lib: net_buf: usage helper functions

Add helper functions for querying the internal fields of
`struct net_buf_pool` when `CONFIG_NET_BUF_POOL_USAGE` is enabled.

Signed-off-by: Jordan Yates <[email protected]>

Author: JordanYates

include/zephyr/net_buf.h

@@ -1372,6 +1372,40 @@ struct net_buf_pool *net_buf_pool_get(int id);
  */
 int net_buf_id(const struct net_buf *buf);
 
+#if defined(CONFIG_NET_BUF_POOL_USAGE) || defined(__DOXYGEN__)
+/**
+ * @brief Get the number of buffers currently available to claim from a pool.
+ *
+ * Note that the number of available buffers might already have changed by the time this
+ * function returns if other threads are also allocating or freeing buffers from the
+ * pool.
+ *
+ * @kconfig_dep{CONFIG_NET_BUF_POOL_USAGE}
+ *
+ * @param pool Which pool to check
+ *
+ * @return Number of buffers currently available in the pool
+ */
+static inline size_t net_buf_get_available(struct net_buf_pool *pool)
+{
+	return (size_t)atomic_get(&pool->avail_count);
+}
+
+/**
+ * @brief Get the maximum number of buffers simultaneously claimed from a pool.
+ *
+ * @kconfig_dep{CONFIG_NET_BUF_POOL_USAGE}
+ *
+ * @param pool Which pool to check
+ *
+ * @return Maximum number of buffers simultaneously claimed from the pool
+ */
+static inline size_t net_buf_get_max_used(struct net_buf_pool *pool)
+{
+	return (size_t)pool->max_used;
+}
+#endif /* defined(CONFIG_NET_BUF_POOL_USAGE) || defined(__DOXYGEN__) */
+
 /**
  * @brief Allocate a new fixed buffer from a pool.
  *

tests/lib/net_buf/buf/prj.conf

@@ -1,5 +1,6 @@
 CONFIG_NET_BUF=y
-CONFIG_HEAP_MEM_POOL_SIZE=4096
+CONFIG_NET_BUF_POOL_USAGE=y
+CONFIG_HEAP_MEM_POOL_SIZE=2048
 #CONFIG_NET_BUF_LOG=y
 #CONFIG_NET_BUF_LOG_LEVEL_DBG=y
 CONFIG_ZTEST=y

tests/lib/net_buf/buf/src/main.c

@@ -146,14 +146,20 @@ ZTEST(net_buf_tests, test_net_buf_1)
 	int i;
 
 	for (i = 0; i < bufs_pool.buf_count; i++) {
+		zassert_equal(bufs_pool.buf_count - i, net_buf_get_available(&bufs_pool));
+		/* Assertion requires that this test runs first */
+		zassert_equal(i, net_buf_get_max_used(&bufs_pool));
 		buf = net_buf_alloc_len(&bufs_pool, 74, K_NO_WAIT);
 		zassert_not_null(buf, "Failed to get buffer");
 		bufs[i] = buf;
 	}
 
 	for (i = 0; i < ARRAY_SIZE(bufs); i++) {
+		zassert_equal(i, net_buf_get_available(&bufs_pool));
+		zassert_equal(ARRAY_SIZE(bufs), net_buf_get_max_used(&bufs_pool));
 		net_buf_unref(bufs[i]);
 	}
+	zassert_equal(bufs_pool.buf_count, net_buf_get_available(&bufs_pool));
 
 	zassert_equal(destroy_called, ARRAY_SIZE(bufs),
 		      "Incorrect destroy callback count");