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    SubjectRe: [PATCH 2/4] spi: split up spi_new_device() to allow two stage registration.
    On Sat, May 24, 2008 at 12:43 AM, Grant Likely
    <grant.likely@secretlab.ca> wrote:
    > On Wed, May 21, 2008 at 6:17 PM, David Brownell <david-b@pacbell.net> wrote:
    >> On Friday 16 May 2008, Grant Likely wrote:
    >>>
    >>> This patch splits the allocation and registration portions of code out
    >>> of spi_new_device() and creates three new functions; spi_alloc_device(),
    >>> spi_register_device(), and spi_device_release().
    >>
    >> I have no problem with the first two, but why the last?
    >>
    >> If the devices are always allocated by spi_alloc_device() as
    >> they should be -- probably through an intermediary -- the
    >> only public function necessary for that cleanup should be
    >> the existing spi_dev_put().
    >
    > Ah, okay. I'm still a bit fuzzy on the device model conventions.
    > I'll remove that then.

    I've dug into this some more. spi_alloc_device only allocates the
    memory. It doesn't call device_initialize() to initialize the kref.
    All of that behaviour is handled within device_register(). Therefore
    if a driver uses spi_alloc_device() and then if a later part of the
    initialization fails before spi_register_device() is called, then the
    alloc'd memory needs to be freed, but spi_dev_put() won't work because
    the kobj isn't set up so I need another function to handle freeing it
    in on a failure path.

    Should I switch things around to do device_initialize() in the alloc
    function and call device_add() instead of device_register() in the
    spi_register_device() function? Is that sufficient to make
    put_device() work?

    Cheers,
    g.

    --
    Grant Likely, B.Sc., P.Eng.
    Secret Lab Technologies Ltd.


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