Alan Stern <[EMAIL PROTECTED]> writes: > On Wed, 31 Jan 2007, Joe Wells wrote: > >> Thanks very much for your advice, Alan!
Thanks again! Your information is very helpful. >> 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. Agreed. But I think it would take many days to track down, given my level of kernel hacking expertise (none). Unfortunately I can't justify that given that I have a working workaround. >> > 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 Very helpful pointer. Okay, so I have now figured out that my USB controller is the "Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family)", and it is documented that this does not implement port power control. The "lsusb --verbose" output also indicates the lack of port power control. >> > 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. When I "modprobe uhci_hcd", will this detect the USB device plugged in and do all the necessary hotplug events? >> If I run "lsmod | egrep 'hci|usb'", I get this output: >> >> [ bunch of stuff deleted ] >> >> 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. Right, I should have known that. >> 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. I've determined that it is uhci_hcd that I need to remove. Do I need to make sure that any kernel modules related specifically to the USB device are unloaded first? (I suppose I will do this anyway, but I am curious.) The lsmod output does not list any other modules as depending on uhci_hcd. > Alan Stern Thanks for any additional help anyone can give! -- Joe Wells ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ Linux-usb-users@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-users
