sbd_calc_section_sum
s = sbd_calc_section_sum(*ppsms, (*ppsms)->sms_size);
t.sms_chksum = sbd_calc_section_sum(&t, sizeof (t));
sbd_calc_section_sum(sms, sms->sms_size);
sms->sms_chksum = sbd_calc_section_sum(sms, sms->sms_size);
t.sms_chksum = sbd_calc_section_sum(&t, sizeof (t));
if (sbd_calc_section_sum(unused_sms,
sbd_calc_section_sum(&sms_before_unused,
sbd_calc_section_sum(unused_sms, unused_sms->sms_size);