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    SubjectRe: [PATCH 07/19] timberdale: mfd_cell is now implicitly available to drivers
    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?

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