On Tue, 22 Sep 2015, Oliver Neukum wrote:

Indeed. We can handle output to suspended devices by waking them.
I don't see why this case is different. We are talking about input
only.

quoted

The runtime-PM "usage" value for these devices is a little tricky to 
calculate.  It should be nonzero if there are any open files _and_ the 
device isn't "inhibited".  I don't know the best way to represent that 
kind of condition in the runtime PM framework.

Does that make sense in the generic framework at all? I still
think that drivers should cease IO for input in such cases.
That should involve a common callback, but no counter.

I'm not sure I understand what you're saying.  Are you suggesting that
this "inhibit" mechanism should involve a new callback different from
the existing runtime-PM callbacks?  And when this new callback is
invoked, drivers should cancel existing input requests (these devices
are input-only) and go to low power?

This would create a parallel runtime-PM mechanism which is independent
of the existing one.  Is that really a good idea?

Alan Stern