From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andres Salomon Subject: Re: [PATCH 07/19] timberdale: mfd_cell is now implicitly available to drivers Date: Fri, 1 Apr 2011 17:10:01 -0700 Message-ID: <20110401171001.61283e2d@debxo> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Grant Likely Cc: Samuel Ortiz , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Mark Brown , khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org, ben-linux-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org, Peter Korsgaard , Mauro Carvalho Chehab , David Brownell , linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-media-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, Mocean Laboratories , Greg Kroah-Hartman List-Id: linux-i2c@vger.kernel.org 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. =A0Not 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). =A0For 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 { > >> =A0 =A0 =A0 =A0 struct platform_devce pdev; > >> =A0 =A0 =A0 =A0 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 n= o > >> way to protect against this so it is probably a bad idea. > >> > >> Or, mfd_cell could be added to platform_device directly which woul= d > >> *by far* be the safest option at the cost of every platform_device > >> having a mostly unused mfd_cell pointer. =A0Not 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. >=20 > [cc'ing gregkh because we're talking about modifying struct > platform_device] >=20 > 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? >=20 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).