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    SubjectRe: [rt2x00-users] ieee80211_tx_status: headroom too small
    From
    On Sun, Nov 22, 2009 at 7:47 AM, Gertjan van Wingerde
    <gwingerde@gmail.com> wrote:
    > On 11/22/09 08:09, David Ellingsworth wrote:
    >> On Sat, Nov 21, 2009 at 10:27 AM, Gertjan van Wingerde
    >> <gwingerde@gmail.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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