bregister_t
#define BTBYTE(what) bregister_t what:8; int :24
#define BTWORD(what) bregister_t what:16; int: 16
#define BTLONG(what) bregister_t what:32
bregister_t color_ctl_swap :4; /* d8 */
bregister_t color_ctl_gamma :1;
bregister_t color_ctl_rgb_ded :1;
bregister_t color_ctl_color_bars :1;
bregister_t color_ctl_ext_frmrate :1;