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

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Date:	Tue, 8 Mar 2016 17:18:06 +0000
From:	Jon Hunter <jonathanh@...dia.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
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 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.

Cheers
Jon