Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755598Ab1DBAKR (ORCPT ); Fri, 1 Apr 2011 20:10:17 -0400 Received: from LUNGE.MIT.EDU ([18.54.1.69]:34554 "EHLO lunge.queued.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752849Ab1DBAKP convert rfc822-to-8bit (ORCPT ); Fri, 1 Apr 2011 20:10:15 -0400 Date: Fri, 1 Apr 2011 17:10:01 -0700 From: Andres Salomon To: Grant Likely Cc: Samuel Ortiz , linux-kernel@vger.kernel.org, Mark Brown , khali@linux-fr.org, ben-linux@fluff.org, Peter Korsgaard , Mauro Carvalho Chehab , David Brownell , linux-i2c@vger.kernel.org, linux-media@vger.kernel.org, netdev@vger.kernel.org, spi-devel-general@lists.sourceforge.net, Mocean Laboratories , Greg Kroah-Hartman Subject: Re: [PATCH 07/19] timberdale: mfd_cell is now implicitly available to drivers Message-ID: <20110401171001.61283e2d@debxo> In-Reply-To: References: <20110202195417.228e2656@queued.net> <20110202200812.3d8d6cba@queued.net> <20110331230522.GI437@ponder.secretlab.ca> <20110401112030.GA3447@sortiz-mobl> <20110401104756.2f5c6f7a@debxo> <20110401235239.GE29397@sortiz-mobl> X-Mailer: Claws Mail 3.7.6 (GTK+ 2.20.1; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3055 Lines: 72 On Fri, 1 Apr 2011 17:58:44 -0600 Grant Likely wrote: > On Fri, Apr 1, 2011 at 5:52 PM, Samuel Ortiz > wrote: > > On Fri, Apr 01, 2011 at 11:56:35AM -0600, Grant Likely wrote: > >> On Fri, Apr 1, 2011 at 11:47 AM, Andres Salomon > >> wrote: > >> > On Fri, 1 Apr 2011 13:20:31 +0200 > >> > Samuel Ortiz wrote: > >> > > >> >> Hi Grant, > >> >> > >> >> On Thu, Mar 31, 2011 at 05:05:22PM -0600, Grant Likely wrote: > >> > [...] > >> >> > Gah. ?Not all devices instantiated via mfd will be an mfd > >> >> > device, which means that the driver may very well expect an > >> >> > *entirely different* platform_device pointer; which further > >> >> > means a very high potential of incorrectly dereferenced > >> >> > structures (as evidenced by a patch series that is not > >> >> > bisectable). ?For instance, the xilinx ip cores are used by > >> >> > more than just mfd. > >> >> I agree. Since the vast majority of the MFD subdevices are MFD > >> >> specific IPs, I overlooked that part. The impacted drivers are > >> >> the timberdale and the DaVinci voice codec ones. > >> > >> Another option is you could do this for MFD devices: > >> > >> struct mfd_device { > >> ? ? ? ? struct platform_devce pdev; > >> ? ? ? ? struct mfd_cell *cell; > >> }; > >> > >> However, that requires that drivers using the mfd_cell will *never* > >> get instantiated outside of the mfd infrastructure, and there is no > >> way to protect against this so it is probably a bad idea. > >> > >> Or, mfd_cell could be added to platform_device directly which would > >> *by far* be the safest option at the cost of every platform_device > >> having a mostly unused mfd_cell pointer. ?Not a significant cost > >> in my opinion. > > I thought about this one, but I had the impression people would > > want to kill me for adding an MFD specific pointer to > > platform_device. I guess it's worth giving it a try since it would > > be a simple and safe solution. I'll look at it later this weekend. > > > > Thanks for the input. > > [cc'ing gregkh because we're talking about modifying struct > platform_device] > > I'll back you up on this one. It is a far better solution than the > alternatives. At least with mfd, it covers a large set of devices. I > think there is a strong argument for doing this. Or alternatively, > the particular interesting fields from mfd_cell could be added to > platform_device. What information do child devices need access to? > This was one of the things I was originally tempted to do (adding mfd fields to platform_device). I didn't think it would fly. I can look at this stuff or help out once I have a stable internet connection and I'm all moved in to my new place (which should be Wednesday). -- 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/