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Date: Wed, 19 Dec 2018 08:03:40 +0000
From: Lee Jones <lee.jones@...aro.org>
To: Paul Gortmaker <paul.gortmaker@...driver.com>
Cc: linux-kernel@...r.kernel.org, Alessandro Rubini <rubini@...dd.com>,
Arnd Bergmann <arnd@...db.de>,
Charles Keepax <ckeepax@...nsource.cirrus.com>,
Cory Maccarrone <darkstar6262@...il.com>,
Davide Ciminaghi <ciminaghi@...dd.com>,
Dong Aisheng <dong.aisheng@...aro.org>,
Graeme Gregory <gg@...mlogic.co.uk>,
Guennadi Liakhovetski <g.liakhovetski@....de>,
Haojian Zhuang <haojian.zhuang@...vell.com>,
Jin Park <jinyoungp@...dia.com>,
Jorge Eduardo Candelaria <jedu@...mlogic.co.uk>,
Laxman Dewangan <ldewangan@...dia.com>,
Linus Walleij <linus.walleij@...aro.org>,
Mark Brown <broonie@...nsource.wolfsonmicro.com>,
Mattias Nilsson <mattias.i.nilsson@...ricsson.com>,
Michael Hennerich <michael.hennerich@...log.com>,
Tony Lindgren <tony@...mide.com>,
Venu Byravarasu <vbyravarasu@...dia.com>,
linux-omap@...r.kernel.org, patches@...nsource.cirrus.com
Subject: Re: [PATCH v4 00/18] mfd: demodularization of non-modular drivers
To all recipients (therefore, not a top post ;D ),
So far, so good. Please keep the reviews coming.
On Mon, 17 Dec 2018, Paul Gortmaker wrote:
> [v3 --> v4: delete now unused exit fcn from wm835x core; add more acks
> now all in chrono order, re-test.]
>
> [v2 --> v3: drop diasemi commits as they will be modularized; delete
> now unused exit fcn from wm831x core; add more acks; re-test.]
>
> [v1 --> v2: add some more commits as requested by Lee (MFD maintainer),
> update the 00/NN text; re-do build and link testing on new linux-next. ]
>
> This group of MFD drivers are all controlled by "bool" Kconfig settings,
> but contain various amounts of largely pointless uses of infrastructure
> related to modular operations, even though they can't be built modular.
>
> We can easily remove/replace all of it. We are trying to make driver
> code consistent with the Makefiles/Kconfigs that control them. This
> means not using modular functions/macros for drivers that can never be
> built as a module. Some of the downfalls this oversight leads to are:
>
> (1) it is easy to accidentally write unused module_exit and remove code
> (2) it can be misleading when reading the source, thinking it can be
> modular when the Makefile and/or Kconfig prohibit it
> (3) it requires the include of the module.h header file which in turn
> includes nearly everything else, thus adding a lot of CPP overhead.
> (4) it gets copied/replicated into other drivers and spreads quickly.
>
> What we see in current drivers falls into one or more of the following
> categories:
>
> 1) include of <linux/module.h> when it simply isn't needed
>
> 2) Use of MODULE_LICENSE, MODULE_DEVICE_TABLE, MODULE_AUTHOR etc.
> macros that are no-ops for non-modular drivers.
>
> 3) Creation of a module_exit() function that will be compiled and
> linked in but never actually called for non-modular drivers.
>
> 4) Addition of a platform_driver ".remove" function that is bound
> into the struct but will never be called for non-module use cases.
>
> Solution to #1 --> #3 is simple ; we just delete the related code.
>
> The solution to #4 is similar - we delete the ".remove" function and
> the binding into the platform_driver struct. However, since the same
> ".remove" function could also be triggered by an "unbind" (such as for
> pass-through of a device to a guest instance) - so we also explicitly
> disable any unbind for the driver.
>
> The unbind mask allows us to ensure we will see if there was some odd
> corner case out there that was relying on it. Typically it would be a
> multi-port ethernet card passing a port through to a guest, so a
> sensible use case in MFD drivers seems highly unlikely. This same
> solution has already been used in multiple other mainline subsystems.
