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Message-ID: <20181205180843.GD23156@windriver.com>
Date: Wed, 5 Dec 2018 13:08:43 -0500
From: Paul Gortmaker <paul.gortmaker@...driver.com>
To: Steve Twiss <stwiss.opensource@...semi.com>
CC: Lee Jones <lee.jones@...aro.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Arnd Bergmann <arnd@...db.de>,
Cory Maccarrone <darkstar6262@...il.com>,
David Dajun Chen <david.chen@...semi.com>,
Dong Aisheng <dong.aisheng@...aro.org>,
Eric Miao <eric.miao@...vell.com>,
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>,
Mike Rapoport <mike@...pulab.co.il>,
Tony Lindgren <tony@...mide.com>,
Venu Byravarasu <vbyravarasu@...dia.com>,
"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
"patches@...nsource.cirrus.com" <patches@...nsource.cirrus.com>,
Support Opensource <Support.Opensource@...semi.com>
Subject: Re: [PATCH v2 00/22] mfd: demodularization of non-modular drivers
[RE: [PATCH v2 00/22] mfd: demodularization of non-modular drivers] On 05/12/2018 (Wed 12:01) Steve Twiss wrote:
> Hi Paul,
>
> On 03 December 2018 04:23, Paul Gortmaker wrote:
>
> > Subject: [PATCH v2 00/22] mfd: demodularization of non-modular drivers
> >
> > [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.
>
> For the DA9052 and DA9055, changes:
>
> - drivers/mfd/da9052-core.c | 11 -----------
> - drivers/mfd/da9052-i2c.c | 22 ++-------------------
> - drivers/mfd/da9052-irq.c | 1 -
> - drivers/mfd/da9052-spi.c | 22 ++-------------------
> - drivers/mfd/da9055-core.c | 13 ++-----------
> - drivers/mfd/da9055-i2c.c | 24 ++---------------------
>
> The responsibility can fall back to Dialog for these changes. We will
> submit Kconfig patches for these and make them explicitly non-modular.
> This will remove the ambiguity caused by the Kconfig bool options.
[typo noted: non-modular ---> modular]
Great, I'll look forward to seeing those patches to convert these
drivers to modular in the near future, and I'll not re-send mine.
Thanks,
P.
--
>
> Regards,
> Steve
>
> > 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: Arnd Bergmann <arnd@...db.de>
> > Cc: Cory Maccarrone <darkstar6262@...il.com>
> > Cc: David Dajun Chen <dchen@...semi.com>
> > Cc: Dong Aisheng <dong.aisheng@...aro.org>
> > Cc: Eric Miao <eric.miao@...vell.com>
> > 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: Mike Rapoport <mike@...pulab.co.il>
> > Cc: Tony Lindgren <tony@...mide.com>
> > Cc: Venu Byravarasu <vbyravarasu@...dia.com>
> > Cc: linux-omap@...r.kernel.org
> > Cc: patches@...nsource.cirrus.com
> > Cc: Support Opensource <support.opensource@...semi.com>
> >
> >
> > Paul Gortmaker (22):
> > mfd: aat2870-core: Make it explicitly non-modular
> > mfd: adp5520: Make it explicitly non-modular
> > mfd: as3711: Make it explicitly non-modular
> > mfd: da903x: Make it explicitly non-modular
> > mfd: da9052-*: Make it explicitly non-modular
> > mfd: da9055-i2c: Make it explicitly non-modular
> > mfd: da9055-core: 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_ tags from non-modular code
> > mfd: wm8350-i2c: Make it explicitly non-modular
> > mfd: wm8350-core: drop unused MODULE_ tags 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/da903x.c | 26 +++----------------------
> > drivers/mfd/da9052-core.c | 11 -----------
> > drivers/mfd/da9052-i2c.c | 22 ++-------------------
> > drivers/mfd/da9052-irq.c | 1 -
> > drivers/mfd/da9052-spi.c | 22 ++-------------------
> > drivers/mfd/da9055-core.c | 13 ++-----------
> > drivers/mfd/da9055-i2c.c | 24 ++---------------------
> > 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 | 7 ++-----
> > drivers/mfd/wm831x-i2c.c | 20 ++------------------
> > drivers/mfd/wm831x-spi.c | 24 ++---------------------
> > drivers/mfd/wm8350-core.c | 6 ++----
> > drivers/mfd/wm8350-i2c.c | 24 +----------------------
> > drivers/mfd/wm8400-core.c | 18 +++---------------
> > include/linux/mfd/da9052/da9052.h | 1 -
> > 26 files changed, 52 insertions(+), 407 deletions(-)
> >
> > --
> > 2.7.4
>
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