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

On Fri, Apr 01, 2011 at 11:56:35AM -0600, Grant Likely wrote:

On Fri, Apr 1, 2011 at 11:47 AM, Andres Salomon [off-list ref] wrote:

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On Fri, 1 Apr 2011 13:20:31 +0200
Samuel Ortiz [off-list ref] wrote:

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Hi Grant,

On Thu, Mar 31, 2011 at 05:05:22PM -0600, Grant Likely wrote:

[...]

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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.

Cheers,
Samuel.

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