linux-kernel - Re: [PATCH v2 1/2] clocksource: track usage

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Message-ID: <alpine.DEB.2.11.1501201148550.5526@nanos>
Date:	Tue, 20 Jan 2015 11:51:59 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
cc:	John Stultz <john.stultz@...aro.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] clocksource: track usage

On Fri, 16 Jan 2015, Alexandre Belloni wrote:
> diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
> index abcafaa20b86..7735902fc5f6 100644
> --- a/include/linux/clocksource.h
> +++ b/include/linux/clocksource.h
> @@ -210,6 +210,8 @@ struct clocksource {
>  #define CLOCK_SOURCE_SUSPEND_NONSTOP		0x80
>  #define CLOCK_SOURCE_RESELECT			0x100
>  
> +#define CLOCK_SOURCE_USED			0x200

You track whether the clocksource is enabled or not, right?

>  /* simplify initialization of mask field */
>  #define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)
>  
> @@ -282,6 +284,8 @@ static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift)
>  
>  extern int clocksource_register(struct clocksource*);
>  extern int clocksource_unregister(struct clocksource*);
> +extern int clocksource_enable(struct clocksource *);
> +extern void clocksource_disable(struct clocksource *);

This should be in kernel/time/timekeeping_internal.h

>  extern void clocksource_touch_watchdog(void);
>  extern struct clocksource* clocksource_get_next(void);
>  extern void clocksource_change_rating(struct clocksource *cs, int rating);
> diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
> index b79f39bda7e1..03cfc5a08e3b 100644
> --- a/kernel/time/clocksource.c
> +++ b/kernel/time/clocksource.c
> @@ -889,6 +889,36 @@ int clocksource_unregister(struct clocksource *cs)
>  }
>  EXPORT_SYMBOL(clocksource_unregister);
>  
> +/**
> + * clocksource_enable - enable a registered clocksource
> + * @cs:	clocksource to enable
> + */
> +int clocksource_enable(struct clocksource *cs)
> +{
> +	int ret = 0;
> +
> +	if (cs->enable)
> +		ret = cs->enable(cs);
> +
> +	if (!ret)
> +		cs->flags |= CLOCK_SOURCE_USED;
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(clocksource_enable);

Why on earth do you want to export that?

> +/**
> + * clocksource_disable - disable a registered clocksource
> + * @cs:	clocksource to disable
> + */
> +void clocksource_disable(struct clocksource *cs)
> +{
> +	cs->flags &= ~CLOCK_SOURCE_USED;
> +	if (cs->disable)
> +		cs->disable(cs);
> +}
> +EXPORT_SYMBOL(clocksource_disable);

Ditto.

Thanks,

	tglx
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