Post-probing filters: ModemManager Reference Manual

## Post-probing filters

Post-probing filters are required to identify whether a plugin can handle a given modem, in special cases where the information retrieved from udev is either not enough or wrong. This covers, for example, RS232 modems connected through a RS232 to USB converter, where udev-reported vendor ID is that of the converter, not the one of the modem.

- Allowed vendor strings

  Plugins can provide a list of vendor strings to be used as post-probing filters. If the vendor string reported by the device via AT commands is found in the list provided by the plugin, the plugin will report that it can handle this modem.

  This filter is specified by the MM_PLUGIN_ALLOWED_VENDOR_STRINGS property in the MMPlugin object provided by the plugin.

- Product strings

  Plugins can provide a list of pairs of vendor and product strings to be used as post-probing filters.

  If the vendor and product string pair reported by the device via AT commands is found in the 'allowed' list provided by the plugin, the plugin will report that it can handle this modem. This additional filter should be used when the plugin is expected to work only with a given specific product of a given vendor.

  If the vendor and product string pair reported by the device via AT commands is found in the 'forbidden list provided by the plugin, the plugin will report that it cannot handle this modem. This additional filter should be used when the plugin supports all devices of a given vendor, except for some specific ones.

  These filters are specified by the MM_PLUGIN_ALLOWED_PRODUCT_STRINGS and MM_PLUGIN_FORBIDDEN_PRODUCT_STRINGS properties in the MMPlugin object provided by the plugin.

- Icera support

  Plugins can specify that they only support Icera-based modems, or that they do not support any Icera-based modem. When either of this configurations is enabled, the Icera support checks will be included in the probing sequence, and the result of the check will help to determine whether the plugin supports the modem or not.

  This filter is specified by the MM_PLUGIN_ALLOWED_ICERA and MM_PLUGIN_FORBIDDEN_ICERA properties in the MMPlugin object provided by the plugin.

Plugins which require post-probing filters will always be sorted last, and therefore they will be the last ones being checked for pre-probing filters. This is due to the fact that we need to assume that these plugins aren't able to determine port support just with pre-probing filters, as we want to avoid unnecessary probing sequences launched. Also note that the Generic plugin is anyway always the last one in the list.