dca_gather
err = dca_gather(data, reqp->dr_ibuf_kaddr, SHA1LEN, 1);
err = dca_gather(sig, reqp->dr_ibuf_kaddr+SHA1LEN, DSAPARTLEN, 1);
err = dca_gather(sig, reqp->dr_ibuf_kaddr+SHA1LEN+DSAPARTLEN,
err = dca_gather(data, reqp->dr_ibuf_kaddr, SHA1LEN, 1);
int dca_gather(crypto_data_t *, char *, int, int);