"port not candidate" error message with DELL Wireless 5570 (aka Sierra Wireless AirPrime 7W5P6)

[Giuseppe Sacco]

Hello Aleksander,
please find my answers below.

Il giorno mar, 16/06/2020 alle 09.29 +0200, Aleksander Morgado ha
scritto:
> Hey Giuseppe,
> 
> > I am not at all an expert of modem manager but I hope this is the right
> > place where to post my question.
> > 
> > I am trying to use a WWAN module on a laptop. The module is named "Dell
> > Wireless 5570 HSPA+ (42Mbps) Mobile Broadband Card" (a.k.a. Sierra
> > Wireless AirPrime 7W5P6).
> > 
> 
> What distro and distro version are you using?

I am using a Debian testing machine with amd64 architecture:

$ lsb_release -a
No LSB modules are available.
Distributor ID:	Debian
Description:	
Debian GNU/Linux bullseye/sid
Release:	testing
Codename:	bullsey
e

> > It is listed like this:
> > 
> > $ lsusb --verbose -d 413c: | head -17
> > 
> > Bus 003 Device 003: ID 413c:81a3 Dell Computer Corp.
> > Device Descriptor:
> >   bLength                18
> >   bDescriptorType         1
> >   bcdUSB               2.00
> >   bDeviceClass            0
> >   bDeviceSubClass         0
> >   bDeviceProtocol         0
> >   bMaxPacketSize0        64
> >   idVendor           0x413c Dell Computer Corp.
> >   idProduct          0x81a3
> >   bcdDevice            0.06
> >   iManufacturer           1 Sierra Wireless, Incorporated
> >   iProduct                2 Dell Wireless 5570 HSPA+ (42Mbps) Mobile Broadband Card
> >   iSerial                 3
> >   bNumConfigurations      2
> > 
> > 
> > The card is not used by modemmanager, in fact I does write:
> > 
> 
> What version of ModemManager are you using?

$ dpkg -l modemmanager
[...]
ii  modemmanager   1.12.10-0.2  amd64        D-Bus service for managing modems

> > ModemManager[7979]: <debug> [1592288162.080686] (usbmisc/cdc-wdm0):
> > adding device at sysfs path:
> > /sys/devices/pci0000:00/0000:00:1d.0/usb3/3-1/3-1.6/3-
> > 1.6:2.12/usbmisc/cdc-wdm0
> > ModemManager[7979]: <debug> [1592288162.080759] (usbmisc/cdc-wdm0):
> > port not candidate
> > 
> 
> This happens when the cdc-wdm port doesn't have the ID_MM_CANDIDATE
> udev tag. Does your system have the
> /lib/udev/rules.d/80-mm-candidate.rules file? What are its contents?
> Does your system have udev daemon running?

yes, the file is present

$ grep '^[^#]' /lib/udev/rules.d/80-mm-candidate.rules
ACTION!="add|change|move|bind", GOTO="mm_candidate_end"
KERNEL=="rfcomm*", DEVPATH=="*/virtual/*", GOTO="mm_candidate_end"
SUBSYSTEM=="tty", ENV{ID_MM_CANDIDATE}="1"
SUBSYSTEM=="net", ENV{ID_MM_CANDIDATE}="1"
KERNEL=="cdc-wdm*", SUBSYSTEM=="usb", ENV{ID_MM_CANDIDATE}="1"
KERNEL=="cdc-wdm*", SUBSYSTEM=="usbmisc", ENV{ID_MM_CANDIDATE}="1"
LABEL="mm_candidate_end"

sure, udev is running

$ systemctl status systemd-udevd.service
● systemd-udevd.service - udev Kernel Device Manager
     Loaded: loaded (/lib/systemd/system/systemd-udevd.service; static; vendor preset: enabled)
     Active: active (running) since Tue 2020-06-16 07:51:02 CEST; 7h ago
TriggeredBy: ● systemd-udevd-control.socket
             ● systemd-udevd-kernel.socket
       Docs: man:systemd-udevd.service(8)
             man:udev(7)
   Main PID: 466 (systemd-udevd)
     Status: "Processing with 32 children at max"
      Tasks: 1
     Memory: 33.0M
     CGroup: /system.slice/systemd-udevd.service
             └─466 /lib/systemd/systemd-udevd

but it seems the ID_MM_CANDIDATE variable isn't there.

$ udevadm info /dev/cdc-wdm0
P: /devices/pci0000:00/0000:00:1d.0/usb3/3-1/3-1.6/3-1.6:2.12/usbmisc/cdc-wdm0
N: cdc-wdm0
L: 0
E: DEVPATH=/devices/pci0000:00/0000:00:1d.0/usb3/3-1/3-1.6/3-1.6:2.12/usbmisc/cdc-wdm0
E: DEVNAME=/dev/cdc-wdm0
E: MAJOR=180
E: MINOR=0
E: SUBSYSTEM=usbmisc

Even reinserting the device, the tag is not attached:

$ udevadm  trigger --verbose --action=remove /dev/cdc-wdm0
/sys/devices/pci0000:00/0000:00:1d.0/usb3/3-1/3-1.6/3-1.6:2.12/usbmisc/cdc-wdm0

$ udevadm  trigger --verbose --action=add /dev/cdc-wdm0
/sys/devices/pci0000:00/0000:00:1d.0/usb3/3-1/3-1.6/3-1.6:2.12/usbmisc/cdc-wdm0

$ udevadm info /dev/cdc-wdm0
P: /devices/pci0000:00/0000:00:1d.0/usb3/3-1/3-1.6/3-1.6:2.12/usbmisc/cdc-wdm0
N: cdc-wdm0
L: 0
E: DEVPATH=/devices/pci0000:00/0000:00:1d.0/usb3/3-1/3-1.6/3-1.6:2.12/usbmisc/cdc-wdm0
E: DEVNAME=/dev/cdc-wdm0
E: MAJOR=180
E: MINOR=0
E: SUBSYSTEM=usbmisc

Bye,
Giuseppe