Re: [PATCH] Fix ambiguous grammar for devicetree rule

[David Gibson <david-xT8FGy+AXnRB3Ne2BGzF6laj5H9X9Tb+@public.gmane.org>]

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On Mon, Nov 20, 2017 at 05:12:18PM +0000, Grant Likely wrote:
> From: Grant Likely <grant-72MMKEujIeWYvcOBcYx38pOp/cRyR9/c930Pai70D+E@public.gmane.org>
> 
> Commit 737b2df3, "overlay: Add syntactic sugar version of overlays"
> introduced an empty rule for "devicetree" that created ambiguities in
> the grammar and causes the following warning:
> 
>          BISON dtc-parser.tab.c
>   dtc-parser.y: warning: 3 shift/reduce conflicts [-Wconflicts-sr]
> 
> Fix the grammar by explicitly testing for the condition the
> new overlay grammar wants to use. This means duplicating a very small
> amount of grammar processing code, but the alternative seems to be a
> more invasive reorganization of the devicetree rule. Better to fix it
> this way now and save the reorg for a separate patch
> 
> Signed-off-by: Grant Likely <grant.likely-5wv7dgnIgG8@public.gmane.org>
> Cc: Pantelis Antoniou <pantelis.antoniou-OWPKS81ov/FWk0Htik3J/w@public.gmane.org>
> Cc: David Gibson <david-xT8FGy+AXnRB3Ne2BGzF6laj5H9X9Tb+@public.gmane.org>

Strictly speaking this makes a behavioural change, since an entirely
empty overlay is no longer allowed.  I think that's an acceptable
change, though.

Applied.

> ---
>  dtc-parser.y | 17 +++++++++++------
>  dtc.h        |  2 +-
>  livetree.c   |  3 ++-
>  3 files changed, 14 insertions(+), 8 deletions(-)
> 
> diff --git a/dtc-parser.y b/dtc-parser.y
> index affc81a..44af170 100644
> --- a/dtc-parser.y
> +++ b/dtc-parser.y
> @@ -166,7 +166,17 @@ devicetree:
>  		{
>  			$$ = merge_nodes($1, $3);
>  		}
> -
> +	| DT_REF nodedef
> +		{
> +			/*
> +			 * We rely on the rule being always:
> +			 *   versioninfo plugindecl memreserves devicetree
> +			 * so $-1 is what we want (plugindecl)
> +			 */
> +			if (!($<flags>-1 & DTSF_PLUGIN))
> +				ERROR(&@2, "Label or path %s not found", $1);
> +			$$ = add_orphan_node(name_node(build_node(NULL, NULL), ""), $2, $1);
> +		}
>  	| devicetree DT_LABEL DT_REF nodedef
>  		{
>  			struct node *target = get_node_by_ref($1, $3);
> @@ -209,11 +219,6 @@ devicetree:
>  
>  			$$ = $1;
>  		}
> -	| /* empty */
> -		{
> -			/* build empty node */
> -			$$ = name_node(build_node(NULL, NULL), "");
> -		}
>  	;
>  
>  nodedef:
> diff --git a/dtc.h b/dtc.h
> index 35cf926..84187a1 100644
> --- a/dtc.h
> +++ b/dtc.h
> @@ -203,7 +203,7 @@ struct node *build_node_delete(void);
>  struct node *name_node(struct node *node, char *name);
>  struct node *chain_node(struct node *first, struct node *list);
>  struct node *merge_nodes(struct node *old_node, struct node *new_node);
> -void add_orphan_node(struct node *old_node, struct node *new_node, char *ref);
> +struct node *add_orphan_node(struct node *old_node, struct node *new_node, char *ref);
>  
>  void add_property(struct node *node, struct property *prop);
>  void delete_property_by_name(struct node *node, char *name);
> diff --git a/livetree.c b/livetree.c
> index 6846ad2..4a3d893 100644
> --- a/livetree.c
> +++ b/livetree.c
> @@ -216,7 +216,7 @@ struct node *merge_nodes(struct node *old_node, struct node *new_node)
>  	return old_node;
>  }
>  
> -void add_orphan_node(struct node *dt, struct node *new_node, char *ref)
> +struct node * add_orphan_node(struct node *dt, struct node *new_node, char *ref)
>  {
>  	static unsigned int next_orphan_fragment = 0;
>  	struct node *node;
> @@ -236,6 +236,7 @@ void add_orphan_node(struct node *dt, struct node *new_node, char *ref)
>  	name_node(node, name);
>  
>  	add_child(dt, node);
> +	return dt;
>  }
>  
>  struct node *chain_node(struct node *first, struct node *list)

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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