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Tue, 20 Oct 2020 16:25:29 -0700 (PDT) Subject: Re: [RFC PATCH v3 3/9] software_node: Fix failure to hold refcount in software_node_get_next_child To: Sakari Ailus Cc: linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, linux.walleij@linaro.org, prabhakar.mahadev-lad.rj@bp.renesas.com, heikki.krogerus@linux.intel.com, dmitry.torokhov@gmail.com, laurent.pinchart+renesas@ideasonboard.com, kieran.bingham+renesas@ideasonboard.com, jacopo+renesas@jmondi.org, robh@kernel.org, davem@davemloft.net, linux@rasmusvillemoes.dk, andriy.shevchenko@linux.intel.com, sergey.senozhatsky@gmail.com, rostedt@goodmis.org, pmladek@suse.com, mchehab@kernel.org, tian.shu.qiu@intel.com, bingbu.cao@intel.com, sakari.ailus@linux.intel.com, yong.zhi@intel.com, rafael@kernel.org, gregkh@linuxfoundation.org, kitakar@gmail.com, dan.carpenter@oracle.org References: <20201019225903.14276-1-djrscally@gmail.com> <20201019225903.14276-4-djrscally@gmail.com> <20201020133148.GB843@valkosipuli.retiisi.org.uk> From: Dan Scally Message-ID: Date: Wed, 21 Oct 2020 00:25:28 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201020133148.GB843@valkosipuli.retiisi.org.uk> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Sakari On 20/10/2020 14:31, Sakari Ailus wrote: > Hi Daniel, > > On Mon, Oct 19, 2020 at 11:58:57PM +0100, Daniel Scally wrote: >> The software_node_get_next_child() function currently does not hold a kref >> to the child software_node; fix that. >> >> Fixes: 59abd83672f7 ("drivers: base: Introducing software nodes to the firmware node framework") >> Signed-off-by: Daniel Scally >> --- >> Changes in v3: >> - split out from the full software_node_graph*() patch >> >> drivers/base/swnode.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c >> index f01b1cc61..741149b90 100644 >> --- a/drivers/base/swnode.c >> +++ b/drivers/base/swnode.c >> @@ -450,7 +450,7 @@ software_node_get_next_child(const struct fwnode_handle *fwnode, >> c = list_next_entry(c, entry); >> else >> c = list_first_entry(&p->children, struct swnode, entry); >> - return &c->fwnode; >> + return software_node_get(&c->fwnode); > I believe similarly, the function should drop the reference to the previous > node, and not expect the caller to do this. The OF equivalent does the > same. I think I prefer it this way myself, since the alternative is having to explicitly call *_node_get() on a returned child if you want to keep it but also keep iterating. But I agree that it's important to take a consistent approach. I'll add that too; this will mean swnode_graph_find_next_port() and software_node_graph_get_next_endpoint() in patch 4 of this series will need changing slightly to square away their references.