From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Kirsher Subject: Re: DMA coalescing - ethtool vs. kernel Date: Mon, 27 Nov 2017 10:32:48 -0800 Message-ID: <1511807568.2996.2.camel@intel.com> References: <20171123123158.l6tu6hq2wgdstj4v@unicorn.suse.cz> Reply-To: jeffrey.t.kirsher@intel.com Mime-Version: 1.0 Content-Type: multipart/signed; micalg="pgp-sha256"; protocol="application/pgp-signature"; boundary="=-huKY/keof0uaUaddZT0b" Cc: netdev@vger.kernel.org, Paul Greenwalt , Stephen Hemminger To: Michal Kubecek , "John W. Linville" Return-path: Received: from mga02.intel.com ([134.134.136.20]:50529 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752935AbdK0SbP (ORCPT ); Mon, 27 Nov 2017 13:31:15 -0500 In-Reply-To: <20171123123158.l6tu6hq2wgdstj4v@unicorn.suse.cz> Sender: netdev-owner@vger.kernel.org List-ID: --=-huKY/keof0uaUaddZT0b Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2017-11-23 at 13:31 +0100, Michal Kubecek wrote: > Hello, >=20 > while digging through the interface between ethtool and kernel, > I noticed that ethtool commit 5dd7bfbc5079 ("ethtool: Add DMA > Coalescing > support") added new member dmac into struct ethtool_coalesce which is > part of kernel UAPI but there is no kernel counterpart to this change > in > master, net or net-next tree. >=20 > This doesn't cause any serious trouble as with userspace structure > longer than kernel thinks, kernel would simply ignore the extra > member > so that the feature "only" doesn't work. But I doubt such change > could > be accepted to kernel side of the interface as new kernel would then > overflow shorter structure passed by older ethtool. Stephen Hemminger > mentioned the ABI compatibility issue when this patch was submitted: >=20 > https://patchwork.ozlabs.org/patch/806049/#1757846 >=20 > Does it make sense to have ethtool feature without kernel > counterpart? You are correct Michal. It appears this was over looked when John applied this patch to ethtool. We have dropped this change (as well as the kernel side changes) for now. John- please revert the change to add DMA coalescing in ethtool. --=-huKY/keof0uaUaddZT0b Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEEiTyZWz+nnTrOJ1LZ5W/vlVpL7c4FAlocWlAACgkQ5W/vlVpL 7c5iNQ//T3SLq1NTlqKZ+9LpZHaCxXLG3tBMNcJ/4aDE0enM8fgpwc7Ys5me3uQu s0uDbBdJ5jpGtaqqRwbJFU+XXaGGE7bqlTdMLLYZ8Ywfbr4IcriLGew5Dq+OOftn Zd6iC5LdJyd2OFVEU+pzX0gncWwrpwa7AtU2gNW+oXemoNAyaem+iL1RJWfr2kdI HMItiYNXq2l1x4qyHorI1LnadgNgqqHRP75hSkz8Zf5hUDURXPb6AzYSLqEGLBU8 exzFoOgKbobYS54TuPEeeC51AjJJK3177L12IsPO/0P4XsUCpcRPg1SYLkEAsAzv md6GbNB7EZYpmJl9we2dXlpqlDg1Js5bLcKGwZ9KdxkunLGoITnbl4zNuU3Fs2RW sTaE+jE3+82jFSoVmgPOkeZu9x48qx4gBZVX8/MD8NyPomFOs9AMl2RKJFOZ6WY3 NZGN2J8XFKFMXRN0SC9pZFgB0ku3GgioHSWkQd7n+cW2PwuvrlJZkucFFtp0kliX bDI2HYb177ny6QB6KKVYGM38nqCQ4qZV0VYJyYxS321ddo52iLO3ZSGnzzIKUL+J T7oj48bedWEY0YmW7DJ9HUMtJSgncnumcVzkX7GJxi2uplwPLVN3dfPFOt07umqH ELrk9OSTMIxb8XHVHodtgpiq8tncBAKNXDUM/w6PugXC0C5Qe7U= =ezgr -----END PGP SIGNATURE----- --=-huKY/keof0uaUaddZT0b--