pca955x_psc_to_period
if (period < pca955x_psc_to_period(pca955x, 0) ||
period > pca955x_psc_to_period(pca955x, 0xff)) {
period = pca955x_psc_to_period(pca955x, psc);
pca955x->blink_period = pca955x_psc_to_period(pca955x, psc0);