Re: [RESEND PATCH v3 07/32] media: v4l: async: Drop unneeded list entry initialisation

From: Sakari Ailus <sakari.ailus@linux.intel.com>
To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: linux-media@vger.kernel.org,
	Philipp Zabel <p.zabel@pengutronix.de>,
	hverkuil@xs4all.nl, Francesco Dolcini <francesco@dolcini.it>,
	aishwarya.kothari@toradex.com, Robert Foss <rfoss@kernel.org>,
	Todor Tomov <todor.too@gmail.com>,
	Hyun Kwon <hyun.kwon@xilinx.com>,
	bingbu.cao@intel.com, niklas.soderlund@ragnatech.se,
	Kieran Bingham <kieran.bingham@ideasonboard.com>,
	Benjamin Mugnier <benjamin.mugnier@foss.st.com>,
	Sylvain Petinot <sylvain.petinot@foss.st.com>,
	Eugen Hristev <eugen.hristev@collabora.com>,
	Nicolas Ferre <nicolas.ferre@microchip.com>,
	Maxime Ripard <mripard@kernel.org>,
	Rui Miguel Silva <rmfrfs@gmail.com>,
	Fabio Estevam <festevam@gmail.com>,
	Bryan O'Donoghue <bryan.odonoghue@linaro.org>,
	Sylwester Nawrocki <s.nawrocki@samsung.com>,
	Dafna Hirschfeld <dafna@fastmail.com>,
	Hugues Fruchet <hugues.fruchet@foss.st.com>,
	Yong Deng <yong.deng@magewell.com>,
	Paul Kocialkowski <paul.kocialkowski@bootlin.com>,
	"Lad, Prabhakar" <prabhakar.csengg@gmail.com>,
	Benoit Parrot <bparrot@ti.com>,
	Steve Longerbeam <slongerbeam@gmail.com>,
	Thierry Reding <thierry.reding@gmail.com>,
	Jonathan Hunter <jonathanh@nvidia.com>,
	Sowjanya Komatineni <skomatineni@nvidia.com>,
	Marco Felsch <m.felsch@pengutronix.de>
Subject: Re: [RESEND PATCH v3 07/32] media: v4l: async: Drop unneeded list entry initialisation
Date: Tue, 13 Jun 2023 14:08:38 +0000	[thread overview]
Message-ID: <ZIh4ZnLx3sbYX9D+@kekkonen.localdomain> (raw)
In-Reply-To: <ZIh2i7HqUsbSfZ9i@kekkonen.localdomain>

On Tue, Jun 13, 2023 at 02:00:43PM +0000, Sakari Ailus wrote:
> Hi Laurent,
> 
> On Tue, May 30, 2023 at 05:46:50AM +0300, Laurent Pinchart wrote:
> > Hi Sakari,
> > 
> > Thank you for the patch.
> > 
> > On Thu, May 25, 2023 at 12:15:50PM +0300, Sakari Ailus wrote:
> > > The list entry is initialised as a head in v4l2_async_register_subdev()
> > > just before being added to the list. This isn't needed, drop the
> > > initialisation.
> > 
> > Is this really unneeded ? Before the initialization and the list_add()
> > call there are a few code paths that can access the async_list. For
> > instance, the error path calls v4l2_async_cleanup(), which calls
> > 
> > 	list_del_init(&sd->async_list);
> > 
> > That won't work well on an uninitialized (or zero-initialized)
> > list_head.
> 
> I think you're right, I'll drop this patch. This initialisation will be
> removed in a later patch though, as the list will be redundant soon.

Actually the list and the field remains, although it becomes unnecessary to
initialise it. I'll see if this patch would be meaningful later on in the
series or squashed to another patch.

-- 
Sakari Ailus