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From:   "zhuguangqing83" <zhuguangqing83@gmail.com>
To:     "'Rafael J. Wysocki'" <rafael@kernel.org>
Cc:     "'Rafael J. Wysocki'" <rjw@rjwysocki.net>,
        "'Daniel Lezcano'" <daniel.lezcano@linaro.org>,
        "'Linux PM'" <linux-pm@vger.kernel.org>,
        "'Linux Kernel Mailing List'" <linux-kernel@vger.kernel.org>,
        "'zhuguangqing'" <zhuguangqing@xiaomi.com>
Subject: Re: [PATCH] cpuidle: change #ifdef for the declaration of cpuidle_enter_s2idle()
Date:   Sat, 26 Sep 2020 09:30:06 +0800
Message-ID: <00d901d693a4$93195980$b94c0c80$@gmail.com>
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> On Thu, Sep 24, 2020 at 10:01 AM <zhuguangqing83@gmail.com> wrote:
> >
> > From: zhuguangqing <zhuguangqing@xiaomi.com>
> >
> > Currently, if CONFIG_SUSPEND=n and CONFIG_CPU_IDLE=y, the function
> > cpuidle_enter_s2idle() is declared but not defined, it may cause error
> > when cpuidle_enter_s2idle() is called.
> >
> > If CONFIG_SUSPEND=y and CONFIG_CPU_IDLE=n, the function
> > cpuidle_enter_s2idle() is defined as "return -ENODEV;" which is not
> > supposed to be.
> >
> > Change #ifdef CONFIG_CPU_IDLE to #ifdef CONFIG_SUSPEND for
> > cpuidle_enter_s2idle() in cpuidle.h, which is consistent with its
> > defination in cpuidle.c.
> 
> Well, what about the case when CONFIG_SUSPEND is set, but CONFIG_CPU_IDLE
> isn't?
> 

When CONFIG_SUSPEND is set, but CONFIG_CPU_IDLE isn't, the function
cpuidle_enter_s2idle() is defined in cpuidle.c, but the defination in
cpuidle.c is not used actually because CONFIG_CPU_IDLE isn't set, we
only use its defination as "return -ENODEV;" in cpuidle.h.

> >
> > Signed-off-by: zhuguangqing <zhuguangqing@xiaomi.com>
> > ---
> >  include/linux/cpuidle.h | 14 +++++++++-----
> >  1 file changed, 9 insertions(+), 5 deletions(-)
> >
> > diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
> > index 6175c77bf25e..2aa8cead1727 100644
> > --- a/include/linux/cpuidle.h
> > +++ b/include/linux/cpuidle.h
> > @@ -216,22 +216,26 @@ static inline struct cpuidle_device
> *cpuidle_get_device(void) {return NULL; }
> >  extern int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
> >                                       struct cpuidle_device *dev,
> >                                       u64 latency_limit_ns);
> > -extern int cpuidle_enter_s2idle(struct cpuidle_driver *drv,
> > -                               struct cpuidle_device *dev);
> >  extern void cpuidle_use_deepest_state(u64 latency_limit_ns);
> >  #else
> >  static inline int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
> >                                              struct cpuidle_device *dev,
> >                                              u64 latency_limit_ns)
> >  {return -ENODEV; }
> > -static inline int cpuidle_enter_s2idle(struct cpuidle_driver *drv,
> > -                                      struct cpuidle_device *dev)
> > -{return -ENODEV; }
> >  static inline void cpuidle_use_deepest_state(u64 latency_limit_ns)
> >  {
> >  }
> >  #endif
> >
> > +#ifdef CONFIG_SUSPEND
> > +extern int cpuidle_enter_s2idle(struct cpuidle_driver *drv,
> > +                               struct cpuidle_device *dev);
> > +#else
> > +static inline int cpuidle_enter_s2idle(struct cpuidle_driver *drv,
> > +                                      struct cpuidle_device *dev)
> > +{return -ENODEV; }
> > +#endif
> > +
> >  /* kernel/sched/idle.c */
> >  extern void sched_idle_set_state(struct cpuidle_state *idle_state);
> >  extern void default_idle_call(void);
> > --
> > 2.17.1
> >