linux-kernel - Re: [PATCH 1/2] PM / clk: Add stubs for pm_clk

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Date:	Tue, 08 Mar 2016 23:58:23 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Jon Hunter <jonathanh@...dia.com>
Cc:	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-tegra@...r.kernel.org
Subject: Re: [PATCH 1/2] PM / clk: Add stubs for pm_clk_suspend/resume

On Tuesday, March 08, 2016 05:18:06 PM Jon Hunter wrote:
> 
> On 04/03/16 15:33, Jon Hunter wrote:
> > The functions pm_clk_suspend() and pm_clk_resume() cannot be used
> > directly within the main body of a function, because when CONFIG_PM_CLK
> > is not defined the functions are defined as NULL and this will lead to
> > a compilation error.
> > 
> > Add stubs functions for pm_clk_suspend() and pm_clk_resume() so that
> > these functions may be called directly.
> > 
> > Please note that these functions are currently assigned to function
> > pointers in the PM domain core and so to avoid have a valid function
> > pointer defined when CONFIG_PM_CLK is not defined, define
> > GENPD_FLAG_PM_CLK as 0 when CONFIG_PM_CLK is not defined to ensure
> > the stubs are not populated as valid function pointers.
> > 
> > Signed-off-by: Jon Hunter <jonathanh@...dia.com>
> > ---
> >  include/linux/pm_clock.h  | 10 ++++++++--
> >  include/linux/pm_domain.h |  4 ++++
> >  2 files changed, 12 insertions(+), 2 deletions(-)
> > 
> > diff --git a/include/linux/pm_clock.h b/include/linux/pm_clock.h
> > index 25266c600021..ffefbf2df1aa 100644
> > --- a/include/linux/pm_clock.h
> > +++ b/include/linux/pm_clock.h
> > @@ -72,8 +72,14 @@ static inline int pm_clk_add_clk(struct device *dev, struct clk *clk)
> >  static inline void pm_clk_remove(struct device *dev, const char *con_id)
> >  {
> >  }
> > -#define pm_clk_suspend	NULL
> > -#define pm_clk_resume	NULL
> > +static inline int pm_clk_suspend(struct device *dev)
> > +{
> > +	return -EINVAL;
> > +}
> > +static inline int pm_clk_resume(struct device *dev)
> > +{
> > +	return -EINVAL;
> > +}
> >  #endif
> >  
> >  #ifdef CONFIG_HAVE_CLK
> > diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
> > index 49cd8890b873..1074c2073df8 100644
> > --- a/include/linux/pm_domain.h
> > +++ b/include/linux/pm_domain.h
> > @@ -17,7 +17,11 @@
> >  #include <linux/notifier.h>
> >  
> >  /* Defines used for the flags field in the struct generic_pm_domain */
> > +#ifdef CONFIG_PM_CLK
> >  #define GENPD_FLAG_PM_CLK	(1U << 0) /* PM domain uses PM clk */
> > +#else
> > +#define GENPD_FLAG_PM_CLK	0
> > +#endif
> >  
> >  #define GENPD_MAX_NUM_STATES	8 /* Number of possible low power states */
> 
> Thinking about this some more, the alternative is for drivers using
> PM_CLK to select it. Would that be appropriate? If so, we would not need
> these stubs.

Well, I don't see why it might not be appropriate.

Thanks,
Rafael