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 X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 773F1C43441 for ; Wed, 10 Oct 2018 12:27:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2A5A92085B for ; Wed, 10 Oct 2018 12:27:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=sirena.org.uk header.i=@sirena.org.uk header.b="mM6RK+no" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2A5A92085B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726786AbeJJTtN (ORCPT ); Wed, 10 Oct 2018 15:49:13 -0400 Received: from heliosphere.sirena.org.uk ([172.104.155.198]:33186 "EHLO heliosphere.sirena.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726206AbeJJTtN (ORCPT ); Wed, 10 Oct 2018 15:49:13 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sirena.org.uk; s=20170815-heliosphere; h=In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=/RyiIqBenmYoKgcwOZD7iOC6N9mY5DROH0g28Aj6zIY=; b=mM6RK+noIlHdwxLmqQ4dh+Lh7 W2Y+65y8mxTH5MSwIw0S79Zb8HB+cDwhwUkvEshd8SWVCSHR1iD+3KYnYczts1lE2+S6jK9UxEnyI 9fo0syzmtybJmQvBvT5c5rwUcu2dlsbsAuO+a00e0StdbnYNml3i4ByrZyeLg2g0sV8Uo=; Received: from cpc102320-sgyl38-2-0-cust46.18-2.cable.virginm.net ([82.37.168.47] helo=debutante.sirena.org.uk) by heliosphere.sirena.org.uk with esmtpa (Exim 4.89) (envelope-from ) id 1gADa2-0007mb-Uj; Wed, 10 Oct 2018 12:27:10 +0000 Received: by debutante.sirena.org.uk (Postfix, from userid 1000) id 84EEA1122395; Wed, 10 Oct 2018 13:27:10 +0100 (BST) Date: Wed, 10 Oct 2018 13:27:10 +0100 From: Mark Brown To: "Woodhouse, David" Cc: "Shenhar, Talel" , "linux-spi@vger.kernel.org" , "mark.rutland@arm.com" , "linux-kernel@vger.kernel.org" , "Krupnik, Ronen" , "Wasserstrom, Barak" , "robh+dt@kernel.org" , "devicetree@vger.kernel.org" Subject: Re: [PATCH 1/2] dt-bindings: spi: dw: add cs-override property Message-ID: <20181010122710.GE6294@sirena.org.uk> References: <1539155293-21750-1-git-send-email-talel@amazon.com> <20181010101825.GA6294@sirena.org.uk> <20181010112753.GC6294@sirena.org.uk> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="lkTb+7nhmha7W+c3" Content-Disposition: inline In-Reply-To: X-Cookie: Phasers locked on target, Captain. User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --lkTb+7nhmha7W+c3 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wed, Oct 10, 2018 at 11:58:40AM +0000, Woodhouse, David wrote: > On Wed, 2018-10-10 at 12:27 +0100, Mark Brown wrote: > > If this is a modified IP with additional features then it should be > > given a new compatible string rather than having a property - it's not > > just configuration of the existing IP, it's a new thing and we may find > > there are other quirks that have to be taken care of for it. > No. > It's an extension of the existing IP which is explicitly designed to be > compatible with existing drivers via an opt-in feature. That's totally normal and something that there's already infrastructure to handle, plenty of other IPs have new versions with new features - you can just add a new compatible string and use that to decide which features to enable, and if it's backwards compatible with old versions of the driver supporting older hardware then you can list multiple compatibles. As we just discussed on IRC this is partly a policy thing now I've been told that it's a modified version of the hardware rather than a configuration or integration option, it's easier than having implementations of new features trickle out from the vendor and needing to enable them all one by one in device trees (which does happen). > Which is exactly what we've spent the last decade or two trying to beat > hardware designers into doing, instead of randomly breaking > compatibility for no good reason. That's great and we get to reuse all the driver code with a quirk (a quirk which fixes the hardware to be more compatible with devices, this is a really good hardware change). Ideally we'd be able to enumerate things like IP versions and options from hardware but that's a more entertaining problem. Having said all this if there are production systems using this property, especially production systems where people other than the system integrator can realistically deploy their own kernel separate to the device tree, then supporting those existing DTs even if they're not doing the ideal thing might be the best thing. You mentioned that this might be the case, can you check what the status is there please? --lkTb+7nhmha7W+c3 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAlu98B0ACgkQJNaLcl1U h9CPmgf/QMp2J8iPAnRVpTDGziEgyOEXdplvLf6fW0m4v5MSMSHJwgyrloZCVcVf xnb5GsQaR89mnaqqd8FRJJ+VR13+4JWkqZTe5W4ha9MrpovU3EttyeQUSa0LDpEL CuOHEvsG5lUy9szgAc2MRlf0Vf1gnCF0JtCGLWnoVC9qCHDQxQPyruhomrFdGdI3 3rXFbStZd6RmWtlfgu7f2V66oOc2FZwcMw/4ElO5IIUM1msI5PPgR1wCzO5SOkgy fIQeVsMPs8mD3tq25/SkrxXv+rzNthkLTCHIod3jgmorCo9X2MvdZyoL9PN4s71w o+xEojB7gcFcnud/EsHARj/OvSnXGQ== =vsxh -----END PGP SIGNATURE----- --lkTb+7nhmha7W+c3--