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

[Paul Cercueil]

Hi Richard,

Le lun., août 8 2022 at 10:53:54 +0100, Richard Fitzgerald 
<rf@xxxxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxx>
> > Cc: patches@xxxxxxxxxxxxxxxxxxxxx
> > ---
> >   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),
> >   	},