[RFC] ethtool: Support ETHTOOL_GSTATS2 command.

[Michal Kubecek]

On Tue, Mar 20, 2018 at 08:39:33AM -0700, Ben Greear wrote:
> On 03/20/2018 03:37 AM, Michal Kubecek wrote:
> > 
> > IMHO it would be more practical to set "0 means same as GSTATS" as a
> > rule and make ethtool_get_stats() a wrapper for ethtool_get_stats2() to
> > avoid code duplication (or perhaps a use fall-through in the switch). It
> > would also allow drivers to provide only one of the callbacks.
> 
> Yes, but that would require changing all drivers at once, and would make backporting
> and out-of-tree drivers harder to manage.  I had low hopes that this feature would
> make it upstream, so I didn't want to propose any large changes up front.

I don't think so. What I mean is:

(a) driver implements ->get_ethtool_stats2() callback; then we use it
    for GSTATS2
(b) driver does not implement get_ethtool_stats2() but implements
    ->get_ethtool_stats(); then we call for GSTATS2 if level is zero,
    otherwise GSTATS2 returns -EINVAL

and GSTATS is always translated to GSTATS2 with level 0, either by
defining ethtool_get_stats() as a wrapper or by fall-through in the
switch statement.

This way, most drivers could be left untouched and only those which
would implement non-default levels would provide ->get_ethtool_stats2()
callback instead of ->get_ethtool_stats().

Michal Kubecek