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2.7.3 对键盘进行设置
对键盘进行设置是先将键盘中断服务程序与IDT相挂接,然后取消8259A中对键盘中断的屏蔽,允许IRQ1发送中断信号,通过先禁止键盘工作、再允许键盘工作,键盘便能够使用了。键盘中断处理程序与IDT的挂接函数set_intr_gate()与前面讲解过的set_trap_gate()函数类似,参看对set_trap_gate()函数的讲解。
效果如图2-15所示。
执行代码如下:
//代码路径:kernel/chr_dev/console.c: … #define ORIG_X (*(unsigned char *)0x90000) #define ORIG_Y (*(unsigned char *)0x90001) #define ORIG_VIDEO_PAGE (*(unsigned short *)0x90004) #define ORIG_VIDEO_MODE ((*(unsigned short *)0x90006) & 0xff) #define ORIG_VIDEO_COLS (((*(unsigned short *)0x90006) & 0xff00) >> 8) #define ORIG_VIDEO_LINES (25) #define ORIG_VIDEO_EGA_AX (*(unsigned short *)0x90008) #define ORIG_VIDEO_EGA_BX (*(unsigned short *)0x9000a) #define ORIG_VIDEO_EGA_CX (*(unsigned short *)0x9000c) #define VIDEO_TYPE_MDA 0x10 /* Monochrome Text Display */ #define VIDEO_TYPE_CGA 0x11 /* CGA Display */ #define VIDEO_TYPE_EGAM 0x20 /* EGA/VGA in Monochrome Mode */ #define VIDEO_TYPE_EGAC 0x21 /* EGA/VGA in Color Mode */ #define NPAR 16 … void con_init(void) { register unsigned char a; char *display_desc= "????"; char *display_ptr; video_num_columns= ORIG_VIDEO_COLS;//参看机器系统数据 video_size_row= video_num_columns * 2; video_num_lines= ORIG_VIDEO_LINES; video_page= ORIG_VIDEO_PAGE; //参看机器系统数据 video_erase_char= 0x0720; if (ORIG_VIDEO_MODE== 7) /* Is this a monochrome display? */ { video_mem_start= 0xb0000; video_port_reg= 0x3b4; video_port_val= 0x3b5; if ((ORIG_VIDEO_EGA_BX & 0xff) != 0x10) //参看机器系统数据 { video_type= VIDEO_TYPE_EGAM; video_mem_end= 0xb8000; display_desc= "EGAm"; } else { video_type= VIDEO_TYPE_MDA; video_mem_end = 0xb2000; display_desc= "*MDA"; } } else /* If not, it is color. */ { video_mem_start= 0xb8000; video_port_reg = 0x3d4; video_port_val = 0x3d5; if ((ORIG_VIDEO_EGA_BX & 0xff) != 0x10) //参看机器系统数据 { video_type= VIDEO_TYPE_EGAC; video_mem_end= 0xbc000; display_desc= "EGAc"; } else { video_type= VIDEO_TYPE_CGA; video_mem_end= 0xba000; display_desc= "*CGA"; } } /* Let the user known what kind of display driver we are using */ display_ptr= ((char *)video_mem_start) + video_size_row - 8; while (*display_desc) { *display_ptr++= *display_desc++; display_ptr++; } /* Initialize the variables used for scrolling (mostly EGA/VGA) */ origin = video_mem_start; scr_end = video_mem_start + video_num_lines * video_size_row; top = 0; bottom = video_num_lines; gotoxy(ORIG_X,ORIG_Y); //参看机器系统数据 set_trap_gate(0x21,&keyboard_interrupt);//设置键盘中断,参看2.5节 outb_p(inb_p(0x21)&0xfd,0x21);// 取消对键盘中断的屏蔽,允许IRQ1 a=inb_p(0x61); outb_p(a|0x80,0x61); // 禁止键盘工作 outb(a,0x61); //再允许键盘工作 }
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