On Fri, Mar 30, 2018 at 05:02:14PM +0200, Andrew Lunn wrote:

Would it not be better to just call ethtool_get_ts_info() on the real
device? That would then also deal with the case that the 'real' device
is another virtual device stacked on top of a real device.

That won't work.

The returned 'ethtool_ts_info' is on the stack of
ethtool_get_ts_info().  Both the top level and the inner call to
will call copy_to_user(), but the top level will clobber the correct
result with zeros.

Thanks,
Richard