linux-kernel - Re: [ 08/12] mac80211: zero initialize count field in ieee80211_tx

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Date:	Mon, 12 Mar 2012 21:40:39 +0530
From:	Mohammed Shafi Shajakhan <mohammed@....qualcomm.com>
To:	Ben Hutchings <ben@...adent.org.uk>
CC:	Willy Tarreau <w@....eu>, <linux-kernel@...r.kernel.org>,
	<stable@...r.kernel.org>, Pavel Roskin <proski@....org>,
	"John W. Linville" <linville@...driver.com>
Subject: Re: [ 08/12] mac80211: zero initialize count field in ieee80211_tx_rate

On Monday 12 March 2012 09:25 PM, Mohammed Shafi Shajakhan wrote:
> Hi Ben,
>
> On Monday 12 March 2012 08:53 PM, Ben Hutchings wrote:
>> On Mon, 2012-03-12 at 12:22 +0530, Mohammed Shafi Shajakhan wrote:
>>> Hi Willy,
>>>
>>>> On Mon, Mar 12, 2012 at 10:06:23AM +0530, Mohammed Shafi Shajakhan
>>>> wrote:
>>>>>> So I'm pretty sure this patch is wrong for 2.6.32; it could be
>>>>>> backported but I don't think the change is necessary anyway.
>>>>>
>>>>> true, but i think its better to initialize the count = 0 rather than
>>>>> count = 1, though the older version driver checks for rate[i].idx>= 0
>>>>> in ath_rc_tx_status. while the ath_tx_status has no such iteration in
>>>>> the older driver code.
>>>>
>>>> In practice, if the patch brings nothing and not even correctness, I'd
>>>> rather drop it than make us believe that some issue is fixed. However
>>>> if you think it does happen to fix a real issue in 2.6.32 (possibly
>>>> combined with some other missing patch), please tell me so and I will
>>>> happily undelete it.
>>>>
>>>
>>> we can drop it. also as there was no driver code checking for
>>> rate[i].count in the 2.6.32 driver. i am also not sure this fixes
>>> something in 2.6.32 but the patch itself is correct.
>> [...]
>>
>> Please read and answer the *whole* of my earlier message. The later
>> code in the rate_control_get_rate() function in 2.6.32 does appear to
>> depend on .count = 1, and there may be code elsewhere that does so too.
>>
>
> are you referring to those code in tx.c ieee80211_tx_h_rate_control.
> sorry if i had again missed something.

if you are referring to that rate[0].count should be definitely 
non-zero. at least the first rate should be non-zero as the drivers rate 
control algorithm should properly fill it up, or mac80211's 
rate_control_send_low should fill it up by 1 for 'no ack frames'
(or)  max retries set by the driver for other frames(recently NULL func
  is added connection monitoring frame whose status will be needed).

-- 
thanks,
shafi
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