Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755500Ab3G2Hb2 (ORCPT ); Mon, 29 Jul 2013 03:31:28 -0400 Received: from mail.free-electrons.com ([94.23.35.102]:46272 "EHLO mail.free-electrons.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1752861Ab3G2Hb0 (ORCPT ); Mon, 29 Jul 2013 03:31:26 -0400 Date: Mon, 29 Jul 2013 09:31:23 +0200 From: Maxime Ripard To: Richard Cochran Cc: Tomasz Figa , Arend van Spriel , Olof Johansson , Mark Brown , Mark Rutland , "devicetree@vger.kernel.org" , "ksummit-2013-discuss@lists.linuxfoundation.org" , Russell King - ARM Linux , Ian Campbell , Pawel Moll , Stephen Warren , Domenico Andreoli , "rob.herring@calxeda.com" , "linux-kernel@vger.kernel.org" , Jason Gunthorpe , Dave P Martin , "linux-arm-kernel@lists.infradead.org" Subject: Re: [Ksummit-2013-discuss] DT bindings as ABI [was: Do we have people interested in device tree janitoring / cleanup?] Message-ID: <20130729073123.GB1441@lukather> References: <20130725175702.GC22291@e106331-lin.cambridge.arm.com> <1441731.8CGUI1tUxh@flatron> <20130728085650.GA4683@netboy> <1416484.XDfk5G56BI@flatron> <20130728131901.GA8864@netboy> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="NtwzykIc2mflq5ck" Content-Disposition: inline In-Reply-To: <20130728131901.GA8864@netboy> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2743 Lines: 78 --NtwzykIc2mflq5ck Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi, On Sun, Jul 28, 2013 at 03:19:03PM +0200, Richard Cochran wrote: > On Sun, Jul 28, 2013 at 11:12:53AM +0200, Tomasz Figa wrote: >=20 > > I'm not really sure what effect on users this has. Maybe you should def= ine=20 > > "users". >=20 > ... >=20 > > Care to explain this reasoning? >=20 > Use Case > ~~~~~~~~ >=20 > User acquires a machine running ARM Linux version 3.x, with u-boot > and dtb in a read only flash partition. The board boots and works just > fine. However, for his application, the user requires a new kernel > feature that appeared in version 3.y where y > x. He compiles the new > kernel, and it also works. I'm afraid this kind of use case will never be properly supported, DT stable ABI or not. Think about this: what kernel will actually be shipped in that board? Most likely, it will be a BSP kernel from the vendor. Does the vendor will have made that commitment to have a stable ABI for the DT? Will it use the same bindings than mainline? Do we want to support all the crazy bindings every vendor will come up with? I'm afraid the answer to these three questions will most of the time be "no.". That doesn't mean we shouldn't aim for *mainline* having a stable DT ABI, but that kind of use case doesn't seem very realistic to me. Maxime --=20 Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com --NtwzykIc2mflq5ck Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQIcBAEBAgAGBQJR9hpLAAoJEBx+YmzsjxAgFBIP/2DfiQyJXDnvqyXEgO3yzLzO gRFRGAK+4XzmBmWFkSu0UYm6P1Oe3kcJhn3lsW4GyiT5iQiKl86+dRCfGH/Zn88k 8EtM+EwObDvShBpdjcEFd42hgTr0STn1vX+rW8T8jct3TNW40c2FCy8v5XoFbpIC Od+SRnPpe6SWC/M0X/C34WFSKgvY4ywp7cAbWX2DLjEB8qqms1IxD0dZQJsFDLLC mgPC3UdJCHCnwcaixIkYQbkMpIe4QXGW5eZ1KecHBsjmFgNLZjIZtOhguWpCxqBY +oAoJTdMfA4SyJ0MhUwPVid4WnLpUGATN68KaneFR50VnE9V41tBAZYZw616K+Li jHs8itaRS7rRDs32T2p27wZ0gPhnbzizazNfm6+dCgHlIceZkuQw6l6gUyOhSqcE MXGhd6OfK0GabBvSId8PtbovZ0+Nsg803rx6kIzjFmeB8hmcz3D1eHtuXxzp+V4u Iz6Xra7Ugnm2rKamxZm+/yUmslUi7te7LhmGE4Cc7Vw81+0LSHkGk8tw5D96Bbux Vjnn1EVvOu3pY+4Ia5f80QRBaWwhotS4RelGqqWMuIwM4BCgPt3t4WkWHI65kTBW YUsNl67du+iShyvJuFVgMqXWumY4kB7WmCmrd+UHfLrSEX4XOKMp7p1+whQTj3MC NuI164D4ColZiyBR9ZnO =P2Cy -----END PGP SIGNATURE----- --NtwzykIc2mflq5ck-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/