From: Grant Likely <grant.likely@linaro.org>
To: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
Michael Walle <michael@walle.cc>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Rob Herring <robh+dt@kernel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Sakari Ailus <sakari.ailus@linux.intel.com>,
Saravana Kannan <saravanak@google.com>
Subject: Re: fwnode_for_each_child_node() and OF backend discrepancy
Date: Wed, 29 Jun 2022 14:01:00 +0100 [thread overview]
Message-ID: <30D246E1-B0C7-404A-B690-A894AA79A524@linaro.org> (raw)
In-Reply-To: <CAJZ5v0g1VqJ2_2MtKGv-sHmKVQ12Rmj9r3Lr6D9wjmUYJwtoCw@mail.gmail.com>
> On 29 Jun 2022, at 11:50, Rafael J. Wysocki <rafael@kernel.org> wrote:
>
> On Tue, Jun 28, 2022 at 12:32 PM Krzysztof Kozlowski
> <krzysztof.kozlowski@linaro.org> wrote:
>>
>> On 27/06/2022 15:33, Rafael J. Wysocki wrote:
>>> On Mon, Jun 27, 2022 at 3:08 PM Krzysztof Kozlowski
>>> <krzysztof.kozlowski@linaro.org> wrote:
>>>>
>>>> On 27/06/2022 14:49, Michael Walle wrote:
>>>>> Hi,
>>>>>
>>>>> I tired to iterate over all child nodes, regardless if they are
>>>>> available
>>>>> or not. Now there is that handy fwnode_for_each_child_node() (and the
>>>>> fwnode_for_each_available_child_node()). The only thing is the OF
>>>>> backend
>>>>> already skips disabled nodes [1], making fwnode_for_each_child_node()
>>>>> and
>>>>> fwnode_for_each_available_child_node() behave the same with the OF
>>>>> backend.
>>>>>
>>>>> Doesn't seem to be noticed by anyone for now. I'm not sure how to fix
>>>>> that
>>>>> one. fwnode_for_each_child_node() and also fwnode_get_next_child_node()
>>>>> are
>>>>> used by a handful of drivers. I've looked at some, but couldn't decide
>>>>> whether they really want to iterate over all child nodes or just the
>>>>> enabled
>>>>> ones.
>>>>
>>>> If I get it correctly, this was introduced by 8a0662d9ed29 ("Driver
>>>> core: Unified interface for firmware node properties")
>>>> .
>>>
>>> Originally it was, but then it has been reworked a few times.
>>>
>>> The backend callbacks were introduced by Sakari, in particular.
>>
>> I see you as an author of 8a0662d9ed29 which adds
>> device_get_next_child_node() and uses of_get_next_available_child()
>> instead of of_get_next_child(). Although it was back in 2014, so maybe
>> it will be tricky to get original intention. :)
>
> The OF part of this was based on Grant's suggestions. My
> understanding at that time was that this was the right thing to do for
> OF and nobody told me otherwise.
>
>> Which commit do you mean when you refer to Sakari's work?
>
> 3708184afc77 device property: Move FW type specific functionality to
> FW specific files
>
> However, it didn't change the "available" vs "any" behavior for OF.
Back in the mists of time indeed. I don’t remember anything specific about all/available variants of the fwnode_ helpers. Auditing the existing users is probably needed to decide whether or not it can be changed.
g.
>
>>>
>>>> The question to Rafael - what was your intention when you added
>>>> device_get_next_child_node() looking only for available nodes?
>>>
>>> That depends on the backend.
>>
>> We talk about OF backend. In your commit device_get_next_child_node for
>> OF uses explicitly available node, not any node.
>
> Yes, it does.
>
> If that doesn't match the cases in which it is used, I guess it can be adjusted.
>
>>> fwnode_for_each_available_child_node() is more specific and IIRC it
>>> was introduced for fw_devlink (CC Saravana).
>>>
>>>> My understanding is that this implementation should be consistent with
>>>> OF implementation, so fwnode_get_next_child_node=get any child.
>>>
>>> IIUC, the OF implementation is not consistent with the
>>> fwnode_get_next_child_node=get any child thing.
>>>
>>>> However maybe ACPI treats it somehow differently?
>>>
>>> acpi_get_next_subnode() simply returns the next subnode it can find.
>
> I guess that the confusion is related to what "available" means for ACPI and OF.
>
> In the ACPI case it means "this a device object corresponding to a
> device that is present". In OF it is related to the "status" property
> AFAICS.
next prev parent reply other threads:[~2022-06-29 13:01 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-27 12:49 fwnode_for_each_child_node() and OF backend discrepancy Michael Walle
2022-06-27 13:08 ` Krzysztof Kozlowski
2022-06-27 13:33 ` Rafael J. Wysocki
2022-06-28 10:32 ` Krzysztof Kozlowski
2022-06-28 14:41 ` Sakari Ailus
2022-06-29 10:50 ` Rafael J. Wysocki
2022-06-29 13:01 ` Grant Likely [this message]
2022-06-28 11:10 ` Andy Shevchenko
2022-06-28 11:36 ` Michael Walle
2022-06-28 13:11 ` Andy Shevchenko
2022-06-28 13:23 ` Michael Walle
2022-06-28 13:29 ` Andy Shevchenko
2022-06-28 13:47 ` Michael Walle
2022-06-28 13:51 ` Krzysztof Kozlowski
2022-06-28 14:22 ` Michael Walle
2022-06-28 14:36 ` Krzysztof Kozlowski
2022-06-28 15:09 ` Michael Walle
2022-06-28 15:17 ` Krzysztof Kozlowski
2022-06-28 20:28 ` Andy Shevchenko
2022-06-28 20:52 ` Horatiu Vultur
2022-06-28 21:07 ` Michael Walle
2022-06-30 20:16 ` Horatiu Vultur
2022-06-30 21:00 ` Michael Walle
2022-06-30 21:21 ` Vladimir Oltean
2022-06-30 21:32 ` Michael Walle
2022-06-28 21:59 ` Vladimir Oltean
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