From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932790AbaHYNeR (ORCPT ); Mon, 25 Aug 2014 09:34:17 -0400 Received: from jdl.com ([208.123.74.7]:42353 "EHLO jdl.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755778AbaHYNeM (ORCPT ); Mon, 25 Aug 2014 09:34:12 -0400 X-Greylist: delayed 1492 seconds by postgrey-1.27 at vger.kernel.org; Mon, 25 Aug 2014 09:34:12 EDT Message-Id: To: Thierry Reding cc: Mark Rutland , Alexander Holler , "grant.likely@linaro.org" , "linux-kernel@vger.kernel.org" , "devicetree@vger.kernel.org" , Russell King , Greg Kroah-Hartman , Rob Herring , Arnd Bergmann , "linux-arm-kernel@lists.infradead.org" Subject: Re: [RFC PATCH 0/9] dt: dependencies (for deterministic driver initialization order based on the DT) In-reply-to: <20140825093931.GB2399@ulmo> References: <1399913280-6915-1-git-send-email-holler@ahsoftware.de> <20140514141914.446F7C4153D@trevor.secretlab.ca> <20140821140211.GD19293@ulmo.nvidia.com> <53F64624.5000403@ahsoftware.de> <20140822131919.GX21734@leverpostej> <20140825093931.GB2399@ulmo> Comments: In-reply-to Thierry Reding message dated "Mon, 25 Aug 2014 11:39:32 +0200." Date: Mon, 25 Aug 2014 08:08:59 -0500 From: Jon Loeliger X-Spam-Score: 0.8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > Anyway, instead of going back and forth between "deferred probe is good" > and "deferred probe is bad", how about we do something useful now and > concentrate on how to make use of the information we have in DT with the > goal to reduce the number of cases where deferred probing is required? Good idea. The proposal on the table is to allow the probe code to make a topological sort of the devices based on dependency information either implied, explicitly stated or both. That is likely a fundamentally correct approach. I believe some of the issues that need to be resolved are: 1) What constitutes a dependency? 2) How is that dependency expressed? 3) How do we add missing dependencies? 4) Backward compatability problems. There are other questions, of course. Is it a topsort per bus? Are there required "early devices"? Should the inter-node dependencies be expressed at each node, or in a separate hierarchy within the DTS? Others. HTH, jdl