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| author | john stultz <johnstul@us.ibm.com> | 2006-06-26 00:25:07 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-06-26 09:58:20 -0700 |
| commit | 260a42309b31cbc54eb4b6b85649e412bcad053f (patch) | |
| tree | 51efc7bb51075b0d25d0e8465d3c056e6a57fe16 /kernel | |
| parent | ad596171ed635c51a9eef829187af100cbf8dcf7 (diff) | |
| download | linux-260a42309b31cbc54eb4b6b85649e412bcad053f.tar.gz linux-260a42309b31cbc54eb4b6b85649e412bcad053f.tar.bz2 linux-260a42309b31cbc54eb4b6b85649e412bcad053f.zip | |
[PATCH] Time: Let user request precision from current_tick_length()
Change the current_tick_length() function so it takes an argument which
specifies how much precision to return in shifted nanoseconds. This provides
a simple way to convert between NTPs internal nanoseconds shifted by
(SHIFT_SCALE - 10) to other shifted nanosecond units that are used by the
clocksource abstraction.
Signed-off-by: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/timer.c | 21 |
1 files changed, 17 insertions, 4 deletions
diff --git a/kernel/timer.c b/kernel/timer.c index 524c7f638365..623f9ea198d8 100644 --- a/kernel/timer.c +++ b/kernel/timer.c @@ -780,16 +780,29 @@ static void update_wall_time_one_tick(void) * Return how long ticks are at the moment, that is, how much time * update_wall_time_one_tick will add to xtime next time we call it * (assuming no calls to do_adjtimex in the meantime). - * The return value is in fixed-point nanoseconds with SHIFT_SCALE-10 - * bits to the right of the binary point. + * The return value is in fixed-point nanoseconds shifted by the + * specified number of bits to the right of the binary point. * This function has no side-effects. */ -u64 current_tick_length(void) +u64 current_tick_length(long shift) { long delta_nsec; + u64 ret; + /* calculate the finest interval NTP will allow. + * ie: nanosecond value shifted by (SHIFT_SCALE - 10) + */ delta_nsec = tick_nsec + adjtime_adjustment() * 1000; - return ((u64) delta_nsec << (SHIFT_SCALE - 10)) + time_adj; + ret = ((u64) delta_nsec << (SHIFT_SCALE - 10)) + time_adj; + + /* convert from (SHIFT_SCALE - 10) to specified shift scale: */ + shift = shift - (SHIFT_SCALE - 10); + if (shift < 0) + ret >>= -shift; + else + ret <<= shift; + + return ret; } /* XXX - all of this timekeeping code should be later moved to time.c */ |