Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752971Ab1DTGoe (ORCPT ); Wed, 20 Apr 2011 02:44:34 -0400 Received: from moutng.kundenserver.de ([212.227.17.8]:61996 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752325Ab1DTGod (ORCPT ); Wed, 20 Apr 2011 02:44:33 -0400 From: Arnd Bergmann To: "Arend van Spriel" Subject: Re: Could I (ab)use bus (struct bus_type) for virtual Broadcom bus? Date: Wed, 20 Apr 2011 08:44:10 +0200 User-Agent: KMail/1.13.5 (Linux/2.6.38+; KDE/4.5.1; x86_64; ; ) Cc: "Greg KH" , =?utf-8?q?Rafa=C5=82_Mi=C5=82ecki?= , "George Kashperko" , "Hauke Mehrtens" , "Russell King" , "linux-kernel@vger.kernel.org" , "linux-wireless@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "Jonas Gorski" , "b43-dev@lists.infradead.org" , "Andy Botting" , "Larry Finger" References: <20110419140257.GA20456@kroah.com> In-Reply-To: MIME-Version: 1.0 Content-Type: Text/Plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <201104200844.10607.arnd@arndb.de> X-Provags-ID: V02:K0:5jb8tsjXRwwMrPULsQf/2Kn5LswhqP0EvKBJMjFDPsx T/kfZJg8YOt9kGm6apBow1T4kn5HyxJXIrrj6gDAYjpoFSNURx I8ABstgxtuXEnaO/i39jLXJL2HMx+UCHAZFjjy8lhP0eNwy9UA 1mtdM5WVxQBlBgXOm7zDTx9ZaALXQ+kYaRBEYy/WSmkoqgHC62 bl1AT7gePrKbhusIjv3ow== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1824 Lines: 47 On Wednesday 20 April 2011 08:39:59 Arend van Spriel wrote: > On Tue, 19 Apr 2011 16:02:57 +0200, Greg KH wrote: > > > Please don't use a platform device, unless there is no other way for > > your device to work. For this device, you are connected to the PCI bus, > > so a platform device does not make sense at all. > > Hi Greg, > > This is only true for a particular usage model. There are two models as > shown below: > > 1) PCI(e) card > ........... > +----------+ : x y z : x, y, and z are cores. > | uC |__________:___|_|_| : > | | PCI-bus : axi-bus : > +----------+ :.........: > bcm chipset > > 2) SoC > ............... > : uC x y z : > : |____|_|_| : > : axi-bus : > :.............: > bcm chipset > > Your statement is true for 1) but in usage model 2) there is no PCI bus. > Also you refer to the chipset when you say 'device'. In the axi bus type > each individual core is registered as a device in the linux device tree. I guess what Greg was referring to is having platform devices for x/y/z here. In case 2, you might still need to have a platform_device for the combination of the three IP cores if they make up one logical device. As mentioned in my reply, it depends a lot on what these cores actually are, e.g. whether you might want to have only one of them active in a given system to drive a specific functionality, or if you always need all three of them. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/