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From:   Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
To:     Johannes Berg <johannes@sipsolutions.net>
Cc:     linux-wireless@vger.kernel.org,
        make-wifi-fast@lists.bufferbloat.net,
        John Crispin <john@phrozen.org>,
        Lorenzo Bianconi <lorenzo@kernel.org>,
        Felix Fietkau <nbd@nbd.name>
Subject: Re: [PATCH RFC/RFT 2/4] mac80211: Add API function to set the last TX bitrate for a station
In-Reply-To: <2518c49c96b8b5233fabcb8bafccba6b8f3155bf.camel@sipsolutions.net>
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Date:   Tue, 01 Oct 2019 11:09:30 +0200
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Johannes Berg <johannes@sipsolutions.net> writes:

> On Thu, 2019-09-19 at 14:22 +0200, Toke H=C3=B8iland-J=C3=B8rgensen wrote=
:
>
> Given a ULL constant:
>
>> +/* constants for calculating reciprocals to avoid division in fast path=
 */
>> +#define IEEE80211_RECIPROCAL_DIVISOR 0x100000000ULL
>
> [...]
>
>> +void ieee80211_sta_set_last_tx_bitrate(struct ieee80211_sta *pubsta,
>> +=09=09=09=09       u32 rate)
>> +{
>> +=09struct sta_info *sta =3D container_of(pubsta, struct sta_info, sta);
>> +
>> +=09sta->last_tx_bitrate =3D rate;
>> +=09sta->last_tx_bitrate_reciprocal =3D ((u64)IEEE80211_RECIPROCAL_DIVIS=
OR / rate);
>
> that cast seems unnecessary?

Yeah. I only remembered to make it a ULL constant later, and forgot to
remove the cast. But I guess this should be using do_div() anyway...

-Toke