RE: [PATCH v3 2/3] wifi: rtl8xxxu: Fix the channel width reporting

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

> -----Original Message-----
> From: Bitterblue Smith <rtl8821cerfe2@gmail.com>
> Sent: Wednesday, November 30, 2022 3:06 AM
> To: linux-wireless@vger.kernel.org
> Cc: Jes Sorensen <Jes.Sorensen@gmail.com>; Ping-Ke Shih <pkshih@realtek.com>
> Subject: [PATCH v3 2/3] wifi: rtl8xxxu: Fix the channel width reporting
> 
> The gen 2 chips RTL8192EU and RTL8188FU periodically send the driver
> reports about the TX rate, and the driver passes these reports to
> sta_statistics. The reports from RTL8192EU may or may not include the
> channel width. The reports from RTL8188FU do not include it.
> 
> Only access the c2h->ra_report.bw field if the report (skb) is big
> enough.
> 
> The other problem fixed here is that the code was actually never
> changing the channel width initially reported by
> rtl8xxxu_bss_info_changed because the value of RATE_INFO_BW_20 is 0.
> 
> Fixes: 0985d3a410ac ("rtl8xxxu: Feed current txrate information for mac80211")
> Signed-off-by: Bitterblue Smith <rtl8821cerfe2@gmail.com>
> ---
> v3:
>  - Don't assume bw will always be 1 byte.
> 
> v2:
>  - Eliminate the magic numbers.
> ---
>  drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
> b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
> index 28f136064297..9799bc5ed60a 100644
> --- a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
> +++ b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
> @@ -5569,7 +5569,6 @@ static void rtl8xxxu_c2hcmd_callback(struct work_struct *work)
>  			rarpt->txrate.flags = 0;
>  			rate = c2h->ra_report.rate;
>  			sgi = c2h->ra_report.sgi;
> -			bw = c2h->ra_report.bw;
> 
>  			if (rate < DESC_RATE_MCS0) {
>  				rarpt->txrate.legacy =
> @@ -5586,8 +5585,14 @@ static void rtl8xxxu_c2hcmd_callback(struct work_struct *work)
>  						RATE_INFO_FLAGS_SHORT_GI;
>  				}
> 
> -				if (bw == RATE_INFO_BW_20)
> -					rarpt->txrate.bw |= RATE_INFO_BW_20;
> +				if (skb->len >= offsetof(typeof(*c2h), ra_report.bw) +
> +						sizeof(c2h->ra_report.bw)) {

Today, I look up if we have a better choice, and offsetofend() can make thing simple.

if (skb->len >= offsetofend(typeof(*c2h), ra_report.bw))

Sorry for the late.

> +					if (c2h->ra_report.bw == RTL8XXXU_CHANNEL_WIDTH_40)
> +						bw = RATE_INFO_BW_40;
> +					else
> +						bw = RATE_INFO_BW_20;
> +					rarpt->txrate.bw = bw;
> +				}
>  			}
>  			bit_rate = cfg80211_calculate_bitrate(&rarpt->txrate);
>  			rarpt->bit_rate = bit_rate;
> --
> 2.38.0
> 
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