linux-kernel - Re: [PATCH V3 2/5] PM / QOS: Pass request type to dev_pm_qos_read

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Date:   Tue, 18 Jun 2019 01:14:15 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Qais.Yousef@....com, mka@...omium.org, juri.lelli@...il.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 2/5] PM / QOS: Pass request type to dev_pm_qos_read_value()

On Monday, June 10, 2019 12:51:33 PM CEST Viresh Kumar wrote:
> In order to use dev_pm_qos_read_value(), and other internal routines to
> it, to read values for different QoS requests, pass request type as a
> parameter to these routines.
> 
> For now, it only supports resume-latency request type.

I don't quite like the structure by which the type arg is passed through the
entire call chain until the switch in dep_pm_qos_raw_read_value().

There is only one direct user of dev_pm_qos_raw_read_value() AFAICS which
is cpuidle. It shouldn't need to suffer the general case overhead, so I would
rename that function to dev_pm_qos_raw_resume_latency() and update cpuidle
accordingly.

Moreover, the callers of __dev_pm_qos_read_value() are interested in the
resume latency value too, so it might make sense to rename this as
__dev_pm_qos_resume_latency(), update its callers and put the switch
into dev_pm_qos_read_value().

Plus the changelog should explain the broader rationale of this change like
for the first patch IMO.