Re: [PATCH 1/5] nubus: Simplify check in remove callback

[Uwe Kleine-König]

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)

> > Apart from that, the compiler might already assume dev->driver being
> > non-NULL after to_nubus_driver(dev->driver) was called.
> 
> I don't understand how a compiler can make that assumption. But then, I 
> don't know why compilers do a lot of the things they do...

Ah, you're right, there is no dereference in container_of, so I might
also be wrong here. I will send a v2 without this last sentence in the
commit log.

Best regards
Uwe

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

Attachment: signature.asc
Description: PGP signature