On 11/24/09 18:19, Ivo van Doorn wrote: > On Monday 23 November 2009, Gertjan van Wingerde wrote: >> Current rt2x00 drivers may result in a "ieee80211_tx_status: headroom too >> small" error message when a frame needs to be properly aligned before >> transmitting it. >> This is because the space needed to ensure proper alignment isn't >> requested from mac80211. >> Fix this by adding sufficient amount of alignment space to the amount >> of headroom requested for TX frames. >> >> Reported-by: David Ellingsworth <david@xxxxxxxxxxxxxxxxx> >> Signed-off-by: Gertjan van Wingerde <gwingerde@xxxxxxxxx> >> --- >> drivers/net/wireless/rt2x00/rt2x00.h | 6 ++++++ >> drivers/net/wireless/rt2x00/rt2x00dev.c | 12 +++++++++++- >> 2 files changed, 17 insertions(+), 1 deletions(-) >> >> diff --git a/drivers/net/wireless/rt2x00/rt2x00.h b/drivers/net/wireless/rt2x00/rt2x00.h >> index 4d841c0..dcfc8c2 100644 >> --- a/drivers/net/wireless/rt2x00/rt2x00.h >> +++ b/drivers/net/wireless/rt2x00/rt2x00.h >> @@ -113,6 +113,12 @@ >> ( ((unsigned long)((__skb)->data + (__header))) & 3 ) >> >> /* >> + * Constants for extra TX headroom for alignment purposes. >> + */ >> +#define RT2X00_ALIGN_SIZE 4 /* Only whole frame needs alignment */ >> +#define RT2X00_L2PAD_SIZE 8 /* Both header & payload need alignment */ > > Now that I think of it, why do we need 8 byte for L2 padding? > Shouldn't we need the same size for regular alignment, L2 padding only indicates > the padding occurs between header and payload rather then before the header only. > So unless I am mistaken about how I coded the header & payload moving in rt2x00lib, > you always need at most 4 bytes. > Nope. If I read the code right then the header can be moved by more than 4 bytes, namely when the payload needs to be shifted more than the header. In that case the header is shifted an extra 4 bytes to make room for the payload. However, 8 is the obvious maximum. --- Gertjan. -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
