Dear Chris Packham,
In message 20200813013727.8186-1-judge.packham@gmail.com you wrote:
When building envtools via tools-only_defconfig the builtin defaults are based on options in the defconfig. For example:
bootcmd=bootp; setenv bootargs root=/dev/nfs nfsroot=${serverip}:${rootpath} ip=${ipaddr}:${serverip}:${gatewayip}:${netmask}:${hostname}::off; bootm bootdelay=2 baudrate=115200 stdin=serial,cros-ec-keyb,usbkbd stdout=serial,vidconsole stderr=serial,vidconsole ethaddr=00:00:11:22:33:44 eth3addr=00:00:11:22:33:45 eth5addr=00:00:11:22:33:46 eth6addr=00:00:11:22:33:47
Having any specific MAC addresses set in the default environment has always been a strict No-Go as it is just begging for trouble.
If this was a real example, that code should be fixed!!
These may or may not be sensible for any particular target. Rather than trying to have a set of defaults that work for every target add a config option to make the default environment completely empty.
An empty default environment is even worse, as you are missing vital settings like baudrate, bootdelay etc. There are good chances to brick your board with such settings.
Best regards,
Wolfgang Denk