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

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Message-ID: <CAFDyS3M1ZqrkGXGqdhTjyJp1eheJsDKLuBC-piC8jBUC=zt45Q@mail.gmail.com>
Date:	Sun, 24 May 2015 17:30:57 +0300
From:	Tal Shorer <tal.shorer@...il.com>
To:	Sudip Mukherjee <sudipm.mukherjee@...il.com>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	Sasha Levin <sasha.levin@...cle.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	USB list <linux-usb@...r.kernel.org>,
	"<linux-kernel@...r.kernel.org>" <linux-kernel@...r.kernel.org>,
	David Cohen <david.a.cohen@...ux.intel.com>,
	Felipe Balbi <balbi@...com>
Subject: Re: [PATCH] usb: ulpi: don't register drivers if bus doesn't exist

Why do we even need that? If you take patch that makes ulpi_init a
subsys_initcall you won't have this problem, and no additional weird
hacks and errors will be needed

On Sun, May 24, 2015 at 11:09 AM, Sudip Mukherjee
<sudipm.mukherjee@...il.com> wrote:
> 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@...cle.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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