On 03/04/2016 02:58 PM, Rafael J. Wysocki wrote:

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How about modifying cpufreq_register_notifier to return an error if the

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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