linux-kernel - Re: [PATCH -next] net: dsa: Simplify with scoped for each OF child loop

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Message-ID: <d44d2e53-6684-4fe5-bcc3-60d387044b63@kernel.org>
Date: Thu, 22 Aug 2024 16:39:38 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Jinjie Ruan <ruanjinjie@...wei.com>, Jakub Kicinski <kuba@...nel.org>
Cc: andrew@...n.ch, f.fainelli@...il.com, olteanv@...il.com,
 davem@...emloft.net, edumazet@...gle.com, pabeni@...hat.com,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] net: dsa: Simplify with scoped for each OF child
 loop

On 22/08/2024 04:07, Jinjie Ruan wrote:
> 
> 
> On 2024/8/22 8:18, Jakub Kicinski wrote:
>> On Tue, 20 Aug 2024 14:58:04 +0800 Jinjie Ruan wrote:
>>> Use scoped for_each_available_child_of_node_scoped() when iterating over
>>> device nodes to make code a bit simpler.
>>
>> Could you add more info here that confirms this works with gotos?
>> I don't recall the details but I thought sometimes the scoped
>> constructs don't do well with gotos. I checked 5 random uses
>> of this loop and 4 of them didn't have gotos.
> 
> Hi, Jakub
> 
>>>From what I understand, for_each_available_child_of_node_scoped() is not
> related to gotos, it only let the iterating child node self-declared and
> automatic release, so the of_node_put(iterating_child_node) can be removed.
> 
> For example, the following use case has goto and use this macro:
> 
> Link:
> https://lore.kernel.org/all/20240813-b4-cleanup-h-of-node-put-other-v1-6-cfb67323a95c@linaro.org/

Jinjie,
You started this after me, shortly after my series, taking the commit
msgs and subjects, and even using my work as reference or explanation of
your patches. Basically you just copy-paste. That's ok, thouogh, but you
could at least Cc me to tell me that you are doing it to avoid
duplication. That would be nice... And you could *try to* understand
what you are doing, so you can answer to such concerns as Jakub raised.
Otherwise how can we know that your code is correct?

Jakub,
Scoped uses in-place variable declarations, thus earlier jumps over it
are not allowed. The code I was converting did not have such jumps, so
was fine. Not sure if this is the case here, because Jinjie Ruan should
have checked it and explained that it is safe.

Best regards,
Krzysztof