On Sat, 28 Jul 2007, Olaf G. wrote: > > It's not possible for the ports on your computer but it is possible > > for certain brands of hub. For example, check out this page: > > > > http://www.gniibe.org/ac-power-by-usb/ac-power-control.html > > > > If you can get the right sort of hub, it just might work. > Nice link! Thanks a lot! > It seems like my hub (very cheap one: Ultron UH-430) supports it - not port > by port but at least "Ganged power switching".
Don't be so sure of that. What usually happens is that hubs report they support power switching in one form or another, but in reality they do not turn off +5 Vbus power when asked to do so. The only way to tell is to test it with a voltmeter, LED, or something similar. > First of all I made some tests with an optical USB mouse because it's easy to > see whether it is powered or not (the dvb stick has no power indicators) Are you certain? The mouse's LED might go off whenever it is suspended, even though Vbus power is still available. > Works fine. I'm able to turn it on and off. > But unfortunately it does not work with the DVB stick. > > Turning it off (uninitialized state) the first time produces no messages, > > turning power on leads to the well known: > hub 1-5:1.0: state 7 ports 4 chg 0000 evt 0002 > hub 1-5:1.0: port 1, status 0101, change 0001, 12 Mb/s > hub 1-5:1.0: debounce: port 1: total 100ms stable 100ms status 0x101 > usb 1-5.1: new high speed USB device using ehci_hcd and address 8 > usb 1-5.1: khubd timed out on ep0in len=0/8 > usb 1-5.1: device descriptor read/8, error -110 > usb 1-5.1: khubd timed out on ep0in len=0/8 > usb 1-5.1: device descriptor read/8, error -110 > usb 1-5.1: new high speed USB device using ehci_hcd and address 9 > usb 1-5.1: khubd timed out on ep0in len=0/8 > usb 1-5.1: device descriptor read/8, error -110 > usb 1-5.1: khubd timed out on ep0in len=0/8 > usb 1-5.1: device descriptor read/8, error -110 > usb 1-5.1: new high speed USB device using ehci_hcd and address 10 > usb 1-5.1: khubd timed out on ep0in len=0/64 > usb 1-5.1: khubd timed out on ep0in len=0/64 > usb 1-5.1: khubd timed out on ep0in len=0/64 > usb 1-5.1: device descriptor read/64, error -110 > usb 1-5.1: khubd timed out on ep0in len=0/64 > > turning power off from now on produces: > usb 1-5.1: device reset changed speed! > hub 1-5:1.0: state 7 ports 4 chg 0000 evt 0002 > > from now on it is always the same. > > Disabling the stick in initilized state and then re-enabling it leads to a > correct detection in WARM state - if the device would have been completely > powered down I'd exected a detection in cold state. Which indicates your hub does _not_ perform power switching. > Anyway - it was a very interesting afternoon - I learned a lot :) - seems > like > I have to face the fact that the DVB stick is unusable in this maschine > without replugging it. Alan Stern ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ Linux-usb-users@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-users
