Re: Implement class_device_update_dev() function

Kay Sievers
2006-07-08T00:26:39Z

On Fri, 2006-07-07 at 09:42 +0200, Marcel Holtmann wrote:
> Hi Greg,
>
> > > for the Bluetooth subsystem integration into the driver model it is
> > > required that we can update the device of a class device at any time.
> >
> > You can? Ick.
> >
> > That messes with my "get rid of struct class_device" plans a bit...
>
> this must not be a class device, but at the moment TTY, network and
> input are still class devices. The Bluetooth subsystem moved away from
> using class devices.
>
> > > For the RFCOMM TTY device for example we create the TTY device and only
> > > when it got opened we create the Bluetooth connection. Once this new
> > > connection has been created we have a device to attach to the class
> > > device of the TTY.
> > >
> > > I came up with the attached patch and it worked fine with the Bluetooth
> > > RFCOMM layer.
> >
> > But userspace should also find out about this change, and this patch
> > prevents that from happening. What about just tearing down the class
> > device and creating a new one? That way userspace knows about the new
> > linkage properly, and any device naming and permission issues can be
> > handled anew?
>
> This won't work for Bluetooth. We create the TTY and its class device
> with tty_register_device() and then the device node is present. Then at
> some point later we open that device and the Bluetooth connection gets
> established. Only when the connection has been established we know the
> device that represents it. So tearing down the class device and creating
> a new one will screw up the application that is using this device node.
>
> Would reissuing the uevent of the class device help here?

How about KOBJ_ONLINE/OFFLINE?

Thanks,
Kay