[dpdk-dev] [PATCH v2 3/5] kvargs: new function to get from key and value

[Olivier Matz <olivier.matz@6wind.com>]

A quite common scenario with kvargs is to lookup for a <key>=<value> in
a kvlist. For instance, check if name=foo is present in
name=toto,name=foo,name=bar. This is currently done in drivers/bus with
rte_kvargs_process() + the rte_kvargs_strcmp() handler.

This approach is not straightforward, and can be replaced by this new
function.

Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
Reviewed-by: Xueming Li <xuemingl@nvidia.com>
---
 drivers/bus/auxiliary/auxiliary_params.c |  9 ++++----
 drivers/bus/vdev/vdev_params.c           | 13 ++---------
 lib/kvargs/rte_kvargs.c                  | 23 +++++++++++++++----
 lib/kvargs/rte_kvargs.h                  | 29 +++++++++++++++++++++++-
 lib/kvargs/version.map                   |  2 ++
 5 files changed, 54 insertions(+), 22 deletions(-)

diff --git a/drivers/bus/auxiliary/auxiliary_params.c b/drivers/bus/auxiliary/auxiliary_params.c
index cd3fa56cb4..a9c7853ed1 100644
--- a/drivers/bus/auxiliary/auxiliary_params.c
+++ b/drivers/bus/auxiliary/auxiliary_params.c
@@ -25,13 +25,12 @@ auxiliary_dev_match(const struct rte_device *dev,
 	      const void *_kvlist)
 {
 	const struct rte_kvargs *kvlist = _kvlist;
-	int ret;
+	const char *key = auxiliary_params_keys[RTE_AUXILIARY_PARAM_NAME];
 
-	ret = rte_kvargs_process(kvlist,
-			auxiliary_params_keys[RTE_AUXILIARY_PARAM_NAME],
-			rte_kvargs_strcmp, (void *)(uintptr_t)dev->name);
+	if (rte_kvargs_get_with_value(kvlist, key, dev->name) == NULL)
+		return -1;
 
-	return ret != 0 ? -1 : 0;
+	return 0;
 }
 
 void *
diff --git a/drivers/bus/vdev/vdev_params.c b/drivers/bus/vdev/vdev_params.c
index 6f74704d1c..37d95395e7 100644
--- a/drivers/bus/vdev/vdev_params.c
+++ b/drivers/bus/vdev/vdev_params.c
@@ -26,19 +26,10 @@ static int
 vdev_dev_match(const struct rte_device *dev,
 	       const void *_kvlist)
 {
-	int ret;
 	const struct rte_kvargs *kvlist = _kvlist;
-	char *name;
+	const char *key = vdev_params_keys[RTE_VDEV_PARAM_NAME];
 
-	/* cannot pass const dev->name to rte_kvargs_process() */
-	name = strdup(dev->name);
-	if (name == NULL)
-		return -1;
-	ret = rte_kvargs_process(kvlist,
-		vdev_params_keys[RTE_VDEV_PARAM_NAME],
-		rte_kvargs_strcmp, name);
-	free(name);
-	if (ret != 0)
+	if (rte_kvargs_get_with_value(kvlist, key, dev->name) == NULL)
 		return -1;
 
 	return 0;
diff --git a/lib/kvargs/rte_kvargs.c b/lib/kvargs/rte_kvargs.c
index 38e9d5c1ca..20abb23183 100644
--- a/lib/kvargs/rte_kvargs.c
+++ b/lib/kvargs/rte_kvargs.c
@@ -204,21 +204,34 @@ rte_kvargs_free(struct rte_kvargs *kvlist)
 	free(kvlist);
 }
 
-/* Lookup a value in an rte_kvargs list by its key. */
+/* Lookup a value in an rte_kvargs list by its key and value. */
 const char *
-rte_kvargs_get(const struct rte_kvargs *kvlist, const char *key)
+rte_kvargs_get_with_value(const struct rte_kvargs *kvlist, const char *key,
+			  const char *value)
 {
 	unsigned int i;
 
-	if (kvlist == NULL || key == NULL)
+	if (kvlist == NULL)
 		return NULL;
 	for (i = 0; i < kvlist->count; ++i) {
-		if (strcmp(kvlist->pairs[i].key, key) == 0)
-			return kvlist->pairs[i].value;
+		if (key != NULL && strcmp(kvlist->pairs[i].key, key) != 0)
+			continue;
+		if (value != NULL && strcmp(kvlist->pairs[i].value, value) != 0)
+			continue;
+		return kvlist->pairs[i].value;
 	}
 	return NULL;
 }
 
+/* Lookup a value in an rte_kvargs list by its key. */
+const char *
+rte_kvargs_get(const struct rte_kvargs *kvlist, const char *key)
+{
+	if (kvlist == NULL || key == NULL)
+		return NULL;
+	return rte_kvargs_get_with_value(kvlist, key, NULL);
+}
+
 /*
  * Parse the arguments "key=value,key=value,..." string and return
  * an allocated structure that contains a key/value list. Also
diff --git a/lib/kvargs/rte_kvargs.h b/lib/kvargs/rte_kvargs.h
index 328f0d3cc6..e40df1bd2a 100644
--- a/lib/kvargs/rte_kvargs.h
+++ b/lib/kvargs/rte_kvargs.h
@@ -116,7 +116,7 @@ void rte_kvargs_free(struct rte_kvargs *kvlist);
 /**
  * Get the value associated with a given key.
  *
- * If multiple key matches, the value of the first one is returned.
+ * If multiple keys match, the value of the first one is returned.
  *
  * The memory returned is allocated as part of the rte_kvargs structure,
  * it must never be modified.
@@ -132,6 +132,33 @@ void rte_kvargs_free(struct rte_kvargs *kvlist);
  */
 const char *rte_kvargs_get(const struct rte_kvargs *kvlist, const char *key);
 
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice
+ *
+ * Get the value associated with a given key and value.
+ *
+ * Find the first entry in the kvlist whose key and value match the
+ * ones passed as argument.
+ *
+ * The memory returned is allocated as part of the rte_kvargs structure,
+ * it must never be modified.
+ *
+ * @param kvlist
+ *   A list of rte_kvargs pair of 'key=value'.
+ * @param key
+ *   The matching key. If NULL, any key will match.
+ * @param value
+ *   The matching value. If NULL, any value will match.
+ *
+ * @return
+ *   NULL if no key matches the input,
+ *   a value associated with a matching key otherwise.
+ */
+__rte_experimental
+const char *rte_kvargs_get_with_value(const struct rte_kvargs *kvlist,
+				      const char *key, const char *value);
+
 /**
  * Call a handler function for each key/value matching the key
  *
diff --git a/lib/kvargs/version.map b/lib/kvargs/version.map
index 236f35c02b..82879b7140 100644
--- a/lib/kvargs/version.map
+++ b/lib/kvargs/version.map
@@ -16,4 +16,6 @@ EXPERIMENTAL {
 
 	rte_kvargs_strcmp;
 
+	# added in 21.11
+	rte_kvargs_get_with_value;
 };
-- 
2.30.2