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Date:   Tue, 29 Nov 2022 16:18:41 +0200
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Subject: Re: [PATCH v2 2/3] wifi: rtl8xxxu: Fix the channel width reporting
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To:     Ping-Ke Shih <pkshih@realtek.com>,
        "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>
Cc:     Jes Sorensen <Jes.Sorensen@gmail.com>
References: <d3018e30-92c6-1e73-3b63-311fc472a41f@gmail.com>
 <adc5b63e-7d8d-d613-661d-579bb9f9fadb@gmail.com>
 <c18a1ea252c340b8a876a62bc735c19e@realtek.com>
From:   Bitterblue Smith <rtl8821cerfe2@gmail.com>
In-Reply-To: <c18a1ea252c340b8a876a62bc735c19e@realtek.com>
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On 29/11/2022 03:22, Ping-Ke Shih wrote:
> 
> 
>> -----Original Message-----
>> From: Bitterblue Smith <rtl8821cerfe2@gmail.com>
>> Sent: Tuesday, November 29, 2022 3:30 AM
>> To: linux-wireless@vger.kernel.org
>> Cc: Jes Sorensen <Jes.Sorensen@gmail.com>; Ping-Ke Shih <pkshih@realtek.com>
>> Subject: [PATCH v2 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>
>> ---
>> v2:
>>  - Eliminate the magic numbers.
>> ---
>>  drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu.h      |  2 ++
>>  drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c | 11 ++++++++---
>>  2 files changed, 10 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu.h
>> b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu.h
>> index d26df4095da0..9be53e0f25cc 100644
>> --- a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu.h
>> +++ b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu.h
>> @@ -1187,6 +1187,8 @@ enum rtl8xxxu_bw_mode {
>>  	RTL8XXXU_CHANNEL_WIDTH_MAX = 5,
>>  };
>>
>> +#define RTL8XXXU_C2H_HDR_LEN	2 /* id and seq */
>> +
>>  struct rtl8723bu_c2h {
>>  	u8 id;
>>  	u8 seq;
>> diff --git a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
>> b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
>> index 28f136064297..352779fe4b78 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 > RTL8XXXU_C2H_HDR_LEN +
>> +					       offsetof(typeof(c2h->ra_report), bw)) {
> 
> I think this is not very intuitive, because this logic is correct only if 'bw' is u8.
> 
> Then, this option may be not bad:
> if (skb->len >= RTL8XXXU_C2H_HDR_LEN + offsetof(typeof(c2h->ra_report), bw) + sizeof(c2h->ra_report.bw))
> 
> or 
> Not need RTL8XXXU_C2H_HDR_LEN. Just use offsetof() to calculate: 
> if (skb->len >= offsetof(typeof(*c2h), ra_report.bw) + sizeof(c2h->ra_report.bw))
> 
Nice! I didn't know offsetof can do that.