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

[Richard Fitzgerald]

On 08/08/2022 11:06, Paul Cercueil wrote:
> 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

Why conditionally export it?

> !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.

The functions will be dropped if they are not referenced. That doesn't
answer why the struct must not be exported.

What is the aim of omitting the struct export?

> 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),
> > >       },