On Fri, 25 Aug 2006, Woodruff, Richard wrote: > > > > ? Wouldn't suspending the entire bus completely stop the > throughput > > > of > > > > any attached device? > > > > > > Not necessarily (right?). If I shut off VBUS then yes then I need > to > > > re-enumerate for sure. One might figure out a cleaver way of > shutting > > > it off and turning it back on in between host requests. > > > > No, you can't do that. Without VBUS power there's no reliable way to > > detect disconnects or media changes. > > That's a good point. I wonder in this case if it is possible to keep a > list of what was there. When you re-power if its not there, it should > be like it was disconnected, then act accordingly. If it is there all > is ok. It seems unlikely that the same PID/VID device would have > replaced it. New devices would show up as not being there before. > > Coding that all up would likely be a bunch of work assuming it was > possible. There have been long discussions about this in the past, mainly focused on suspend-to-disk (which generally turns off all power to the USB controllers). They were pretty much inconclusive; it's safe to assume no progress will be made on supporting this for a long time, if ever. Note that you don't need to replace one device with another having the same PID/VID. It could be the very same device but with new media loaded. That would be just as bad. Alan Stern
