[rt2x00-users] rt2800usb: TX frames are not 4-bytes aligned when kick out to USB host

洪 偉傑 jay.weihung at gmail.com
Mon Feb 14 01:50:18 AEDT 2011

Hi Helmut,
>> Recently I found a strange phenomenon of tx frames that are ready to kick out to USB host are not 4-bytes boundary aligned.
>> At first, after fill out tx HW header descriptor in rt2x00queue_write_tx_descriptor, the skb->data still are 4-bytes aligned.
>> So in theory,  when submit each tx frame to USB host in rt2x00usb_kick_tx_entry should be also 4-bytes aligned,
>> but sometimes the skb->data are really not 4-bytes aligned, and it will cause wrong frame when dongle send out to air.
> How did you notice that some frames are not 4-byte aligned?
I print out skb->data address to see if 4-bytes aligned in two location.
In rt2x00queue_write_tx_descriptor, skb->data address all are 4-bytes aligned.
But in rt2x00usb_kick_tx_entry(), skb->data address sometimes are not 4-bytes aligned.
Under throughput test is easy to reproduce on my place.

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