linux-kernel - Re: [PATCH v2] ahci: st: Switch from CONFIG_PM_SLEEP guards to pm_sleep

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Message-ID: <cfecaa65-f6bc-48c1-9295-9bfe18f13db3@kernel.org>
Date: Fri, 10 Jan 2025 21:02:50 +0900
From: Damien Le Moal <dlemoal@...nel.org>
To: Niklas Cassel <cassel@...nel.org>
Cc: Raphael Gallais-Pou <rgallaispou@...il.com>,
 Patrice Chotard <patrice.chotard@...s.st.com>,
 linux-arm-kernel@...ts.infradead.org, linux-ide@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] ahci: st: Switch from CONFIG_PM_SLEEP guards to
 pm_sleep_ptr()

On 1/10/25 20:23, Niklas Cassel wrote:
>>> -#ifdef CONFIG_PM_SLEEP
>>>  static int st_ahci_suspend(struct device *dev)
>>>  {
>>>  	struct ata_host *host = dev_get_drvdata(dev);
>>> @@ -221,9 +220,8 @@ static int st_ahci_resume(struct device *dev)
>>>  
>>>  	return ahci_platform_resume_host(dev);
>>>  }
>>> -#endif
>>
>> I do not think you can remove the ifdef here. Otherwise, there is going to be a
>> compilation warning when CONFIG_PM_SLEEP is not enabled. No ?
> 
> Look at the pm_sleep_ptr macro:
> include/linux/pm.h:#define pm_sleep_ptr(_ptr) PTR_IF(IS_ENABLED(CONFIG_PM_SLEEP), (_ptr))
> 
> I would expect the function should be optimized out by the compiler
> using dead code elimination.

Indeed. Just tried and no warning. I was expecting a "defined but not used"
warning, but none showed up. So all good.

> Raphael, perhaps you could show the before and after output
> using ./scripts/bloat-o-meter ?
> (When the config is not enabled: before and after your patch.)

No need to do that I guess. But there are 17 other ata driver that set .pm
operations. What about these ? Don't they need the same treatment as ahci_st ?
15 of these also use SIMPLE_DEV_PM_OPS() which can be replaced with
DEFINE_SIMPLE_DEV_PM_OPS() also, no ?

Do you want us to do that cleanup ? (fine with me).

-- 
Damien Le Moal
Western Digital Research