linux-kernel - Re: [PATCH v2 1/5] arch_topology: Introduce thermal pressure update function

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Message-ID: <018a888d-ed39-09a1-9828-cedef23c7701@arm.com>
Date:   Wed, 27 Oct 2021 15:35:14 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Lukasz Luba <lukasz.luba@....com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, sudeep.holla@....com,
        will@...nel.org, catalin.marinas@....com, linux@...linux.org.uk,
        gregkh@...uxfoundation.org, rafael@...nel.org,
        viresh.kumar@...aro.org, amitk@...nel.org,
        daniel.lezcano@...aro.org, amit.kachhap@...il.com,
        thara.gopinath@...aro.org, bjorn.andersson@...aro.org,
        agross@...nel.org
Subject: Re: [PATCH v2 1/5] arch_topology: Introduce thermal pressure update
 function

On 27/10/2021 10:56, Lukasz Luba wrote:
> Hi Dietmar,
> 
> Thank you for having a look at this.
> 
> On 10/26/21 5:51 PM, Dietmar Eggemann wrote:
>> On 15/10/2021 16:45, Lukasz Luba wrote:

[...]

>>> +void topology_thermal_pressure_update(const struct cpumask *cpus,
>>> +                      unsigned long capped_freq)
>>> +{
>>
>> ... why not just s/unsigned long th_pressure/unsigned long capped_freq
>> in existing topology_set_thermal_pressure() and move code the
>> frequency/capacity conversion in there? The patch set will become
>> considerably smaller.
> 
> I've been trying to avoid confusion when changing actually behavior
> of the API function. Thus, introducing new would IMO opinion
> make sure the old 'set' function was expecting proper pressure
> value, while the new 'update' expects frequency.
> 
> I agree that the patch set would be smaller in that case, but I'm
> not sure if that would not hide some issues. This one would
> definitely break compilation of some vendor modules (or drivers
> queuing or under review), not silently passing them through (with wrong
> argument).

I see, since the parameter type list would stay the same, this could
potentially happen.

[...]