/lib/udev/rules.d/77-mm-platform-serial-whitelist.rules is in modemmanager 1.0.0-2ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 | # do not edit this file, it will be overwritten on update
ACTION!="add|change", GOTO="mm_platform_device_whitelist_end"
SUBSYSTEM!="platform", GOTO="mm_platform_device_whitelist_end"
# Be careful here since many devices connected to platform drivers on PCs
# are legacy devices that won't like probing. But often on embedded
# systems serial ports are provided by platform devices.
# Allow atmel_usart
DRIVERS=="atmel_usart", ENV{ID_MM_PLATFORM_DRIVER_PROBE}="1"
LABEL="mm_platform_device_whitelist_end"
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