WiFi: missing regulatory.db and problematic txpower

[mweinelt]

On boot we can see that the regulatory.db is missing and cannot be loaded. I couldn't find it in any debian package.

[   10.197170] platform regulatory.0: firmware: failed to load regulatory.db (-2)
[   10.207175] firmware_class: See https://wiki.debian.org/Firmware for information about missing firmware
[   10.207200] platform regulatory.0: Direct firmware load for regulatory.db failed with error -2
[   10.207213] cfg80211: failed to load regulatory.db

Nevertheless I can set the regulatory domain through hostapds country setting.

# iw reg get
global
country DE: DFS-ETSI
    (2400 - 2483 @ 40), (N/A, 20), (N/A)
    (5150 - 5250 @ 80), (N/A, 20), (N/A), NO-OUTDOOR, AUTO-BW
    (5250 - 5350 @ 80), (N/A, 20), (0 ms), NO-OUTDOOR, DFS, AUTO-BW
    (5470 - 5725 @ 160), (N/A, 26), (0 ms), DFS
    (5725 - 5875 @ 80), (N/A, 13), (N/A)
    (57000 - 66000 @ 2160), (N/A, 40), (N/A)

But apparently it doesn't honor the 20 dBm txpower limit.

# iw dev
phy#0
    Interface wlan0
        ifindex 3
        wdev 0x1
        addr b8:27:eb:bb:b3:d0
        ssid foobar
        type AP
        channel 5 (2432 MHz), width: 20 MHz, center1: 2432 MHz
        txpower 31.00 dBm

Setting a txpower limit via ìw sets txpower to 0.0 dBm.

# iw dev wlan0 set txpower fixed 20
# iw dev
phy#0
    Interface wlan0
        ifindex 3
        wdev 0x1
        addr b8:27:eb:bb:b3:d0
        ssid foobar
        type AP
        channel 5 (2432 MHz), width: 20 MHz, center1: 2432 MHz
        txpower 0.00 dBm

So I revert it back to iw dev wlan0 set txpower auto and it's back up at 31 dBm.

What seems to work is setting the txpower through iwconfig, which uses ioctls instead of netlink.

# iwconfig wlan0 txpower 20
# iw dev
phy#0
    Interface wlan0
        ifindex 3
        wdev 0x1
        addr b8:27:eb:bb:b3:d0
        ssid foobar
        type AP
        channel 5 (2432 MHz), width: 20 MHz, center1: 2432 MHz
        txpower 20.00 dBm

I verified that the signal strength changes considerably between auto (31 dBm) and fixed 20 (0 dBm) and it's not just a visual glitch. Setting the txpower through iwconfig works just fine, just not through iw.

[stapelberg]

Raspbian does not contain regulatory.db either, so I’m not sure where to take it from?

[mweinelt]

regulatory.db is the signed version of the regulatory domain specification, it's being made available at https://wireless.wiki.kernel.org/en/developers/Regulatory/wireless-regdb.

I run stretch on an APU2c4 with an ath10k wifi card and it does not experience this issue, but I cannot find a regulatory.db on that either. Instead it has a regulatory.bin from the wireless-regdb package: https://packages.debian.org/sid/all/wireless-regdb/filelist

Maybe this is related to a recent kernel change.

Edit: Found the debian issue: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=892229

[stapelberg]

Thanks for identifying the Debian issue for this. I’ll close the issue now, as the problem lies with the kernel, not our Raspberry Pi image build.