Bug#621737: linux-image-2.6.32-5-powerpc: ath ignores regulatory domain setting
Hi
On Sunday 10 April 2011, Anton Ivanov wrote:
> On 04/10/11 16:23, Stefan Lippers-Hollmann wrote:
> > Hi
> >
> > On Sunday 10 April 2011, Anton Ivanov wrote:
> >
> >> On 04/10/11 00:55, Ben Hutchings wrote:
> >>
> >>> On Fri, 2011-04-08 at 13:39 +0100, Anton Ivanov wrote:
[...]
> >> Yes. No effect. ath still reads from eeprom.
> >>
> > The EEPROM settings are authoritative, you can only restrict the
> > regulatory settings further to aid regulatory compliance in different
> > regions, but never relax them. Tools like crda always intersect the
> > EEPROM's (OTP in newer chipset generations) with the chosen regulatory
> > domain as provided by wireless-regdb or the in-kernel regdb; regulatory
> > hints like IEEE 802.11d may also restrict the allowed frequencies even
> > further.
> >
> > http://wireless.kernel.org/en/users/Drivers/ath#Regulatory
> >
> > This is intended beaviour and required for FCC compliance (keep in mind
> > that calibration data is also only validated for the given regdomain),
> > not a bug.
> >
>
> So a card that returns only CN from EEPROM is basically intended to be
> sold _ONLY_ in China. Right?
[...]
Correct, it's arguably even illegal to sell in ETSI regions. Although
it's technically a little more complex as Atheros groups regdom regions
with identical mappings together[1], which makes reading the EEPROM
based regulatory domain code a bit strange (the alphabetically first
match corresponding to the regdom group gets printed to dmesg).
In your particular case, with a 2.4 GHz-only AR2417 PHY, 0x52
(APL1_WORLD vs ETSI1_WORLD, GB) doesn't actually do any harm, as 'CN'
allows channel 1-13 just as well as the most permissive regdomains
(ch14 in Japan is only allowed for CSMA/CA == 11 MBit/s, not the more
common OFDM rates (>= 54 MBit/s)). So even though your device is
wrongly programmed, it doesn't actually limit your abilities (unless
you'd add an additional 5 GHz capable card, which would suffer from an
'unfortunate' intersection) - and neither allows you to access
non-public frequency bands. This situation would be seriously worse
(both technically and legally) for 5 GHz operations, but your device
doesn't support that anyways.
country CN:
(2402 - 2482 @ 40), (N/A, 20)
(5735 - 5835 @ 40), (N/A, 30)
country GB:
(2402 - 2482 @ 40), (N/A, 20)
(5170 - 5250 @ 40), (N/A, 20)
(5250 - 5330 @ 40), (N/A, 20), DFS
(5490 - 5710 @ 40), (N/A, 27), DFS
However I'm aware of the sad truth that most commonly sold cards are
wrongly programmed for CN or (worse for 2.4 GHz operations) US...
Regards
Stefan Lippers-Hollmann
[1] http://wireless.kernel.org/en/users/Drivers/ath#line-28
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