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Date:   Mon, 13 Jun 2022 16:23:11 +0530
From:   Viresh Kumar <viresh.kumar@linaro.org>
To:     Lukasz Luba <lukasz.luba@arm.com>
Cc:     linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
        daniel.lezcano@linaro.org, amitk@kernel.org, rui.zhang@intel.com,
        rafael@kernel.org, dietmar.eggemann@arm.com
Subject: Re: [PATCH 1/3] thermal: cpufreq_cooling: Use a copy of local ops
 for each cooling device
Message-ID: <20220613105311.jdyjubid4jrgofwu@vireshk-i7>
References: <20220610100343.32378-1-lukasz.luba@arm.com>
 <20220613091611.ncd2hziu4nbyip4x@vireshk-i7>
 <5bac6f98-e1ba-3584-6eac-21eeaaa0ed26@arm.com>
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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@arm.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.

-- 
viresh