On Thu, 11 Jun 2009, Oliver Neukum wrote: > Am Donnerstag, 11. Juni 2009 16:52:03 schrieb Alan Stern: > > > Under this definition all devices behind an inactive link are suspended, > > > because they can't do any I/O. Which appears to makes sense, because > > > their drivers have to be notified before the link is suspended and the > > > link has to be turned on for the devices to be able to communicate with > > > the CPU and RAM. > > > > > > If this definition is adopted, then it's quite clear that the device can > > > only be suspended if all of its children are suspended and it's always > > > necessary to resume the parent of a device in order to resume the device > > > itself. > > > > Okay, I'll agree to that. It should be made clear that a device which > > is "suspended" according to this definition is not necessarily in a > > low-power state. For example, before powering down the link to a disk > > drive you might want the drive's suspend method to flush the drive's > > cache, but it wouldn't have to spin the drive down. > > This precludes handling busses that have low power states that are > left automatically. If such links are stacked the management of acceptable > latencies cannot be left to the busses. > An actual example are the link states of USB 3.0 I don't understand. Can you explain more fully? Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
