On Wed, 2020-05-20 at 12:43 +0000, Joakim Tjernlund wrote: > On Tue, 2020-05-19 at 14:54 +0200, Greg KH wrote: > > CAUTION: This email originated from outside of the organization. Do > > not click links or open attachments unless you recognize the sender > > and know the content is safe. > > > > > > On Tue, May 19, 2020 at 12:14:55PM +0000, Joakim Tjernlund wrote: > > > Whenever we connect a Linux laptop(4.19.118) to our ttyACM serial > > > gadget we can see som strange > > > chars appearing in our gadget: > > > 03�`3�03�x�x(in hex: 3033 efbf bd60 33ef bfbd 3033 efbf bd78 efbf > > > bd78) > > > They appear witch c.a 1 sec in between. > > > I assume it is the laptops ACM driver emitting those, but why? > > > Can these chars be turned off? > > > > It's a program on your laptop probing the device. Usually > > modemmanager > > or something like that. > > > > greg k-h > > Right you were, it was modemmanager :) If the device has a unique ID that isn't a modem, it can be added to ModemManager's blacklist. Also note that recent versions of ModemManager flipped the logic and will only probe *known* modems, require explicit requests to probe possible modems, and of course won't probe anything on the blacklist. Dan > Fixing that I can occasion se in my DE: > [Wed May 20 14:03:16 2020] cdc_ether 1-6.2:1.0 usb0: unregister > 'cdc_ether' usb-0000:00:14.0-6.2, CDC Ethernet Device > [Wed May 20 14:03:25 2020] usb usb1-port6: disabled by hub (EMI?), > re-enabling... > [Wed May 20 14:03:25 2020] usb 1-6: USB disconnect, device number 85 > [Wed May 20 14:03:25 2020] cdc_acm 1-6.3:1.1: acm_ctrl_irq - > usb_submit_urb failed: -19 > [Wed May 20 14:03:25 2020] usb 1-6-port2: attempt power cycle > [Wed May 20 14:03:26 2020] usb 1-6.3: USB disconnect, device number > 86 > [Wed May 20 14:03:26 2020] cdc_acm 1-6.3:1.1: failed to set dtr/rts > [Wed May 20 14:03:26 2020] usb 1-6: new high-speed USB device number > 94 using xhci_hcd > [Wed May 20 14:03:27 2020] hub 1-6:1.0: USB hub found > [Wed May 20 14:03:27 2020] hub 1-6:1.0: 3 ports detected > [Wed May 20 14:03:27 2020] usb 1-6.2: new high-speed USB device > number 95 using xhci_hcd > [Wed May 20 14:03:27 2020] cdc_ether 1-6.2:1.0 usb0: register > 'cdc_ether' at usb-0000:00:14.0-6.2, CDC Ethernet Device, > 7e:1d:06:c0:3f:3c > [Wed May 20 14:03:27 2020] usb 1-6.3: new high-speed USB device > number 96 using xhci_hcd > [Wed May 20 14:03:27 2020] cdc_acm 1-6.3:1.1: ttyACM0: USB ACM device > > This "disabled by hub (EMI?), re-enabling" may be from: > EM interference sometimes causes bad shielded USB devices to > be shutdown by the hub, this hack enables them again. > > But a another side effect from this is that I get a lot of garbage > chars in the other end, like: > h�^@^@� ^@^@� ^@ > or > X���)H��4Ğ^��� > I wonder if this can be caused by the USB/ACM driver ? > > Jocke
