vidtype.c

详细介绍了一篇关于pci开发的接口芯片

/*  CXL - Copyright (c) 1987-1989 by Mike Smedley - All Rights Reserved  */
/*  VIDTYPE.C   - determines the type of video display adapter  */

#include <conio.h>
#include <dos.h>
#include "cxlvid.h"

#if     defined(_M_IX86)
#define inportb(a)      inp(a)
#endif

#define TIMEOUT 32767

int vidtype(void)
{
    union _REGS regs;
    int v;

    /* Check for PS/2 compatible video BIOS by calling the get */
    /* video configuration function.  If it exists, the video  */
    /* configuration code will be returned in BL.              */
    regs.h.ah=0x1a;
    regs.h.al=0;
    _int86(0x10,&regs,&regs);
    if(regs.h.al==0x1a) {
        switch(regs.h.bl) {
            case 0:
                v=V_NONE;
                break;
            case 1:
                v=V_MDA;
                break;
            case 4:
                v=V_EGA;
                break;
            case 5:
                v=V_EGAMONO;
                break;
            case 7:
                v=V_VGAMONO;
                break;
            case 8:
                v=V_VGA;
                break;
            case 10:
            case 12:
                v=V_MCGA;
                break;
            case 11:
                v=V_MCGAMONO;
                break;
            default:
                v=V_CGA;
        }
    }
    else {

        /* OK, we know that it's not a PS/2 BIOS, so check for an EGA. */
        /* If an EGA exists, BH will contain non-zero if in mono mode. */
        regs.h.ah=0x12;
        regs.x.bx=0x10;
        _int86(0x10,&regs,&regs);
        if(regs.x.bx!=0x10) {
            regs.h.ah=0x12;
            regs.h.bl=0x10;
            _int86(0x10,&regs,&regs);
            v=regs.h.bh?V_EGAMONO:V_EGA;
        }
        else {

            /* Now we know it's not an EGA.  Get the BIOS equipment */
            /* flag and test for CGA, MDA, or no video adapter.     */
            _int86(0x11,&regs,&regs);
            switch(((regs.h.al&0x30)>>4)) {
                case 1:
                case 2:
                    v=V_CGA;
                    break;
                case 3:
                    v=V_MDA;
                    break;
                default:
                    v=V_NONE;
            }
        }
    }
    return(v);
}