Device with variable hard header len

Hi,

Sorry if this a dumb question. Currently I'm programming a driver for
the devices with variable network header len. From the Linux net stack
perspective what should I do: set netdev->hard_header_len to maximum
possible header and use less space that specified there or set
netdev->needed_headroom to that value?

If that metters, I'll be implementing my own set of header_ops in any
case.

Thank you

-- 
With best wishes
Dmitry