Hello Finn,

On Sat, Jul 31, 2021 at 08:32:38PM +1000, Finn Thain wrote:
> On Tue, 27 Jul 2021, Uwe Kleine-König wrote:
> > On Tue, Jul 27, 2021 at 07:50:39PM +1000, Finn Thain wrote:
> > > On Tue, 27 Jul 2021, Uwe Kleine-König wrote:
> > > 
> > > > The driver core only calls a remove callback when the device was 
> > > > successfully bound (aka probed) before. So dev->driver is never 
> > > > NULL.
> > > 
> > > Are you sure dev->driver is non-NULL for the lifetime of the device? A 
> > > quick glance at device_reprobe() makes me wonder about that.
> > 
> > Not for the lifetime of the device, but as long as a driver is bound to 
> > the device. device_reprobe() calls device_driver_detach() after which 
> > the driver is considered unbound and dev->driver is assigned NULL. (via 
> > device_driver_detach -> device_release_driver_internal -> 
> > __device_release_driver)
> 
> Are you saying that this situation does not presently apply to nubus, 
> zorro or superhyway? Or are you saying that the remove callback will never 
> be called in this situation?

I'm saying that if you call device_reprobe() the remove callback is
called before dev->driver becomes NULL. So in the remove callback it's
safe to assume that dev->driver is non-NULL.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |