//  [c]
static const char *vgacon_startup(void)
{
	const char *display_desc = NULL;
	u16 saved1, saved2;
	volatile u16 *p;

	if (screen_info.orig_video_isVGA == VIDEO_TYPE_VLFB ||
	    screen_info.orig_video_isVGA == VIDEO_TYPE_EFI) {
	      no_vga:
#ifdef CONFIG_DUMMY_CONSOLE
		conswitchp = &dummy_con;
		return conswitchp->con_startup();
#else
		return NULL;
#endif
	}

	/* boot_params.screen_info reasonably initialized? */
	if ((screen_info.orig_video_lines == 0) ||
	    (screen_info.orig_video_cols  == 0))
		goto no_vga;

	/* VGA16 modes are not handled by VGACON */
	if ((screen_info.orig_video_mode == 0x0D) ||	/* 320x200/4 */
	    (screen_info.orig_video_mode == 0x0E) ||	/* 640x200/4 */
	    (screen_info.orig_video_mode == 0x10) ||	/* 640x350/4 */
	    (screen_info.orig_video_mode == 0x12) ||	/* 640x480/4 */
	    (screen_info.orig_video_mode == 0x6A))	/* 800x600/4 (VESA) */
		goto no_vga;

	vga_video_num_lines = screen_info.orig_video_lines;
	vga_video_num_columns = screen_info.orig_video_cols;
	vgastate.vgabase = NULL;

	if (screen_info.orig_video_mode == 7) {
		/* Monochrome display */
		vga_vram_base = 0xb0000;
		vga_video_port_reg = VGA_CRT_IM;
		vga_video_port_val = VGA_CRT_DM;
		if ((screen_info.orig_video_ega_bx & 0xff) != 0x10) {
			static struct resource ega_console_resource =
			    { .name	= "ega",
			      .flags	= IORESOURCE_IO,
			      .start	= 0x3B0,
			      .end	= 0x3BF };
			vga_video_type = VIDEO_TYPE_EGAM;
			vga_vram_size = 0x8000;
			display_desc = "EGA+";
			request_resource(&ioport_resource,
					 &ega_console_resource);
		} else {
			static struct resource mda1_console_resource =
			    { .name	= "mda",
			      .flags	= IORESOURCE_IO,
			      .start	= 0x3B0,
			      .end	= 0x3BB };
			static struct resource mda2_console_resource =
			    { .name	= "mda",
			      .flags	= IORESOURCE_IO,
			      .start	= 0x3BF,
			      .end	= 0x3BF };
			vga_video_type = VIDEO_TYPE_MDA;
			vga_vram_size = 0x2000;
			display_desc = "*MDA";
			request_resource(&ioport_resource,
					 &mda1_console_resource);
			request_resource(&ioport_resource,
					 &mda2_console_resource);
			vga_video_font_height = 14;
		}
	} else {
		/* If not, it is color. */
		vga_can_do_color = true;
		vga_vram_base = 0xb8000;
		vga_video_port_reg = VGA_CRT_IC;
		vga_video_port_val = VGA_CRT_DC;
		if ((screen_info.orig_video_ega_bx & 0xff) != 0x10) {
			int i;

			vga_vram_size = 0x8000;

			if (!screen_info.orig_video_isVGA) {
				static struct resource ega_console_resource =
				    { .name	= "ega",
				      .flags	= IORESOURCE_IO,
				      .start	= 0x3C0,
				      .end	= 0x3DF };
				vga_video_type = VIDEO_TYPE_EGAC;
				display_desc = "EGA";
				request_resource(&ioport_resource,
						 &ega_console_resource);
			} else {
				static struct resource vga_console_resource =
				    { .name	= "vga+",
				      .flags	= IORESOURCE_IO,
				      .start	= 0x3C0,
				      .end	= 0x3DF };
				vga_video_type = VIDEO_TYPE_VGAC;
				display_desc = "VGA+";
				request_resource(&ioport_resource,
						 &vga_console_resource);

				/*
				 * Normalise the palette registers, to point
				 * the 16 screen colours to the first 16
				 * DAC entries.
				 */

				for (i = 0; i < 16; i++) {
					inb_p(VGA_IS1_RC);
					outb_p(i, VGA_ATT_W);
					outb_p(i, VGA_ATT_W);
				}
				outb_p(0x20, VGA_ATT_W);

				/*
				 * Now set the DAC registers back to their
				 * default values
				 */
				for (i = 0; i < 16; i++) {
					outb_p(color_table[i], VGA_PEL_IW);
					outb_p(default_red[i], VGA_PEL_D);
					outb_p(default_grn[i], VGA_PEL_D);
					outb_p(default_blu[i], VGA_PEL_D);
				}
			}
		} else {
			static struct resource cga_console_resource =
			    { .name	= "cga",
			      .flags	= IORESOURCE_IO,
			      .start	= 0x3D4,
			      .end	= 0x3D5 };
			vga_video_type = VIDEO_TYPE_CGA;
			vga_vram_size = 0x2000;
			display_desc = "*CGA";
			request_resource(&ioport_resource,
					 &cga_console_resource);
			vga_video_font_height = 8;
		}
	}

	vga_vram_base = VGA_MAP_MEM(vga_vram_base, vga_vram_size);
	vga_vram_end = vga_vram_base + vga_vram_size;

	/*
	 *      Find out if there is a graphics card present.
	 *      Are there smarter methods around?
	 */
	p = (volatile u16 *) vga_vram_base;
	saved1 = scr_readw(p);
	saved2 = scr_readw(p + 1);
	scr_writew(0xAA55, p);
	scr_writew(0x55AA, p + 1);
	if (scr_readw(p) != 0xAA55 || scr_readw(p + 1) != 0x55AA) {
		scr_writew(saved1, p);
		scr_writew(saved2, p + 1);
		goto no_vga;
	}
	scr_writew(0x55AA, p);
	scr_writew(0xAA55, p + 1);
	if (scr_readw(p) != 0x55AA || scr_readw(p + 1) != 0xAA55) {
		scr_writew(saved1, p);
		scr_writew(saved2, p + 1);
		goto no_vga;
	}
	scr_writew(saved1, p);
	scr_writew(saved2, p + 1);

	if (vga_video_type == VIDEO_TYPE_EGAC
	    || vga_video_type == VIDEO_TYPE_VGAC
	    || vga_video_type == VIDEO_TYPE_EGAM) {
		vga_hardscroll_enabled = vga_hardscroll_user_enable;
		vga_default_font_height = screen_info.orig_video_points;
		vga_video_font_height = screen_info.orig_video_points;
		/* This may be suboptimal but is a safe bet - go with it */
		vga_scan_lines =
		    vga_video_font_height * vga_video_num_lines;
	}

	vgacon_xres = screen_info.orig_video_cols * VGA_FONTWIDTH;
	vgacon_yres = vga_scan_lines;

	if (!vga_init_done) {
		vgacon_scrollback_startup();
		vga_init_done = true;
	}

	return display_desc;
}