Driver Reinstall When Switching USB Ports

[Piyono]

One of those things that I've always noticed but never researched is Windows' tendency to reinstall a driver when a USB device is unplugged from one port and plugged into a different port.

It just happened today with an M-Audio Fast Track Pro which I've been using for a couple of weeks. I swapped it to a different port and XP got all excited. "New hardware! Awesome! I know what to do!"

Why does this happen?

]-[

 

[Chewy509]

Most onboard USB ports have individual controller IDs. (Look in device manager, and you'll see a huge group of USB controllers).

Since (according to Windows) you are connecting a device to a "new"/different controller, it has to redo the drivers...

 

[Piyono]

Yeah, but I figured that once a device is installed it's, you know, installed...

Besides, this happens even between two ports on the same controller.

 

[Will Rickards]

I read about this somewhere ... maybe wikipedia? That some devices identify themselves uniquely and some do not. But I can't seem to locate the source of my information.

 

[sechs]

\roothub0\device
is different than
\roothub1\device

Therefore, it has to install new drivers on the new port. It might be nice if it did this silently (ever seen a driver install for an ATA drive?).

 

[mubs]

Not true. This happens even if the device is installed to the same exact port. Just happened with my APC UPS which got unplugged; when I plugged it back in, XP did the same "new hw discovered" shit.

 

[Bozo]

The USB port has to unload the driver when a device is removed. It doesn't know what is going to be installed there next. Hard drive, memory stick, printer? Each would have its own driver.

Bozo :joker:

 

[sechs]

Not true. This happens even if the device is installed to the same exact port. Just happened with my APC UPS which got unplugged; when I plugged it back in, XP did the same "new hw discovered" shit.

Same thing happens with a PCI card. Should one expect USB to be different?

 

[Chewy509]

Just happened with my APC UPS which got unplugged;

Most likely due to the APC driver not supporting "detach" correctly for USB devices.

I have seen this a few times before myself.