v4l2_calc_timeperframe
fps = v4l2_calc_timeperframe(&s->timings);
parm->parm.capture.timeperframe = v4l2_calc_timeperframe(&hdmirx_dev->timings);
EXPORT_SYMBOL_GPL(v4l2_calc_timeperframe);
struct v4l2_fract v4l2_calc_timeperframe(const struct v4l2_dv_timings *t);