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SubjectRe: Handling devices that don't have a bus
On Thu, Mar 30, 2006 at 02:26:26PM -0800, Greg KH wrote:
> On Thu, Mar 30, 2006 at 03:45:50PM -0500, Alan Stern wrote:
> > Greg et al.:
> >
> > I recently tried running the dummy_hcd driver for the first time in a
> > while, and it crashed when the gadget driver was unloaded. It turns out
> > this was because the gadget's embedded struct device is registered without
> > a bus, which triggers an oops when the device's driver is unbound. The
> > oops could be fixed by doing this:
>
> Why not make the dummy gadget a platform device? That should keep this
> from happening, right?
>
> > Index: usb-2.6/drivers/base/dd.c
> > ===================================================================
> > --- usb-2.6.orig/drivers/base/dd.c
> > +++ usb-2.6/drivers/base/dd.c
> > @@ -209,7 +209,7 @@ static void __device_release_driver(stru
> > sysfs_remove_link(&dev->kobj, "driver");
> > klist_remove(&dev->knode_driver);
> >
> > - if (dev->bus->remove)
> > + if (dev->bus && dev->bus->remove)
> > dev->bus->remove(dev);
> > else if (drv->remove)
> > drv->remove(dev);
> >
> > but I'm not so sure this is the right approach. (Russell wrote the line
> > that this would change; that's why I have CC'ed him.) Is the current
> > policy that every device is supposed to belong to a bus?

If a device belongs to a bus, dev->bus will be non-NULL. I don't see
what "every device is supposed to belong to a bus" fits with the problem.

> > Part of the problem here is that most of the USB controllers are platform
> > devices and so belong on the platform bus. That's true of dummy_hcd.
> > But struct usb_gadget contains an embedded struct device, not an embedded
> > struct platform_device... so the gadget _can't_ be registered on its
> > parent's bus.
>
> ah, ick :(

If the device's dev->bus is NULL, we don't register it on the parents
bus, but we do register it in the device tree as a child of the parent
device.

I think there's confusion here.

> I think your patch is the right thing. Care to resend it with a proper
> Signed-off-by: line so I can apply it?

First lets sort out the confusion before applying any patches.

--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of: 2.6 Serial core
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