From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from a.ns.miles-group.at ([95.130.255.143]:65276 "EHLO radon.swed.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753744AbbDGWaz (ORCPT ); Tue, 7 Apr 2015 18:30:55 -0400 Message-ID: <55245A9A.5070606@nod.at> Date: Wed, 08 Apr 2015 00:30:50 +0200 From: Richard Weinberger MIME-Version: 1.0 To: Harald Geyer , Jonathan Cameron , John Stultz , Thomas Gleixner CC: linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCHv2 1/2] timekeeping: Provide new API to get the current time resolution References: <1428405156-6761-1-git-send-email-harald@ccbib.org> <1428405156-6761-2-git-send-email-harald@ccbib.org> In-Reply-To: <1428405156-6761-2-git-send-email-harald@ccbib.org> Content-Type: text/plain; charset=iso-8859-15 Sender: linux-iio-owner@vger.kernel.org List-Id: linux-iio@vger.kernel.org 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 > --- > 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