linux-kernel - Re: [rt2x00-users] ieee80211_tx

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Date:	Sun, 22 Nov 2009 12:59:02 -0500
From:	David Ellingsworth <david@...ntd.dyndns.org>
To:	Gertjan van Wingerde <gwingerde@...il.com>
Cc:	rt2x00 Users List <users@...x00.serialmonkey.com>,
	LKML <linux-kernel@...r.kernel.org>,
	wireless <linux-wireless@...r.kernel.org>
Subject: Re: [rt2x00-users] ieee80211_tx_status: headroom too small

On Sun, Nov 22, 2009 at 7:47 AM, Gertjan van Wingerde
<gwingerde@...il.com> wrote:
> On 11/22/09 08:09, David Ellingsworth wrote:
>> On Sat, Nov 21, 2009 at 10:27 AM, Gertjan van Wingerde
>> <gwingerde@...il.com> wrote:
>>> On 11/21/09 02:30, David Ellingsworth wrote:
>>>> Wasn't sure where to send this, but with the latest 2.6.32-rc8-wl
>>>> kernel built from the wireless-testing repository I'm getting a number
>>>> of "ieee80211_tx_status: headroom too small" errors in my syslog. I'm
>>>> using the rt61pci driver in conjunction with hostap as a wpa2 secured
>>>> access point. The relevant information about my card from lspci is:
>>>>
>>>> 01:08.0 0280: 1814:0301
>>>>         Subsystem: 1458:e934
>>>>         Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV+ VGASnoop-
>>>> ParErr- Stepping- SERR+ FastB2B- DisINTx-
>>>>         Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=slow >TAbort-
>>>> <TAbort- <MAbort- >SERR- <PERR- INTx-
>>>>         Latency: 64, Cache Line Size: 128 bytes
>>>>         Interrupt: pin A routed to IRQ 18
>>>>         Region 0: Memory at fe6f0000 (32-bit, non-prefetchable) [size=32K]
>>>>         Capabilities: [40] Power Management version 2
>>>>                 Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA
>>>> PME(D0-,D1-,D2-,D3hot-,D3cold-)
>>>>                 Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-
>>>>         Kernel driver in use: rt61pci
>>>>
>>>> If you need any other information, I'll be happy to provide it.
>>>>
>>>
>>> Hi David,
>>>
>>> This seems to be caused by the rt2x00 driver not properly declaring its alignment
>>> maneuvring space properly, and thus it doesn't leave enough headroom left for
>>> copying to the monitor interface.
>>>
>>> Can you check whether the attached patch fixes the issue for you?
>>> Note: patch looks a bit bigger than it actually is due to indenting cleanups.
>>>
>>
>> Gertjan,
>>
>> I haven't really been able to test this. The kernel version I was
>> using at the time was 2.6.32-rc7-wl and not 2.6.32-rc8-wl. I'm rather
>> certain the patch will resolve the issue, but I've been unable to get
>> my wireless card to function properly with the latest 2.6.32-rc8-wl
>> master branch. I'm not entirely sure what changed since two days ago,
>> but I know the following:
>>
>> 1. 2.6.32-rc8 from Linus' master branch works fine but still exhibits
>> this issue. However, this patch will not apply on top of 2.6.32-rc8.
>>
>> 2. 2.6.32-rc7-wl(11/19/2009) worked fine with the exception of the
>> above mentioned error. Unable to test patch since I pulled all the
>> recent modifications down.
>> 3. 2.6.32-rc8-wl does not work at all for me, but patch does apply.
>>
>> I'm not entirely sure what the differences are between Linus' master
>> branch of 2.6.32-rc8 and the current 2.6.32-rc8-wl tree are or what
>> changes have been made on the wireless-testing master branch in the
>> last couple of days that are preventing me from fully testing this
>> patch.
>>
>> With the current wireless-testing master branch, 2.6.32-rc8-wl, with
>> and without the patch I can associate and authenticate with my AP but
>> am unable to do anything else. Any attempt to establish a wireless
>> connection thus dies while trying to obtain an ip address via DHCP.
>> Sadly, no errors are logged indicating what the cause of this problem
>> might be. Given that I've only seen these errors after establishing a
>> wireless connection, it's a little difficult for me to test without
>> being able to transmit any data.
>>
>> I don't know if it's worth the effort or not, but if this patch were
>> re-based against Linus' master branch I might be able to test it since
>> my AP at least works with 2.6.32-rc8.
>
> David,
>
> OK. Find attached the patch ported to Linus' tree. It should apply to
> any version of Linus' tree after 2.6.32-rc8.
> I think it is good to get real confirmation that the patch behaves
> as expected.
>
> ---
> Gertjan.
>

Gertjan,

The patch applies but doesn't quite fix the issue with the rt61pci
driver. With the patch applied, I still occasionally receive the error
message. I added a printk after the error to see how much was missing.
It indicates that skb_headroom is 12 and sizeof(*rthdr) is 13 when it
fails.

Regards,

David Ellingsworth
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