I see. Thanks.
I also found DLink DIR-853 A3 - #74 by kar200, which gives some insight in how the dlink-dual-firmware-partitions work:
So it is not like Linksys WRT, instead the bootloader will manage both partitions fully on its own, the user cannot interfer and unlike Linksys the user cannot have 2 different firmware versions deployed at the same time or alternate at will between them:
- On every device boot, before loading the firmware, the boot loader automatically does some sanity checksum tests on both firmware partitions. If one partitions turns out defective, it will automatically be overwritten with the stuff from the other partition
- If both partitions are sane, but differ in content, the image from the first partition gets automatically copied over to the second partition, such that the backup partition is in sync with firmware updates
- then the regular boot process continues (always on the first firmware partition)
So the 2nd firmware partition cannot be reclaimed, but has some good purpose, it's not a complete waste.
Now I also seem to understand why some users report about failed flash processes, but still that router was able to boot back into the previous image. And probably I also understand, why this auto recovery did not work for some users, as the 853-thread mentions that the checksum test is not an indepth know-it-all check.
Unfortunately compiling or changing code of OpenWRT feels way beyond my current brain evolution level. As of now, I am glad to at least be somehow able, to keep up with how OpenWRT works and how new devices fit in. And it's the first time, I deal with an owned device that does not have a device page yet.
But still regarding 1960-partitions, does that mean:
- the firmware partitions have to retain in offset and size as predefined by D-Link? (as otherwise the boot loader would not be able to do its sanity magic anymore or break something?)
- if the space of several extra partitions in between is reclaimed as you suggest, how would those extra partition spaces be used by OpenWRT? Would these then become extra mount points?