[PATCH v4 05/15] software_node: Enforce parent before child ordering of nodes arrays

Daniel Scally
2021-01-03T23:15:55Z

Registering software_nodes with the .parent member set to point to a
currently unregistered software_node has the potential for problems,
so enforce parent -> child ordering in arrays passed in to
software_node_register_nodes().

Software nodes that are children of another software node should be
unregistered before their parent. To allow easy unregistering of an array
of software_nodes ordered parent to child, reverse the order in which
software_node_unregister_nodes() unregisters software_nodes.

Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Daniel Scally <djrscally@gmail.com>
---
Changes in v4:

- None

drivers/base/swnode.c | 42 ++++++++++++++++++++++++++++++------------
1 file changed, 30 insertions(+), 12 deletions(-)

diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c
index 615a0c93e116..ade49173ff8d 100644
--- a/drivers/base/swnode.c
+++ b/drivers/base/swnode.c
@@ -692,7 +692,11 @@ swnode_register(const struct software_node *node, struct swnode *parent,
* software_node_register_nodes - Register an array of software nodes
* @nodes: Zero terminated array of software nodes to be registered
*
- * Register multiple software nodes at once.
+ * Register multiple software nodes at once. If any node in the array
+ * has its .parent pointer set (which can only be to another software_node),
+ * then its parent **must** have been registered before it is; either outside
+ * of this function or by ordering the array such that parent comes before
+ * child.
*/
int software_node_register_nodes(const struct software_node *nodes)
{
@@ -700,14 +704,23 @@ int software_node_register_nodes(const struct software_node *nodes)
int i;

for (i = 0; nodes[i].name; i++) {
- ret = software_node_register(&nodes[i]);
- if (ret) {
- software_node_unregister_nodes(nodes);
- return ret;
+ const struct software_node *parent = nodes[i].parent;
+
+ if (parent && !software_node_to_swnode(parent)) {
+ ret = -EINVAL;
+ goto err_unregister_nodes;
}
+
+ ret = software_node_register(&nodes[i]);
+ if (ret)
+ goto err_unregister_nodes;
}

return 0;
+
+err_unregister_nodes:
+ software_node_unregister_nodes(nodes);
+ return ret;
}
EXPORT_SYMBOL_GPL(software_node_register_nodes);

@@ -715,18 +728,23 @@ EXPORT_SYMBOL_GPL(software_node_register_nodes);
* software_node_unregister_nodes - Unregister an array of software nodes
* @nodes: Zero terminated array of software nodes to be unregistered
*
- * Unregister multiple software nodes at once.
+ * Unregister multiple software nodes at once. If parent pointers are set up
+ * in any of the software nodes then the array **must** be ordered such that
+ * parents come before their children.
*
- * NOTE: Be careful using this call if the nodes had parent pointers set up in
- * them before registering. If so, it is wiser to remove the nodes
- * individually, in the correct order (child before parent) instead of relying
- * on the sequential order of the list of nodes in the array.
+ * NOTE: If you are uncertain whether the array is ordered such that
+ * parents will be unregistered before their children, it is wiser to
+ * remove the nodes individually, in the correct order (child before
+ * parent).
*/
void software_node_unregister_nodes(const struct software_node *nodes)
{
- int i;
+ unsigned int i = 0;
+
+ while (nodes[i].name)
+ i++;

- for (i = 0; nodes[i].name; i++)
+ while (i--)
software_node_unregister(&nodes[i]);
}
EXPORT_SYMBOL_GPL(software_node_unregister_nodes);
--
2.25.1