Plan 9 from Bell Labs kernel images require additional setup to pass configuration information to the kernel. An environment variable named confaddr must be defined with the same value as CONFADDR (see mem.h). Use of this facility is optional, but should be preferable to manual configuration.
When booting an image, arguments supplied to the bootm command will be copied to CONFADDR. If no arguments are specified, the contents of the bootargs environment variable will be copied.
If no command line arguments or bootargs are defined, CONFADDR is left uninitialized to permit manual configuration. For example, PC-style configuration could be simulated by issuing a fatload in bootcmd:
# setenv bootcmd fatload mmc 0 $confaddr plan9.ini; ...; bootm