Russell King - ARM Linux [off-list ref] writes:

On Fri, Sep 26, 2014 at 11:29:56AM +0200, Thomas Gleixner wrote:

quoted

On Thu, 25 Sep 2014, Kevin Hilman wrote:

quoted

Maybe I'm missing something, or maybe we're just lucky and nobody uses
them together, but irq_set_affinity_notifier() only allows a single
notifier to be registered at any given time.  So if you had a system

A single notifier per irq .....

So what about two drivers wanting to use this notifier, but sharing an
interrupt?

It sounds to me like this notifier was misdesigned from the very start,
and it should always have supported multiple notifiers.

I agree.

$SUBJECT patch tries to add that support, and is part of a series
wanting to use these notifiers in the PM QoS subsystem, while at the
same time not breaking existing users.

I suppose this series could be written without $SUBJECT patch, and
crossing fingers in the hopes that an existing user of the notifiers
doesn't also need to use the pm_qos constraints, but that seems like
knowingly leaving an armed landmine laying around.

Kevin