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Date:   Tue, 19 Jul 2022 17:36:33 +0200
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Subject: Re: [PATCH] mac80211: Fix wrong channel bandwidths reported for
 aggregates
To:     Adrian Chadd <adrian@freebsd.org>,
        =?UTF-8?Q?Linus_L=c3=bcssing?= <linus.luessing@c0d3.blue>
Cc:     Johannes Berg <johannes.berg@intel.com>,
        "David S . Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        =?UTF-8?Q?Toke_H=c3=b8iland-J=c3=b8rgensen?= <toke@toke.dk>,
        Kalle Valo <kvalo@kernel.org>, Felix Fietkau <nbd@nbd.name>,
        Simon Wunderlich <sw@simonwunderlich.de>,
        Sven Eckelmann <sven@narfation.org>,
        ath10k <ath10k@lists.infradead.org>,
        linux-wireless <linux-wireless@vger.kernel.org>,
        netdev <netdev@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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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.

Regards, Linus