Re: [rt2x00-users] [PATCH] rt2x00: Further L2 padding fixes.

[Andreas Schwab <schwab@linux-m68k.org>]

Gertjan van Wingerde <gwingerde-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
writes:

> On 11/29/09 00:55, Benoit PAPILLAULT wrote:
>> Gertjan van Wingerde a écrit :
>>> On 11/28/09 22:26, Ivo van Doorn wrote:
>>>>> diff --git a/drivers/net/wireless/rt2x00/rt2x00queue.c b/drivers/net/wireless/rt2x00/rt2x00queue.c
>>>>> index b8f0954..562a344 100644
>>>>> --- a/drivers/net/wireless/rt2x00/rt2x00queue.c
>>>>> +++ b/drivers/net/wireless/rt2x00/rt2x00queue.c
>>>>> @@ -181,7 +181,7 @@ void rt2x00queue_insert_l2pad(struct sk_buff *skb, unsigned int header_length)
>>>>>  	unsigned int frame_length = skb->len;
>>>>>  	unsigned int header_align = ALIGN_SIZE(skb, 0);
>>>>>  	unsigned int payload_align = ALIGN_SIZE(skb, header_length);
>>>>> -	unsigned int l2pad = 4 - (payload_align - header_align);
>>>>> +	unsigned int l2pad = 4 - (header_length & 3);
>> 
>> Humm... is header_length = 24, then your formula gives l2pad = 4. If so,
>> this is wrong. Do I miss something?
>
> No, you are right. The formula needs another & 3 on the overall result to account for that situation.
> So, it should be:
>
> 	unsigned int l2pad = (4 - (header_length & 3)) & 3;

aka
	unsigned int l2pad = -header_length & 3;

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
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