  We give a formula for the cyclotomic valuation of $q$-Pochhammer symbols in
terms of (generalized) Dwork maps. We also obtain a criterion for the
$q$-integrality of basic hypergeometric series in terms of certain step
functions, which generalize Christol step functions. This provides suitable
$q$-analogs of two results proved by Christol: a formula for the $p$-adic
valuation of Pochhammer symbols and a criterion for the $N$-integrality of
hypergeometric series.
