net: buf: Add net_buf_simple_init_with_data

This adds net_bug_simple_init_with_data which can be used to initialize
a net_buf_simple pointer with an external data pointer.

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

include/net/buf.h

@@ -140,6 +140,18 @@ static inline void net_buf_simple_init(struct net_buf_simple *buf,
 	buf->len = 0U;
 }
 
+/**
+ * @brief Initialize a net_buf_simple object with data.
+ *
+ * Initialized buffer object with external data.
+ *
+ * @param buf Buffer to initialize.
+ * @param data External data pointer
+ * @param size Amount of data the pointed data buffer if able to fit.
+ */
+void net_buf_simple_init_with_data(struct net_buf_simple *buf,
+				   void *data, size_t size);
+
 /**
  * @brief Reset buffer
  *

subsys/net/buf.c

@@ -385,10 +385,7 @@ struct net_buf *net_buf_alloc_with_data(struct net_buf_pool *pool,
 		return NULL;
 	}
 
-	buf->__buf = data;
+	net_buf_simple_init_with_data(&buf->b, data, size);
-	buf->data  = data;
-	buf->size  = size;
-	buf->len   = size;
 	buf->flags = NET_BUF_EXTERNAL_DATA;
 
 	return buf;
@@ -427,6 +424,15 @@ struct net_buf *net_buf_get(struct k_fifo *fifo, s32_t timeout)
 	return buf;
 }
 
+void net_buf_simple_init_with_data(struct net_buf_simple *buf,
+				   void *data, size_t size)
+{
+	buf->__buf = data;
+	buf->data  = data;
+	buf->size  = size;
+	buf->len   = size;
+}
+
 void net_buf_simple_reserve(struct net_buf_simple *buf, size_t reserve)
 {
 	NET_BUF_ASSERT(buf);