On Wed, 5 Jun 2024 17:00:02 +0200 Michal Kubiak wrote:

I am afraid checking for NULL won't be enough here.
Normally, when ndo_bpf is called from the user space application, that
callback can be called with NULL too (when the user just wants to unload
the XDP program). In such a case, apart from calling bpf_prog_put(), we
have to rebuild our internal data structures (queues, pointers, counters
etc.) to restore the i40e driver working back in normal mode (with no
XDP program).

Apologizes for asking a question which can be answered by studying 
the code longer, but why do you need to rebuild internal data
structures for a device which is *down*. Unregistering or not.