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    SubjectRe: [PATCH] usb: ulpi: don't register drivers if bus doesn't exist
    On Sun, May 24, 2015 at 12:19:48AM -0700, Greg KH wrote:
    > On Wed, May 20, 2015 at 03:33:26PM -0400, Sasha Levin wrote:
    > > ULPI registers it's bus at module_init so if the bus fails to register, the
    > > module will fail to load and all will be well in the world.
    > >
    > > However, if the ULPI code is built-in rather than a module, the bus
    > > initialization may fail but we'd still try to register drivers later onto
    > > a non-existant bus, which will panic the kernel.
    > >
    > > Fix that by checking that the bus was indeed initialized before trying to
    > > register drivers on top of it.
    > >
    > > Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
    > > ---
    > > drivers/usb/common/ulpi.c | 4 ++++
    > > 1 file changed, 4 insertions(+)
    > >
    > > diff --git a/drivers/usb/common/ulpi.c b/drivers/usb/common/ulpi.c
    > > index 0e6f968..0b0a5e7 100644
    > > --- a/drivers/usb/common/ulpi.c
    > > +++ b/drivers/usb/common/ulpi.c
    > > @@ -132,6 +132,10 @@ int ulpi_register_driver(struct ulpi_driver *drv)
    > > if (!drv->probe)
    > > return -EINVAL;
    > >
    > > + /* Was the bus registered successfully? */
    > > + if (!ulpi_bus.p)
    > > + return -ENODEV;
    >
    > Ick, no, don't go mucking around in the bus internals like this, that's
    > not ok. You should either "know" the bus is registered, or something is
    > really wrong with the design here.
    can't we use a variable which can be initialized to 1 in ulpi_init() if
    the bus registers successfully and later check that?

    regards
    sudip
    >
    > greg k-h
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