[PATCH] ath10k: fix bug in masking of TID value

[PATCH] ath10k: fix bug in masking of TID value

[Erik Stromdahl]

Although the TID mask is 0xf, the modulus operation does still not
produce identical results as the bitwise and operator.

If the TID is 15, the modulus operation will "convert" it to 0, whereas
the bitwise and will keep it as 15.

Signed-off-by: Erik Stromdahl <erik.stromdahl@gmail.com>
---
 drivers/net/wireless/ath/ath10k/htt_tx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/ath/ath10k/htt_tx.c b/drivers/net/wireless/ath/ath10k/htt_tx.c
index 89157c5b5e5f..be5b52aaffa6 100644
--- a/drivers/net/wireless/ath/ath10k/htt_tx.c
+++ b/drivers/net/wireless/ath/ath10k/htt_tx.c
@@ -1056,7 +1056,7 @@ static u8 ath10k_htt_tx_get_tid(struct sk_buff *skb, bool is_eth)
 	if (!is_eth && ieee80211_is_mgmt(hdr->frame_control))
 		return HTT_DATA_TX_EXT_TID_MGMT;
 	else if (cb->flags & ATH10K_SKB_F_QOS)
-		return skb->priority % IEEE80211_QOS_CTL_TID_MASK;
+		return skb->priority & IEEE80211_QOS_CTL_TID_MASK;
 	else
 		return HTT_DATA_TX_EXT_TID_NON_QOS_MCAST_BCAST;
 }
-- 
2.17.0

Re: [PATCH] ath10k: fix bug in masking of TID value

[Kalle Valo]

Erik Stromdahl <erik.stromdahl@gmail.com> writes:

> Although the TID mask is 0xf, the modulus operation does still not
> produce identical results as the bitwise and operator.
>
> If the TID is 15, the modulus operation will "convert" it to 0, whereas
> the bitwise and will keep it as 15.
>
> Signed-off-by: Erik Stromdahl <erik.stromdahl@gmail.com>
> ---
>  drivers/net/wireless/ath/ath10k/htt_tx.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/wireless/ath/ath10k/htt_tx.c b/drivers/net/wireless/ath/ath10k/htt_tx.c
> index 89157c5b5e5f..be5b52aaffa6 100644
> --- a/drivers/net/wireless/ath/ath10k/htt_tx.c
> +++ b/drivers/net/wireless/ath/ath10k/htt_tx.c
> @@ -1056,7 +1056,7 @@ static u8 ath10k_htt_tx_get_tid(struct sk_buff *skb, bool is_eth)
>  	if (!is_eth && ieee80211_is_mgmt(hdr->frame_control))
>  		return HTT_DATA_TX_EXT_TID_MGMT;
>  	else if (cb->flags & ATH10K_SKB_F_QOS)
> -		return skb->priority % IEEE80211_QOS_CTL_TID_MASK;
> +		return skb->priority & IEEE80211_QOS_CTL_TID_MASK;

I guess you just found this during code review? If yes, I'll add that to
the commit log.

-- 
Kalle Valo

Re: [PATCH] ath10k: fix bug in masking of TID value

[Erik Stromdahl]

Hi Kalle,

On 06/15/2018 02:58 PM, Kalle Valo wrote:
> Erik Stromdahl <erik.stromdahl@gmail.com> writes:
> 
>> Although the TID mask is 0xf, the modulus operation does still not
>> produce identical results as the bitwise and operator.
>>
>> If the TID is 15, the modulus operation will "convert" it to 0, whereas
>> the bitwise and will keep it as 15.
>>
>> Signed-off-by: Erik Stromdahl <erik.stromdahl@gmail.com>
>> ---
>>   drivers/net/wireless/ath/ath10k/htt_tx.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/wireless/ath/ath10k/htt_tx.c b/drivers/net/wireless/ath/ath10k/htt_tx.c
>> index 89157c5b5e5f..be5b52aaffa6 100644
>> --- a/drivers/net/wireless/ath/ath10k/htt_tx.c
>> +++ b/drivers/net/wireless/ath/ath10k/htt_tx.c
>> @@ -1056,7 +1056,7 @@ static u8 ath10k_htt_tx_get_tid(struct sk_buff *skb, bool is_eth)
>>   	if (!is_eth && ieee80211_is_mgmt(hdr->frame_control))
>>   		return HTT_DATA_TX_EXT_TID_MGMT;
>>   	else if (cb->flags & ATH10K_SKB_F_QOS)
>> -		return skb->priority % IEEE80211_QOS_CTL_TID_MASK;
>> +		return skb->priority & IEEE80211_QOS_CTL_TID_MASK;
> 
> I guess you just found this during code review? If yes, I'll add that to
> the commit log.
> 
Correct, I kind of stumbled upon it while working with TX bundling for SDIO.

--
Erik

Re: ath10k: fix bug in masking of TID value

[Kalle Valo]

Erik Stromdahl <erik.stromdahl@gmail.com> wrote:

> Although the TID mask is 0xf, the modulus operation does still not
> produce identical results as the bitwise and operator. If the TID is 15, the
> modulus operation will "convert" it to 0, whereas the bitwise and will keep it
> as 15.
> 
> This was found during code review.
> 
> Signed-off-by: Erik Stromdahl <erik.stromdahl@gmail.com>
> Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

Patch applied to ath-next branch of ath.git, thanks.

d1a566bec588 ath10k: fix bug in masking of TID value

-- 
https://patchwork.kernel.org/patch/10466271/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches