linux-kernel - Re: [PATCH v8 2/8] of: Add test managed wrappers for of_overlay_apply()/of_node

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Message-ID: <488b3f944bb892bee74e3d8aae8400e1.sboyd@kernel.org>
Date: Mon, 29 Jul 2024 15:37:14 -0700
From: Stephen Boyd <sboyd@...nel.org>
To: Michael Turquette <mturquette@...libre.com>, Stephen Boyd <sboyd@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org, patches@...ts.linux.dev, kunit-dev@...glegroups.com, linux-kselftest@...r.kernel.org, devicetree@...r.kernel.org, Brendan Higgins <brendan.higgins@...ux.dev>, David Gow <davidgow@...gle.com>, Rae Moar <rmoar@...gle.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Rafael J . Wysocki <rafael@...nel.org>, Rob Herring <robh@...nel.org>, Saravana Kannan <saravanak@...gle.com>, Daniel Latypov <dlatypov@...gle.com>, Christian Marangi <ansuelsmth@...il.com>, Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, Maxime Ripard <maxime@...no.tech>, Geert Uytterhoeven <geert+renesas@...der.be>
Subject: Re: [PATCH v8 2/8] of: Add test managed wrappers for of_overlay_apply()/of_node_put()

Quoting Stephen Boyd (2024-07-18 14:05:01)
> 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@...nel.org>
> Cc: Rob Herring <robh@...nel.org>
> Cc: Saravana Kannan <saravanak@...gle.com>
> Reviewed-by: Rob Herring (Arm) <robh@...nel.org>
> Reviewed-by: David Gow <davidgow@...gle.com>
> Signed-off-by: Stephen Boyd <sboyd@...nel.org>
> ---

Applied to clk-next