From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753391AbaBCTZS (ORCPT ); Mon, 3 Feb 2014 14:25:18 -0500 Received: from top.free-electrons.com ([176.31.233.9]:52540 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752975AbaBCTZQ (ORCPT ); Mon, 3 Feb 2014 14:25:16 -0500 Date: Mon, 3 Feb 2014 20:22:15 +0100 From: Maxime Ripard To: Heiko =?iso-8859-1?Q?St=FCbner?= Cc: Grant Likely , Rob Herring , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Shawn Guo , linux-arm-kernel@lists.infradead.org Subject: Re: [RFC] dtc: add ability to make nodes conditional on them being referenced Message-ID: <20140203192215.GA25625@lukather> References: <1578575.rVWgTPdq1W@phil> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="OXfL5xGRrasGEqWY" Content-Disposition: inline In-Reply-To: <1578575.rVWgTPdq1W@phil> 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 --OXfL5xGRrasGEqWY Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi, On Thu, Jan 30, 2014 at 01:25:56PM +0100, Heiko St=FCbner wrote: > From: Heiko Stuebner >=20 > On i.MX, which carries a lot of pin-groups of which most are unused on > individual boards, they noticed that this plehora of nodes also results > in the runtime-lookup-performance also degrading [0]. >=20 > A i.MX-specific solution defining the pingroups in the board files but > using macros to reference the pingroup-data was not well received >=20 > This patch is trying to solve this issue in a more general way, by > adding the ability to mark nodes as needing to be referenced somewhere > in the tree. >=20 > To mark a node a needing to be referenced it must be prefixed with > /delete-unreferenced/. This makes dtc check the nodes reference-status > when creating the flattened tree, dropping it if unreferenced. >=20 > For example, the i.MX6SL pingroup >=20 > /delete-uneferenced/ pinctrl_ecspi1_1: ecspi1grp-1 { > fsl,pins =3D < > MX6SL_PAD_ECSPI1_MISO__ECSPI1_MISO 0x100b1 > MX6SL_PAD_ECSPI1_MOSI__ECSPI1_MOSI 0x100b1 > MX6SL_PAD_ECSPI1_SCLK__ECSPI1_SCLK 0x100b1 > >; > }; >=20 > would only be included in the dtb if it got referenced somewhere > as pingroup via >=20 > node { > pinctrl-0 <&pinctrl_ecscpi1_1>; > }; >=20 > [0] http://thread.gmane.org/gmane.linux.ports.arm.kernel/275912/ >=20 > Signed-off-by: Heiko Stuebner > --- > This is just the idea I had in [1] explored a bit more. I'm definitely > not sure if this is a valid approach to the problem. > Also this is my first venture into dtc as well as flex and bison :-) . >=20 > [1] http://www.spinics.net/lists/arm-kernel/msg303731.html This is a nice feature to have :) However, I wonder wether it's the right way of implementing it. I'd have another use case for this, which would be to embed a DT in a first-stage bootloader. We have around 7kB available currently for the DT, and this is actually less than any of our (very small already) DTBs. So having this of feature makes complete sense to us too. However, we also have some other tools that require most of the nodes to be in the DTB. So I guess turning wether we should delete a node if unreferenced into a dtc option would make sense, since every DT user will be able to choose, without having to duplicate the DT and make conflicting changes. Maxime --=20 Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com --OXfL5xGRrasGEqWY Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.14 (GNU/Linux) iQIcBAEBAgAGBQJS7+xnAAoJEBx+YmzsjxAgnRcP+weivggq0QOzMwXUjeSDH8hO si8/Q5w6/Nb1uBeluE5aRBFpjxV1uLQdToTe8Lt4lKCujZOypJs3/UaTjN6osjGp 2a3d+E9dixFuGNjD0EYmnpOng+I5xXDnuysQxcbjOD+fnlZfSxkUTfPpMDNozIKV JhwOLcc6vuS31ZCi91RugJ5wJR/l0E94Yg1AHDMJKvYTMMlGAQOYmy4cS9YAF+XV XiaALtJUWX9gK0yEgYmwUUgKFsqZi3vWGUgDFEM/YJ1oLO/n6GWvy2Y3Mbe5TOEb uFOEimpTRIUk8W2rMDqTgOmGPnHyN3zYVqmRAzc/Cvdj35gjTpvhuTqEilkadCRH kqKhsRgkurvpsSXHqLJmjYXz4yCM0r8QNImiczvMf+P5nw/4bt8hSNZ3ZAa1TIwa Imh7rPkVcIfAEndUUWc1dziwOWR8j7kS0fcuFMgMKvto7FYujwmVaozHu8XPjITa 6meKqx+FGszN+IfyzE46SFgxNK74w0zH4BGUV1UsFmi7cVarSAFjm47CCc+DDhac dvkqAYv+CGKCaRQWDgxBqpCr3429/aIdYxDSDa6ssLHL74wKWL6gMt4E4lBN4dHk /V1wH56jNRGNQbf4HRBthQfIXF3a3FUiT5KSO9aioT3FH2l/0WfNWrbzdimaATvS dfkQYqzks2hYtZ4E/zLR =Ca77 -----END PGP SIGNATURE----- --OXfL5xGRrasGEqWY--