Bluetooth: Add flexible buffer byte order swapping function

Since the SMP code needs to swap ordering of variable length buffers add
a convenience function that can be used for any length buffer.
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/smp.c

@@ -64,18 +64,12 @@ struct smp_chan {
 	unsigned long	flags;
 };
 
-static inline void swap128(const u8 src[16], u8 dst[16])
+static inline void swap_buf(const u8 *src, u8 *dst, size_t len)
 {
-	int i;
-	for (i = 0; i < 16; i++)
-		dst[15 - i] = src[i];
-}
+	size_t i;
 
-static inline void swap56(const u8 src[7], u8 dst[7])
-{
-	int i;
-	for (i = 0; i < 7; i++)
-		dst[6 - i] = src[i];
+	for (i = 0; i < len; i++)
+		dst[len - 1 - i] = src[i];
 }
 
 static int smp_e(struct crypto_blkcipher *tfm, const u8 *k, u8 *r)
@@ -94,7 +88,7 @@ static int smp_e(struct crypto_blkcipher *tfm, const u8 *k, u8 *r)
 	desc.flags = 0;
 
 	/* The most significant octet of key corresponds to k[0] */
-	swap128(k, tmp);
+	swap_buf(k, tmp, 16);
 
 	err = crypto_blkcipher_setkey(tfm, tmp, 16);
 	if (err) {
@@ -103,7 +97,7 @@ static int smp_e(struct crypto_blkcipher *tfm, const u8 *k, u8 *r)
 	}
 
 	/* Most significant octet of plaintextData corresponds to data[0] */
-	swap128(r, data);
+	swap_buf(r, data, 16);
 
 	sg_init_one(&sg, data, 16);
 
@@ -112,7 +106,7 @@ static int smp_e(struct crypto_blkcipher *tfm, const u8 *k, u8 *r)
 		BT_ERR("Encrypt data error %d", err);
 
 	/* Most significant octet of encryptedData corresponds to data[0] */
-	swap128(data, r);
+	swap_buf(data, r, 16);
 
 	return err;
 }