Re: [PATCH 2/3] of: Make of_find_node_by_path() handle /aliases

[Frank Rowand]

On 5/21/2014 8:13 PM, Grant Likely wrote:
> On Tue, 20 May 2014 19:46:19 -0700, Frank Rowand <frowand.list@xxxxxxxxx> wrote:
>> On 5/20/2014 7:41 PM, Frank Rowand wrote:
>> < snip >
>>> I will reply to this email with an additional patch that restores the
>>> original behavior.
>> < snip >
>> From: Frank Rowand <frank.rowand@xxxxxxxxxxxxxx>
>>
>> If __of_find_node_by_path() returns parent when the remaining portion of the
>> path is "/" then the behavior of of_find_node_by_path() has changed.
>>
>> Previously, adding an extraneous "/" on the end of a path would result
>> in of_find_node_by_path() not finding a match.
>>
>> Signed-off-by: Frank Rowand <frank.rowand@xxxxxxxxxxxxxx>
>> ---
>>  drivers/of/base.c |   13 ++++++++++++-
>>  1 file changed, 12 insertions(+), 1 deletion(-)
>>
>> Index: b/drivers/of/base.c
>> ===================================================================
>> --- a/drivers/of/base.c
>> +++ b/drivers/of/base.c
>> @@ -778,7 +778,7 @@ static struct device_node *__of_find_nod
>>  	int len = strchrnul(path, '/') - path;
>>  
>>  	if (!len)
>> -		return parent;
>> +		return NULL;
>>  
>>  	for_each_child_of_node(parent, child) {
>>  		const char *name = strrchr(child->full_name, '/');
>> @@ -813,6 +813,17 @@ struct device_node *of_find_node_by_path
>>  	struct property *pp;
>>  	unsigned long flags;
>>  
>> +	if (strcmp(path, "/") == 0) {
>> +		raw_spin_lock_irqsave(&devtree_lock, flags);
>> +		for (; np; np = np->allnext) {
>> +			if (np->full_name && (of_node_cmp(np->full_name, path) == 0)
>> +			    && of_node_get(np))
>> +				break;
>> +		}
>> +		raw_spin_unlock_irqrestore(&devtree_lock, flags);
>> +		return np;
>> +	}
>> +
> 
> Special case for the root node? Could use a comment, and of_allnodes
> will already point to the root node so this could simply be:
> 
> 	if (strcmp(path, "/") == 0)
> 		return of_node_get(np);

Yes, your version below is better.  I was hoping there was a direct way
of getting the node for "/".  It works on my dragonboard.

The comment of why special case "/" is that for the path "/"
__of_find_node_by_path() will return NULL.

> 
> Here's a complete patch:
> 
> commit adc96db6c39ef7b895e75d30dbc69781f6443f1d
> Author: Grant Likely <grant.likely@xxxxxxxxxx>
> Date:   Thu May 22 11:55:31 2014 +0900
> 
>     fix trailing '/' case
> 
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index c05a143b6a70..45ac44c8dfea 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -790,7 +790,7 @@ static struct device_node *__of_find_node_by_path(struct device_node *parent,
>  	int len = strchrnul(path, '/') - path;
>  
>  	if (!len)
> -		return parent;
> +		return NULL;
>  
>  	__for_each_child_of_node(parent, child) {
>  		const char *name = strrchr(child->full_name, '/');
> @@ -820,10 +820,13 @@ static struct device_node *__of_find_node_by_path(struct device_node *parent,
>   */
>  struct device_node *of_find_node_by_path(const char *path)
>  {
> -	struct device_node *np = of_allnodes;
> +	struct device_node *np = NULL;
>  	struct property *pp;
>  	unsigned long flags;
>  
> +	if (strcmp(path, "/") == 0)
> +		return of_node_get(of_allnodes);
> +
>  	/* The path could begin with an alias */
>  	if (*path != '/') {
>  		char *p = strchrnul(path, '/');
> @@ -833,7 +836,6 @@ struct device_node *of_find_node_by_path(const char *path)
>  		if (!of_aliases)
>  			return NULL;
>  
> -		np = NULL;
>  		for_each_property_of_node(of_aliases, pp) {
>  			if (strlen(pp->name) == len && !strncmp(pp->name, path, len)) {
>  				np = of_find_node_by_path(pp->value);
> @@ -847,6 +849,8 @@ struct device_node *of_find_node_by_path(const char *path)
>  
>  	/* Step down the tree matching path components */
>  	raw_spin_lock_irqsave(&devtree_lock, flags);
> +	if (!np)
> +		np = of_node_get(of_allnodes);
>  	while (np && *path == '/') {
>  		path++; /* Increment past '/' delimiter */
>  		np = __of_find_node_by_path(np, path);
> diff --git a/drivers/of/selftest.c b/drivers/of/selftest.c
> index 10900b18fc06..aeb0b5c8b21d 100644
> --- a/drivers/of/selftest.c
> +++ b/drivers/of/selftest.c
> @@ -42,9 +42,7 @@ static void __init of_selftest_find_node_by_name(void)
>  
>  	/* Test if trailing '/' works */
>  	np = of_find_node_by_path("/testcase-data/");
> -	selftest(np && !strcmp("/testcase-data", np->full_name),
> -		"find /testcase-data/ failed\n");
> -	of_node_put(np);
> +	selftest(!np, "trailing '/' on /testcase-data/ should fail\n");
>  
>  	np = of_find_node_by_path("/testcase-data/phandle-tests/consumer-a");
>  	selftest(np && !strcmp("/testcase-data/phandle-tests/consumer-a", np->full_name),
> @@ -58,9 +56,7 @@ static void __init of_selftest_find_node_by_name(void)
>  
>  	/* Test if trailing '/' works on aliases */
>  	np = of_find_node_by_path("testcase-alias/");
> -	selftest(np && !strcmp("/testcase-data", np->full_name),
> -		"find testcase-alias/ failed\n");
> -	of_node_put(np);
> +	selftest(!np, "trailing '/' on testcase-alias/ should fail\n");
>  
>  	np = of_find_node_by_path("testcase-alias/phandle-tests/consumer-a");
>  	selftest(np && !strcmp("/testcase-data/phandle-tests/consumer-a", np->full_name),
> 
> 

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