From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752626Ab2G0TVE (ORCPT ); Fri, 27 Jul 2012 15:21:04 -0400 Received: from out3-smtp.messagingengine.com ([66.111.4.27]:34835 "EHLO out3-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751369Ab2G0TVB (ORCPT ); Fri, 27 Jul 2012 15:21:01 -0400 X-Sasl-enc: SCZ6D5x7/GZ4CFX7eSgS9v3T2jaOdLjUoRXcmhmdKZom 1343416861 Date: Fri, 27 Jul 2012 12:21:00 -0700 From: Greg KH To: Matthew Wilcox 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: <20120727192100.GA2247@kroah.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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120727190821.GO22985@linux.intel.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 03:08:21PM -0400, Matthew Wilcox wrote: > On Fri, Jul 27, 2012 at 11:25:46AM -0700, Greg KH wrote: > > On Fri, Jul 27, 2012 at 02:12:12PM -0400, Matthew Wilcox wrote: > > > I don't see a problem here, but I'm no expert at sysfs / character devices. > > > Alan, Greg, anyone else see any problems with how this character device is > > > created / destroyed? > > > > Yes, see below: > > Thanks! > > > > > + device_create(nvme_char_cl, NULL, MKDEV(nvme_char_major, dev->instance), > > > > + NULL, "nvme%d", dev->instance); > > > > You just created a device at the "root" of sysfs, which is wrong, > > especially when you do have a parent device here. Please use it. > > OK, that makes sense; this device should be the child of the pci_dev that > it belongs to. > > > 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? greg k-h