On Fri, 11 Mar 2005, Adam Belay wrote: > > > Now, that was probably bad example, but I do think some devices might > > > do usefull work even with their parents disabled. > > Yes, but at a logical (class) level the parent device would never be > disabled, right? I guess it would be possible to model such a situation > if we take advantage of the driver class design. I hadn't considered it > before, but I'll try to keep it in mind. It would be interesting to see > how common it might be. > > > > > There's another aspect to it as well. You can suspend the USB host > > controller and then _still_ use the external disk, if the host controller > > is automatically resumed when the next disk I/O request arrives. Whereas > > if you would stop the disk and its driver, the next I/O request might > > simply languish in a plugged queue. I suppose this would depend on > > whether the disk driver was smart enough to leave its queue unplugged > > under the right circumstances, so perhaps this isn't a great example. > > (And you're right about the possibility of data being lost -- although > > it's pretty unlikely -- which makes this an even worse example.) > > > > Alan Stern > > Yes, so I think if we ensure that the parent device is enabled at a > logical level, and that the power source is active, it would be possible > to do such a thing. I'm guessing this is something not to worry about > too much now; do you think so? Agreed. As Patrick said, this is a corner case. Alan Stern
