From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Gibson Subject: Re: Mis?use of aliases Date: Sun, 15 Jul 2012 02:37:01 +1000 Message-ID: <20120714163701.GI11326@truffala.fritz.box> References: <1342218413-30116-1-git-send-email-jon-hunter@ti.com> <1342218413-30116-2-git-send-email-jon-hunter@ti.com> <5000D647.4090200@gmail.com> <50010402.3050502@firmworks.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <50010402.3050502-D5eQfiDGL7eakBO8gow8eQ@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org Sender: "devicetree-discuss" To: Mitch Bradley Cc: device-tree , linux-omap , Tarun Kanti DebBarma , linux-arm List-Id: devicetree@vger.kernel.org On Fri, Jul 13, 2012 at 07:30:42PM -1000, Mitch Bradley wrote: > > I'm not sure this is really a good use of aliases. UARTs use aliases > > because it is important that the UART number to tty number is known and > > fixed. > > This brings up an issue that I've been meaning to comment on. > > The use of phandle-valued properties in the aliases node causes real OFW > implementations some amount of heartburn. The Open Firmware standard > says that the properties in /aliases are string-valued. That's > important, because aliases are shorthand for fragments of full device > specifiers (pathnames that can include arguments to nodes). Phandles > can point to nodes, but can't be relative, and can't encode > per-node-component arguments. Um, so, properties in /aliases should not have phandle values, flat tree or otherwise. Has this been seen in the wild, or are you being misled by the fact that dtc's reference-to-phandle and reference-to-path syntax is very similar: prop = <&fred>; Will generate a phandle valued property, but prop = &fred; Will generate a string (path) valued property. > For binding a Linux unit number to a device node, I would prefer to > decorate the node with a property like "linux,unit#", instead of > breaking the standard semantics of /aliases. I don't see how using aliases for unit numbering (inherently) breaks the semantics of /aliases. If phandle valued properties are being used that is wrong, but it's not necessary for the unit numbering anyway. -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson