On Thu, 30 Oct 2008, Oliver Neukum wrote:

Hi,

I am looking at runtime power management for usb hid devices.
There's a problem with hidraw. As we have no idea, what goes
on between a device and users of hidraw, it seems to me that
such a device should not be subject to runtime power management
without the user's explicit agreement.
But that would be only a kludge. Therefore this is my first draft of
an API to cleanly allow this.

It is based on telling drivers what capabilties a device must provide
to the system, allowing the driver to use the most aggressive runtime
power management compatible with the requirement.
Comments?

Would it make more sense never to autosuspend a device that has an open
hidraw interface?  Then if you want to, you could add an API allowing
the user to tell the kernel to suspend or to resume (if the existing
sysfs interface isn't sufficient).

Alan Stern