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Message-ID: <7c7135cb-ee5d-e7f3-45ca-8b7206312512@cesarb.eti.br>
Date:   Wed, 7 Sep 2022 17:02:01 -0300
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Subject: Re: [wireless-regdb] [PATCH] wireless-regdb: Update regulatory rules
 for Brazil (BR)
To:     Seth Forshee <sforshee@kernel.org>
Cc:     Johannes Berg <johannes@sipsolutions.net>,
        wireless-regdb@lists.infradead.org, linux-wireless@vger.kernel.org
References: <20220901232734.5488-1-cesarb@cesarb.eti.br>
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 <YxiwFLWhsOtJJhrq@do-x1extreme>
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From:   Cesar Eduardo Barros <cesarb@cesarb.eti.br>
In-Reply-To: <YxiwFLWhsOtJJhrq@do-x1extreme>
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Em 07/09/2022 11:52, Seth Forshee escreveu:
> On Fri, Sep 02, 2022 at 07:21:50PM -0300, Cesar Eduardo Barros wrote:
>> Em 02/09/2022 11:53, Johannes Berg escreveu:
>>> On Thu, 2022-09-01 at 20:27 -0300, Cesar Eduardo Barros wrote:
>>>>
>>>> +	# This range ends at 5725 MHz, but channel 144 extends to 5730 MHz.
>>>> +	# Since 5725 ~ 5730 MHz belongs to the next range which has looser
>>>> +	# requirements, we can extend the range by 5 MHz to make the kernel
>>>> +	# happy and be able to use channel 144.
>>>> +	(5470 - 5730 @ 160), (27), DFS
>>>> +	(5730 - 5850 @ 80), (30)
>>>>
>>>
>>> If you do the latter as 160 as well, and add AUTO-BW, couldn't you split
>>> them at 5725 correctly? But I guess it doesn't matter anyway.
>>
>> This was copied from the US rules (including the four-line comment), which
>> have an identical split. If AUTO-BW worked here, I'd expect the US rules to
>> use it.
> 
> AUTO-BW would work, and we have countries using it for this case. Iirc
> for some countries we move the split to 5730 because even though
> 5725-5730 is at a lower power limit the rules allow channel 144 to be
> used at the power limit for 5710-5725. For the US though I think it's
> just historical -- it was done that way initially, and it isn't
> important enough that anyone has cared to change it.

The only country I found in the database that does it that way is IL, 
and it has the power limits in the opposite direction (its 5470 - 5725 
range has a higher power limit than its 5725 - 5875 range, while for BR 
and US it's the former range which has a lower power limit); looking at 
other countries, AU does the manual adjustment with a comment like US, 
while TW has a 5 MHz overlap on its ranges. So the precedent is not 
enough for me to be confident that using the official split together 
with AUTO-BW would allow using channel 144 (and the 40 MHz and 80 MHz 
channels it's part of).

And the single one which does it using AUTO-BW (IL) doesn't change the 
bandwidth of its 5725 - 5875 to 160; is it really necessary to do that 
change to the bandwidth (considering also that channel 144 is not part 
of a pure 160 MHz channel, it could be used only for 80+80)? What about 
the 5150 - 5250 and 5250 - 5350 ranges, do they need also to be changed 
to 160 so that the combined 5170 - 5330 160 MHz channel can be used, or 
does AUTO-BW allow it even though both ranges are declared as allowing 
just 80 MHz channels? What about 80+80 channels?

> But we do generally try to keep the rules matching the official
> documents as much as possible, so for new rules we should split at 5725
> and use AUTO-BW as Johannes suggested. Could you send a v2 with that
> change?

Well, it's not exactly a new rule (the current database already has a 
5490 - 5730 @ 160 rule), but we could treat it that way since we're 
mostly rewriting them all (and the original didn't say where that came 
from).

Since I'm not certain that AUTO-BW will be interpreted as expected, 
before doing that change, I'll try to see if I can test it first on my 
laptop (by sheer luck, I happen to be using the 5650 - 5730 80 MHz 
channel right now, so I'd just have to see if it still connects at 80 
MHz, assuming I can somehow convince the kernel to load a modified 
file). Or would you prefer me to send the patch first (with or without a 
change in the channel bandwidths)?

-- 
Cesar Eduardo Barros
cesarb@cesarb.eti.br