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Date:   Sat, 31 Jul 2021 20:32:38 +1000 (AEST)
From:   Finn Thain <fthain@linux-m68k.org>
To:     =?UTF-8?Q?Uwe_Kleine-K=C3=B6nig?= <u.kleine-koenig@pengutronix.de>
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
In-Reply-To: <20210727114220.7drjl6xvvlwetaod@pengutronix.de>
Message-ID: <4b44c8a4-7d2b-83d-60fa-2d4e4f8284db@linux-m68k.org>
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> <20210727114220.7drjl6xvvlwetaod@pengutronix.de>
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On Tue, 27 Jul 2021, Uwe Kleine-K=C3=B6nig wrote:

> On Tue, Jul 27, 2021 at 07:50:39PM +1000, Finn Thain wrote:
> > On Tue, 27 Jul 2021, Uwe Kleine-K=C3=B6nig wrote:
> >=20
> > > The driver core only calls a remove callback when the device was=20
> > > successfully bound (aka probed) before. So dev->driver is never=20
> > > NULL.
> >=20
> > Are you sure dev->driver is non-NULL for the lifetime of the device? A=
=20
> > quick glance at device_reprobe() makes me wonder about that.
>=20
> Not for the lifetime of the device, but as long as a driver is bound to=
=20
> the device. device_reprobe() calls device_driver_detach() after which=20
> the driver is considered unbound and dev->driver is assigned NULL. (via=
=20
> device_driver_detach -> device_release_driver_internal ->=20
> __device_release_driver)
>=20

Are you saying that this situation does not presently apply to nubus,=20
zorro or superhyway? Or are you saying that the remove callback will never=
=20
be called in this situation?

Perhaps the device_reprobe() API should be documented accordingly, so that=
=20
a missing NULL check can be added if need be. Perhaps it is better to just=
=20
leave this pattern as is (i.e. keep the NULL check).
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