From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751050AbaEWBOm (ORCPT ); Thu, 22 May 2014 21:14:42 -0400 Received: from mail-pa0-f50.google.com ([209.85.220.50]:43927 "EHLO mail-pa0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750863AbaEWBOk (ORCPT ); Thu, 22 May 2014 21:14:40 -0400 Message-ID: <537EA0FE.9000809@gmail.com> Date: Thu, 22 May 2014 18:14:38 -0700 From: Frank Rowand Reply-To: frowand.list@gmail.com User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/20130801 Thunderbird/17.0.8 MIME-Version: 1.0 To: Grant Likely CC: linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, David Daney , Pantelis Antoniou Subject: Re: [PATCH 2/3] of: Make of_find_node_by_path() handle /aliases References: <1399993115-21552-1-git-send-email-grant.likely@linaro.org> <1399993115-21552-3-git-send-email-grant.likely@linaro.org> <53757D25.1060005@gmail.com> <20140516105444.C1DB7C42277@trevor.secretlab.ca> <20140518092730.109AAC40B8A@trevor.secretlab.ca> <537C1252.3090900@gmail.com> <20140522011600.C0014C40B13@trevor.secretlab.ca> In-Reply-To: <20140522011600.C0014C40B13@trevor.secretlab.ca> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/21/2014 6:16 PM, Grant Likely wrote: > On Tue, 20 May 2014 19:41:22 -0700, Frank Rowand wrote: >> On 5/18/2014 2:27 AM, Grant Likely wrote: >>> On Fri, 16 May 2014 11:54:44 +0100, Grant Likely wrote: >>>> On Thu, 15 May 2014 19:51:17 -0700, Frank Rowand 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 >>>>>> Signed-off-by: Pantelis Antoniou >>>>>> [grant.likely: Rework to not require allocating at runtime] >>>>>> Acked-by: Rob Herring >>>>>> Signed-off-by: Grant Likely >>>>>> --- >>>>>> 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. > > Ah, I see. That raises the question about what the behaviour /should/ > be. Off the top of my head, matching against a trailing '/' seems to be > okay. Are there situations that you see or can think of where matching > would be the wrong thing to do? I have not thought of a case where matching against a trailing '/' would hurt anything. It just seemed better to be consistent in naming.