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    SubjectRe: x86, microcode: Conversion from sysdev class caused regression
    + Dave.

    On Wed, Apr 11, 2012 at 07:06:21PM +0200, Kay Sievers wrote:
    > > The reason for the error is that subsys_interface_register() doesn't
    > > handle the return value of sif->add_dev (and there's also no unwinding
    > > of the interface registration). Instead subsys_interface_register
    > > always returns 0.
    >
    > Which is the intended behaviour of 'subsystem interfaces' from the
    > driver-core perspective. It should not matter if one of a bunch of
    > devices do not 'like' this 'interface'. It is the same model as a
    > 'driver', we do not cancel the link-in of a driver if one device does
    > not like the driver.

    But you're not looking at the return value of sif->add_dev which looks
    strange to me. Let me put it this way: why do you have return values to
    ->add_dev's interface then if you're not going to look at them?

    A warning that one of the dev_add's failed could probably make sense
    here...

    [..]

    > I think a quick return in the microcode driver, for a device which has
    > no active interface state is the best solution here.

    Actually, it is even easier: the code clumsily does:

    sysfs_create_group
    microcode_init_cpu
    if (err)
    sysfs_remove_group

    so we go and create sysfs group, THEN check whether this CPU is
    supported and if not, remove the group again which is a bunch of crap if
    you ask me. The right way to go should be:

    microcode_init_cpu
    if (err)
    return;
    sysfs_create_group

    and then there's no need to do all that sysfs group dancing. Andreas,
    let me know if you wanna do it, or I should take care of it.

    Thanks.

    --
    Regards/Gruss,
    Boris.

    Advanced Micro Devices GmbH
    Einsteinring 24, 85609 Dornach
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