Subject: Re: [PATCH] of: require a match on all fields of of_device_id

From: Rob Herring <[email-masked]>
Date: Tue, 17 Jul 2012 21:38:17 -0500

On 07/17/2012 08:11 PM, Scott Wood wrote:
> Commit 107a84e61cdd3406c842a0e4be7efffd3a05dba6 ("of: match by compatible
> property first") breaks the gianfar ethernet driver found on various
> Freescale PPC chips.

You do know this is reverted, right?

> 
> There are, for unfortunate historical reasons, two nodes with a
> compatible of "gianfar".  One has a device_type of "network" and the
> other has device_type of "mdio".  The match entries look like this:
> 
>>         {
>>                 .type = "mdio",
>>                 .compatible = "gianfar",
>>         },
> 
> and
> 
>>         {
>>                 .type = "network",
>>                 .compatible = "gianfar",
>>         },
> 
> With the above patch, both nodes get probed by the first driver, because
> nothing else in the match struct is looked at if there's a compatible
> match.
> 
> Signed-off-by: Scott Wood <[email-masked]>

Here's my fix (untested) which is a bit simpler. I'm assuming if we care
about which compatible string we are matching to, then we require name
and type are blank and we only care about compatible strings.

diff --git a/drivers/of/base.c b/drivers/of/base.c
index eada3f4..6e10004 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -518,6 +518,9 @@ static const struct of_device_id
*of_match_compat(const struct of_device_id *mat
                const char *cp = matches->compatible;
                int len = strlen(cp);

+               if (matches->name[0] || matches->type[0])
+                       continue;
+
                if (len > 0 && of_compat_cmp(compat, cp, len) == 0)
                        return matches;

@@ -557,7 +560,10 @@ const struct of_device_id *of_match_node(const
struct of_device_id *matches,
                if (matches->type[0])
                        match &= node->type
                                && !strcmp(matches->type, node->type);
-               if (match && !matches->compatible[0])
+               if (matches->compatible[0])
+                       match &= of_device_is_compatible(node,
+                                               matches->compatible);
+               if (match)
                        return matches;
                matches++;
        }

> ---
>  drivers/of/base.c |   44 ++++++++++++++++++++++++++++++++------------
>  1 file changed, 32 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index bc86ea2..4e707cc 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -511,14 +511,37 @@ out:
>  }
>  EXPORT_SYMBOL(of_find_node_with_property);
>  
> -static const struct of_device_id *of_match_compat(const struct of_device_id *matches,
> -						  const char *compat)
> +/*
> + * Tell if an device_node matches the non-compatible fields of
> + * a specific of_match element.
> + */
> +static bool of_match_one_noncompat(const struct of_device_id *match,
> +				   const struct device_node *node)
> +{
> +	bool is_match = true;
> +
> +	if (match->name[0])
> +		is_match &= node->name && !strcmp(match->name, node->name);
> +	if (match->type[0])
> +		is_match &= node->type && !strcmp(match->type, node->type);
> +
> +	return is_match;
> +}
> +
> +/*
> + * Find an OF match using the supplied compatible string, rather than
> + * the node's entire string list.
> + */
> +static const struct of_device_id *of_match_compat(
> +	const struct of_device_id *matches, const char *compat,
> +	const struct device_node *node)
>  {
>  	while (matches->name[0] || matches->type[0] || matches->compatible[0]) {
>  		const char *cp = matches->compatible;
>  		int len = strlen(cp);
>  
> -		if (len > 0 && of_compat_cmp(compat, cp, len) == 0)
> +		if (len > 0 && of_compat_cmp(compat, cp, len) == 0 &&
> +		    of_match_one_noncompat(matches, node))
>  			return matches;
>  
>  		matches++;
> @@ -544,23 +567,20 @@ const struct of_device_id *of_match_node(const struct of_device_id *matches,
>  		return NULL;
>  
>  	of_property_for_each_string(node, "compatible", prop, cp) {
> -		const struct of_device_id *match = of_match_compat(matches, cp);
> +		const struct of_device_id *match =
> +			of_match_compat(matches, cp, node);
>  		if (match)
>  			return match;
>  	}
>  
>  	while (matches->name[0] || matches->type[0] || matches->compatible[0]) {
> -		int match = 1;
> -		if (matches->name[0])
> -			match &= node->name
> -				&& !strcmp(matches->name, node->name);
> -		if (matches->type[0])
> -			match &= node->type
> -				&& !strcmp(matches->type, node->type);
> -		if (match && !matches->compatible[0])
> +		if (of_match_one_noncompat(matches, node) &&
> +		    !matches->compatible[0])
>  			return matches;
> +
>  		matches++;
>  	}
> +
>  	return NULL;
>  }
>  EXPORT_SYMBOL(of_match_node);
>