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

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Message-ID: <CAPDyKFpUUPzqonNBrFq68h8QOVxardvf2q7AuEQVeUJ-S2726A@mail.gmail.com>
Date:   Fri, 7 Jan 2022 17:33:04 +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 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?

The similar comment/question applies for patch5.

>
> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> Acked-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>

Kind regards
Uffe

> ---
>
> Notes:
>     v2: Remove useless empty line
>
>  include/linux/pm.h | 32 +++++++++++++++++++++++++++++---
>  1 file changed, 29 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/pm.h b/include/linux/pm.h
> index 389e600df233..b82f40e701ab 100644
> --- a/include/linux/pm.h
> +++ b/include/linux/pm.h
> @@ -8,6 +8,7 @@
>  #ifndef _LINUX_PM_H
>  #define _LINUX_PM_H
>
> +#include <linux/export.h>
>  #include <linux/list.h>
>  #include <linux/workqueue.h>
>  #include <linux/spinlock.h>
> @@ -357,14 +358,39 @@ struct dev_pm_ops {
>  #define SET_RUNTIME_PM_OPS(suspend_fn, resume_fn, idle_fn)
>  #endif
>
> +#define _DEFINE_DEV_PM_OPS(name, \
> +                          suspend_fn, resume_fn, \
> +                          runtime_suspend_fn, runtime_resume_fn, idle_fn) \
> +const struct dev_pm_ops name = { \
> +       SYSTEM_SLEEP_PM_OPS(suspend_fn, resume_fn) \
> +       RUNTIME_PM_OPS(runtime_suspend_fn, runtime_resume_fn, idle_fn) \
> +}
> +
>  /*
>   * Use this if you want to use the same suspend and resume callbacks for suspend
>   * to RAM and hibernation.
>   */
>  #define DEFINE_SIMPLE_DEV_PM_OPS(name, suspend_fn, resume_fn) \
> -const struct dev_pm_ops name = { \
> -       SYSTEM_SLEEP_PM_OPS(suspend_fn, resume_fn) \
> -}
> +       _DEFINE_DEV_PM_OPS(name, suspend_fn, resume_fn, NULL, NULL, NULL)
> +
> +#ifdef CONFIG_PM
> +#define _EXPORT_DEV_PM_OPS(name, suspend_fn, resume_fn, runtime_suspend_fn, \
> +                          runtime_resume_fn, idle_fn, sec) \
> +       _DEFINE_DEV_PM_OPS(name, suspend_fn, resume_fn, runtime_suspend_fn, \
> +                          runtime_resume_fn, idle_fn); \
> +       _EXPORT_SYMBOL(name, sec)
> +#else
> +#define _EXPORT_DEV_PM_OPS(name, suspend_fn, resume_fn, runtime_suspend_fn, \
> +                          runtime_resume_fn, idle_fn, sec) \
> +static __maybe_unused _DEFINE_DEV_PM_OPS(__static_##name, suspend_fn, \
> +                                        resume_fn, runtime_suspend_fn, \
> +                                        runtime_resume_fn, idle_fn)
> +#endif
> +
> +#define EXPORT_SIMPLE_DEV_PM_OPS(name, suspend_fn, resume_fn) \
> +       _EXPORT_DEV_PM_OPS(name, suspend_fn, resume_fn, NULL, NULL, NULL, "")
> +#define EXPORT_GPL_SIMPLE_DEV_PM_OPS(name, suspend_fn, resume_fn) \
> +       _EXPORT_DEV_PM_OPS(name, suspend_fn, resume_fn, NULL, NULL, NULL, "_gpl")
>
>  /* Deprecated. Use DEFINE_SIMPLE_DEV_PM_OPS() instead. */
>  #define SIMPLE_DEV_PM_OPS(name, suspend_fn, resume_fn) \
> --
> 2.34.1
>