Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752863Ab0K2VmZ (ORCPT ); Mon, 29 Nov 2010 16:42:25 -0500 Received: from kroah.org ([198.145.64.141]:36078 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751222Ab0K2VmY (ORCPT ); Mon, 29 Nov 2010 16:42:24 -0500 Date: Mon, 29 Nov 2010 13:41:28 -0800 From: Greg KH To: Guennadi Liakhovetski Cc: Jonathan Corbet , linux-kernel@vger.kernel.org Subject: Re: [PATCH/RFC] core: add a function to safely try to get device driver owner Message-ID: <20101129214128.GA9691@kroah.com> References: <20101129131737.3dd6eb03@bike.lwn.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1878 Lines: 43 On Mon, Nov 29, 2010 at 09:54:10PM +0100, Guennadi Liakhovetski wrote: > Hi Jon > > On Mon, 29 Nov 2010, Jonathan Corbet wrote: > > > On Mon, 29 Nov 2010 20:43:28 +0100 (CET) > > Guennadi Liakhovetski wrote: > > > > > When two drivers interoperate without an explicit dependency, it is often > > > required to prevent one of them from being unloaded safely by dereferencing > > > dev->driver->owner. This patch provides a generic function to do this in a > > > race-free way. > > > > I must ask: why not, instead, make the dependency explicit? In > > particular, this looks like an application for the proposed media > > controller code, which is meant to model the connections between otherwise > > independent devices. The fact that your example comes from V4L2 (which is > > the current domain of the media controller) also argues that way. > > Sorry, don't see a good way to do this. This function is for a general > dependency, where you don't have that driver, we are checking for register > with us, so, the only way to get to it is via dev->driver->owner. Wait, what? The device is already bound to a driver, right, so why would you care about "locking" the module into memory? What could this possibly be used for? > And I also don't want to move registering the device into the > dependant driver and then wait (with a timeout) for a driver to probe > with it... I just want to verify, whether a driver has attached to > that device and whether I can lock it down. Who cares if a driver is attached to any device? And again, why would you want to "lock it down"? confused, greg k-h -- 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/