Re: [PATCH 13/14] ARM: configs: sync multi_v5_defconfig from savedefconfig

From: Arnd Bergmann <arnd@arndb.de>
To: Andre Przywara <andre.przywara@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>, Maxime Ripard <mripard@kernel.org>,
	Chen-Yu Tsai <wens@csie.org>,
	 Jernej Skrabec <jernej.skrabec@gmail.com>,
	Samuel Holland <samuel@sholland.org>,
	 Rob Herring <robh+dt@kernel.org>,
	Mesih Kilinc <mesihkilinc@gmail.com>,
	 Icenowy Zheng <icenowy@aosc.io>,
	Jesse Taube <mr.bossman075@gmail.com>,
	 Giulio Benetti <giulio.benetti@benettiengineering.com>,
	 George Hilliard <thirtythreeforty@gmail.com>,
	DTML <devicetree@vger.kernel.org>,
	 Linux ARM <linux-arm-kernel@lists.infradead.org>,
	linux-sunxi@lists.linux.dev,
	 Russell King <linux@armlinux.org.uk>,
	Olof Johansson <olof@lixom.net>, SoC Team <soc@kernel.org>
Subject: Re: [PATCH 13/14] ARM: configs: sync multi_v5_defconfig from savedefconfig
Date: Tue, 8 Mar 2022 14:40:39 +0100	[thread overview]
Message-ID: <CAK8P3a3g_zPW5xEFRku3TsZTdovevwyxyWVaN_=eD+FN2G8YLg@mail.gmail.com> (raw)
In-Reply-To: <20220308120750.0bbe0122@donnerap.cambridge.arm.com>

On Tue, Mar 8, 2022 at 1:07 PM Andre Przywara <andre.przywara@arm.com> wrote:
> If you find that useful, I can try to find those dependency chains for the
> other options, but I definitely lack the knowledge about the history of
> those old platforms, so I can't reason about them. But I could present you
> the findings and you can then say what to do?

Back to this point: the most interesting ones are those that broke because of
some added dependency, or an option that got renamed. This is what I would
use to find the root cause in a scripted way (after identifying the last "good"
version):

$ git bisect run bash -c "make -s O=obj-arm ARCH=arm
multi_v5_defconfig && grep CONFIG_DRM_PANEL_SIMPLE  obj-arm/.config"

You can group the ones that went away because of a deleted platform
or driver, or those that are just default-enabled now, but for cases that
no longer use a driver that may be needed by some platform, just
having the information about what patch broke them usually tells us
what happened. We still need to decide on an appropriate action then,
which could be to include the new dependency explicitly, or to remove
the entire platform that used the driver because we find that the maintainers
never noticed it breaking.

         Arnd