From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261169AbUFSAaf (ORCPT ); Fri, 18 Jun 2004 20:30:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263770AbUFSA1C (ORCPT ); Fri, 18 Jun 2004 20:27:02 -0400 Received: from mail.kroah.org ([65.200.24.183]:46819 "EHLO perch.kroah.org") by vger.kernel.org with ESMTP id S261925AbUFSAY6 (ORCPT ); Fri, 18 Jun 2004 20:24:58 -0400 Date: Fri, 18 Jun 2004 17:03:56 -0700 From: Greg KH To: Alan Stern Cc: James Bottomley , Kernel development list Subject: Re: BUG(?): class_device_driver_link() Message-ID: <20040619000356.GC24902@kroah.com> References: <20040618202305.GB18008@kroah.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.6i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 18, 2004 at 05:36:52PM -0400, Alan Stern wrote: > On Fri, 18 Jun 2004, Greg KH wrote: > > > On Fri, Jun 18, 2004 at 04:12:32PM -0400, Alan Stern wrote: > > > Greg: > > > > > > I'm not sure if this is a bug or not, but it is inconsistent behavior in > > > sysfs. > > > > > > When a class_device is added, if it has a regular device associated with > > > it and that device has a driver, a symlink is added from the class_device > > > to the driver. However, if the class_device is added _first_ and the > > > driver later, this symlink is not created. It's not clear that there's > > > any good way to create it, especially if the class_device is added by the > > > bus layer and the device driver itself is unaware of the class_device. > > > > Yes, this is the way it was designed. The thinking was that a device > > would be registered to a driver by the time the class code was > > initialized for it. > > That seems reasonable, but obviously it doesn't work if the driver is > loaded much later. The driver is the piece of code that creates a class device, so that can not happen (scsi model excluded). > > > Is this a known problem? It definitely affects the sd driver, and maybe > > > others. > > > > The sd use of classes is a monumental hack. So much that every time I > > see one of them in the hall at work I run the other way just to avoid > > talking about it again :) > > > > No, seriously, if this is a problem for the sd driver, we should fix it. > > I'm not sure that it's a problem -- all that happens is the "driver" > symlink under the class_device's directory isn't present. Also, it will > affect every SCSI device, not just SCSI disks, since the class_device > management is done by the central SCSI core. > > > > There is a related side-effect that is a bit unpleasant. The symlink from > > > the class_device to the driver increments the driver's refcount. > > > > Yes, that is a recent change. > > Okay, that explains why I never used to have these difficulties. > > > > Since > > > the driver is unaware of the class_device, it doesn't know to remove the > > > symlink when its release() method runs. > > > > The symlink should be removed by the class, right? > > Sure. But when you rmmod the driver, the class doesn't know that anything > has happened. There is no link from the driver to the class_device; the > links all go the other way. Again, the driver owns the class device. scsi has something wrong again. Time to stop avoiding everyone at work... thanks, greg k-h