linux-kernel - Re: [PATCH 20/28] mfd: arizona: Remove #ifdef guards for PM related functions

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Date:   Mon, 08 Aug 2022 12:06:29 +0200
From:   Paul Cercueil <paul@...pouillou.net>
To:     Richard Fitzgerald <rf@...nsource.cirrus.com>
Cc:     Lee Jones <lee.jones@...aro.org>, linux-kernel@...r.kernel.org,
        patches@...nsource.cirrus.com
Subject: Re: [PATCH 20/28] mfd: arizona: Remove #ifdef guards for PM related
 functions

Hi Richard,

Le lun., août 8 2022 at 10:53:54 +0100, Richard Fitzgerald 
<rf@...nsource.cirrus.com> a écrit :
> On 07/08/2022 15:52, Paul Cercueil wrote:
>> Only export the arizona_pm_ops if CONFIG_PM is set, but leave the
>> suspend/resume functions (and related code) outside #ifdef guards.
>> 
>> If CONFIG_PM is not set, the arizona_pm_ops will be defined as
>> "static __maybe_unused", and the structure plus all the callbacks 
>> will
>> be automatically dropped by the compiler.
>> 
>> The advantage is then that these functions are now always compiled
>> independently of any Kconfig option, and thanks to that bugs and
>> regressions are easier to catch.
>> 
>> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
>> Cc: patches@...nsource.cirrus.com
>> ---
>>   drivers/mfd/arizona-core.c | 21 +++++++++++----------
>>   drivers/mfd/arizona-i2c.c  |  2 +-
>>   drivers/mfd/arizona-spi.c  |  2 +-
>>   3 files changed, 13 insertions(+), 12 deletions(-)
>> 
>> diff --git a/drivers/mfd/arizona-core.c b/drivers/mfd/arizona-core.c
>> index cbf1dd90b70d..c1acc9521f83 100644
>> --- a/drivers/mfd/arizona-core.c
>> +++ b/drivers/mfd/arizona-core.c
>> @@ -480,7 +480,6 @@ static int wm5102_clear_write_sequencer(struct 
>> arizona *arizona)
>>   	return 0;
>>   }
>>   -#ifdef CONFIG_PM
>>   static int arizona_isolate_dcvdd(struct arizona *arizona)
> 
> __maybe_unused?

No need. The symbols are always referenced.

>>   {
>>   	int ret;
>> @@ -742,9 +741,7 @@ static int arizona_runtime_suspend(struct device 
>> *dev)
> 
> __maybe_unused?
> 
>>     	return 0;
>>   }
>> -#endif
>>   -#ifdef CONFIG_PM_SLEEP
>>   static int arizona_suspend(struct device *dev)
> 
> __maybe_unused?
> 
>>   {
>>   	struct arizona *arizona = dev_get_drvdata(dev);
>> @@ -784,17 +781,21 @@ static int arizona_resume(struct device *dev)
> 
> __maybe_unused?
> 
>>     	return 0;
>>   }
>> -#endif
>>   +#ifndef CONFIG_PM
>> +static __maybe_unused
>> +#endif
> 
> No need to ifdef a __maybe_unused.

Yes, it is needed, because the symbol is conditionally exported. If 
!CONFIG_PM, we want the compiler to discard the dev_pm_ops and all the 
callbacks, hence the "static __maybe_unused". That's the same trick 
used in _EXPORT_DEV_PM_OPS().

(note that this patch is broken as it does not change the struct name, 
in the !PM case, which causes conflicts with the .h. I'll fix in v2)

>>   const struct dev_pm_ops arizona_pm_ops = {
>> -	SET_RUNTIME_PM_OPS(arizona_runtime_suspend,
>> -			   arizona_runtime_resume,
>> -			   NULL)
>> -	SET_SYSTEM_SLEEP_PM_OPS(arizona_suspend, arizona_resume)
>> -	SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(arizona_suspend_noirq,
>> -				      arizona_resume_noirq)
>> +	RUNTIME_PM_OPS(arizona_runtime_suspend,
>> +		       arizona_runtime_resume,
>> +		       NULL)
>> +	SYSTEM_SLEEP_PM_OPS(arizona_suspend, arizona_resume)
>> +	NOIRQ_SYSTEM_SLEEP_PM_OPS(arizona_suspend_noirq,
>> +				  arizona_resume_noirq)
>>   };
>> +#ifdef CONFIG_PM
>>   EXPORT_SYMBOL_GPL(arizona_pm_ops);
>> +#endif
> 
> This ifdeffing is ugly. Why must the structure only be exported if
> CONFIG_PM is set?

So that all the PM code is garbage-collected by the compiler if 
!CONFIG_PM.

Ideally I would use something like EXPORT_SIMPLE_DEV_PM_OPS() which 
would make the patch much cleaner, but it doesn't support noirq 
callbacks - and that's why I suggested in the cover letter that maybe a 
new PM macro can be added if this patch is deemed too messy.

Cheers,
-Paul

>>     #ifdef CONFIG_OF
>>   static int arizona_of_get_core_pdata(struct arizona *arizona)
>> diff --git a/drivers/mfd/arizona-i2c.c b/drivers/mfd/arizona-i2c.c
>> index 6d83e6b9a692..8799d9183bee 100644
>> --- a/drivers/mfd/arizona-i2c.c
>> +++ b/drivers/mfd/arizona-i2c.c
>> @@ -119,7 +119,7 @@ static const struct of_device_id 
>> arizona_i2c_of_match[] = {
>>   static struct i2c_driver arizona_i2c_driver = {
>>   	.driver = {
>>   		.name	= "arizona",
>> -		.pm	= &arizona_pm_ops,
>> +		.pm	= pm_ptr(&arizona_pm_ops),
>>   		.of_match_table	= of_match_ptr(arizona_i2c_of_match),
>>   	},
>>   	.probe		= arizona_i2c_probe,
>> diff --git a/drivers/mfd/arizona-spi.c b/drivers/mfd/arizona-spi.c
>> index 941b0267d09d..da05b966d48c 100644
>> --- a/drivers/mfd/arizona-spi.c
>> +++ b/drivers/mfd/arizona-spi.c
>> @@ -282,7 +282,7 @@ static const struct of_device_id 
>> arizona_spi_of_match[] = {
>>   static struct spi_driver arizona_spi_driver = {
>>   	.driver = {
>>   		.name	= "arizona",
>> -		.pm	= &arizona_pm_ops,
>> +		.pm	= pm_ptr(&arizona_pm_ops),
>>   		.of_match_table	= of_match_ptr(arizona_spi_of_match),
>>   		.acpi_match_table = ACPI_PTR(arizona_acpi_match),
>>   	},