15.05 is here! - with AC! - Xiaomi Mini

Quick update on giving 15.05 a try, since it's final this should be good.
I decided to go for a full reset, ie a fresh clean install.
ssh into the xiaomi then
wget, sysupgrade, telnet and change passwd,

note: luci came pre-installed in 15.05, and uhttpd was running so I suppose you could've pointed your browsers  straight at 192.168.1.1 after flashing, if you preferred.

2.4Ghz wireless came up as expected.
Still no luck with the 5GHz though :(

W00t w00t, figured it out - ac probably has been working for a while but there's a bug in the DFS mechanism that prevents it from coming up - it looks like this in the log

daemon.notice netifd: radio0 (27335): wlan0: interface state HT_SCAN->DFS
daemon.notice netifd: radio0 (27335): wlan0: DFS-CAC-START freq=5300 chan=60 sec_chan=1, width=1, seg0=58, seg1=0, cac_time=60s
daemon.notice netifd: radio0 (27335): DFS start_dfs_cac() failed, -1

 but it can be worked around easily enough:
configure wifi as you would any other wifi but under 'advanced settings' be sure to set the country code, then choose a channel wich does NOT require DFS. Different regulatory domains have different DFS requirements - you can check what the driver thinks it needs to do with

root@OpenWrt:/# iw reg get
country RU: DFS-ETSI
        (2402 - 2482 @ 40), (N/A, 20), (N/A)
        (5170 - 5250 @ 80), (N/A, 20), (N/A)
        (5250 - 5330 @ 80), (N/A, 20), (0 ms), DFS
        (5650 - 5730 @ 80), (N/A, 30), (0 ms), DFS
        (5735 - 5835 @ 80), (N/A, 30), (N/A)
therefore this config will result in a working 802.11ac by not requiring DFS as channel 149 sits in the bracket that does not require DFS.

root@OpenWrt:/etc/config# cat wireless

config wifi-device 'radio0'
        option type 'mac80211'
        option hwmode '11a'
        option path 'pci0000:00/0000:00:00.0/0000:01:00.0'
        option txpower '20'
        option htmode 'VHT80'
        option country 'RU'
        option channel '149'
performance seemed fine, copied a file from the NAS behind the xiaomi at about 12MB/s
(compared to 2MB/s when on the 2.4G)

!note:after a reboot I had to bring up the 5G manually, eventhough luci indicated it was up.

wifi up radio0

!update:there's still some instability in the 5G, it works but periodically the connections seems to freeze, and then continue. Not quite ready for prime time yet.