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    SubjectRe: [RFC PATCH 1/2] serial: 8250: Add a notifier chain for driver registration.
    On 03/17/2011 05:18 AM, Alan Cox wrote:
    > On Wed, 16 Mar 2011 18:26:06 -0700
    > David Daney<ddaney@caviumnetworks.com> wrote:
    >
    >> The 8250 driver is a bit weird in that in addition to supporting
    >> platform devices, extra devices can be added by calling
    >> serial8250_register_port().
    >>
    >> The problem is that if we call serial8250_register_port() before the
    >> driver is initialized Bad Things happen (we dereference NULL
    >> pointers).
    >>
    >> There doesn't seem to be a general way to know if a driver has been
    >> initialized
    >
    > I've had a bigger dig into this. I think the correct answer is probably
    > "always go via platform devices or similar". That *is* the notifier in
    > the kernel of today. serial8250_register_port ultimately should I think
    > ultimatly become an internal helper.
    >

    That was kind of my thought too. However we have all sorts of things
    calling serial8250_register_port(). Things like:

    8250_pci.c
    of_serial.c
    8250_acorn.c
    8250_gsc.c
    .
    .
    .

    The resulting view of the drivers in sysfs is that the little stub code
    that calls serial8250_register_port() is shown as the driver rather than
    serial8250. But I suppose that is a matter of aesthetics more than
    function.

    All those 'stub drivers' are relying on the ordering of module_init
    calls caused indirectly by the Makefile layout. The path of least
    resistance is your suggestion that I use late_initcall() in my driver
    stub. I actually tried that before hacking up this patch, but didn't
    like the idea of relying on *_initcall() ordering being necessary for
    correct initialization.

    David Daney


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