Am Mittwoch, 14. März 2007 15:16 schrieb Alan Stern:
> On Wed, 14 Mar 2007, Oliver Neukum wrote:
>
> > Am Dienstag, 13. März 2007 21:37 schrieb Alan Stern:
> > > +/**
> > > + * usb_external_resume_device - external resume of a USB device and its
> > > interfaces
> > > + * @udev: the usb_device to resume
> > > + *
> > > + * This routine handles external resume requests: ones not generated
> > > + * internally by a USB driver (autoresume) but rather coming from the
> > > user
> > > + * (via sysfs), the PM core (system resume), or the device itself (remote
> > > + * wakeup). @udev's usage counter is unaffected.
> > > + *
> > > + * The caller must hold @udev's device lock.
> > > + */
> > > +int usb_external_resume_device(struct usb_device *udev)
> > > {
> >
> > > + usb_pm_lock(udev);
> > > + udev->auto_pm = 0;
> > > + status = usb_resume_both(udev);
> > > + usb_pm_unlock(udev);
> > > +
> > > + /* Now that the device is awake, we can start trying to autosuspend
> > > + * it again. */
> > > + if (status == 0)
> > > + usb_try_autosuspend_device(udev);
> > > return status;
> >
> > Is itr sensible to resume a device which autosuspend had suspended?
>
> Sure. For example, let's say the user writes "-1" to the
> power/autosuspend file. The kernel sets the delay to -1 (thereby
> disabling autosuspend in the future) and wakes up the device.
>
> Or maybe the device sends a remote wakeup request, so the kernel has to
> resume it.
Or the system wakes up. And all devices sleeping while the system wasn't
suspended wake up. Unless I am mistaken this way you can _increase_
power consumption if you suspend your system often enough, with enough
devices and long enough a timeout for autosuspend.
And remember, any DMA means no deep sleep states.
Regards
Oliver
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