From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from bh-25.webhostbox.net (bh-25.webhostbox.net [208.91.199.152]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 28B441A0FB0 for ; Sat, 21 Feb 2015 10:53:45 +1100 (AEDT) Received: from mailnull by bh-25.webhostbox.net with sa-checked (Exim 4.82) (envelope-from ) id 1YOxOB-000gVo-Dq for linuxppc-dev@lists.ozlabs.org; Fri, 20 Feb 2015 23:53:43 +0000 Message-ID: <54E7C8C7.40001@roeck-us.net> Date: Fri, 20 Feb 2015 15:52:39 -0800 From: Guenter Roeck MIME-Version: 1.0 To: Cedric Le Goater Subject: Re: [RFC PATCH 0/3] hwmon: (ibmpowernv) add DTS support References: <1423117857-32759-1-git-send-email-clg@fr.ibm.com> <1424444857-13805-1-git-send-email-clg@fr.ibm.com> <20150220165212.GE22752@roeck-us.net> <54E795FA.1090005@fr.ibm.com> In-Reply-To: <54E795FA.1090005@fr.ibm.com> Content-Type: text/plain; charset=windows-1252; format=flowed Cc: Stewart Smith , lm-sensors@lm-sensors.org, Neelesh Gupta , skiboot@lists.ozlabs.org, linuxppc-dev@lists.ozlabs.org, Jean Delvare List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 02/20/2015 12:15 PM, Cedric Le Goater wrote: > On 02/20/2015 05:52 PM, Guenter Roeck wrote: >> On Fri, Feb 20, 2015 at 04:07:34PM +0100, Cédric Le Goater wrote: >>> Hello ! >>> >>> These patches rework the ibmpowernv driver to support the new device >>> tree as proposed by this patchset on the skiboot mailing list : >>> >>> https://lists.ozlabs.org/pipermail/skiboot/2015-February/000457.html >>> >>> They are based on Linux 3.19 and were tested on IBM Power and Open Power >>> systems running trusty. >>> >>> The main issue is that the new device tree is incompatible with the >>> previous ibmpowernv drivers. The consequence is no powernv sensors >>> on systems with such a opal/linux configuration. >>> >> I don't think that would be acceptable. There must be lots of such >> systems out there. Why does it have to be incompatible ? >> Can't it support both the old and new versions ? > > I should have provided more explanation in the Linux patchset. Sorry > for that. Here is the rationale behind this brutal code change. > > The initial ibmpowernv driver was designed in the early days of the > powernv platform and the device tree it is using to expose the sensors > has some limitations that makes it difficult to add new ones. The current > layout of the device tree is also tightly coupled to IBM Power systems > and their service processor (FSP). Open Power systems are different and > need a different solution. > > It is to get more sensors out the P8 (and there are quite a few) that > the OPAL patchset [1] proposes a new device tree. On the Linux side, it > feels simpler to make a jump forward and break the compatibility than > to maintain multiple branches of code just to keep alive an early v1 > of the ibmpowernv driver. > Would it possibly be appropriate to write a different driver for the new device tree ? Guenter