linux-kernel - Re: [PATCH 0/4] media: Add devm-managed helper functions for media and V4L2 subsystems

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID:
 <PN3P287MB1829D71FB3C2B41FF28D6A198B5FA@PN3P287MB1829.INDP287.PROD.OUTLOOK.COM>
Date: Wed, 23 Jul 2025 14:08:03 +0000
From: Tarang Raval <tarang.raval@...iconsignals.io>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
CC: "sakari.ailus@...ux.intel.com" <sakari.ailus@...ux.intel.com>,
	"hverkuil@...all.nl" <hverkuil@...all.nl>, Mauro Carvalho Chehab
	<mchehab@...nel.org>, Ricardo Ribalda <ribalda@...omium.org>, Hans de Goede
	<hansg@...nel.org>, James Cowgill <james.cowgill@...ize.com>, Yunke Cao
	<yunkec@...gle.com>, Tomi Valkeinen <tomi.valkeinen@...asonboard.com>, Lad
 Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>, Tommaso Merciai
	<tomm.merciai@...il.com>, "linux-media@...r.kernel.org"
	<linux-media@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/4] media: Add devm-managed helper functions for media
 and V4L2 subsystems

Hi Laurent,

> On Wed, Jul 23, 2025 at 03:55:04PM +0530, Tarang Raval wrote:
> > This patch series introduces devm-managed versions of several commonly used
> > media and V4L2 initialization functions. These helpers simplify resource
> > management by leveraging the devres infrastructure, ensuring automatic
> > cleanup when the associated device is detached or the driver is unloaded.
> 
> I'll let Sakari review this, but overall, I don't think we want to take
> this direction. Objects need to be refcounted instead of freed at remove
> time. 

I agree that refcounting could provide more robust lifetime management,
especially for shared resources. I will think in this direction, explore 
implementing refcounting for these objects, and share an RFC for your 
feedback.

> This patch series doesn't necessarily cause a regression as such,
> but it will make it more difficult to fix life time management issues in
> V4L2.

Could you clarify how devm-managed helpers might complicate lifetime 
management in V4L2? Understanding specific issues will help me design 
a solution that aligns with the subsystem’s needs while keeping cleanup 
simple.

Best Regards,
Tarang

> > Tested with IMX219 and OV2735 camera sensors on an i.MX8MP-based platform.
> >
> > Tarang Raval (4):
> >   media: mc: Add devm_media_entity_pads_init() helper
> >   media: v4l: async: Add devm_v4l2_async_register_subdev_sensor() helper
> >   media: v4l2: subdev: Add devm_v4l2_subdev_init_finalize() helper
> >   media: v4l2-ctrls: Add devm_v4l2_ctrl_handler_init() helper
> >
> >  drivers/media/mc/mc-entity.c              | 19 +++++++++++++++++++
> >  drivers/media/v4l2-core/v4l2-async.c      | 19 +++++++++++++++++++
> >  drivers/media/v4l2-core/v4l2-ctrls-core.c | 20 ++++++++++++++++++++
> >  drivers/media/v4l2-core/v4l2-subdev.c     | 18 ++++++++++++++++++
> >  include/media/media-entity.h              | 20 ++++++++++++++++++++
> >  include/media/v4l2-async.h                | 18 ++++++++++++++++++
> >  include/media/v4l2-ctrls.h                | 19 +++++++++++++++++++
> >  include/media/v4l2-subdev.h               | 17 +++++++++++++++++
> >  8 files changed, 150 insertions(+)
> >
> 
> --
> Regards,
> 
> Laurent Pinchart