On Tue, Aug 10, 2010 at 09:24:23AM -0700, Philip Rakity wrote:

quoted

quoted

* Headroom in SKB for 802.11 not included in the patch since that
 varies based on 802.11 a/b/g/n.

I don't think this is true?

(The 11a/b/n on-the-air preambles are of different lengths (and are
sent at different rates), but that isn't visible to software.)

802.11b/g headers are larger and if not handled by firmware in an
offload engine are programmed by the driver.  There needs to be room
for 

a) Frame Control (2 bytes)
b) AID (2 bytes)
c) address-1 (6 bytes)
d) address-2 (6 bytes)
e) address-3 (6 bytes)
f) seqfrag  (2 bytes)
g) address-4 (6 bytes) 

or 30 bytes.

Depends on the driver and/or whether you are doing WDS.

mwl8k always needs 30 bytes due to hardware pecularities (while the
4-address-with-QoS header is 32 bytes, the QoS field is always passed
in the TX descriptor), but other drivers might need 32 bytes (and not
30 bytes) for 4-address-with-QoS headers, or might not need 30 or 32
bytes for transmitting 3-address or 2-address frames.

11n needs more.

Really?  Pointer?

Some of these fields ARE visible to s/w.

Where did I say that they are not?

What I said was that the _preambles_ are not visible to software.