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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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