linux-kernel - Re: [PATCH] mac80211: Fix wrong channel bandwidths reported for aggregates

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Message-ID: <87cze0kq5d.fsf@toke.dk>
Date:   Wed, 20 Jul 2022 12:57:34 +0200
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Linus Lüssing <ll@...onwunderlich.de>,
        Adrian Chadd <adrian@...ebsd.org>,
        Linus Lüssing <linus.luessing@...3.blue>
Cc:     Johannes Berg <johannes.berg@...el.com>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, Kalle Valo <kvalo@...nel.org>,
        Felix Fietkau <nbd@....name>,
        Simon Wunderlich <sw@...onwunderlich.de>,
        Sven Eckelmann <sven@...fation.org>,
        ath10k <ath10k@...ts.infradead.org>,
        linux-wireless <linux-wireless@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mac80211: Fix wrong channel bandwidths reported for
 aggregates

Linus Lüssing <ll@...onwunderlich.de> writes:

> On 19/07/2022 17:03, Adrian Chadd wrote:
>> Hi!
>> 
>> It's not a hardware bug. Dating back to the original AR5416 11n chip,
>> most flags aren't valid for subframes in an aggregate. Only the final
>> frame has valid flags. This was explicitly covered internally way back
>> when.
>
> Ah, thanks for the clarification! I see it in the datasheet for the 
> QCA9531, too, now. And thanks for the confirmation, that what we are 
> doing so far is not correct for ath9k.
>
> Words 0+2 are valid for all RX descriptors, 0+2+11 valid for the last RX 
> descriptor of each packet and 0-11 for the last RX descriptor of an 
> aggregate or last RX descriptor of a stand-alone packet. Or in other 
> words, word 4, which contains the 20 vs. 40 MHz indicator, is invalid 
> for any aggregate sub-frame other than the last one. I can rename that 
> in the commit message.
>
>
> Another approach that also came to my mind was introducing more explicit 
> flags in cfg80211.h's "struct rate_info", like a RATE_INFO_BW_UNKNOWN in 
> "enum rate_info_bw" and/or RATE_INFO_FLAGS_UNKNOWN in "enum 
> rate_info_flags". And setting those flags in ath9k_cmn_process_rate().
>
> The current approach is smaller though, as it simply uses the already 
> existing flags. If anyone has any preferences, please let me know.

I have no objections to doing it in mac80211 like you're proposing here :)

-Toke