linux-kernel - Re: [PATCH 0/8] DEV_PM

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Date:   Wed, 5 Jan 2022 10:17:37 +0000
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Paul Cercueil <paul@...pouillou.net>
CC:     "Rafael J . Wysocki" <rafael@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Jonathan Cameron <jic23@...nel.org>,
        "Lars-Peter Clausen" <lars@...afoo.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        "Arnd Bergmann" <arnd@...db.de>, Len Brown <len.brown@...el.com>,
        Pavel Machek <pavel@....cz>, <list@...ndingux.net>,
        <linux-iio@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-mips@...r.kernel.org>, <linux-mmc@...r.kernel.org>,
        <linux-pm@...r.kernel.org>
Subject: Re: [PATCH 0/8] DEV_PM_OPS macros rework

On Tue, 4 Jan 2022 21:42:06 +0000
Paul Cercueil <paul@...pouillou.net> wrote:

> Hi,
> 
> This set of commits rework a bit the *_DEV_PM_OPS() macros that were
> introduced recently.
> 
> - Remove the DEFINE_UNIVERSAL_DEV_PM_OPS() macro, since I highly doubt
>   anything is going to use it. The macro it replaces
>   (UNIVERSAL_DEV_PM_OPS) seems to only be used incorrectly in code that
>   hasn't been updated in ages.
> 
> - Remove the static qualifier in DEFINE_SIMPLE_DEV_PM_OPS, so that the
>   macro is more in line with what's done elsewhere in the kernel.
> 
> - Add a DEFINE_RUNTIME_DEV_PM_OPS() macro, for use with drivers that use
>   runtime PM, and use runtime_pm_force_suspend/runtime_pm_force_resume
>   as their system sleep callbacks.
> 
> - Add EXPORT_*_DEV_PM_OPS macros, which can be used for when the
>   underlying dev_pm_ops is to be exported. With CONFIG_PM set, the
>   symbol is exported as you would expect. With CONFIG_PM disabled, the
>   dev_pm_ops is garbage-collected along with the suspend/resume
>   callbacks.
> 
> - Update the two places which used DEFINE_SIMPLE_DEV_PM_OPS, to add back
>   the "static" qualifier that was stripped from the macro.
> 
> - Update one driver to use EXPORT_RUNTIME_DEV_PM_OPS(), just to showcase
>   how to use this macro in the case where a dev_pm_ops is to be
>   exported.
>   Note that the driver itself is GPL, and the symbol is only used within
>   a GPL driver, so I would assume the symbol would be exported as GPL.
>   But it was not the case in the original code, so I did not change the
>   behaviour.
> 
> Feedback welcome.

Comments on individual patches (in particular bad pick for that final example ;)

Given how late we are in the cycle, I'd argue we 'need' patches 2 (+ 5,6 which
should probably be all one patch to avoid introducing then fixing a warning in
different patches).  The others could wait for the following cycle if needed.

It would slow down a few patches I have queued up behind this, but most of them
would be unaffected so it wouldn't annoy me too much. Can't speak for others
however!

Jonathan

> 
> Cheers,
> -Paul
> 
> 
> Paul Cercueil (8):
>   PM: core: Remove DEFINE_UNIVERSAL_DEV_PM_OPS() macro
>   PM: core: Remove static qualifier in DEFINE_SIMPLE_DEV_PM_OPS macro
>   PM: core: Add EXPORT[_GPL]_SIMPLE_DEV_PM_OPS macros
>   PM: runtime: Add DEFINE_RUNTIME_DEV_PM_OPS() macro
>   PM: runtime: Add EXPORT[_GPL]_RUNTIME_DEV_PM_OPS macros
>   mmc: mxc: Make dev_pm_ops struct static
>   mmc: jz4740: Make dev_pm_ops struct static
>   iio: gyro: mpu3050: Use new PM macros
> 
>  drivers/iio/gyro/mpu3050-core.c | 13 +++-----
>  drivers/iio/gyro/mpu3050-i2c.c  |  2 +-
>  drivers/mmc/host/jz4740_mmc.c   |  4 +--
>  drivers/mmc/host/mxcmmc.c       |  2 +-
>  include/linux/pm.h              | 53 +++++++++++++++++++++++----------
>  include/linux/pm_runtime.h      | 21 +++++++++++++
>  6 files changed, 67 insertions(+), 28 deletions(-)
>