linux-kernel - Re: [PATCH v2 3/6] PM: core: Add EXPORT[_GPL]_SIMPLE_DEV_PM

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Date:   Fri, 7 Jan 2022 18:11:34 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     "Rafael J . Wysocki" <rafael@...nel.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,
        Jonathan Cameron <jonathan.cameron@...wei.com>
Subject: Re: [PATCH v2 3/6] PM: core: Add EXPORT[_GPL]_SIMPLE_DEV_PM_OPS macros

On Fri, 7 Jan 2022 at 17:43, Paul Cercueil <paul@...pouillou.net> wrote:
>
>
>
> Le ven., janv. 7 2022 at 17:33:04 +0100, Ulf Hansson
> <ulf.hansson@...aro.org> a écrit :
> > On Wed, 5 Jan 2022 at 19:30, Paul Cercueil <paul@...pouillou.net>
> > wrote:
> >>
> >>  These macros are defined conditionally, according to CONFIG_PM:
> >>  - if CONFIG_PM is enabled, these macros resolve to
> >>    DEFINE_SIMPLE_DEV_PM_OPS(), and the dev_pm_ops symbol will be
> >>    exported.
> >>
> >>  - if CONFIG_PM is disabled, these macros will result in a dummy
> >> static
> >>    dev_pm_ops to be created with the __maybe_unused flag. The
> >> dev_pm_ops
> >>    will then be discarded by the compiler, along with the provided
> >>    callback functions if they are not used anywhere else.
> >>
> >>  In the second case, the symbol is not exported, which should be
> >>  perfectly fine - users of the symbol should all use the pm_ptr() or
> >>  pm_sleep_ptr() macro, so the dev_pm_ops marked as "extern" in the
> >>  client's code will never be accessed.
> >
> > How common is it to export the dev_pm_ops? Do we really need a macro
> > for this?
>
> $ rgrep EXPORT_SYMBOL drivers/ |grep pm_ops |wc -l
> 44
>
> That should be enough to justify a macro.

Yep, certainly! I will take a closer look beginning next week.

[...]

Kind regards
Uffe