From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752644Ab2G0Uay (ORCPT ); Fri, 27 Jul 2012 16:30:54 -0400 Received: from mga14.intel.com ([143.182.124.37]:38168 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752268Ab2G0Uax (ORCPT ); Fri, 27 Jul 2012 16:30:53 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.71,315,1320652800"; d="scan'208";a="127715225" Date: Fri, 27 Jul 2012 16:30:51 -0400 From: Matthew Wilcox To: Greg KH Cc: Keith Busch , linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, Alan Cox Subject: Re: [PATCH] NVMe: Add a character device for each nvme device Message-ID: <20120727203051.GQ22985@linux.intel.com> References: <1343407458-29909-1-git-send-email-keith.busch@intel.com> <20120727181212.GM22985@linux.intel.com> <20120727182546.GA23874@kroah.com> <20120727190821.GO22985@linux.intel.com> <20120727192100.GA2247@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120727192100.GA2247@kroah.com> 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 Fri, Jul 27, 2012 at 12:21:00PM -0700, Greg KH wrote: > > > Also, why are you creating your own class? Can't this just be a misc > > > device? And if you want to create your own class, please don't, use a > > > bus, as that is what is really happening here, right? We are trying to > > > move away from using 'struct class' wherever possible (one of these days > > > we'll just remove it...) > > > > What we're trying to achieve here is to create one character device > > per NVMe controller that gets plugged in. Each NVMe controller is-a > > PCI function. The reason we're trying to do this is so that we can send > > commands to the NVMe controller, even when there is no storage present > > (eg a drive is shipped from the factory with no configured storage). > > > > So we have no particular desire to create a new struct class, or struct > > bus. If we can create a misc device per PCIe function that's bound to our > > driver, that's great! Can you recommend a driver that does this already? > > I don't think there is one, but it shouldn't be that hard to just create > a 'struct misdevice' for each one of the devices you want to create, > would it? > > But, as you really are a "specific type", a bus_type might be overkill, > so the original use of device_create() should be fine. Just be sure to > fix the parent pointer issue, and you should be fine, right? Works for me. I don't think we're going to have any software that depends on it being a class or a bus, so it's easy to change later. All we really care about is /dev/nvmeN being created.