From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261763AbUFRUrk (ORCPT ); Fri, 18 Jun 2004 16:47:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262356AbUFRUpk (ORCPT ); Fri, 18 Jun 2004 16:45:40 -0400 Received: from mail.kroah.org ([65.200.24.183]:27788 "EHLO perch.kroah.org") by vger.kernel.org with ESMTP id S262085AbUFRUl1 (ORCPT ); Fri, 18 Jun 2004 16:41:27 -0400 Date: Fri, 18 Jun 2004 13:23:05 -0700 From: Greg KH To: Alan Stern Cc: James Bottomley , Kernel development list Subject: Re: BUG(?): class_device_driver_link() Message-ID: <20040618202305.GB18008@kroah.com> References: 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 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. > 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. > 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. > 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? > Consequently, if the driver is > modprobed before the device exists and rmmod'ed after the device is added, > the rmmod will hang until the device also goes away. But if the driver is > modprobed _after_ the device exists then the rmmod will complete > immediately. > > Perhaps the answer is that the bus layer must take these things into > account. Or perhaps a struct device should somehow know about all the > class_devices that refer to it. Hm, I was not wanting to have to have struct device know about classes, only classes knowing about struct devices. Any input here would be appreciated. thanks, greg k-h