On Sun, Mar 20, 2016 at 06:57:30PM +0100, Guido Trentalancia wrote: > Hello Greg ! > > On dom, 2016-03-20 at 10:34 -0700, Greg KH wrote: > > On Sun, Mar 20, 2016 at 06:09:57PM +0100, Guido Trentalancia wrote: > > > > > > [ 1295.575679] usb 6-2: FTDI USB Serial Device converter now > > > attached > > > to ttyUSB1 > > > [ 1302.204285] usb usb6-port2: disabled by hub (EMI?), re- > > > enabling... > > > > > > *** NOTE: EMI is probably still present here *** > > > > > > [ 1303.205202] usb 6-2: USB disconnect, device number 6 > > > [ 1303.205907] ftdi_sio ttyUSB1: FTDI USB Serial Device converter > > > now > > > disconnected from ttyUSB1 > > > [ 1303.205950] ftdi_sio 6-2:1.0: device disconnected > > > [ 1303.414089] usb 6-2: new full-speed USB device number 7 using > > > uhci_hcd > > > [ 1303.526226] usb 6-2: device descriptor read/64, error -71 > > > [ 1303.894228] usb 6-2: new full-speed USB device number 8 using > > > uhci_hcd > > > [ 1304.006185] usb 6-2: device descriptor read/64, error -71 > > > [ 1304.219089] usb 6-2: device descriptor read/64, error -71 > > > [ 1304.422107] usb 6-2: new full-speed USB device number 9 using > > > uhci_hcd > > > [ 1304.640020] usb 6-2: device not accepting address 9, error -71 > > > [ 1304.752024] usb 6-2: new full-speed USB device number 10 using > > > uhci_hcd > > > [ 1305.160020] usb 6-2: device not accepting address 10, error -71 > > > [ 1305.160038] hub 6-0:1.0: unable to enumerate USB device on port > > > 2 > > > > > > *** NOTE: Device is permanently disabled at this point *** > > > > > > I don't know whether my analysis is correct (and therefore the > > > proposed > > > solution appropriate), as reproducing the problem is very > > > difficult... > > > > > > Module parameters are "icky", isn't there some way we can just > > dynamically determine this (i.e. fall back to longer and longer wait > > times?) > > No, we cannot in general predict how long EMI lasts. > > But, for example, I have a known source of EMI close to the computer > (RF transmitter) and I know it lasts a couple of seconds, therefore I > am able to set up the parameter correctly. > > Also, I believe once it fails the first time, the device is permanently > disabled by the USB driver (I am no USB driver expert, do you confirm > ?). Therefore, by the way the driver is actually designed, it is not > possible to try again with a longer wait interval. And it's much more > complicate, plus you still have to hard-code a maximum value I > suppose... Yes, this needs more work, and again, don't use a module parameter please, make it "automatic" if at all possible. thanks, greg k-h -- 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
