On Wed, 9 Mar 2005, Adam Belay wrote: > > This partly a question of definitions and usage. However, if a parent's > > change of state can be made transparent to the child device driver (i.e., > > the parent resumes automatically whenever the child driver tries to do > > anything), then why shouldn't the parent suspend itself without suspending > > the child? > > I think your not drawing a distinction between physical and logical > (class) devices. A physical device can be turned off, but the logical > child device is allowed to remain on. However, A physical child to a > physical device must be powered off before the parent. Perhaps this was > your intention? Normally yes, I agree, we will want to suspend children before parents. But your argument isn't valid; a physical child to a physical device might very well have its own external power supply. Then it wouldn't be necessary for the child to be off at the time the parent is turned off. Consider a USB disk drive as an example. If it plugs into the wall then it doesn't need to be spun down when its USB hub is suspended. Of course if you want to power down both devices, then certainly the child should be turned off first. Alan Stern
