vga_get_crtc
int vga_get_crtc(int, int);
msl = vga_get_crtc(VGA_REG_BASE, VGA_CRTC_MAX_SCAN_LINE) & 0x1f;
s = vga_get_crtc(VGA_REG_BASE, VGA_CRTC_CURSOR_START) & 0xC0;
e = vga_get_crtc(VGA_REG_BASE, VGA_CRTC_CURSOR_END);
addr = (vga_get_crtc(VGA_REG_BASE, VGA_CRTC_CURSOR_LOC_HIGH) << 8) +
vga_get_crtc(VGA_REG_BASE, VGA_CRTC_CURSOR_LOC_LOW);