linux-kernel - Re: [PATCH V3 09/13] cpufreq: governor: Move common sysfs tunables to cpufreq

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Message-ID: <CAJZ5v0gwaO0yBWKODdEzMwYUGgQvoaBv8Qt9_yCSJub5P1ftMg@mail.gmail.com>
Date:	Mon, 8 Feb 2016 13:58:49 +0100
From:	"Rafael J. Wysocki" <rafael@...nel.org>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Rafael Wysocki <rjw@...ysocki.net>,
	Juri Lelli <juri.lelli@....com>,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Saravana Kannan <skannan@...eaurora.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Michael Turquette <mturquette@...libre.com>,
	Steve Muckle <steve.muckle@...aro.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Morten Rasmussen <morten.rasmussen@....com>,
	dietmar.eggemann@....com,
	Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V3 09/13] cpufreq: governor: Move common sysfs tunables to cpufreq_governor.c

On Mon, Feb 8, 2016 at 12:39 PM, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> We have got five common sysfs tunables between ondemand and conservative
> governors, move their callbacks to cpufreq_governor.c to get rid of
> redundant code.
>
> Because of minor differences in the implementation of the callbacks,
> some more per-governor callbacks are introduced in order to not
> introduce any more "governor == ONDEMAND/CONSERVATIVE" like checks.

My most fundamental concern here is that attributes that don't apply
to a particular governor should not appear in sysfs at all when that
governor is in use (instead of appearing and always returning -EINVAL
which is sort of silly).

That doesn't mean the common code cannot access them, though.  They
still can be present in the data structure, but it may be a good idea
to set them to special values clearly meaning "invalid" then.

Thanks,
Rafael