OpenWrt package and udev rules

[Aleksander Morgado]

Hey!

> I noticed that the package comes with the udev rules.  Why is that?  The
> are explicitly installed by the makefile install rule:
>
> define Package/modemmanager/install
>         $(INSTALL_DIR) $(1)/lib/udev/rules.d
>         $(INSTALL_DATA) $(PKG_INSTALL_DIR)/lib/udev/rules.d/*.rules $(1)/lib/udev/rules.d
>
>
> are these used anywhere?  If not, then I suggest dropping them.  This
> will never be a small package, obviously. But I still believe the
> OpwnWrt way-of-things is to strip away anything not absolutely required.
>

Oh, all those rules are used even in OpenWRT, if they are not being
applied correctly, then it's a bug. See this simple parser
implementation for the rules that is the one being run when not using
udev:
https://gitlab.freedesktop.org/mobile-broadband/ModemManager/blob/master/src/kerneldevice/mm-kernel-device-generic-rules.c

That said, this is not the first time I've thought of just getting rid
of all udev rules and switch to other means of achieving the same
thing. The not-so-recent changes reporting "bind" events broke our
rules and I'm not sure there is much benefit (if any at all) relying
on udev rules for things like blacklists or port type hints. A set of
"quirk/config files" as done in e.g. fwupd could be a better option
IMO. If we did that, we could use the same logic to apply the rules
both when using udev and when using ReportKernelEvent().

> It would be nice if this functionality actually was there, though..  I
> am having some problems when booting my combined console server and
> modem manager OpenWrt box.  ModemManager probes ttyUSB[0-3], which are
> supposed to be used by conserver:
>
> ModemManager: hotplug: error: modem not detected at sysfs path
> [2289]: <info>  Modem: state changed (unknown -> disabled)
> [2289]: <warn>  (ttyUSB3): serial port closing_wait was reset!
> [2289]: <warn>  (ttyUSB3): couldn't set serial port closing_wait to none: Not a tty
> [2289]: <warn>  (ttyUSB1): serial port closing_wait was reset!
> [2289]: <warn>  (ttyUSB1): couldn't set serial port closing_wait to none: Not a tty
> [2289]: <warn>  (ttyUSB0): serial port closing_wait was reset!
> [2289]: <warn>  (ttyUSB0): couldn't set serial port closing_wait to none: Not a tty
> [2289]: <info>  [device /sys/devices/platform/soc/soc:internal-regs/f1050000.usb/usb1/1-1] creating modem with plugin 'Generic' and '4' ports
> [2289]: <warn>  Could not grab port (tty/ttyUSB3): 'Cannot add port 'tty/ttyUSB3', unhandled serial type'
> [2289]: <warn>  Could not grab port (tty/ttyUSB2): 'Cannot add port 'tty/ttyUSB2', unhandled serial type'
> [2289]: <warn>  Could not grab port (tty/ttyUSB1): 'Cannot add port 'tty/ttyUSB1', unhandled serial type'
> [2289]: <warn>  Could not grab port (tty/ttyUSB0): 'Cannot add port 'tty/ttyUSB0', unhandled serial type'
> [2289]: <warn>  Couldn't create modem for device '/sys/devices/platform/soc/soc:internal-regs/f1050000.usb/usb1/1-1': Failed to find primary AT port
> ModemManager: hotplug: modem exported successfully at /sys/devices/platform/soc/soc:pcie at 82000000/pci0000:00/0000:00:01.0/0000:01:00.0/usb3/3-2
>
>
> It would be nice to avoid this by blacklisting this device, like I would
> have done on a system with udev.  Is there any way to make the OpenWrt
> hotplug scripts avoid a specific USB device?
>

Just add a ID_MM_DEVICE_IGNORE rule as you would have done with udev,
and restart the daemon.

Also, could you please retry running ModemManager with
"--filter-policy=STRICT" (e.g. just edit the /etc/init.d/modemmanager
file to add that)? I would suggest we switch to that filter policy for
the defaults everywhere, including openwrt. When using that filter
policy, a USB device that only exposes ttyUSB ports would not be
probed automatically.

-- 
Aleksander
https://aleksander.es