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

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Message-ID: <184e8aa3278.279b.9b12b7fc0a3841636cfb5e919b41b954@broadcom.com>
Date:   Tue, 06 Dec 2022 19:19:39 +0100
From:   Arend Van Spriel <arend.vanspriel@...adcom.com>
To:     Bitterblue Smith <rtl8821cerfe2@...il.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 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
>>




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