On Fri, 2 Jan 2009, Yan Li wrote: > Now I know 3 methods supposed can be used to shut the device: > 1. (Alan Stern said Windows use this) cut the USB port's power I said no such thing! In fact, I said exactly the opposite: Windows does _not_ cut the port's power. Instead it disables the port. > 2. send STOP SCSI command to stop it Note that this is different. The START-STOP command is used to spin-up or spin-down a disk. It does not affect the state of the data link. > 3. put it into suspend mode As far as the device is concerned, there is essentially no difference between 1 and 3. When the device's upstream port is disabled, the device must go into suspend mode. The best approach is to send a SYNCHRONIZE CACHE command followed by START-STOP (if the device supports it), and then to disable or suspend the port. In Linux, those two commands will be sent automatically if you unbind the device from usb-storage. The suspend has to be done manually unless you have set up a udev rule (or something equivalent) to enable autosuspend for the device. Of course, this requires CONFIG_USB_SUSPEND. 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
