On Wed, 23 Sep 2009, Yang Fei-AFY095 wrote: > I think I was confused by the logic :(, so for any non-high-speed udev, > skip_sys_resume would be set to 1, but for high speed udev, > skip_sys_resume would be set only if udev->parent is valid. > > I'm still not sure how to interprete the comment "High-speed root hubs > are an exception; they need to resume whenever the system wakes up in > order for USB-PERSIST port handover to work properly". What is broken if > we set skip_sys_resume regardless of the speed? Then USB-PERSIST port handover won't work. If a full-speed device is attached to the computer, and the UHCI or OHCI host controller gets reset or loses power during a system suspend, then during resume the kernel will believe that the device was unplugged and then replugged. If the device was a USB drive and it contained a mounted filesystem then the filesystem will become unusable. 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
