Received-SPF: pass (google.com: domain of linux-kernel+bounces-155421-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.80.249 as permitted sender) client-ip=147.75.80.249;
Date: Tue, 23 Apr 2024 10:05:30 -0500
From: Rob Herring <robh@kernel.org>
To: Stephen Boyd <sboyd@kernel.org>
Cc: Maxime Ripard <maxime@cerno.tech>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Brendan Higgins <brendan.higgins@linux.dev>,
	Rae Moar <rmoar@google.com>, linux-kselftest@vger.kernel.org,
	David Gow <davidgow@google.com>,
	Christian Marangi <ansuelsmth@gmail.com>,
	linux-kernel@vger.kernel.org,
	"Rafael J . Wysocki" <rafael@kernel.org>,
	kunit-dev@googlegroups.com, patches@lists.linux.dev,
	linux-clk@vger.kernel.org,
	Michael Turquette <mturquette@baylibre.com>,
	Saravana Kannan <saravanak@google.com>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Daniel Latypov <dlatypov@google.com>, devicetree@vger.kernel.org
Subject: Re: [PATCH v4 01/10] of: Add test managed wrappers for
 of_overlay_apply()/of_node_put()
Message-ID: <171388470076.215446.15104256542666415343.robh@kernel.org>
References: <20240422232404.213174-1-sboyd@kernel.org>
 <20240422232404.213174-2-sboyd@kernel.org>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20240422232404.213174-2-sboyd@kernel.org>


On Mon, 22 Apr 2024 16:23:54 -0700, Stephen Boyd wrote:
> Add test managed wrappers for of_overlay_apply() that automatically
> removes the overlay when the test is finished. This API is intended for
> use by KUnit tests that test code which relies on 'struct device_node's
> and of_*() APIs.
> 
> KUnit tests will call of_overlay_apply_kunit() to load an overlay that's
> been built into the kernel image. When the test is complete, the overlay
> will be removed.
> 
> This has a few benefits:
> 
>  1) It keeps the tests hermetic because the overlay is removed when the
>     test is complete. Tests won't even be aware that an overlay was
>     loaded in another test.
> 
>  2) The overlay code can live right next to the unit test that loads it.
>     The overlay and the unit test can be compiled into one kernel module
>     if desired.
> 
>  3) We can test different device tree configurations by loading
>     different overlays. The overlays can be written for a specific test,
>     and there can be many of them loaded per-test without needing to jam
>     all possible combinations into one DTB.
> 
>  4) It also allows KUnit to test device tree dependent code on any
>     architecture, not just UML. This allows KUnit tests to test
>     architecture specific device tree code.
> 
> There are some potential pitfalls though. Test authors need to be
> careful to not overwrite properties in the live tree. The easiest way to
> do this is to add and remove nodes with a 'kunit-' prefix, almost
> guaranteeing that the same node won't be present in the tree loaded at
> boot.
> 
> Suggested-by: Rob Herring <robh@kernel.org>
> Cc: Rob Herring <robh@kernel.org>
> Cc: Saravana Kannan <saravanak@google.com>
> Signed-off-by: Stephen Boyd <sboyd@kernel.org>
> ---
>  Documentation/dev-tools/kunit/api/index.rst | 11 +++
>  Documentation/dev-tools/kunit/api/of.rst    | 13 +++
>  drivers/of/Makefile                         |  1 +
>  drivers/of/of_kunit.c                       | 99 +++++++++++++++++++++
>  include/kunit/of.h                          | 94 +++++++++++++++++++
>  5 files changed, 218 insertions(+)
>  create mode 100644 Documentation/dev-tools/kunit/api/of.rst
>  create mode 100644 drivers/of/of_kunit.c
>  create mode 100644 include/kunit/of.h
> 

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>