RE: [PATCH] wifi: rtlwifi: Fix setting the basic rates

[Ping-Ke Shih <pkshih@realtek.com>]

> -----Original Message-----
> From: Bitterblue Smith <rtl8821cerfe2@gmail.com>
> Sent: Sunday, February 18, 2024 4:20 AM
> To: linux-wireless@vger.kernel.org
> Cc: Ping-Ke Shih <pkshih@realtek.com>; Larry Finger <Larry.Finger@lwfinger.net>
> Subject: [PATCH] wifi: rtlwifi: Fix setting the basic rates

Though driver sets register via enum HW_VAR_BASIC_RATE, but actually it uses
supported rates as ACK and RTS rates, so I think it would be clearer to
mention "fix setting of RTS rate" in subject.

Others look good to me. 

> 
> RTL8192CU transmits RTS frames at 48M instead of the expected 24M.
> This is because rtlwifi never writes REG_INIRTS_RATE_SEL, because when
> rtl_op_bss_info_changed() is called with BSS_CHANGED_BASIC_RATES (and
> BSS_CHANGED_BSSID) it calls ieee80211_find_sta(), which returns NULL,
> and the code skips over the part that handles BSS_CHANGED_BASIC_RATES.
> 
> A bit later rtl_op_bss_info_changed() is called with BSS_CHANGED_ASSOC.
> At this point ieee80211_find_sta() works, so set the basic rates from
> here.
> 
> Some of the code from BSS_CHANGED_BSSID which needs ieee80211_find_sta()
> was already duplicated under BSS_CHANGED_ASSOC, so delete it from
> BSS_CHANGED_BSSID.
> 
> Signed-off-by: Bitterblue Smith <rtl8821cerfe2@gmail.com>
> ---
> 
> I'm not sure if this is enough. Should we also handle
> BSS_CHANGED_BASIC_RATES? But bss_conf->basic_rates is only 0xf (CCK
> rates only) and the out-of-tree Realtek drivers want to use the 6, 12,
> and 24M rates as well. If ieee80211_find_sta() returns NULL, how can we
> know if OFDM rates are supported?
> 
> I'm also not sure if it's okay to set the basic rates later than
> originally intended, but it's still better than never.

bss_conf->basic_rates is from AP beacon basically, and only the supported rates
with 0x80 bit are basic rates, which is minimum rates requirement to the AP.
Thus, I think it is not suitable to consider basic rates as RTS rate. 

Ping-Ke