Messages in this thread | | | From | Grant Likely <> | Date | Fri, 1 Apr 2011 17:58:44 -0600 | Subject | Re: [PATCH 07/19] timberdale: mfd_cell is now implicitly available to drivers |
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On Fri, Apr 1, 2011 at 5:52 PM, Samuel Ortiz <sameo@linux.intel.com> 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 <dilinger@queued.net> wrote: >> > On Fri, 1 Apr 2011 13:20:31 +0200 >> > Samuel Ortiz <sameo@linux.intel.com> 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?
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