linux-kernel - Re: [PATCH 1/3] thermal: cpufreq_cooling: Use a copy of local ops for each cooling device

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Date:   Mon, 13 Jun 2022 12:23:25 +0100
From:   Lukasz Luba <lukasz.luba@....com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        daniel.lezcano@...aro.org, amitk@...nel.org, rui.zhang@...el.com,
        rafael@...nel.org, dietmar.eggemann@....com
Subject: Re: [PATCH 1/3] thermal: cpufreq_cooling: Use a copy of local ops for
 each cooling device



On 6/13/22 11:53, Viresh Kumar wrote:
> On 13-06-22, 11:37, Lukasz Luba wrote:
>> Hi Viresh,
>>
>> Thank you for the ACKs in the other patches and suggestion in this one.
>>
>> On 6/13/22 10:16, Viresh Kumar wrote:
>>> On 10-06-22, 11:03, Lukasz Luba wrote:
>>>> It is very unlikely that one CPU cluster would have the EM and some other
>>>> won't have it (because EM registration failed or DT lacks needed entry).
>>>> Although, we should avoid modifying global variable with callbacks anyway.
>>>> Redesign this and add safety for such situation.
>>>>
>>>> Signed-off-by: Lukasz Luba <lukasz.luba@....com>
>>>> ---
>>>>    drivers/thermal/cpufreq_cooling.c | 16 +++++++++++++---
>>>>    1 file changed, 13 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/thermal/cpufreq_cooling.c b/drivers/thermal/cpufreq_cooling.c
>>>> index b8151d95a806..e33183785fac 100644
>>>> --- a/drivers/thermal/cpufreq_cooling.c
>>>> +++ b/drivers/thermal/cpufreq_cooling.c
>>>> @@ -554,7 +554,12 @@ __cpufreq_cooling_register(struct device_node *np,
>>>>    	/* max_level is an index, not a counter */
>>>>    	cpufreq_cdev->max_level = i - 1;
>>>> -	cooling_ops = &cpufreq_cooling_ops;
>>>> +	cooling_ops = kmemdup(&cpufreq_cooling_ops, sizeof(*cooling_ops),
>>>> +			      GFP_KERNEL);
>>>
>>> I don't like the way we are duplicating the ops here. Instead of this it would
>>> be better to add the OPs field in the cooling device structure and fill its
>>> fields from here. The ops structure will be allocated with the cooling device
>>> itself.
>>>
>>
>> I think I know what you mean. Make sense. There are quite a few
>> different cooling types of devices which are using the API
>> thermal_of_cooling_device_register() with the custom 'ops'. We
>> probably don't want to disturb that well working drivers and ecosystem.
> 
> I was just suggesting to update "struct cpufreq_cooling_device" :)
> 
> This is what I was, wrongly, referring to as cooling device.
> 
> I should have written the exact structure name instead, my bad.
> 

No worries. Thanks, I'll send a v2 with these changes.