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Date:   Sat, 31 Jul 2021 14:05:15 +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: <20210731120515.xkr64yvnczchxz4s@pengutronix.de>
References: <20210727080840.3550927-1-u.kleine-koenig@pengutronix.de>
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 <d74ccd1-116d-9450-5ee4-8d5074998872@linux-m68k.org>
 <20210727114220.7drjl6xvvlwetaod@pengutronix.de>
 <4b44c8a4-7d2b-83d-60fa-2d4e4f8284db@linux-m68k.org>
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Hello Finn,

On Sat, Jul 31, 2021 at 08:32:38PM +1000, Finn Thain wrote:
> On Tue, 27 Jul 2021, Uwe Kleine-K=F6nig wrote:
> > 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=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 neve=
r=20
> 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

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

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