linux-kernel - Re: [PATCH 2/3] of: Make of_find_node_by

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Message-ID: <537C1252.3090900@gmail.com>
Date:	Tue, 20 May 2014 19:41:22 -0700
From:	Frank Rowand <frowand.list@...il.com>
To:	Grant Likely <grant.likely@...aro.org>
CC:	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	David Daney <david.daney@...ium.com>,
	Pantelis Antoniou <pantelis.antoniou@...sulko.com>
Subject: Re: [PATCH 2/3] of: Make of_find_node_by_path() handle /aliases

On 5/18/2014 2:27 AM, Grant Likely wrote:

> On Fri, 16 May 2014 11:54:44 +0100, Grant Likely <grant.likely@...aro.org> wrote:

>> On Thu, 15 May 2014 19:51:17 -0700, Frank Rowand <frowand.list@...il.com> wrote:

>>> On 5/13/2014 7:58 AM, Grant Likely wrote:

>>>> Make of_find_node_by_path() handle aliases as prefixes. To make this

>>>> work the name search is refactored to search by path component instead

>>>> of by full string. This should be a more efficient search, and it makes

>>>> it possible to start a search at a subnode of a tree.

>>>>

>>>> Signed-off-by: David Daney <david.daney@...ium.com>

>>>> Signed-off-by: Pantelis Antoniou <pantelis.antoniou@...sulko.com>

>>>> [grant.likely: Rework to not require allocating at runtime]

>>>> Acked-by: Rob Herring <robh@...nel.org>

>>>> Signed-off-by: Grant Likely <grant.likely@...aro.org>

>>>> ---

>>>>  drivers/of/base.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++----

>>>>  1 file changed, 56 insertions(+), 4 deletions(-)

>>>>

>>>> diff --git a/drivers/of/base.c b/drivers/of/base.c

>>>> index 6e240698353b..60089b9a3014 100644

>>>> --- a/drivers/of/base.c

>>>> +++ b/drivers/of/base.c

>>>> @@ -771,9 +771,38 @@ struct device_node *of_get_child_by_name(const struct device_node *node,

>>>>  }

>>>>  EXPORT_SYMBOL(of_get_child_by_name);

>>>>  

>>>> +static struct device_node *__of_find_node_by_path(struct device_node *parent,

>>>> +						const char *path)

>>>> +{

>>>> +	struct device_node *child;

>>>> +	int len = strchrnul(path, '/') - path;

>>>> +

>>>> +	if (!len)

>>>> +		return parent;

>>>

>>> (!len) is true if the the final character of the path passed into of_find_node_by_path()

>>> was "/".  Strictly speaking, ->full_name will never end with "/", so the return value

>>> should be NULL, indicating that the match fails.

>>

>> Ah, good catch. I should add a test case for that.

> 

> In my testing this looks okay. The while loop that calls into

> __of_find_node_by_path() looks like this:

> 

> 	while (np && *path == '/') {

> 		path++; /* Increment past '/' delimiter */

> 		np = __of_find_node_by_path(np, path);

> 		path = strchrnul(path, '/');

> 	}

> 

> If the path ends with a '/', then the loop will go around one more time.

> The pointer will be incremented to point at the null character and len

> will be null because strchrnul() will point at the last item.



Yes, that was my point.  The old version of of_find_node_by_path() would not

find a match if the path ended with a "/" (unless the full path was "/").

This patch series changes the behavior to be a match.


I will reply to this email with an additional patch that restores the

original behavior.


If you move the additional test cases you provide below and the test cases

in patch 3 to the beginning of the series, you can see the before and after

behavior of adding patch 1 and patch 2.


> 

> I've added a couple of test cases to make sure it works correctly:

> 

> diff --git a/drivers/of/selftest.c b/drivers/of/selftest.c

> index a9d00e8c17ea..10900b18fc06 100644

> --- a/drivers/of/selftest.c

> +++ b/drivers/of/selftest.c

> @@ -40,6 +40,12 @@ static void __init of_selftest_find_node_by_name(void)

>  	 	"find /testcase-data failed\n");

>  	of_node_put(np);

>  

> +	/* 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);

> +

>  	np = of_find_node_by_path("/testcase-data/phandle-tests/consumer-a");

>  	selftest(np && !strcmp("/testcase-data/phandle-tests/consumer-a", np->full_name),

>  	 	"find /testcase-data/phandle-tests/consumer-a failed\n");

> @@ -50,6 +56,12 @@ static void __init of_selftest_find_node_by_name(void)

>  	 	"find testcase-alias failed\n");

>  	of_node_put(np);

>  

> +	/* 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);

> +

>  	np = of_find_node_by_path("testcase-alias/phandle-tests/consumer-a");

>  	selftest(np && !strcmp("/testcase-data/phandle-tests/consumer-a", np->full_name),

>  	 	"find testcase-alias/phandle-tests/consumer-a failed\n");

> 

> g.

> 

> 

>>

>>>

>>>> +

>>>> +	for_each_child_of_node(parent, child) {

>>>> +		const char *name = strrchr(child->full_name, '/');

>>>> +		if (WARN(!name, "malformed device_node %s\n", child->full_name))

>>>> +			continue;

>>>> +		name++;


< snip >

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