The question is in the subject line, but why do we restrict ourselves to small (potentially tiny) system image by preserving the (apparently unused) radio calibration data partition and the (apparently redundant) copy of the PLC firmware partitions? I could use the space...
NB. I have a TL-WPA8630P(UK) V2.0 with firmware 2.0.2 Build 20170509 Rel.58359 on it. As I mentioned elsewhere it turns out I could flash it with TP-Link's EU V2.0 firmware 2.0.3 Build 20171018 Rel.36564, which made me think it was similar enough to try flashing OpenWrt with a v2.0-eu factory image. If anyone wants an image of the 2.0.2 Build 20170509 Rel.58359, tell me how and I'll send it, before I flash my second unit over to OpenWrt.
Openwrt tries to preserve a device's state so that it's possible to go back to the original firmware. That's probably why some partitions aren't cleared and used.
Take a look at https://github.com/openwrt/openwrt/pull/4500 where you can find a change that would give you some additional free space to install packages.
I shall have to go and read more about what I might lose with the tiny target.
But doesn't the downloadable TP-Link firmware include at least the PLC firmware anyway? So it would be safe to blow that away? How would I check?
Take a look at this if you haven't found it yet (it's linked from the github PR). I think it answers your questions (and I don't know any details so I'm of little help )
Thanks for all that! More reading and possibly risking bricking one of my devices...
Though tbh my time would probably be better spent working out how to install Cat5 - when the PLCs claim 600Mbps I get 95Mbps, and if they say 300Mbps I get 45Mbps, and both add the dreaded bufferbloat
FYI openwrt needs & uses the factory radio calibration data and MAC addresses
Yes, that unused 1MiB PLC space is such a waste. It would have been great for OpenWrt if TP-Link had put it beside the rootfs (or better yet inside the rootfs). You can see there is a mix of device-specific and settings partitions alongside the different firmware partitions, which must have been a headache for them to handle when rolling out firmware updates. But we should still be thankful to them for being able to run it at all in this age of locked down hardware
I updated the partition explanation in the Wiki here.
If you want to test the "unofficial BETA" ath79-tiny build with LuCi + 1MB free space, see this comment