013.08.21
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../kernel/Serial.c
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/*
* 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 <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 init(int port)
{
outb_p(0x80,port+3);/* set DLAB of line control reg *///線控製寄存器，將第7位置1是開放除法因子鎖存器地址位
outb_p(0x30,port);/* LS of divisor (48 -> 2400 bps *///將波特率設為2400（低有效位）
outb_p(0x00,port+1);/* MS of divisor *///將波特率的最高有效位保存入該寄存器
outb_p(0x03,port+3);/* reset DLAB *///將DLAB設為0，幀設為8位（通常是8位）
outb_p(0x0b,port+4);/* set DTR,RTS, OUT_2 *///設置數據終端準備好線（DTR）的狀態，設置請求發送線（RTS）的狀態，out_2用於開放中斷請求
outb_p(0x0d,port+1);/* enable all intrs but writes */
(void)inb(port);/* read data port to reset things (?) *///獲取接收緩衝區數據字節
}
void rs_init(void)
{
set_intr_gate(0x24,rs1_interrupt);//串行口端口3F8的中斷好是0x24
set_intr_gate(0x23,rs2_interrupt);//串行口端口2F8的中斷好是0x23
init(tty_table[1].read_q.data);//初始化2個串行端口
init(tty_table[2].read_q.data);
outb(inb_p(0x21)&0xE7,0x21);//控製中斷控製器對中斷請求線0--7的操作
}
/*
* 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(inb_p(tty->write_q.data+1)|0x02,tty->write_q.data+1);//將寄存器的第2位（傳送位）置1，開放傳送中斷
sti();
}
最後更新：2017-04-03 16:49:00