Function crypto_lookup_kdriver

freebsd/opencrypto/crypto.c:1565–1606

* Choose a driver for an asymmetric crypto request. */

 * Choose a driver for an asymmetric crypto request.
 */
static struct cryptocap *
crypto_lookup_kdriver(struct cryptkop *krp)
{
	struct cryptocap *cap;
	uint32_t crid;

	/* If this request is requeued, it might already have a driver. */
	cap = krp->krp_cap;
	if (cap != NULL)
		return (cap);

	/* Use krp_crid to choose a driver. */
	crid = krp->krp_crid;
	if ((crid & (CRYPTOCAP_F_HARDWARE | CRYPTOCAP_F_SOFTWARE)) == 0) {
		cap = crypto_checkdriver(crid);
		if (cap != NULL) {
			/*
			 * Driver present, it must support the
			 * necessary algorithm and, if s/w drivers are
			 * excluded, it must be registered as
			 * hardware-backed.
			 */
			if (!kdriver_suitable(cap, krp) ||
			    (!crypto_devallowsoft &&
			    (cap->cc_flags & CRYPTOCAP_F_HARDWARE) == 0))
				cap = NULL;
		}
	} else {
		/*
		 * No requested driver; select based on crid flags.
		 */
		if (!crypto_devallowsoft)	/* NB: disallow s/w drivers */
			crid &= ~CRYPTOCAP_F_SOFTWARE;
		cap = crypto_select_kdriver(krp, crid);
	}

	if (cap != NULL) {
		krp->krp_cap = cap_ref(cap);
		krp->krp_hid = cap->cc_hid;
	}
	return (cap);
}

/*
 * Dispatch an asymmetric crypto request.