linux-kernel - Re: [PATCH v1] PM: Discard runtime_xx() handles using pm

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Message-ID: <04b87029f2237e209d8c8b620d009692d80eea2f.camel@crapouillou.net>
Date: Thu, 20 Feb 2025 13:15:19 +0100
From: Paul Cercueil <paul@...pouillou.net>
To: Raag Jadav <raag.jadav@...el.com>, rafael@...nel.org, 
	andriy.shevchenko@...ux.intel.com
Cc: linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] PM: Discard runtime_xx() handles using pm_ptr()

Hi Raag,

Le jeudi 20 février 2025 à 13:33 +0530, Raag Jadav a écrit :
> Discard runtime_xx() handles in RUNTIME_PM_OPS() using pm_ptr() macro
> and drop unnecessary CONFIG_PM ifdeffery.

So the RUNTIME_PM_OPS() is newer and people should use that, but we're
not yet at the point where the older SET_RUNTIME_PM_OPS() macro can be
dropped.

The difference is that in the !CONFIG_PM case, the former will
reference the suspend/resume functions, but they will be detected as
dead code; on the other hand, the latter macro won't reference them at
all. Many drivers still wrap their suspend/resume functions in a #ifdef
CONFIG_PM to avoid warnings about unused static functions. Therefore if
you unconditionally force the use of the first macro everywhere, many
drivers will fail to compile in the !CONFIG_PM case.

As for adding pm_ptr() inside RUNTIME_PM_OPS(), it is unnecesary, as
the whole pm_ops struct should be referenced through pm_ptr() or
pm_sleep_ptr() anyway, which means that the whole struct and the
callback functions will be garbage-collected if PM is disabled.

Cheers,
-Paul

> Signed-off-by: Raag Jadav <raag.jadav@...el.com>
> ---
> PS: I'm not very confident about this but thought I'd give it a try.
> 
>  include/linux/pm.h | 10 +++-------
>  1 file changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/include/linux/pm.h b/include/linux/pm.h
> index 78855d794342..416561c60e81 100644
> --- a/include/linux/pm.h
> +++ b/include/linux/pm.h
> @@ -334,9 +334,9 @@ struct dev_pm_ops {
>  	.restore_noirq = pm_sleep_ptr(resume_fn),
>  
>  #define RUNTIME_PM_OPS(suspend_fn, resume_fn, idle_fn) \
> -	.runtime_suspend = suspend_fn, \
> -	.runtime_resume = resume_fn, \
> -	.runtime_idle = idle_fn,
> +	.runtime_suspend = pm_ptr(suspend_fn), \
> +	.runtime_resume = pm_ptr(resume_fn), \
> +	.runtime_idle = pm_ptr(idle_fn),
>  
>  #ifdef CONFIG_PM_SLEEP
>  #define SET_SYSTEM_SLEEP_PM_OPS(suspend_fn, resume_fn) \
> @@ -359,12 +359,8 @@ struct dev_pm_ops {
>  #define SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(suspend_fn, resume_fn)
>  #endif
>  
> -#ifdef CONFIG_PM
>  #define SET_RUNTIME_PM_OPS(suspend_fn, resume_fn, idle_fn) \
>  	RUNTIME_PM_OPS(suspend_fn, resume_fn, idle_fn)
> -#else
> -#define SET_RUNTIME_PM_OPS(suspend_fn, resume_fn, idle_fn)
> -#endif
>  
>  #define _DEFINE_DEV_PM_OPS(name, \
>  			   suspend_fn, resume_fn, \