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

[Arend van Spriel <arend@broadcom.com>]

On 05/03/15 21:07, Johannes Berg wrote:
> 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.

I don't either, but I had a bunch of test systems that I wanted to get 
going.

> 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

I have to learn about the per-cpu operations someday so why not now 
while spending two weeks vacation ;-)

Thanks,
Arend