On Sun, 11 Jan 2015, vichy wrote: > hi Alan: > > > >> 3. for host part, runtime suspend/resume is only doing port > >> suspend/resume or both host and port going to suspend/resume? > > > > Only the port. However, when _all_ the devices attached to the host > > controlluer go into runtime suspend, the controller itself will also be > > put into runtime suspend. > here "controller itself will also be put into runtime suspend." mean > the controller itself will put into suspend or root hub ports will put > in suspend? Firstly, you should realize that a hub port can be put into suspend _only_ if a device is plugged into it. If nothing is plugged into a port then the port cannot be put into suspend. Secondly, you should realize that putting a USB device into suspend means the same thing as suspending the hub port the device is plugged into. Thirdly, you should realize therefore that if _all_ the devices attached to the host controller are in runtime suspend, then all the connected ports must be suspended. (And none of the disconnected ports can be suspended, since it is impossible to suspend a disconnected port.) Fourthly, you should realize that "controller itself will also be put into runtime suspend" means the controller itself will be put into runtime suspend. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
