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Date:   Tue, 27 Jul 2021 13:42:20 +0200
From:   Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= <u.kleine-koenig@pengutronix.de>
To:     Finn Thain <fthain@linux-m68k.org>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-m68k@lists.linux-m68k.org, linux-kernel@vger.kernel.org,
        kernel@pengutronix.de
Subject: Re: [PATCH 1/5] nubus: Simplify check in remove callback
Message-ID: <20210727114220.7drjl6xvvlwetaod@pengutronix.de>
References: <20210727080840.3550927-1-u.kleine-koenig@pengutronix.de>
 <20210727080840.3550927-2-u.kleine-koenig@pengutronix.de>
 <d74ccd1-116d-9450-5ee4-8d5074998872@linux-m68k.org>
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On Tue, Jul 27, 2021 at 07:50:39PM +1000, Finn Thain wrote:
> On Tue, 27 Jul 2021, Uwe Kleine-K=F6nig wrote:
>=20
> > The driver core only calls a remove callback when the device was
> > successfully bound (aka probed) before. So dev->driver is never NULL.
>=20
> 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.
>=20
> I don't understand how a compiler can make that assumption. But then, I=
=20
> 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

--=20
Pengutronix e.K.                           | Uwe Kleine-K=F6nig            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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