From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753997AbcILQ3N (ORCPT ); Mon, 12 Sep 2016 12:29:13 -0400 Received: from smtpoutz300.laposte.net ([178.22.154.200]:55097 "EHLO smtp.laposte.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751882AbcILQ3J (ORCPT ); Mon, 12 Sep 2016 12:29:09 -0400 Subject: Re: ARM, SoC: About the use DT-defined properties by 3rd-party drivers To: Warner Losh , Mark Rutland References: <57BDAF2E.10502@laposte.net> <57D69FB1.2020801@laposte.net> <20160912123809.GB13741@leverpostej> <57D6AA54.6000208@laposte.net> <20160912135549.GA14165@leverpostej> Cc: devicetree , Mason , Timur Tabi , Linux ARM , LKML From: Sebastian Frias Message-ID: <57D6D7D2.7030507@laposte.net> Date: Mon, 12 Sep 2016 18:29:06 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-VR-SrcIP: 78.31.43.6 X-VR-FullState: 0 X-VR-Score: -100 X-VR-Cause-1: gggruggvucftvghtrhhoucdtuddrfeeluddrieekgddutddvucdltddurdefledtrddttddmucetufdo X-VR-Cause-2: teggodetrfdotffvucfrrhhofhhilhgvmecunfetrffquffvgfenuceurghilhhouhhtmecuhedttden X-VR-Cause-3: ucesvcftvggtihhpihgvnhhtshculddquddttddmnecujfgurhepuffvfhfhkffffgggjggtgfesthej X-VR-Cause-4: rgdttdefjeenucfhrhhomhepufgvsggrshhtihgrnhcuhfhrihgrshcuoehsfhekgeeslhgrphhoshht X-VR-Cause-5: vgdrnhgvtheqnecukfhppeejkedrfedurdegfedrieenucfrrghrrghmpehmohguvgepshhmthhpohhu X-VR-Cause-6: thdphhgvlhhopegludejvddrvdejrddtrddvudegngdpihhnvghtpeejkedrfedurdegfedriedpmhgr X-VR-Cause-7: ihhlfhhrohhmpehsfhekgeeslhgrphhoshhtvgdrnhgvthdprhgtphhtthhopehimhhpsegsshguihhm X-VR-Cause-8: phdrtghomh X-VR-AvState: No X-VR-State: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Warner, On 09/12/2016 04:26 PM, Warner Losh wrote: > On Mon, Sep 12, 2016 at 8:01 AM, Mark Rutland wrote: >>> Since the question seems understood, do you have an example of other SoC's >>> doing something similar? >> >> I do not have an example. I know that others are using DT for data >> beyond what Linux or another OS requires, but it's my understanding that >> that is typically in a separate DTB. > > Just to clarify: FreeBSD uses, for the most part, the DTB's that the > 'vendor' ships, which is quite often the same ones included in Linux. > There's some exceptions where the bindings weren't really hardware > independent, or where the abstraction model was really Linux specific > (for things like the HDMI stack). > > However, with the advent of overlays, one would think that a vendor > could easily include an overlay with the DTB data for the devices they > don't wish to, or cannot for other reasons release. It seems like the > perfect mechanism to comply with the rules about inclusion of nodes in > the DTS. Vendors are free to document these nodes and don't require > the Linux kernel include them in the Documents directory to do so. > There have been recent efforts to move this documentation to a third > party to maintain. This is very interesting, do you have a more concrete example of such usage? The overlay technique could be a solution, but so is forking and distributing a non-documented DT. That's why I'd put this solution a little bit lower than just exposing the entire HW description through the DT. Best regards, Sebastian