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    SubjectRe: [RFC] [PATCH] Device Tree on ARM platform
    On Wed, May 27, 2009 at 08:21:16PM +0100, Russell King - ARM Linux wrote:
    > On Wed, May 27, 2009 at 03:13:55PM -0400, Jon Smirl wrote:
    > > On Wed, May 27, 2009 at 3:08 PM, Scott Wood <> wrote:
    > > > I'm not talking about platform specific code, I'm talking about code to
    > > > retrieve information about a device from the device tree.  There would not
    > > > be separate instances of this for "platforms X, Y and Z", just one
    > > > of_platform binding in each driver.  It's no different than having a
    > > > platform bus binding, except in the data structures used.
    > > >
    > > > But to restate, having external glue to create platform devices from the
    > > > device tree is fine if that's what you want to do.  We used to do that, but
    > > > it was a pain compared to keeping everything in one place.  Your experience
    > > > may differ.
    > >
    > > Could 'struct platform_device' and 'struct of_platform_device" be
    > > unified into a single structure? It's personal preference whether the
    > > internal representation of the hardware is done via a device tree or
    > > snippets of platform code, but do we need to have to different device
    > > types?
    > That's a damned good question - platform devices have been around since
    > the dawn of the device model, so the real question which needs to be
    > asked is: what was the reason that of_platform_device created rather
    > than unifying it with the already provided platform_device ?
    > BTW, I can find no such struct "of_platform_device" in include/linux.
    > Is it specific to each and every OF implementation?

    They should be unified. I believe the problem was at the time
    of_platform devices came into existence there was no arch-specific
    field in the device structure that could be used to hold a reference
    to the devtree node.

    Since then, the fiddliness of doing the conversion has always just
    outweighed the impetus to do so. The of_platform bus model is
    conceptually completely broken, but in practice only slightly broken
    for all common cases.

    I've been meaning at several times to replace the of_platform bus
    infrastructure with a system to traverse the OF tree and construct
    platform devices (or other un-probeable bus devices, e.g. i2c) based
    on a table of constructor functions. It's just always been edged out
    by other work.

    David Gibson | I'll have my music baroque, and my code
    david AT | minimalist, thank you. NOT _the_ _other_
    | _way_ _around_!
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