On Sat, Sep 22, 2012 at 12:07 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > 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 Yes, 1-2.1 is a built-in usbnet device, but there are four hubs, and 3 are connected into another one. > what happens. 'lsusb' is still OK even the autosuspend_delay of 1-2.1 is set as zero. > > 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. It depends on the use frequency of 'lsusb', doesn't it? Thanks, -- Ming Lei -- 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
