From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756066Ab2DEUIo (ORCPT ); Thu, 5 Apr 2012 16:08:44 -0400 Received: from wolverine01.qualcomm.com ([199.106.114.254]:20640 "EHLO wolverine01.qualcomm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756021Ab2DEUIc (ORCPT ); Thu, 5 Apr 2012 16:08:32 -0400 X-IronPort-AV: E=McAfee;i="5400,1158,6671"; a="179291080" Date: Thu, 5 Apr 2012 13:08:29 -0700 From: David Brown To: Stephen Warren Cc: devicetree-discuss@lists.ozlabs.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: Point-to-point bus in device tree Message-ID: <20120405200829.GA29747@codeaurora.org> References: <20120405181509.GA28693@codeaurora.org> <4F7DF142.5050601@wwwdotorg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4F7DF142.5050601@wwwdotorg.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 05, 2012 at 01:23:46PM -0600, Stephen Warren wrote: > On 04/05/2012 12:15 PM, David Brown wrote: > > Some MSM SoCs have a small serial-type "bus" that is used to > > communicate with the PMIC devices. This interface is always > > point-to-point. I'm doing a device-tree conversion of the driver that > > Ken Heitke posted last year . > > > > A naive conversion to device tree, would result in something like > > this: > > > > qcom,ssbi@500000 { > > compatible = "qcom,ssbi"; > > reg = <0x500000 0x1000>; > > qcom,controller-type = "ssbi"; > > > > qcom,pmic8058@0 { > > reg = <0x0 0x01>; > > ... > > } > > } > > > > There would end up being an extraneous register for the device on the > > other end (there are no addresses), and there would need to be code in > > the ssbi driver to traverse this small tree to find these nodes. > > Isn't that extra code simply: > > of_platform_populate(pdev->dev.of_node, NULL, NULL, &pdev->dev); > > That seems like pretty low overhead. True, but it still bothers me to have to have a bogus register. David -- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.