Re: [XEN][PATCH v5 06/17] xen/device-tree: Add device_tree_find_node_by_path() to find nodes in device tree

[Michal Orzel <michal.orzel@xxxxxxx>]

Hi Vikram,

On 11/04/2023 21:16, Vikram Garhwal wrote:
> 
> 
> Add device_tree_find_node_by_path() to find a matching node with path for a
> dt_device_node.
> 
> Reason behind this function:
>     Each time overlay nodes are added using .dtbo, a new fdt(memcpy of
>     device_tree_flattened) is created and updated with overlay nodes. This
>     updated fdt is further unflattened to a dt_host_new. Next, we need to find
>     the overlay nodes in dt_host_new, find the overlay node's parent in 
> dt_host
>     and add the nodes as child under their parent in the dt_host. Thus we need
>     this function to search for node in different unflattened device trees.
You do not mention making dt_find_node_by_path() static inline.

> 
> Signed-off-by: Vikram Garhwal <vikram.garhwal@xxxxxxx>
> ---
>  xen/common/device_tree.c      |  5 +++--
>  xen/include/xen/device_tree.h | 17 +++++++++++++++--
>  2 files changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c
> index bf847b2584..507b4ac5b6 100644
> --- a/xen/common/device_tree.c
> +++ b/xen/common/device_tree.c
> @@ -358,11 +358,12 @@ struct dt_device_node *dt_find_node_by_type(struct 
> dt_device_node *from,
>      return np;
>  }
> 
> -struct dt_device_node *dt_find_node_by_path(const char *path)
> +struct dt_device_node *device_tree_find_node_by_path(struct dt_device_node 
> *dt,
> +                                                     const char *path)
>  {
>      struct dt_device_node *np;
> 
> -    dt_for_each_device_node(dt_host, np)
> +    dt_for_each_device_node(dt, np)
>          if ( np->full_name && (dt_node_cmp(np->full_name, path) == 0) )
>              break;
> 
> diff --git a/xen/include/xen/device_tree.h b/xen/include/xen/device_tree.h
> index 58ac12abe3..998f972ebc 100644
> --- a/xen/include/xen/device_tree.h
> +++ b/xen/include/xen/device_tree.h
> @@ -534,13 +534,26 @@ struct dt_device_node *dt_find_node_by_type(struct 
> dt_device_node *from,
>  struct dt_device_node *dt_find_node_by_alias(const char *alias);
> 
>  /**
> - * dt_find_node_by_path - Find a node matching a full DT path
> + * device_tree_find_node_by_path - Generic function to find a node matching 
> the
> + * full DT path for any given unflatten device tree
> + * @dt_node: The device tree to search
This should be @dt to match the parameter. Also, shouldn't the description say:
"the node to start searching from"
or
"device tree root node"

FWICS, you expect to pass a root node as dt node. However, in 
device_tree_find_node_by_path()
you do not check if a provided node is a root node or not (e.g. no parent). Is 
this intended?

~Michal