>
> Build testing was done on drivers/mfd for allyesconfig on x86_64, ARM
> and ARM-64 on a recent linux-next checkout.
>
> Paul.
>
> ---
>
> Cc: Alessandro Rubini <rubini@...dd.com>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: Charles Keepax <ckeepax@...nsource.cirrus.com>
> Cc: Cory Maccarrone <darkstar6262@...il.com>
> Cc: Davide Ciminaghi <ciminaghi@...dd.com>
> Cc: Dong Aisheng <dong.aisheng@...aro.org>
> Cc: Graeme Gregory <gg@...mlogic.co.uk>
> Cc: Guennadi Liakhovetski <g.liakhovetski@....de>
> Cc: Haojian Zhuang <haojian.zhuang@...vell.com>
> Cc: Jin Park <jinyoungp@...dia.com>
> Cc: Jorge Eduardo Candelaria <jedu@...mlogic.co.uk>
> Cc: Laxman Dewangan <ldewangan@...dia.com>
> Cc: Lee Jones <lee.jones@...aro.org>
> Cc: Linus Walleij <linus.walleij@...aro.org>
> Cc: Mark Brown <broonie@...nsource.wolfsonmicro.com>
> Cc: Mattias Nilsson <mattias.i.nilsson@...ricsson.com>
> Cc: Michael Hennerich <michael.hennerich@...log.com>
> Cc: Tony Lindgren <tony@...mide.com>
> Cc: Venu Byravarasu <vbyravarasu@...dia.com>
> Cc: linux-omap@...r.kernel.org
> Cc: patches@...nsource.cirrus.com
>
>
> Paul Gortmaker (18):
> mfd: aat2870-core: Make it explicitly non-modular
> mfd: adp5520: Make it explicitly non-modular
> mfd: as3711: Make it explicitly non-modular
> mfd: db8500-prcmu: drop unused MODULE_ tags from non-modular code
> mfd: htc-i2cpld: Make it explicitly non-modular
> mfd: max8925-core: drop unused MODULE_ tags from non-modular code
> mfd: rc5t583: Make it explicitly non-modular
> mfd: sta2x11: drop unused MODULE_ tags from non-modular code
> mfd: syscon: Make it explicitly non-modular
> mfd: tps65090: Make it explicitly non-modular
> mfd: tps65910: Make it explicitly non-modular
> mfd: tps80031: Make it explicitly non-modular
> mfd: wm831x-spi: Make it explicitly non-modular
> mfd: wm831x-i2c: Make it explicitly non-modular
> mfd: wm831x-core: drop unused module infrastructure from non-modular code
> mfd: wm8350-i2c: Make it explicitly non-modular
> mfd: wm8350-core: drop unused module infrastructure from non-modular code
> mfd: wm8400-core: Make it explicitly non-modular
>
> drivers/mfd/aat2870-core.c | 40 +++-------------------------------------
> drivers/mfd/adp5520.c | 30 +++++++-----------------------
> drivers/mfd/as3711.c | 14 --------------
> drivers/mfd/db8500-prcmu.c | 10 ++++------
> drivers/mfd/htc-i2cpld.c | 18 +-----------------
> drivers/mfd/max8925-core.c | 7 +------
> drivers/mfd/rc5t583.c | 14 --------------
> drivers/mfd/sta2x11-mfd.c | 10 ++++------
> drivers/mfd/syscon.c | 12 +-----------
> drivers/mfd/tps65090.c | 30 +++++-------------------------
> drivers/mfd/tps65910.c | 18 +-----------------
> drivers/mfd/tps80031.c | 37 ++-----------------------------------
> drivers/mfd/wm831x-core.c | 15 ++-------------
> drivers/mfd/wm831x-i2c.c | 20 ++------------------
> drivers/mfd/wm831x-spi.c | 24 ++----------------------
> drivers/mfd/wm8350-core.c | 30 ++----------------------------
> drivers/mfd/wm8350-i2c.c | 24 +-----------------------
> drivers/mfd/wm8400-core.c | 18 +++---------------
> include/linux/mfd/wm831x/core.h | 1 -
> include/linux/mfd/wm8350/core.h | 1 -
> 20 files changed, 41 insertions(+), 332 deletions(-)
>
--
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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