From mboxrd@z Thu Jan  1 00:00:00 1970
From: Steve Muckle <steve.muckle@linaro.org>
Subject: Re: [PATCH v2 6/10] cpufreq: Support for fast frequency switching
Date: Fri, 4 Mar 2016 15:59:14 -0800
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To: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>, Linux PM list <linux-pm@vger.kernel.org>, Juri Lelli <juri.lelli@arm.com>, ACPI Devel Maling List <linux-acpi@vger.kernel.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Peter Zijlstra <peterz@infradead.org>, Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>, Viresh Kumar <viresh.kumar@linaro.org>, Vincent Guittot <vincent.guittot@linaro.org>, Michael Turquette <mturquette@baylibre.com>, Ingo Molnar <mingo@kernel.org>

On 03/04/2016 02:58 PM, Rafael J. Wysocki wrote:
>>> How about modifying cpufreq_register_notifier to return an error if the
>>> >> driver has a fast_switch callback installed and an attempt to register a
>>> >> transition notifier is made?
>> >
>> > That sounds like a good idea.
>
> Transition notifiers may be registered before the driver is
> registered, so that won't help in all cases.

Could that hole be closed by a similar check in
cpufreq_register_driver()? I.e. if the transition_notifier list is not
empty, fail to register the driver (if the driver has a fast_switch
routine)?

Or alternatively, the fast_switch routine is not installed.

thanks,
Steve