linux-kernel - Re: [PATCH 2/2] media: v4l2-async: Make subdev notifier cleanup conditional

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Date:   Wed, 9 Jun 2021 15:01:16 +0200
From:   Paul Kocialkowski <paul.kocialkowski@...tlin.com>
To:     Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Niklas Söderlund 
        <niklas.soderlund+renesas@...natech.se>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Sebastian Reichel <sre@...nel.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH 2/2] media: v4l2-async: Make subdev notifier cleanup
 conditional

Hi Sakari,

On Wed 09 Jun 21, 15:27, Sakari Ailus wrote:
> Hi Paul,
> 
> On Wed, Jun 09, 2021 at 01:54:57PM +0200, Paul Kocialkowski wrote:
> > A dedicated subdev notified is registered when using the helper
> > dedicated to sensors (v4l2_async_register_subdev_sensor_common),
> > but this is not the case when a driver uses v4l2_async_register_subdev
> > directly.
> 
> Is this a problem?
> 
> The notifier unregistration and cleanup functions should be safe to call on
> a notifier that's not been initialised or registered. The same goes for
> kfree with NULL argument.

I think you're right, the functions and kfree are indeed safe.
I think I mixed things up with debugging an issue and assumed this was part
of the fix I needed.

Sorry for the noise!

Paul

-- 
Paul Kocialkowski, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com

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