From mboxrd@z Thu Jan 1 00:00:00 1970 From: Grant Likely Subject: Re: [PATCH 07/19] timberdale: mfd_cell is now implicitly available to drivers Date: Fri, 1 Apr 2011 17:58:44 -0600 Message-ID: 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 Cc: Andres Salomon , 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 To: Samuel Ortiz Return-path: In-Reply-To: <20110401235239.GE29397@sortiz-mobl> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-spi.vger.kernel.org On Fri, Apr 1, 2011 at 5:52 PM, Samuel Ortiz wr= ote: > 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 dev= ice, >> >> > 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 xili= nx 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 th= e >> >> 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 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. =A0Not a significant cost i= n 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_de= vice] 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.