block: sed-opal: reuse response_get_token to decrease code duplication

response_get_token had already been in place, its functionality had
been duplicated within response_get_{u64,bytestring} with the same error
handling. Unify the handling by reusing response_get_token within the
other functions.
Co-authored-by: Jonas Rabenstein <jonas.rabenstein@studium.uni-erlangen.de>
Signed-off-by: David Kozub <zub@linux.fjfi.cvut.cz>
Signed-off-by: Jonas Rabenstein <jonas.rabenstein@studium.uni-erlangen.de>
Reviewed-by: Scott Bauer <sbauer@plzdonthack.me>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jon Derrick <jonathan.derrick@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/sed-opal.c

@@ -883,27 +883,19 @@ static size_t response_get_string(const struct parsed_resp *resp, int n,
 				  const char **store)
 {
 	u8 skip;
-	const struct opal_resp_tok *token;
+	const struct opal_resp_tok *tok;
 
 	*store = NULL;
-	if (!resp) {
-		pr_debug("Response is NULL\n");
-		return 0;
-	}
-
-	if (n >= resp->num) {
-		pr_debug("Response has %d tokens. Can't access %d\n",
-			 resp->num, n);
+	tok = response_get_token(resp, n);
+	if (IS_ERR(tok))
 		return 0;
-	}
 
-	token = &resp->toks[n];
-	if (token->type != OPAL_DTA_TOKENID_BYTESTRING) {
+	if (tok->type != OPAL_DTA_TOKENID_BYTESTRING) {
 		pr_debug("Token is not a byte string!\n");
 		return 0;
 	}
 
-	switch (token->width) {
+	switch (tok->width) {
 	case OPAL_WIDTH_TINY:
 	case OPAL_WIDTH_SHORT:
 		skip = 1;
@@ -919,37 +911,29 @@ static size_t response_get_string(const struct parsed_resp *resp, int n,
 		return 0;
 	}
 
-	*store = token->pos + skip;
-	return token->len - skip;
+	*store = tok->pos + skip;
+	return tok->len - skip;
 }
 
 static u64 response_get_u64(const struct parsed_resp *resp, int n)
 {
-	if (!resp) {
-		pr_debug("Response is NULL\n");
-		return 0;
-	}
+	const struct opal_resp_tok *tok;
 
-	if (n >= resp->num) {
-		pr_debug("Response has %d tokens. Can't access %d\n",
-			 resp->num, n);
+	tok = response_get_token(resp, n);
+	if (IS_ERR(tok))
 		return 0;
-	}
 
-	if (resp->toks[n].type != OPAL_DTA_TOKENID_UINT) {
-		pr_debug("Token is not unsigned it: %d\n",
-			 resp->toks[n].type);
+	if (tok->type != OPAL_DTA_TOKENID_UINT) {
+		pr_debug("Token is not unsigned int: %d\n", tok->type);
 		return 0;
 	}
 
-	if (!(resp->toks[n].width == OPAL_WIDTH_TINY ||
-	      resp->toks[n].width == OPAL_WIDTH_SHORT)) {
-		pr_debug("Atom is not short or tiny: %d\n",
-			 resp->toks[n].width);
+	if (tok->width != OPAL_WIDTH_TINY && tok->width != OPAL_WIDTH_SHORT) {
+		pr_debug("Atom is not short or tiny: %d\n", tok->width);
 		return 0;
 	}
 
-	return resp->toks[n].stored.u;
+	return tok->stored.u;
 }
 
 static bool response_token_matches(const struct opal_resp_tok *token, u8 match)