On Sun, 13 Jun 2004, Paul Ionescu wrote: > Is possible to power down an usb device using sysfs or procfs ?
The short answer is: No. In more detail: It depends on the type of hub you plug the device into, or the type of USB controller on your computer (if you plug the device directly into the computer). Some are capable of turning off power to individual ports and some aren't. In any case, the USB system code in Linux doesn't include any easy way to manipulate the power settings using procfs or sysfs. > Something like "safe eject device" in windoze ? That's a totally different matter. The "safe eject device" mechanism doesn't affect the power so much as other important things, like whether the disk is mounted. Clearly you can unmount a USB disk before unplugging it -- and you don't need procfs or sysfs to do so! > I have a USB hdd, powered by the usb bus, and before I plug it out, I > would like to power it off. Why? There's nothing wrong with powering it off by unplugging it from its power source (which in this case is the USB bus). > If I rmmod the ehci_hcd module, it seems that the device is powering > off, but then all my usb 2 devices are off :( > The same if I have an usb1 device but with rmmod uhci_hcd, I will power > off all usb1 devices. A less dramatic approach might be to tell the driver modules to stop controlling a particular USB controller. However, there is no way to do that. > Is it possible to power down individual USB devices ? Not in Linux. It _is_ possible to suspend them (in the latest kernel versions), which reduces their power usage to a minimum level. Alan Stern ------------------------------------------------------- This SF.Net email is sponsored by the new InstallShield X. >From Windows to Linux, servers to mobile, InstallShield X is the one installation-authoring solution that does it all. Learn more and evaluate today! http://www.installshield.com/Dev2Dev/0504 _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
