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

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Message-ID: <20150524080940.GA4033@sudip-PC>
Date:	Sun, 24 May 2015 13:39:40 +0530
From:	Sudip Mukherjee <sudipm.mukherjee@...il.com>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	Sasha Levin <sasha.levin@...cle.com>,
	heikki.krogerus@...ux.intel.com, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, david.a.cohen@...ux.intel.com,
	balbi@...com
Subject: Re: [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@...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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