[PATCH] mac80211: Fix wrong channel bandwidths reported for aggregates

Linus Lüssing ll at simonwunderlich.de
Tue Jul 19 08:36:33 PDT 2022

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

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