Re: [PATCH -next] misc: rtsx: fix build for CONFIG_PM not set

[Paul Cercueil]

Hi Jonathan,

Le dim., mars 6 2022 at 15:12:12 +0000, Jonathan Cameron 
<Jonathan.Cameron@xxxxxxxxxx> a écrit :
> On Sun, 27 Feb 2022 17:56:31 +0000
> Paul Cercueil <paul@xxxxxxxxxxxxxxx> wrote:
>
> >  Le dim., févr. 27 2022 at 18:51:38 +0100, Arnd Bergmann
> >  <arnd@xxxxxxxx> a écrit :
> >  > On Sun, Feb 27, 2022 at 6:46 PM Paul Cercueil 
> > <paul@xxxxxxxxxxxxxxx>
> >  > wrote:
> >  >>  Le dim., févr. 27 2022 at 18:30:16 +0100, Arnd Bergmann
> >  >>
> >  >>  There could be a DEFINE_DEV_PM_OPS(), but I don't think that's
> >  >> really
> >  >>  needed - you can very well declare your struct dev_pm_ops 
> > without
> >  >> using
> >  >>  one of these macros. Just make sure to use the 
> > SYSTEM_SLEEP_PM_OPS /
> >  >>  RUNTIME_PM_OPS macros for the callbacks and pm_ptr() for the
> >  >> device.pm
> >  >>  pointer.
> >  >
> >  > Ah, of course, so it comes down to
> >  > s/SET_SYSTEM_SLEEP_PM_OPS/SYSTEM_SLEEP_PM_OPS/ while
> >  > removing all the #ifdef an __maybe_unused annotations. The 
> > pm_ptr()
> >  > in driver.pm makes this slightly more optimized AFAICT, but has no
> >  > effect on behavior, right?
> >
> >  The use of SYSTEM_SLEEP_PM_OPS makes sure that the callbacks are
> >  dropped if the dev_pm_ops is dead code, and the pm_ptr() must be 
> > used
> >  for the compiler to know that the dev_pm_ops is dead code.
> >
> >  -Paul
>
> Hi Paul,
>
> We have one remaining case which is still ugly to do.
> Where both SYSTEM_SLEEP_PM_OPS/RUNTIME_PM_OPS are set and
> the dev_pm_ops structure is exported.
>
> For that one we still need to expose #ifdef fun in the
> drivers I think.
>
> Any suggestions on a clean solution for that?

Use the _EXPORT_DEV_PM_OPS() macro?

If you make it call __EXPORT_SYMBOL() (with two underscores instead of 
one) you can specify the namespace as well. All you need then is a nice 
wrapper macro in pm_runtime.h, that can be used in the driver.

Cheers,
-Paul

> Currently I have this...
>
> #ifdef CONFIG_PM
> const struct dev_pm_ops bmc150_magn_pm_ops = {
> 	SYSTEM_SLEEP_PM_OPS(...)
> 	RUNTIME_PM_OPS(...)
> };
> EXPORT_SYMBOL_NS(bmc150_magn_pm_ops, IIO_BMC150_MAGN);
> #else
> static const __maybe_unused dev_pm_ops bmc150_magn_pm_ops = {
> 	SYSTEM_SLEEP_PM_OPS(...)
> 	RUNTIME_PM_OPS(...)
> };
> #endif
> Not super clean but perhaps we do need
> EXPORT_NS_DEV_PM_OPS
> EXPORT_NS_GPL_DEV_PM_OPS
> and potentially the non namespaced versions.
>
> Thanks,
>
> Jonathan