参考《linux内核完全注释》和网上相关文章
/*
* 控制台显示操作
*/
/*
* linux/kernel/console.c
*
* (C) 1991 Linus Torvalds
*/
/*
* console.c
*
* This module implements the console io functions
* 'void con_init(void)'
* 'void con_write(struct tty_queue * queue)'
* Hopefully this will be a rather complete VT102 implementation.
*
* Beeping thanks to John T Kohl.
*/
/**********************
* con_init con_write *
**********************/
/*
* NOTE!!! We sometimes disable and enable interrupts for a short while
* (to put a word in video IO), but this will work even for keyboard
* interrupts. We know interrupts aren't enabled when getting a keyboard
* interrupt, as we use trap-gates. Hopefully all is well.
*/
/*
* Code to check for different video-cards mostly by Galen Hunt,
* <g-hunt@ee.utah.edu>
*/
#include <linux/sched.h>
#include <linux/tty.h> // 定义tty_struct结构，串行通信方面的参数和常量
#include <asm/io.h> // 硬件对应的汇编io指令
#include <asm/system.h>
/*
* These are set up by the setup-routine at boot-time:
*/
#define ORIG_X (*(unsigned char *)0x90000) // 光标列号
#define ORIG_Y (*(unsigned char *)0x90001) // 光标行号
#define ORIG_VIDEO_PAGE (*(unsigned short *)0x90004) // 显示页面
#define ORIG_VIDEO_MODE ((*(unsigned short *)0x90006) & 0xff) // 显示模式
#define ORIG_VIDEO_COLS (((*(unsigned short *)0x90006) & 0xff00) >> 8) // 字符列数
#define ORIG_VIDEO_LINES (25) // 字符行数
#define ORIG_VIDEO_EGA_AX (*(unsigned short *)0x90008) // ？？
#define ORIG_VIDEO_EGA_BX (*(unsigned short *)0x9000a) // 显示内存大小和色彩模式
#define ORIG_VIDEO_EGA_CX (*(unsigned short *)0x9000c) // 显示卡特性参数
#define VIDEO_TYPE_MDA 0x10 /* Monochrome Text Display,单色文本 */
#define VIDEO_TYPE_CGA 0x11
