devmap_ctxinit
static struct devmap_ctx *devmap_ctxinit(dev_t, ulong_t);
dhp->dh_ctx = devmap_ctxinit(dev,
newdhp->dh_ctx = devmap_ctxinit(newdhp->dh_dev,
newdhp->dh_ctx = devmap_ctxinit(newdhp->dh_dev,