Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755187AbbETRT5 (ORCPT ); Wed, 20 May 2015 13:19:57 -0400 Received: from mail-pa0-f54.google.com ([209.85.220.54]:34545 "EHLO mail-pa0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755092AbbETRTv (ORCPT ); Wed, 20 May 2015 13:19:51 -0400 From: John Stultz To: LKML Cc: Harald Geyer , Thomas Gleixner , Ingo Molnar , John Stultz Subject: [PATCH 2/7] timekeeping: Provide new API to get the current time resolution Date: Wed, 20 May 2015 10:19:31 -0700 Message-Id: <1432142376-2077-3-git-send-email-john.stultz@linaro.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1432142376-2077-1-git-send-email-john.stultz@linaro.org> References: <1432142376-2077-1-git-send-email-john.stultz@linaro.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2407 Lines: 73 From: 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. Cc: Thomas Gleixner Cc: Ingo Molnar Signed-off-by: Harald Geyer [jstultz: Tweaked to make it build after upstream changes] Signed-off-by: John Stultz --- include/linux/timekeeping.h | 1 + kernel/time/timekeeping.c | 17 +++++++++++++++++ 2 files changed, 18 insertions(+) diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h index 99176af..9af5c12 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 3365e32..85d3763 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -702,6 +702,23 @@ 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_mono.mult >> tk->tkr_mono.shift; + } while (read_seqcount_retry(&tk_core.seq, seq)); + + return nsecs; +} +EXPORT_SYMBOL_GPL(ktime_get_resolution_ns); + static ktime_t *offsets[TK_OFFS_MAX] = { [TK_OFFS_REAL] = &tk_core.timekeeper.offs_real, [TK_OFFS_BOOT] = &tk_core.timekeeper.offs_boot, -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/