Re: [PATCH] usb: ulpi: don't register drivers if bus doesn't exist

[Lu, Baolu]

On 05/21/2015 05:22 AM, David Cohen wrote:
> Hi,
>
> 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
> A minor comment: s/it's/its/
>
> > 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@xxxxxxxxxx>
> > ---
> >   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;
> > +
> Good catch. Otherwise it may trigger BUG() on driver_register().
> I wonder if it would be nice to have a macro for that checking :)
>
> Anyway,
>
> Reviewed-by: David Cohen <david.a.cohen@xxxxxxxxxxxxxxx>

Well, I was also encountering panic issue when running it on
Intel Bay Trail tablets. In my case, it's due to the execution
sequence. When ulpi bus is built-in, driver or device registered
before ulpi bus registration.

Thanks,
Baolu

> >   	drv->driver.bus = &ulpi_bus;
> >   
> >   	return driver_register(&drv->driver);
> > --
> > 1.7.10.4
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