EM9191 does not bring up the serial interface, works in MBIM-only USB composition

[dl5162]

@nkefalas

I:* If#= 3 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=00 Driver=(none)
E:  Ad=83(I) Atr=03(Int.) MxPS=  10 Ivl=32ms
E:  Ad=82(I) Atr=02(Bulk) MxPS=1024 Ivl=0ms
E:  Ad=01(O) Atr=02(Bulk) MxPS=1024 Ivl=0ms

This is a serial function with no driver bound. Most likely the AT command port you are looking for.

@nkefalas

I:* If#= 4 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=ff Prot=30 Driver=(none)
E:  Ad=84(I) Atr=02(Bulk) MxPS=1024 Ivl=0ms
E:  Ad=02(O) Atr=02(Bulk) MxPS=1024 Ivl=0ms

This is a DM function with no driver bound. We recongnize that based on the ff/ff/30 class/subclass/protocol code, which seems to be used universally by the newer Qualcomm chips (sdx55 etc).

So your modem is exposing the functions you are looking for. There just isn’t any driver for them yet. There was a patch posted earlier, but it needed some minor adjustmends and the process stopped for some reason. See the thread around https://www.spinics.net/lists/linux-usb/msg214218.html

(Johan is the usb-serial maintainer)

You could patch one of the usb serial drivers yourself, or you can temporarily workound the lack of support by dynamically add the device to one of them. I usually recommend the option driver for such temporary workarounds because it makes few assumptions about device layout and will bind to pretty much anything. The only problem with that is that the command order is important. If you do this before other drivers have had a chance, then you might end up with the option driver “stealing” all device functions.

Temporary workaround until the device is supported:

modprobe option
echo 1199 90d3 >/sys/bus/usb-serial/drivers/option1/new_id