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Subject: Re: [PATCH 1/3] dt-bindings: net: wireless: mt76: add power-limits
 node
To:     Rob Herring <robh@kernel.org>
Cc:     linux-wireless@vger.kernel.org, devicetree@vger.kernel.org
References: <20200529161929.24751-1-nbd@nbd.name>
 <20200529212637.GA2994957@bogus>
From:   Felix Fietkau <nbd@nbd.name>
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Date:   Sat, 30 May 2020 09:05:07 +0200
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On 2020-05-29 23:26, Rob Herring wrote:
> On Fri, May 29, 2020 at 06:19:27PM +0200, Felix Fietkau wrote:
>> This subnode can be used to set per-rate tx power limits either per
>> country code / regdomain or globally.
>> These limits are typically provided by the device manufacturers and are
>> used to limit sideband emissions and stay within regulatory limits
> 
> How do other WiFi chips handle this? If this is added to DT, then it 
> should be common for all WiFi h/w.
Most devices store this data in EEPROM, and the way it's handled also
varies across different chips. QCA has EEPROM data that only provides
limits for edge channels (called "conformance test limits")
The only other example I could find of a driver that stores it in DT is
mwifiex, which uses an opaque short array of bytes that is passed to the
firmware directly.
So I don't think it makes sense to put this in the common bindings.
On the other hand, I did try to keep the format as generic and
extensible as possible, so we could always move it over from mt76 to the
common binding once we encounter another driver that needs something
like this.

- Felix