linux-kernel - Re: [PATCH 00/30] ARM: pxa: remove all unused boards&drivers

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Date:   Thu, 20 Oct 2022 09:30:03 +0200
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Robert Jarzmik" <jarzmik.robert@...nge.fr>,
        "Arnd Bergmann" <arnd@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org,
        "Daniel Mack" <daniel@...que.org>,
        "Haojian Zhuang" <haojian.zhuang@...il.com>,
        linux-kernel@...r.kernel.org,
        "Alan Stern" <stern@...land.harvard.edu>,
        "Alexandre Belloni" <alexandre.belloni@...tlin.com>,
        "Bartosz Golaszewski" <brgl@...ev.pl>,
        "Damien Le Moal" <damien.lemoal@...nsource.wdc.com>,
        "Dmitry Torokhov" <dmitry.torokhov@...il.com>,
        "Dominik Brodowski" <linux@...inikbrodowski.net>,
        "Felipe Balbi" <balbi@...nel.org>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Helge Deller" <deller@....de>, perex@...ex.cz,
        jingoohan1@...il.com, "Lee Jones" <lee@...nel.org>,
        kernel@...tstofly.org, lgirdwood@...il.com,
        "Linus Walleij" <linus.walleij@...aro.org>, marek.vasut@...il.com,
        "Mark Brown" <broonie@...nel.org>, mkpetch@...ernode.on.net,
        "Miquel Raynal" <miquel.raynal@...tlin.com>,
        lost.distance@...oo.com, philipp.zabel@...il.com,
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        "Sudip Mukherjee" <sudipm.mukherjee@...il.com>, tiwai@...e.com,
        "Ulf Hansson" <ulf.hansson@...aro.org>,
        "Vignesh Raghavendra" <vigneshr@...com>,
        "Viresh Kumar" <viresh.kumar@...aro.org>,
        "Wolfram Sang" <wsa+renesas@...g-engineering.com>,
        linux-pm@...r.kernel.org, linux-ide@...r.kernel.org,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        linux-input@...r.kernel.org, patches@...nsource.cirrus.com,
        linux-leds@...r.kernel.org,
        "linux-mmc @ vger . kernel . org" <linux-mmc@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
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        linux-usb@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-fbdev@...r.kernel.org, alsa-devel@...a-project.org
Subject: Re: [PATCH 00/30] ARM: pxa: remove all unused boards&drivers

On Wed, Oct 19, 2022, at 23:13, Robert Jarzmik wrote:
> Arnd Bergmann <arnd@...nel.org> writes:
>
>> From: Arnd Bergmann <arnd@...db.de>
> ...zip...
>
>> A good number of drivers become impossible to select after this, so
>> each of these also get dropped. I'm including the driver patches in the
>> series here and can either merge them through the soc tree, or they
>> can get picked up by the individual subsystem maintainers. Since both
>> the platform and the drivers get removed, the order should not matter.
> This part is a bit ... bothering.
> I at least identified these :
>>  delete mode 100644 drivers/input/touchscreen/wm9705.c
>>  delete mode 100644 drivers/input/touchscreen/wm9712.c
>>  delete mode 100644 drivers/input/touchscreen/wm9713.c
>>  delete mode 100644 drivers/input/touchscreen/wm97xx-core.c
>>  delete mode 100644 drivers/mfd/wm97xx-core.c
>>  delete mode 100644 sound/ac97/bus.c
>>  delete mode 100644 sound/ac97/codec.c
>>  delete mode 100644 sound/ac97/snd_ac97_compat.c
>
> For the existing platforms working with devicetree support (mioa701 for
> example), the wm9713 was properly used, providing both sound support and input
> touchscreen.
> So was the a97 part, providing a framework to make the wm9713 work.
>
> So I'm wondering how the choice to chop these drivers was done, and it is
> necessary to remove them. If so, maybe pxa support in the kernel should be
> removed all together, as people playing with it loose part of the working DT
> platforms they had.

If the files are used for DT based machines, then they should
definitely stay, the intention of my series was to only remove
known dead code.

What I did was to remove CONFIG_UNUSED_BOARD_FILES and then
recursively trim out all code that could be compiled in
before but not after this change, assuming that this would
be safe.

What I see here is that AC97_BUS_NEW and SND_PXA2XX_SOC_AC97
are selected by eight legacy board files (tosa, e740, e750,
e800, em_x270, palm27x, zylonite and mioa701), but no
DT based machine, so without CONFIG_UNUSED_BOARD_FILES, the
entire AC97_BUS_NEW infrastructure and all drivers depending
on this became dead code.

Unfortunately I ran into problems sending out the rest of the
series after sending the cover letter, so the explanations
I put in the individual patches were not here. See [1] for the
actual series.

Since it looks like I'll have to redo half of the PXA patches
after leaving AC97_BUS_NEW in, I won't post the full version
first.

Any idea where I went wrong here? Did I make a mistake in
following the Kconfig dependencies, or are some parts of this
incorrectly annotated?

     Arnd

[1] https://git.kernel.org/pub/scm/linux/kernel/git/soc/soc.git/log/?h=boardfile-remove&id=73c4b7cfbc2b2