netdev - Re: [PATCH] drivers: rewrite and remove a superfluous parameter.

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Date:   Tue, 6 Dec 2022 20:40:26 +0200
From:   Bitterblue Smith <rtl8821cerfe2@...il.com>
To:     Arend Van Spriel <arend.vanspriel@...adcom.com>,
        JunASAKA <JunASAKA@...040330.moe>, Jes.Sorensen@...il.com
Cc:     kvalo@...nel.org, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers: rewrite and remove a superfluous parameter.

On 06/12/2022 20:19, Arend Van Spriel wrote:
> On December 6, 2022 6:59:36 PM Arend Van Spriel <arend.vanspriel@...adcom.com> wrote:
> 
>> On November 29, 2022 3:06:37 PM Bitterblue Smith <rtl8821cerfe2@...il.com>
>> wrote:
>>
>>> On 29/11/2022 06:34, JunASAKA wrote:
>>>> I noticed there is a superfluous "*hdr" parameter in rtl8xxxu module
>>>> when I am trying to fix some bugs for the rtl8192eu wifi dongle. This
>>>> parameter can be removed and then gained from the skb object to make the
>>>> function more beautiful.
>>>>
>>>> Signed-off-by: JunASAKA <JunASAKA@...040330.moe>
>>>> ---
>>>> drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c | 5 +++--
>>>> 1 file changed, 3 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
>>>> b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
>>>> index ac641a56efb0..4c3d97e8e51f 100644
>>>> --- a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
>>>> +++ b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
>>>> @@ -4767,9 +4767,10 @@ static u32 rtl8xxxu_80211_to_rtl_queue(u32 queue)
>>>> return rtlqueue;
>>>> }
>>>>
>>>> -static u32 rtl8xxxu_queue_select(struct ieee80211_hdr *hdr, struct sk_buff
>>>> *skb)
>>>> +static u32 rtl8xxxu_queue_select(struct sk_buff *skb)
>>>> {
>>>> u32 queue;
>>>> + struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
>>>>
>>>> if (ieee80211_is_mgmt(hdr->frame_control))
>>>> queue = TXDESC_QUEUE_MGNT;
>>>> @@ -5118,7 +5119,7 @@ static void rtl8xxxu_tx(struct ieee80211_hw *hw,
>>>> if (control && control->sta)
>>>> sta = control->sta;
>>>>
>>>> - queue = rtl8xxxu_queue_select(hdr, skb);
>>>> + queue = rtl8xxxu_queue_select(skb);
>>>>
>>>> tx_desc = skb_push(skb, tx_desc_size);
>>>
>>> See the recent discussion about this here:
>>> https://lore.kernel.org/linux-wireless/acd30174-4541-7343-e49a-badd199f4151@gmail.com/
>>> https://lore.kernel.org/linux-wireless/2af44c28-1c12-46b9-85b9-011560bf7f7e@gmail.com/
>>
>> Not sure why I looked but I did. You may want to look at rtl8xxxu_tx()
>> which is the .tx callback that mac80211 uses and the first statement in
>> there is also assuming skb->data points to the 802.11 header.
> 
> Here the documentation of the .tx callback:
> 
> @tx: Handler that 802.11 module calls for each transmitted frame.
> * skb contains the buffer *starting from the IEEE 802.11 header*.
> * The low-level driver should send the frame out based on
> * configuration in the TX control data. This handler should,
> * preferably, never fail and stop queues appropriately.
> * Must be atomic.
> 
> I don't see any pushes or pulls before the queue select so that would mean mac80211 is not complying to the described behavior.
> 
> Regards,
> Arend
> 
>>
>> Regards,
>> Arend
>>>
> 
> 
> 
mac80211 is behaving as described in the documentation, as far as I know.
Technically, rtl8xxxu_queue_select's hdr parameter is not needed.