On Wed, 2013-08-14 at 13:24 +0530, Vivek Gautam wrote: > Hi all, > > > Going through the power suspend/resume sequence of USB, got hit by a doubt. > > I am not able to figure out how the USB core driver takes care of It doesn't. > devices and root-hubs across suspend/resume. Are the device contexts > saved somewhere and then restored back on resume ? Usually not. The state of interfaces are the responsibility of interface drivers (colloquially called device drivers). Most devices just don't offer an API for saving state. The drivers recreate as opposed to restore the state. > How does the suspend/resume sequence taken care by "drivers/usb/core/.." ? The generic driver core guarantees that suspend()/resume() are called in the right sequence. > One more question here: > If a hub on USB bus is getting re-enumerated, is it really necessary > that its child devices shall also be re-enumerated ? Is there someway Yes. > out in which we can save the child-devices' context pointers and then > once hub has been re-enumerated back, we restore back them. How do you know they are identical? HTH Oliver -- 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
