How nm-modem-probe work?

[代尔欣 <daierxin gmail com>]

Hi all,
   I have a HuaWei EM770 modem. Through add rules in udev I can make NM0.7.1.998 found it and work. But I have to set the ID_NM_MODEM_GSM=1 in the rules like 77-nm-zte-port-types.rules. This make udevadm_get_modem_capabilities(Do not have libudev support) return correct bits. But in 77-nm-probe-modem-capabilities.rules, it does not set any related environment value and just call nm-modem-probe instead. I suppose nm-modem-probe set related environment value? But from the codes nm-modem-probe.c, It seems not. How this work? Need libudev support?

Thank!