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Fri, 18 Dec 2020 14:19:06 -0800 (PST) Subject: Re: [PATCH v2 04/12] software_node: Enforce parent before child ordering of nodes arrays To: Laurent Pinchart Cc: linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, linux-media@vger.kernel.org, devel@acpica.org, rjw@rjwysocki.net, lenb@kernel.org, gregkh@linuxfoundation.org, yong.zhi@intel.com, sakari.ailus@linux.intel.com, bingbu.cao@intel.com, tian.shu.qiu@intel.com, mchehab@kernel.org, robert.moore@intel.com, erik.kaneda@intel.com, pmladek@suse.com, rostedt@goodmis.org, sergey.senozhatsky@gmail.com, andriy.shevchenko@linux.intel.com, linux@rasmusvillemoes.dk, laurent.pinchart+renesas@ideasonboard.com, jacopo+renesas@jmondi.org, kieran.bingham+renesas@ideasonboard.com, linus.walleij@linaro.org, heikki.krogerus@linux.intel.com, kitakar@gmail.com, jorhand@linux.microsoft.com References: <20201217234337.1983732-1-djrscally@gmail.com> <20201217234337.1983732-5-djrscally@gmail.com> From: Daniel Scally Message-ID: <0b7cac02-ea34-6068-a1f6-de4bb34dca5a@gmail.com> Date: Fri, 18 Dec 2020 22:19:05 +0000 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: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Laurent On 18/12/2020 16:02, Laurent Pinchart wrote: > Hi Daniel, > > Thank you for the patch. > > On Thu, Dec 17, 2020 at 11:43:29PM +0000, Daniel Scally wrote: >> Registering software_nodes with the .parent member set to point to a >> currently unregistered software_node has the potential for problems, >> so enforce parent -> child ordering in arrays passed in to >> software_node_register_nodes(). >> >> Software nodes that are children of another software node should be >> unregistered before their parent. To allow easy unregistering of an array >> of software_nodes ordered parent to child, reverse the order in which >> software_node_unregister_nodes() unregisters software_nodes. >> >> Suggested-by: Andy Shevchenko >> Signed-off-by: Daniel Scally >> --- >> Changes in v2: >> >> - Squashed the patches that originally touched these separately >> - Updated documentation >> >> drivers/base/swnode.c | 43 ++++++++++++++++++++++++++++++------------- >> 1 file changed, 30 insertions(+), 13 deletions(-) >> >> diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c >> index 615a0c93e116..cfd1faea48a7 100644 >> --- a/drivers/base/swnode.c >> +++ b/drivers/base/swnode.c >> @@ -692,7 +692,10 @@ swnode_register(const struct software_node *node, struct swnode *parent, >> * software_node_register_nodes - Register an array of software nodes >> * @nodes: Zero terminated array of software nodes to be registered >> * >> - * Register multiple software nodes at once. >> + * Register multiple software nodes at once. If any node in the array >> + * has it's .parent pointer set, then it's parent **must** have been >> + * registered before it is; either outside of this function or by >> + * ordering the array such that parent comes before child. >> */ >> int software_node_register_nodes(const struct software_node *nodes) >> { >> @@ -700,33 +703,47 @@ int software_node_register_nodes(const struct software_node *nodes) >> int i; >> >> for (i = 0; nodes[i].name; i++) { >> - ret = software_node_register(&nodes[i]); >> - if (ret) { >> - software_node_unregister_nodes(nodes); >> - return ret; >> + const struct software_node *parent = nodes[i].parent; >> + >> + if (parent && !software_node_to_swnode(parent)) { >> + ret = -EINVAL; >> + goto err_unregister_nodes; >> } >> + >> + ret = software_node_register(&nodes[i]); >> + if (ret) >> + goto err_unregister_nodes; >> } >> >> return 0; >> + >> +err_unregister_nodes: >> + software_node_unregister_nodes(nodes); >> + return ret; >> } >> EXPORT_SYMBOL_GPL(software_node_register_nodes); >> >> /** >> * software_node_unregister_nodes - Unregister an array of software nodes >> - * @nodes: Zero terminated array of software nodes to be unregistered >> + * @nodes: Zero terminated array of software nodes to be unregistered. > > Not sure if this is needed. Hah, of course. Hangover from the last version (when I had made that line two sentences) > >> * >> - * Unregister multiple software nodes at once. >> + * Unregister multiple software nodes at once. If parent pointers are set up >> + * in any of the software nodes then the array MUST be ordered such that > > I'd either replace **must** above with MUST, or use **must** here. I'm > not sure if kerneldoc handles emphasis with **must**, if it does that > seems a bit nicer to me, but it's really up to you. Honestly I haven't delved into kerneldoc yet, but either way I think **must** is better in both places - will change. > Reviewed-by: Laurent Pinchart Thank you! > >> + * parents come before their children. >> * >> - * NOTE: Be careful using this call if the nodes had parent pointers set up in >> - * them before registering. If so, it is wiser to remove the nodes >> - * individually, in the correct order (child before parent) instead of relying >> - * on the sequential order of the list of nodes in the array. >> + * NOTE: If you are uncertain whether the array is ordered such that >> + * parents will be unregistered before their children, it is wiser to >> + * remove the nodes individually, in the correct order (child before >> + * parent). >> */ >> void software_node_unregister_nodes(const struct software_node *nodes) >> { >> - int i; >> + unsigned int i = 0; >> + >> + while (nodes[i].name) >> + i++; >> >> - for (i = 0; nodes[i].name; i++) >> + while (i--) >> software_node_unregister(&nodes[i]); >> } >> EXPORT_SYMBOL_GPL(software_node_unregister_nodes); >