linux-kernel - Re: [PATCH] PM: Add EXPORT macros for exporting PM functions

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Date:   Mon, 13 Feb 2023 16:43:56 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Richard Fitzgerald <rf@...nsource.cirrus.com>
Cc:     rafael@...nel.org, pavel@....cz, len.brown@...el.com,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        patches@...nsource.cirrus.com
Subject: Re: [PATCH] PM: Add EXPORT macros for exporting PM functions

On Mon, Feb 13, 2023 at 2:20 PM Richard Fitzgerald
<rf@...nsource.cirrus.com> wrote:
>
> Add a set of macros for exporting functions only if CONFIG_PM
> is enabled.
>
> The naming follows the style of the standard EXPORT_SYMBOL_*()
> macros that they replace.
>
> Sometimes a module wants to export PM functions directly to other
> drivers, not a complete struct dev_pm_ops. A typical example is
> where a core library exports the generic (shared) implementation
> and calling code wraps one or more of these in custom code.
>
> Signed-off-by: Richard Fitzgerald <rf@...nsource.cirrus.com>
> ---
>  include/linux/pm.h | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/include/linux/pm.h b/include/linux/pm.h
> index 93cd34f00822..21618f7087f8 100644
> --- a/include/linux/pm.h
> +++ b/include/linux/pm.h
> @@ -379,9 +379,17 @@ const struct dev_pm_ops name = { \
>         const struct dev_pm_ops name;                                   \
>         __EXPORT_SYMBOL(name, sec, ns);                                 \
>         const struct dev_pm_ops name
> +#define EXPORT_PM_FN(name)             EXPORT_SYMBOL(name)
> +#define EXPORT_PM_FN_GPL(name)         EXPORT_SYMBOL_GPL(name)
> +#define EXPORT_PM_FN_NS(name, ns)      EXPORT_SYMBOL_NS(name, ns)
> +#define EXPORT_PM_FN_NS_GPL(name, ns)  EXPORT_SYMBOL_NS_GPL(name, ns)

Why are the non-GPL variants needed?

>  #else
>  #define _EXPORT_DEV_PM_OPS(name, sec, ns)                              \
>         static __maybe_unused const struct dev_pm_ops __static_##name
> +#define EXPORT_PM_FN(name)
> +#define EXPORT_PM_FN_GPL(name)
> +#define EXPORT_PM_FN_NS(name, ns)
> +#define EXPORT_PM_FN_NS_GPL(name, ns)
>  #endif
>
>  #define EXPORT_DEV_PM_OPS(name) _EXPORT_DEV_PM_OPS(name, "", "")
> --
> 2.30.2
>