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 12:00:57 -0600 Message-ID: References: <20110202195417.228e2656@queued.net> <20110202200812.3d8d6cba@queued.net> <20110331230522.GI437@ponder.secretlab.ca> <20110401112030.GA3447@sortiz-mobl> <20110401104756.2f5c6f7a@debxo> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: Sender: netdev-owner@vger.kernel.org To: Andres Salomon Cc: Samuel Ortiz , linux-kernel@vger.kernel.org, Mark Brown , khali@linux-fr.org, ben-linux@fluff.org, Peter Korsgaard , Mauro Carvalho Chehab , linux-i2c@vger.kernel.org, linux-media@vger.kernel.org, netdev@vger.kernel.org, spi-devel-general@lists.sourceforge.net, Mocean Laboratories List-Id: linux-i2c@vger.kernel.org On Fri, Apr 1, 2011 at 11:56 AM, 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 devic= e, >>> > which means that the driver may very well expect an *entirely >>> > different* platform_device pointer; which further means a very hi= gh >>> > 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 =A0struct platform_devce pdev; > =A0 =A0 =A0 =A0struct 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 in= my > opinion. > > One last option is I'm prototyping a way to add type-safe structure > pointers to a device, but that requires nasty CPP tricks and it's not > complete yet. =A0The cure might be worse than the disease here. And yet another option is to create a mfd_bus_type, but that probably isn't helpful since the one of the purposes of MFDs is that it is a collection of non-detectable memory mapped devices that platform_bus_type is intended to handle. g.