From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753268AbcGSJh0 (ORCPT ); Tue, 19 Jul 2016 05:37:26 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35834 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753160AbcGSJhW (ORCPT ); Tue, 19 Jul 2016 05:37:22 -0400 Date: Tue, 19 Jul 2016 11:37:15 +0200 From: Benjamin Tissoires To: Andrew Duggan Cc: linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, Dmitry Torokhov , Linus Walleij , Jiri Kosina , Vincent Huang , Nick Dyer , Chris Healy Subject: Re: [PATCH v3 1/8] Input: synaptics-rmi4: Use of_get_child_by_name() instead of of_find_node_by_name() Message-ID: <20160719093714.GU4663@mail.corp.redhat.com> References: <1468476488-7935-1-git-send-email-aduggan@synaptics.com> <20160718144820.GL4663@mail.corp.redhat.com> <578D627C.3020800@synaptics.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <578D627C.3020800@synaptics.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Tue, 19 Jul 2016 09:37:22 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Jul 18 2016 or thereabouts, Andrew Duggan wrote: > On 07/18/2016 07:48 AM, Benjamin Tissoires wrote: > >On Jul 13 2016 or thereabouts, Andrew Duggan wrote: > >>Calling of_find_node_by_name() assumes that the caller has incremented > >>the refcount of the of_node being passed in. Currently, the caller is > >>not incrementing the refcount of the of_node which results in the node > >>being prematurely freed when of_find_node_by_name() calls of_node_put() > >>on it. Instead use of_get_child_by_name() which does not call put on the > >>of_node. > >There are 2 other differences in using of_get_child_by_name() in place > >of of_find_node_by_name(). One is that now we are following the OF tree > >while the spinlock is not held. I think it's fine in our case. The > >other difference is that the returned of_node has not been called > >of_node_get() on it. I am not 100% sure, but I think it might be good to > >call of_node_get() on the of node here, and in remove call > >of_node_put(), just to be sure we don't use the of_node while it has > >been freed. > > The comment for of_get_child_by_name() says that it returns an of_node with > the refcount incremented (drivers/of/base.c:717). Also, that the caller > needs to call of_node_put() when finished with it. I take that to mean that > the of_node_get() has been done for me by of_get_child_by_name(). Then > rmi_unregister_function() calls of_node_put() when unregistered the function > device undoing of_get_child_by_name()'s increment of the refcount. > > Unless I am missing something I think the current implementation is correct. > Hopefully, it is since this patch has already landed in Linus's tree. Oh, then OK. Sorry for coming late in the party then :) Cheers, Benjamin > > Andrew > > > > >Cheers, > >Benjamin > > > >>Signed-off-by: Andrew Duggan > >>--- > >> drivers/input/rmi4/rmi_bus.c | 4 ++-- > >> 1 file changed, 2 insertions(+), 2 deletions(-) > >> > >>diff --git a/drivers/input/rmi4/rmi_bus.c b/drivers/input/rmi4/rmi_bus.c > >>index b368b05..253df96 100644 > >>--- a/drivers/input/rmi4/rmi_bus.c > >>+++ b/drivers/input/rmi4/rmi_bus.c > >>@@ -157,11 +157,11 @@ static int rmi_function_match(struct device *dev, struct device_driver *drv) > >> static void rmi_function_of_probe(struct rmi_function *fn) > >> { > >> char of_name[9]; > >>+ struct device_node *node = fn->rmi_dev->xport->dev->of_node; > >> snprintf(of_name, sizeof(of_name), "rmi4-f%02x", > >> fn->fd.function_number); > >>- fn->dev.of_node = of_find_node_by_name( > >>- fn->rmi_dev->xport->dev->of_node, of_name); > >>+ fn->dev.of_node = of_get_child_by_name(node, of_name); > >> } > >> #else > >> static inline void rmi_function_of_probe(struct rmi_function *fn) > >>-- > >>2.5.0 > >> >