fb_pack
tab[0] = fb_pack(bgcolor, bgcolor, BITS_PER_LONG/2);
tab[1] = fb_pack(bgcolor, fgcolor, BITS_PER_LONG/2);
tab[2] = fb_pack(fgcolor, bgcolor, BITS_PER_LONG/2);
tab[3] = fb_pack(fgcolor, fgcolor, BITS_PER_LONG/2);