Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755022Ab1DAX7I (ORCPT ); Fri, 1 Apr 2011 19:59:08 -0400 Received: from mail-yi0-f46.google.com ([209.85.218.46]:45401 "EHLO mail-yi0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753048Ab1DAX7G convert rfc822-to-8bit (ORCPT ); Fri, 1 Apr 2011 19:59:06 -0400 MIME-Version: 1.0 In-Reply-To: <20110401235239.GE29397@sortiz-mobl> 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> From: Grant Likely Date: Fri, 1 Apr 2011 17:58:44 -0600 X-Google-Sender-Auth: xCZ_t1AxyASy5ptJcoeaRoGhOI8 Message-ID: Subject: Re: [PATCH 07/19] timberdale: mfd_cell is now implicitly available to drivers To: Samuel Ortiz Cc: Andres Salomon , 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 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: 2579 Lines: 56 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? g. -- 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/