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Subject: Re: [RFC 4/7] mac80211: add freq_offset to RX status
To:     Johannes Berg <johannes@sipsolutions.net>
Cc:     linux-wireless <linux-wireless@vger.kernel.org>
References: <20200401062150.3324-1-thomas@adapt-ip.com>
 <20200401062150.3324-5-thomas@adapt-ip.com>
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From:   Thomas Pedersen <thomas@adapt-ip.com>
Message-ID: <62c642d8-1372-6021-b362-3be8d8d22a4c@adapt-ip.com>
Date:   Wed, 1 Apr 2020 10:58:27 -0700
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On 4/1/20 12:08 AM, Johannes Berg wrote:
> On Tue, 2020-03-31 at 23:21 -0700, Thomas Pedersen wrote:
>> RX status needs a KHz component, so add freq_offset. We
>> can make ampdu_reference u16 since it is probably
>> sufficient to be able to distinguish 64k different
>> A-MPDUs.
> 
> Is that necessary? Reads like we have 2 bytes free there?

Indeed there is, maybe this wasn't the case on 4.9 where I originally
wrote this patch.

> And we only need 13 bits for the frequency (up to 8192 MHz, 60 GHz isn't
> supported), so we could take out a few fractional ones for the S1G part?

Makes sense, and yeah we really don't need 2 whole bytes to essentially
express "+0.5 MHz". Will shorten the frequency and just use a single bit
indicating offset or not.

> Dunno, I mean, we probably also don't need the A-MPDU reference, even
> radiotap doesn't make much representation on this, but it sort of
> implies that it should be unique in a capture file, for which 16 bits
> wouldn't be enough? (should probably clarify that though and say that
> you should look only "close by" or something?)

Yeah. I'll drop this for now, but maybe the space will come in handy in
the future.

-- 
thomas