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 :) 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
