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

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Date:	Tue, 26 May 2015 19:41:18 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	David Cohen <david.a.cohen@...ux.intel.com>
Cc:	Bjørn Mork <bjorn@...k.no>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Tal Shorer <tal.shorer@...il.com>,
	Sudip Mukherjee <sudipm.mukherjee@...il.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	USB list <linux-usb@...r.kernel.org>,
	"<linux-kernel@...r.kernel.org>" <linux-kernel@...r.kernel.org>,
	Felipe Balbi <balbi@...com>,
	Lu Baolu <baolu.lu@...ux.intel.com>
Subject: Re: [PATCH] usb: ulpi: don't register drivers if bus doesn't exist

On Tue, May 26, 2015 at 10:54:01AM -0700, David Cohen wrote:
> Hi,
> 
> On Mon, May 25, 2015 at 07:00:13PM +0200, Bjørn Mork wrote:
> > Greg KH <gregkh@...uxfoundation.org> writes:
> > 
> > > If there are other bus drivers that do this, I'll go fix them up,
> > > pointers to those files would be appreciated.
> > 
> > git grep -E 'if .*\.p\W' found a couple of interesting candidates you
> > might want to check out:
> > 
> >  drivers/i2c/i2c-core.c: if (unlikely(WARN_ON(!i2c_bus_type.p))) {
> >  drivers/i2c/i2c-core.c: if (unlikely(WARN_ON(!i2c_bus_type.p)))
> >  drivers/spmi/spmi.c:    if (WARN_ON(!spmi_bus_type.p))
> > 
> > And this looks somewhat suspicious too, but could very well be OK for
> > all I know (very close to nothing :)
> > 
> >  drivers/gpio/gpiolib-sysfs.c:   if (!gpio_class.p) {
> >  drivers/gpio/gpiolib-sysfs.c:   if (!gpio_class.p)
> 
> I think we need a clear statement on how to proceed on this case.

Don't mess with bus->p.  I can rename it to
"do_not_touch_this_isnt_for_you" if people think that would make it more
obvious that a private data structure shouldn't be messed with in any
way.  Outside of the driver core, you have no knowledge that even if it
is a pointer, what that means with regards to anything.

thanks,

greg k-h
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