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Date:      Tue, 17 Apr 2012 11:12:49 -0700
From:      Adrian Chadd <adrian@freebsd.org>
To:        freebsd-wireless@freebsd.org
Subject:   Question: IEEE80211_RATE_BASIC versus IEEE80211_RATE_MCS ?
Message-ID:  <CAJ-Vmo=L8jhvBwoLpF1Hu1M870ZV%2Bp-G5Vn6HW-HCFV842KLBw@mail.gmail.com>

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Hi,

So after doing some digging into the rate representation, I've
discovered that both IEEE80211_RATE_BASIC and IEEE80211_RATE_MCS are
represented as the high bit set (ie, 0x80.)

My query is - how exactly should we be representing rates, and is
there a clear, consistent, non-overlapping use case for where each is
used?

This shows up in setbasicrates(), where the 11na/11ng modes have the
OFDM/CCK (respectively) rates set as basic, just like for 11a/11bg,
however the high bit is set. ifconfig(8) at least just looks at the tx
rateset list (which setbasicrates is setting up for us) and
mis-interpreting the high bit as MCS, rather than as "basic".

Any ideas/suggestions? I'd be tempted to create a 'ratecode_t' that is
a uint8_t struct, then finding/fixing all instances where ratecode is
being passed in as a uint8_t, but that may be slightly overkill.



Adrian



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