[CRYPTO] api: Add crypto_attr_alg_name

This patch adds a new helper crypto_attr_alg_name which is basically the
first half of crypto_attr_alg.  That is, it returns an algorithm name
parameter as a string without looking it up.  The caller can then look it
up immediately or defer it until later.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/algapi.c

@@ -472,7 +472,7 @@ int crypto_check_attr_type(struct rtattr **tb, u32 type)
 }
 EXPORT_SYMBOL_GPL(crypto_check_attr_type);
 
-struct crypto_alg *crypto_attr_alg(struct rtattr *rta, u32 type, u32 mask)
+const char *crypto_attr_alg_name(struct rtattr *rta)
 {
 	struct crypto_attr_alg *alga;
 
@@ -486,7 +486,21 @@ struct crypto_alg *crypto_attr_alg(struct rtattr *rta, u32 type, u32 mask)
 	alga = RTA_DATA(rta);
 	alga->name[CRYPTO_MAX_ALG_NAME - 1] = 0;
 
-	return crypto_alg_mod_lookup(alga->name, type, mask);
+	return alga->name;
+}
+EXPORT_SYMBOL_GPL(crypto_attr_alg_name);
+
+struct crypto_alg *crypto_attr_alg(struct rtattr *rta, u32 type, u32 mask)
+{
+	const char *name;
+	int err;
+
+	name = crypto_attr_alg_name(rta);
+	err = PTR_ERR(name);
+	if (IS_ERR(name))
+		return ERR_PTR(err);
+
+	return crypto_alg_mod_lookup(name, type, mask);
 }
 EXPORT_SYMBOL_GPL(crypto_attr_alg);
 

include/crypto/algapi.h

@@ -113,6 +113,7 @@ struct crypto_tfm *crypto_spawn_tfm(struct crypto_spawn *spawn, u32 type,
 
 struct crypto_attr_type *crypto_get_attr_type(struct rtattr **tb);
 int crypto_check_attr_type(struct rtattr **tb, u32 type);
+const char *crypto_attr_alg_name(struct rtattr *rta);
 struct crypto_alg *crypto_attr_alg(struct rtattr *rta, u32 type, u32 mask);
 int crypto_attr_u32(struct rtattr *rta, u32 *num);
 struct crypto_instance *crypto_alloc_instance(const char *name,