On Mon, 26 Dec 2005, Paul Ionescu wrote: > Hi Alan, > > I have a FC4 with kernel 2.6.14-1.1653_FC4, and I wanted to test suspend > and even power off a USB device. > > I plugged a USB flash disk at 3-1 and tried to suspend it: > cd /sys/bus/usb/devices > echo -n 3 > 3-1/3-1\:1.0/power/state ; echo -n 3 > 3-1/power/state ; echo > -n 3 > usb3/power/state > > While all "state" files changed value to "3", tested with "cat state" in > each case, the LED on the usb flash disk is still ON, and I can > mount/access it without echoing "0" in the state file. > Actually, I don't think that the device is suspended at all. > Am I doing something wrong ?
No, but I forgot to mention a very important requirement in my earlier message. For this runtime USB power management stuff to work, you _must_ set the CONFIG_USB_SUSPEND kernel configuration option. And FC4 does not set it; so to make things work you will have to rebuild the USB drivers. There's one other thing to note: Power off is different from suspend. Many USB host controllers are not capable of turning off the power to their ports. (All external hubs are supposed to have this capability, however.) So if you have a USB device plugged directly into your computer, you may indeed be able to suspend it but you probably won't be able to power it off. Alan Stern ------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Do you grep through log files for problems? Stop! Download the new AJAX search engine that makes searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! http://ads.osdn.com/?ad_id=7637&alloc_id=16865&op=click _______________________________________________ [email protected] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
