From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6D673ECAAD5 for ; Tue, 6 Sep 2022 16:12:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238571AbiIFQMr (ORCPT ); Tue, 6 Sep 2022 12:12:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54168 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232989AbiIFQMT (ORCPT ); Tue, 6 Sep 2022 12:12:19 -0400 Received: from sibelius.xs4all.nl (80-61-163-207.fixed.kpn.net [80.61.163.207]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4EA5B22B30; Tue, 6 Sep 2022 08:38:15 -0700 (PDT) Received: from localhost (bloch.sibelius.xs4all.nl [local]) by bloch.sibelius.xs4all.nl (OpenSMTPD) with ESMTPA id d845d1c6; Tue, 6 Sep 2022 17:38:12 +0200 (CEST) Date: Tue, 6 Sep 2022 17:38:12 +0200 (CEST) From: Mark Kettenis To: "Russell King (Oracle)" Cc: marcan@marcan.st, linus.walleij@linaro.org, robh@kernel.org, krzysztof.kozlowski@linaro.org, arnd@arndb.de, lee@kernel.org, alyssa@rosenzweig.io, asahi@lists.linux.dev, brgl@bgdev.pl, linux-arm-kernel@lists.infradead.org, linux-gpio@vger.kernel.org, sven@svenpeter.dev, krzysztof.kozlowski+dt@linaro.org, devicetree@vger.kernel.org In-Reply-To: Subject: Re: [PATCH 1/6] dt-bindings: mfd: add binding for Apple Mac System Management Controller References: <20220902172808.GB52527-robh@kernel.org> <909bb4e7-5bd2-2903-5bba-87ae37f3448a@marcan.st> <5b75dc7e-5337-73eb-450f-b72f479793c4@marcan.st> Message-ID: Precedence: bulk List-ID: X-Mailing-List: linux-gpio@vger.kernel.org > Date: Tue, 6 Sep 2022 15:54:50 +0100 > From: "Russell King (Oracle)" > > On Tue, Sep 06, 2022 at 04:25:49PM +0200, Mark Kettenis wrote: > > > Date: Tue, 6 Sep 2022 22:53:47 +0900 > > > From: Hector Martin > > > > > > I agree that this is something to think about (I was about to reply on > > > the subject). > > > > > > I can think of two ways: using `reg` for the key name, but that feels > > > icky since it's ASCII and not *really* a register number/address, or > > > something like this: > > > > > > gpio@0 { > > > apple,smc-key-base = "gP00"; > > > ... > > > } > > > > > > gpio@1 { > > > apple,smc-key-base = "gp00"; > > > ... > > > } > > > > This would still require us to add a (one-cell) "reg" property and > > would require adding the appropriate "#address-cells" and > > "#size-cells" properties to the SMC node. > > Yes, and at that point, as I suggested, it probably would be better > to use: > > #address-cells = <1>; > #size-cells = <0>; > > gpio@67503030 { > reg = <0x67503030>; > }; > > gpio@67703030 { > reg = <0x67703030>; > }; > > Then the "reg" has a meaning that is directly related to the SMC. > > > > But this ties back to the device enumeration too, since right now the DT > > > does not drive that (we'd have to add the subdevice to the mfd subdevice > > > list somehow anyway, if we don't switch to compatibles). > > > > > > I'd love to hear Rob's opinion on this one, and also whether the > > > existing Linux and OpenBSD code would currently find gpio@0 {} instead > > > of gpio {} for backwards compat. > > > > The OpenBSD driver does a lookup by name and the "@0" is part of that > > name. So that would break backwards compat. > > Oh, that's annoying - and is a different behaviour to Linux. > > On Linux, we only look at the node name up to the @ when matching (see > of_node_name_eq() in drivers/of/base.c, so it doesn't matter to Linux > what follows the @ when you try to look up a node named "gpio" - you'll > find gpio@anythingyoulike. So maybe I should change our code to match what Linux does. OpenBSD 7.2 is scheduled for release on November 1st, and I can probably get that change in quickly. If we can hold off updating the device trees in the Asahi installer until then the transition should be smooth enough. > > Maybe just name the slave GPIO controller "gpio-slave"? If we add > > compatibles, the compatibles for the nodes should propbably be > > different such that we can switch to do a lookup by compatible? > > I don't think the DT folk would be happy with "gpio-slave" because > node names are supposed to be generic. I don't think that rule applies to "named" sub-nodes like this where the name is actually significant. > Also, "slave" probably isn't a good choice of name in this modern > era given past history. Yes, we don't have to follow Apple's terminology here. > Rather than the above, we could use "reg" to indicate which GPIO > controller we're talking about, and lookup the reg value in a table > to give the key. So gpio@0, reg=<0> => gP00, gpio@1, reg=<1> => gp00. > gpio@2, reg=<2> => whatever next. > > That sounds like it won't break the existing OpenBSD. > > -- > RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ > FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last! >