Re: [PATCH v3 4/4] of: improve reporting invalid overlay target path

[Rob Herring <robh@kernel.org>]

On Wed, Feb 14, 2018 at 09:35:46PM -0800, frowand.list@gmail.com wrote:
> From: Frank Rowand <frank.rowand@sony.com>
> 
> Errors while developing the patch to create of_overlay_fdt_apply()
> exposed inadequate error messages to debug problems when overlay
> devicetree fragment nodes contain an invalid target path.  Improve
> the messages in find_target_node() to remedy this.
> 
> Signed-off-by: Frank Rowand <frank.rowand@sony.com>
> ---
> 
> changes from v2:
>   - add fragment node name as suggested by Geert
>   - existing error message printed short node name, thus not
>     discriminating between fragments; change to full node name
>   - existing error message printed node address, which is devicetree
>     internal debugging, not useful in an overlay apply error message;
>     remove node address from message
> 
>  drivers/of/overlay.c | 22 ++++++++++++++++------
>  1 file changed, 16 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
> index 5f6c5569e97d..852e566d7744 100644
> --- a/drivers/of/overlay.c
> +++ b/drivers/of/overlay.c
> @@ -488,20 +488,30 @@ static int build_changeset(struct overlay_changeset *ovcs)
>   */
>  static struct device_node *find_target_node(struct device_node *info_node)
>  {
> +	struct device_node *node;
>  	const char *path;
>  	u32 val;
>  	int ret;
>  
>  	ret = of_property_read_u32(info_node, "target", &val);
> -	if (!ret)
> -		return of_find_node_by_phandle(val);
> +	if (!ret) {
> +		node = of_find_node_by_phandle(val);
> +		if (!node)
> +			pr_err("find target, node: %pOF, phandle 0x%x not found\n",

I'm wondering if the core should print the error rather than having all 
the callers do it. The question is whether there are cases where failing 
is okay? I guess sometimes we use 0 to skip cells, but the core handle 
not printing an error in that case.

Rob

> +			       info_node, val);
> +		return node;
> +	}
>  
>  	ret = of_property_read_string(info_node, "target-path", &path);
> -	if (!ret)
> -		return of_find_node_by_path(path);
> +	if (!ret) {
> +		node =  of_find_node_by_path(path);
> +		if (!node)
> +			pr_err("find target, node: %pOF, path '%s' not found\n",
> +			       info_node, path);
> +		return node;
> +	}
>  
> -	pr_err("Failed to find target for node %p (%s)\n",
> -		info_node, info_node->name);
> +	pr_err("find target, node: %pOF, no target property\n", info_node);
>  
>  	return NULL;
>  }
> -- 
> Frank Rowand <frank.rowand@sony.com>
>