linux-kernel - Re: [RFC][patch 4/5] clocksource_read/clocksource_read

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Date:	Tue, 21 Jul 2009 15:01:14 -0700
From:	john stultz <johnstul@...ibm.com>
To:	Martin Schwidefsky <schwidefsky@...ibm.com>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC][patch 4/5] clocksource_read/clocksource_read_raw inline
 functions

On Tue, 2009-07-21 at 21:17 +0200, Martin Schwidefsky wrote:
> plain text document attachment (clocksource-read-ns.diff)
> From: Martin Schwidefsky <schwidefsky@...ibm.com>
> 
> Add clocksource_read / clocksource_read_raw inline functions and use
> them for getnstimeofday, ktime_get, ktime_get_ts and getrawmonotonic.
> 
> Cc: Ingo Molnar <mingo@...e.hu>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: john stultz <johnstul@...ibm.com>
> Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
> ---
>  include/linux/clocksource.h |   45 +++++++++++++++++++++++++++++++++++++++++++
>  kernel/time/timekeeping.c   |   46 +++-----------------------------------------
>  2 files changed, 49 insertions(+), 42 deletions(-)
> 
> Index: linux-2.6/include/linux/clocksource.h
> ===================================================================
> --- linux-2.6.orig/include/linux/clocksource.h
> +++ linux-2.6/include/linux/clocksource.h
> @@ -284,6 +284,51 @@ static inline s64 cyc2ns(struct clocksou
>  	return ret;
>  }
> 
> +/**
> + * clocksource_read: - Read nanosecond delta from clocksource.
> + * @cs:		pointer to clocksource being read
> + *
> + * Read from the clock source and return the clock value converted
> + * to nanoseconds.
> + */
> +static inline s64 clocksource_read(struct clocksource *cs)
> +{
> +	cycle_t cycle_now, cycle_delta;
> +
> +	/* read clocksource: */
> +	cycle_now = cs->read(cs);
> +
> +	/* calculate the delta since the last update_wall_time: */
> +	cycle_delta = (cycle_now - cs->cycle_last) & cs->mask;
> +
> +	/* convert to nanoseconds: */
> +	return cyc2ns(cs, cycle_delta);
> +}

Oof. So you took out clocksource_read() only to replace with a different
function with the same name? If this move is necessary, could we call
these clocksource_get_ns()/clocksource_get_raw_ns() to avoid the
confusion?

thanks
-john


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