From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Holler Subject: Re: [RFC PATCH 0/9] dt: dependencies (for deterministic driver initialization order based on the DT) Date: Tue, 26 Aug 2014 09:56:43 +0200 Message-ID: <53FC3DBB.7000407@ahsoftware.de> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jon Loeliger , Thierry Reding Cc: Mark Rutland , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Russell King , Arnd Bergmann , Greg Kroah-Hartman , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Rob Herring , "grant.likely-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org" , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" List-Id: devicetree@vger.kernel.org Am 25.08.2014 15:08, schrieb Jon Loeliger: >> > >> 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? In my patches phandles are used. That works pretty good for almost all DTs. So almost all dependencies are already declared in a DT and almost no changes to the DT are necessary. The only binding I've seen where it doesn't work is remote-endpoint, because that binding isn't a directed dependency. So one of the two places where such a binding occurs needs a "no-dependencies = " to avoid circular dependencies which can be solved. > 2) How is that dependency expressed? Already there in form of phandles. > 3) How do we add missing dependencies? My patches offer the possibility to extend or reduce the list of (automatically generated) dependencies by using "[no-]dependencies = < list of phandles >;" > 4) Backward compatability problems. None in my approach. The DT just includes an additional binding to circumvent the missing but needed type information for phandles. Regards, Alexander Holler -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html