Re: [PATCH v5 05/15] software_node: Enforce parent before child ordering of nodes arrays

Heikki Krogerus
2021-01-07T14:06:12Z

On Thu, Jan 07, 2021 at 01:28:28PM +0000, Daniel Scally wrote:
> 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>

Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>

> ---
> Changes in v5:
>
> - 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 4fcc1a6fb724..166c5cc73f39 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

--
heikki