crypto: skcipher - Add default key size helper

While converting ecryptfs over to skcipher I found that it needs
to pick a default key size if one isn't given.  Rather than having
it poke into the guts of the algorithm to get max_keysize, let's
provide a helper that is meant to give a sane default (just in
case we ever get an algorithm that has no maximum key size).
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/skcipher.c

@@ -118,7 +118,7 @@ static int crypto_init_skcipher_ops_blkcipher(struct crypto_tfm *tfm)
 	skcipher->decrypt = skcipher_decrypt_blkcipher;
 
 	skcipher->ivsize = crypto_blkcipher_ivsize(blkcipher);
-	skcipher->has_setkey = calg->cra_blkcipher.max_keysize;
+	skcipher->keysize = calg->cra_blkcipher.max_keysize;
 
 	return 0;
 }
@@ -211,7 +211,7 @@ static int crypto_init_skcipher_ops_ablkcipher(struct crypto_tfm *tfm)
 	skcipher->ivsize = crypto_ablkcipher_ivsize(ablkcipher);
 	skcipher->reqsize = crypto_ablkcipher_reqsize(ablkcipher) +
 			    sizeof(struct ablkcipher_request);
-	skcipher->has_setkey = calg->cra_ablkcipher.max_keysize;
+	skcipher->keysize = calg->cra_ablkcipher.max_keysize;
 
 	return 0;
 }

include/crypto/skcipher.h

@@ -60,8 +60,7 @@ struct crypto_skcipher {
 
 	unsigned int ivsize;
 	unsigned int reqsize;
-
-	bool has_setkey;
+	unsigned int keysize;
 
 	struct crypto_tfm base;
 };
@@ -309,7 +308,13 @@ static inline int crypto_skcipher_setkey(struct crypto_skcipher *tfm,
 
 static inline bool crypto_skcipher_has_setkey(struct crypto_skcipher *tfm)
 {
-	return tfm->has_setkey;
+	return tfm->keysize;
+}
+
+static inline unsigned int crypto_skcipher_default_keysize(
+	struct crypto_skcipher *tfm)
+{
+	return tfm->keysize;
 }
 
 /**