Function vesa_GetModeInfo

sys/msdos/vidvesa.c:201–255

Retrieve the mode info block */

/* Retrieve the mode info block */
static boolean
vesa_GetModeInfo(unsigned mode, struct ModeInfoBlock *info)
{
    int mode_info_sel = -1; /* custodial */
    int mode_info_seg;
    __dpmi_regs regs;

    mode_info_seg = __dpmi_allocate_dos_memory(
            (sizeof(*info) + 15) / 16,
            &mode_info_sel);
    if (mode_info_seg < 0) goto error;

    memset(info, 0, sizeof(*info));
    dosmemput(info, sizeof(*info), mode_info_seg * 16L);

    memset(&regs, 0, sizeof(regs));
    regs.x.ax = 0x4F01;
    regs.x.cx = mode;
    regs.x.di = 0;
    regs.x.es = mode_info_seg;
    (void) __dpmi_int(VIDEO_BIOS, &regs);

    if (regs.x.ax != 0x004F) goto error;
    dosmemget(mode_info_seg * 16L, sizeof(*info), info);
    if (!(info->ModeAttributes & 0x0001)) goto error;

    if (!(info->ModeAttributes & 0x0002)) {
        /* Older VESA BIOS that did not return certain mode properties, but
           that has fixed mode numbers; search the table to find the right
           mode properties */

        unsigned i;

        for (i = 0; i < SIZE(old_mode_table); ++i) {
            if (mode == old_mode_table[i].mode) {
                break;
            }
        }
        if (i >= SIZE(old_mode_table)) goto error;

        info->XResolution = old_mode_table[i].XResolution;
        info->YResolution = old_mode_table[i].YResolution;
        info->NumberOfPlanes = 1;
        info->BitsPerPixel = old_mode_table[i].BitsPerPixel;
        info->NumberOfBanks = 1;
        info->MemoryModel = old_mode_table[i].MemoryModel;
    }

    __dpmi_free_dos_memory(mode_info_sel);
    return TRUE;

error:
    if (mode_info_sel != -1) __dpmi_free_dos_memory(mode_info_sel);
    return FALSE;
}

static unsigned
vesa_map_frame_buffer(unsigned phys_addr, unsigned size)