When learning openwrt, I personally understood that this dual image needs uboot support, but after looking at the uboot code for a week, I didn't find it (a bit confused). I want to ask senior openwrt development experts whether it is supported by default. If it is, how can I enable this function? thanks.
That depends on how the vendor has set up u-boot and the OEM flash partitioning, as well as the question if the OpenWrt porters have properly hooked it up.
There is no generic answer, it depends on the device and the current support state.
vendor is the magic word here, since openwrt usually don't replace the boot loader.
Thanks. We are looking for the right vendor.