[SOLVED] usb broadband modem has to be re-plug in order to be recognized as /dev/ttyUSBx

72rcfj789w93 · 01-25-2018, 06:03 AM

OS: slackware 14.2

I am using kppp to connect to internet via usb mobile broadband modem. On kppp I set /dev/ttyUSB1 as modem device. The problem is that slackware seems unable to detect the device automatically during boot up.

if I do

Code:

ls /dev

ttyUSBx is not in the list. It will be in the list either after:
1. I re-plug the device (once I arrived in Desktop Environment), or
2. I re-boot into slackware after running windows first (dual boot)

some outputs from lsusb and dmesg:
lsusb (when the device is undetected):

Code:

Bus 001 Device 005: ID 1c9e:98ff OMEGA TECHNOLOGY 
Bus 001 Device 002: ID 1f71:3301  
..........

lsusb (when the device is detected):

Code:

Bus 001 Device 005: ID 1c9e:9801 OMEGA TECHNOLOGY                                     
Bus 001 Device 002: ID 1f71:3301                                                      
........

OMEGA TECHNOLOGY is the device.

dmesg (when undetected):

Code:

...
[    8.047037] usb 1-6: new high-speed USB device number 5 using ehci-pci
[    8.163989] usb 1-6: New USB device found, idVendor=1c9e, idProduct=98ff
[    8.164071] usb 1-6: New USB device strings: Mfr=3, Product=2, SerialNumber=4
[    8.164145] usb 1-6: Product: USB Modem
[    8.164187] usb 1-6: Manufacturer: USB Modem
[    8.164232] usb 1-6: SerialNumber: 1234567890ABCDEF
...

dmesg (when detected after I unplug and then re-plug the device):

Code:

...
[  877.365666] usb 1-6: USB disconnect, device number 5
[  883.475037] usb 1-6: new high-speed USB device number 6 using ehci-pci
[  883.591993] usb 1-6: New USB device found, idVendor=1c9e, idProduct=98ff
[  883.591998] usb 1-6: New USB device strings: Mfr=3, Product=2, SerialNumber=4
[  883.592011] usb 1-6: Product: USB Modem
[  883.592021] usb 1-6: Manufacturer: USB Modem
[  883.592024] usb 1-6: SerialNumber: 1234567890ABCDEF
[  883.645083] usb-storage 1-6:1.0: USB Mass Storage device detected
[  883.645202] scsi host7: usb-storage 1-6:1.0
[  884.608919] usb 1-6: USB disconnect, device number 6
[  884.919099] usb 1-6: new high-speed USB device number 7 using ehci-pci
[  885.035994] usb 1-6: New USB device found, idVendor=1c9e, idProduct=9801
[  885.036000] usb 1-6: New USB device strings: Mfr=3, Product=2, SerialNumber=4
[  885.036016] usb 1-6: Product: USB Modem
[  885.036024] usb 1-6: Manufacturer: USB Modem
[  885.036027] usb 1-6: SerialNumber: 1234567890ABCDEF
[  885.087316] usbserial_generic 1-6:1.0: The "generic" usb-serial driver is only for testing and one-off prototypes.
[  885.087322] usbserial_generic 1-6:1.0: Tell linux-usb@vger.kernel.org to add your device to a proper driver.
[  885.087325] usbserial_generic 1-6:1.0: generic converter detected
[  885.087433] usb 1-6: generic converter now attached to ttyUSB0
[  885.087552] usbserial_generic 1-6:1.1: The "generic" usb-serial driver is only for testing and one-off prototypes.
[  885.087556] usbserial_generic 1-6:1.1: Tell linux-usb@vger.kernel.org to add your device to a proper driver.
[  885.087558] usbserial_generic 1-6:1.1: generic converter detected
[  885.087647] usb 1-6: generic converter now attached to ttyUSB1
...

as you can see after I re-plug the device new idProduct 9801 has been detected and generic converter now attached to ttyUSB1.

what should I do so that slackware will automatically detect ttyUSBx?

thanks

ferrari · 01-26-2018, 12:27 AM

I'm not a Slackware user, but I'm going to speculate a bit that usb_modeswitch (which is called by a matching udev rule) works when the kernel uevent is detected, but when the device is present at boot no such event takes place, and so the device remain on storage device mode. It might work if udev is retriggered (not sure if reloading rules is necessary)....

Code:

udevadm control --reload-rules && udevadm trigger

If this works to get the mode-switching working for a device plugged in at boot, then it could be added to to a suitable init script perhaps.

Another possible workaround involves some code to reset the USB bus (or a particular ) device, which will cause it to be re-initialised and the kernel uevent generated which will result in the udev rule being matched and usb_modeswitch being triggered

72rcfj789w93 · 01-26-2018, 06:11 AM

Quote:

Originally Posted by ferrari

I'm not a Slackware user, but I'm going to speculate a bit that usb_modeswitch (which is called by a matching udev rule) works when the kernel uevent is detected, but when the device is present at boot no such event takes place, and so the device remain on storage device mode. It might work if udev is retriggered (not sure if reloading rules is necessary)....

Code:

udevadm control --reload-rules && udevadm trigger

If this works to get the mode-switching working for a device plugged in at boot, then it could be added to to a suitable init script perhaps.

Another possible workaround involves some code to reset the USB bus (or a particular ) device, which will cause it to be re-initialised and the kernel uevent generated which will result in the udev rule being matched and usb_modeswitch being triggered

I am playing around with usb_modeswitch until I found this command

Code:

usb_modeswitch -v 0x1c9e -p 0x98ff -V 0x1c9e -P 0x9801 -S

I put it into rc.local file. and It seems OK now.

Thanks for your information anyway

I'll take a look into that later.

ferrari · 01-26-2018, 02:34 PM

Glad to have been of guidance. Udev calls usb_modeswitch in essentially the same way, and has a directory (/usr/share/usb_modeswitch/) containing various chipsets and switching details which it uses to implement the switching. Calling it manually like this does the same, so another means to the same end.