linux-kernel - Re: [PATCH v2 3/5] thermal: devfreq_cooling: add new registration functions with Energy Model

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Message-ID: <a152499a-e486-10b6-3f69-cc3704807767@arm.com>
Date:   Wed, 2 Dec 2020 11:54:00 +0000
From:   Lukasz Luba <lukasz.luba@....com>
To:     Ionela Voinescu <ionela.voinescu@....com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, rui.zhang@...el.com,
        amit.kucheria@...durent.com, daniel.lezcano@...aro.org,
        orjan.eide@....com, robh@...nel.org,
        alyssa.rosenzweig@...labora.com, steven.price@....com,
        airlied@...ux.ie, daniel@...ll.ch
Subject: Re: [PATCH v2 3/5] thermal: devfreq_cooling: add new registration
 functions with Energy Model



On 12/2/20 11:49 AM, Ionela Voinescu wrote:
> On Wednesday 02 Dec 2020 at 11:14:02 (+0000), Lukasz Luba wrote:
>> Hi Ionela,
>>
>> On 12/2/20 10:24 AM, Ionela Voinescu wrote:
>>> Hi Lukasz,
>>>
>>> On Wednesday 18 Nov 2020 at 12:03:56 (+0000), Lukasz Luba wrote:
>>
>> [snip]
>>
>>>> +	struct device_node *np = NULL;
>>
>> [snip]
>>
>>>> +
>>>> +	if (dev->of_node)
>>>> +		np = of_node_get(dev->of_node);
>>>> +
>>>
>>> Should np be checked before use? I'm not sure if it's better to do the
>>> assign first and then the check on np before use. It depends on the
>>> consequences of passing a NULL node pointer later on.
>>
>> The np is actually dev->of_node (or left NULL, as set at the begging).
>> The only meaning of the line above is to increment the counter and then
>> decrement if CONFIG_OF_DYNAMIC was used.
>> The devfreq_cooling_register() has np = NULL and the registration can
>> handle it, so we should be OK here as well.
>>
> 
> Yes, I just wanted to make sure later registration can handle np = NULL,
> or whether we need to bail out.
> 
> In this case, you can drop both ifs - for (dev->of_node) before get and
> for np before put below, as of_node_get/of_node_put can handle NULL
> pointers themselves.

Right. I agree, I will resend this patch with that small change.
Thank you for having a look at it.

Lukasz

> 
> Thanks,
> Ionela.
>