On Wed, 2005-03-09 at 11:08 -0500, Alan Stern wrote: > On Tue, 8 Mar 2005, Adam Belay wrote: > > > I'm not sure if I agree that a parent can be suspended without first suspending > > its children. In general, a parent device can be lowered in power only if the > > context and operation of the child devices are maintained. If the change in > > state does not affect the operation of child devices, then it really isn't a > > "suspend". > > 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? > > Consider a driver for a disk device, which has a "gendisk" child. The > idea of suspending a gendisk doesn't really make sense, since a gendisk > isn't a physical device. So the driver might want to spin down and > suspend the physical disk without suspending the gendisk child. Yeah, I'm in favor of such an approach. Thanks, Adam
