On Wed, 31 Jan 2007, Joe Wells wrote:
> Thanks very much for your advice, Alan!
>
> Alan Stern <[EMAIL PROTECTED]> writes:
>
> > On Wed, 31 Jan 2007, Joe Wells wrote:
> >
> >> I want to simulate the effect of unplugging a USB device and
> >> plugging it back in without having to physically unplug it. Is it
> >> possible to "unplug" a USB device by software actions alone? If
> >> so, could someone please tell me how?
> >
> > It depends on exactly what you want to simulate.
>
> I have a piece of hardware that works reliably when I unplug it from
> the USB port and remove associated kernel modules between every two
> openings of the device file. It works unreliably when I don't follow
> this procedure. (Yes, obviously something is buggy, but which piece
> of hardware or software has the bug is unclear and I have a procedure
> that works.)
Okay... but finding and fixing the bug might let you use a much simpler
procedure.
> > For example, unplugging a USB device will interrupt the +5 V power
> > it receives from the bus. With most PC systems, the USB hardware
> > does not permit you to do this in software.
>
> How would I find out if I can turn off the power to the USB port in
> software? If it could be done on a particular computer, which
> software actions would do it?
I was speaking conservatively. As far as I know, _no_ personal computer
systems allow you to turn off the power to the USB bus, without shutting
down the entire computer. Some brands of USB hub do allow it; see the
description on this web page:
http://www.gniibe.org/ac-power-by-usb/ac-power-control.html
> > Other aspects of replugging (in particular, the device reset it
> > causes) can indeed be carried out in software.
> >
> >> In case it matters, I am only using one USB device, so resetting
> >> the entire USB subsystem would not be a problem for me.
> >
> > In that case it would be enough to unload the USB controller driver
> > and then load it back. For instance, "rmmod ohci-hcd ; modprobe
> > ohci-hcd". The actual driver to use will depend on your system and
> > on the USB device in question; check the system log to find out.
>
> If I run "lsmod | egrep 'hci|usb'", I get this output:
>
> usbserial 29992 2 keyspan_pda,keyspan
> hsfusbcd2 59352 0
> hsfserial 21444 6
> hsfusbcd2,hsfmc97sis,hsfmc97ati,hsfmc97ali,hsfmc97via,hsfpcibasic2
> hsfengine 1312916 7
> hsfusbcd2,hsfmc97sis,hsfmc97ati,hsfmc97ali,hsfmc97via,hsfpcibasic2,hsfserial
> hsfosspec 88680 8
> hsfusbcd2,hsfmc97sis,hsfmc97ati,hsfmc97ali,hsfmc97via,hsfpcibasic2,hsfserial,hsfengine
> hsfsoar 85704 6
> hsfusbcd2,hsfmc97sis,hsfmc97ati,hsfmc97ali,hsfmc97via,hsfpcibasic2
> hci_usb 14292 2
> bluetooth 44068 7 rfcomm,l2cap,hci_usb
> ohci1394 31856 0
> ieee1394 299544 2 sbp2,ohci1394
> ehci_hcd 30152 0
> uhci_hcd 21260 0
> usbcore 117312 9
> keyspan_pda,keyspan,usbserial,hsfusbcd2,hsfosspec,hci_usb,ehci_hcd,uhci_hcd
>
> Which of these modules should go? I'm guessing that ohci1394 is my
> USB controller driver (see my lspci output quoted from previous
> message below), but it is not clear to me.
No, ohci1394 is a Firewire driver. "Firewire" is Apple's name for the
technology which is more generally available in the IEEE-1394
specification.
> Would I need also to
> remove usbcore? (If I need to remove usbcore, then I would need to
> understand what all of the hsf* modules are doing, because they would
> need to be unloaded first.) What about ehci_hcd and uhci_hcd?
You don't need to remove usbcore. You do need to remove either or both of
ehci-hcd and uhci-hcd, depending on what bus speed your USB device runs
at.
Alan Stern
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