On Fri, 21 Sep 2012, Ming Lei wrote: > On Fri, Sep 21, 2012 at 12:49 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > > > The results will be more impressive if you plug three of the hubs > > directly into the fourth and attach the fourth hub to the computer. > > See all the logs in the below link for the test case above. > > http://kernel.ubuntu.com/~ming/kernel/usb/hub/ > > Hope the test can eliminate your concern on the problem. No, it doesn't. Your results were distorted by the fact that the 1-2.1 device wasn't a hub and consequently had a 2-second autosuspend timeout. Try setting its timeout to 0 (pretend it's a hub) and see what happens. Even in this test, the root hub was resumed and suspended 3 times instead of only once. > IMO, the only effect is that 'lsusb' becomes a bit slow, :-) It also wastes power by suspending and resuming devices multiple times. The purpose of the autosuspend mechanism is to save power, not to waste it. 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
