Accessing length value in the L-SIG field (PHY header)

[makesens86]

I am trying to get the length of currently receiving packet.
When I checked 'ath_rx_status' info, It looks like the received 'rs_datalen' field is updated after all the packet is received in the rx buffer.
So I think accessing the length field in L-SIG field (PHY header) can be a solution.
But I can't find any way to access it throughout firmware source code. Is there any way to do it?
Or can L-SIG field be accessed only by hardware?

Thank you.
Hyunjoong Lee.