Re: [PATCH v2 0/4] media: add and use fwnode_graph_for_each_endpoint_scoped()

From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Frank Li <Frank.li@oss.nxp.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Daniel Scally <djrscally@gmail.com>,
	Heikki Krogerus <heikki.krogerus@linux.intel.com>,
	Sakari Ailus <sakari.ailus@linux.intel.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Danilo Krummrich <dakr@kernel.org>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Dafna Hirschfeld <dafna@fastmail.com>,
	Heiko Stuebner <heiko@sntech.de>,
	Bryan O'Donoghue <bryan.odonoghue@linaro.org>,
	Vladimir Zapolskiy <vladimir.zapolskiy@linaro.org>,
	Loic Poulain <loic.poulain@oss.qualcomm.com>,
	driver-core@lists.linux.dev, linux-acpi@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-media@vger.kernel.org,
	linux-rockchip@lists.infradead.org,
	linux-arm-kernel@lists.infradead.org,
	linux-arm-msm@vger.kernel.org, imx@lists.linux.dev,
	Guoniu Zhou <guoniu.zhou@nxp.com>, Frank Li <Frank.Li@nxp.com>,
	Guoniu Zhou <guoniu.zhou@oss.nxp.com>
Subject: Re: [PATCH v2 0/4] media: add and use fwnode_graph_for_each_endpoint_scoped()
Date: Wed, 24 Jun 2026 23:02:37 +0300	[thread overview]
Message-ID: <20260624200237.GJ851255@killaraus.ideasonboard.com> (raw)
In-Reply-To: <ajwxcn2LXS8InAjZ@SMW015318>

On Wed, Jun 24, 2026 at 02:35:14PM -0500, Frank Li wrote:
> On Wed, Jun 24, 2026 at 10:19:35PM +0300, Laurent Pinchart wrote:
> > On Wed, Jun 24, 2026 at 01:00:08PM -0400, Frank.Li@oss.nxp.com wrote:
> > > Add new helper macro fwnode_graph_for_each_endpoint_scoped() and use it
> > > simplify media code.
> > >
> > > Typical example should qualcomm's driver (camss.c), the v4l2_mc.c and
> > > rkisp1-dev.c only silience improvement.
> > >
> > > Anyways, *_for_each_*_scoped() already use widely and make code clean.
> > >
> > > Build test only.
> > >
> > > Sakari Ailus:
> > > 	when I try to improve the patch
> > > "Add common helper library for 1-to-1 subdev registration", I found need
> > > camss.c pattern, so I create this small improvement firstly.
> >
> > Those are nice cleanups, thank you.
> >
> > After applying this series, the only left users of the
> > fwnode_graph_for_each_endpoint() macro are in drivers/base/property.c.
> 
> I already checked previously, two place use it.
> 
> fwnode_graph_get_endpoint_count(), it will go though all endpoints, last
> ep is NULL, which totally equial to scoped() version.
> 
> another one fwnode_graph_get_endpoint_by_id(), which return ep, expect
> caller to call put().
> 
> if use scoped() version, need use no_free_ptr() at return, which make think
> a little bit complex.

It would introduce a tiny bit of extra complexity there, but the
advantage (in my opinion) is that we'll be able to remove the less safe
fwnode_graph_for_each_endpoint() macro.

Now one may argue that the risk of
fwnode_graph_for_each_endpoint_scoped() is returning the iterator
without using no_free_ptr(). I wonder if that would be easier to catch
in static analysis tools than the current pattern that leaks a reference
when exiting the loop early.

> It'd better leave these as it.

-- 
Regards,

Laurent Pinchart

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