Am 07.04.2015 um 13:12 schrieb Harald Geyer:
> This patch series introduces a new function
> u32 ktime_get_resolution_ns(void)
> which allows to clean up some driver code.
>
> In particular the IIO subsystem has a function to provide timestamps for
> events but no means to get their resolution. So currently the dht11 driver
> tries to guess the resolution in a rather messy and convoluted way. We
> can do much better with the new code.
>
> This API is not designed to be exposed to user space.
>
> This has been tested on i386, sunxi and mxs.
>
> Signed-off-by: Harald Geyer <har...@ccbib.org>
> ---
> changes since V1:
> Improved commit message.
>
> include/linux/timekeeping.h | 1 +
> kernel/time/timekeeping.c | 17 +++++++++++++++++
> 2 files changed, 18 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
> index 3eaae47..983b61e 100644
> --- a/include/linux/timekeeping.h
> +++ b/include/linux/timekeeping.h
> @@ -163,6 +163,7 @@ extern ktime_t ktime_get(void);
> extern ktime_t ktime_get_with_offset(enum tk_offsets offs);
> extern ktime_t ktime_mono_to_any(ktime_t tmono, enum tk_offsets offs);
> extern ktime_t ktime_get_raw(void);
> +extern u32 ktime_get_resolution_ns(void);
>
> /**
> * ktime_get_real - get the real (wall-) time in ktime_t format
> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
> index 91db941..8efd964 100644
> --- a/kernel/time/timekeeping.c
> +++ b/kernel/time/timekeeping.c
> @@ -586,6 +586,23 @@ ktime_t ktime_get(void)
> }
> EXPORT_SYMBOL_GPL(ktime_get);
>
> +u32 ktime_get_resolution_ns(void)
> +{
> + struct timekeeper *tk = &tk_core.timekeeper;
> + unsigned int seq;
> + u32 nsecs;
> +
> + WARN_ON(timekeeping_suspended);
> +
> + do {
> + seq = read_seqcount_begin(&tk_core.seq);
> + nsecs = tk->tkr.mult >> tk->tkr.shift;
> + } while (read_seqcount_retry(&tk_core.seq, seq));
> +
> + return nsecs;
> +}
> +EXPORT_SYMBOL_GPL(ktime_get_resolution_ns);
Hmm, isn't this ktime_get_raw_ns()?
Thanks,
//richard
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