Re: [PATCH] backports: mac80211: revert to old stats behaviour for older kernels

[Johannes Berg <johannes@sipsolutions.net>]

On Fri, 2015-05-01 at 15:46 +0200, Arend van Spriel wrote:
> Commit 5a490510ba5f ("mac80211: use per-CPU TX/RX statistics") introduced
> the use of per-cpu statistics, ie. struct netdevice::tstats. This is not
> supported in kernel 3.14 and older.
> 
> Signed-off-by: Arend van Spriel <arend@broadcom.com>
> ---
> I am not entirely sure whether 3.14 is the correct version to check for. The
> functionality seems introduced there but there were some subsequent patches
> on the per-cpu netdev stats functionality.

I don't really like just reverting to the old behaviour - that'll make
this very hard to port.

What part of this isn't supported? Is there no pointer whatsoever that
we can use? We still implement the ndo_getstats64 [or whatever it's
called] ourselves anyway, so we don't really use any API here apart from
 * netdev_alloc_pcpu_stats, which is trivially backported
 * dev->tstats, which is just a single pointer and we could use anything
else,
   even perhaps in sdata

johannes