From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933758AbcBCRRL (ORCPT ); Wed, 3 Feb 2016 12:17:11 -0500 Received: from mail-pa0-f67.google.com ([209.85.220.67]:33289 "EHLO mail-pa0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932779AbcBCRRG (ORCPT ); Wed, 3 Feb 2016 12:17:06 -0500 From: Joshua Clayton To: Alexandre Belloni , Alessandro Zummo Cc: rtc-linux@googlegroups.com, linux-kernel@vger.kernel.org, Joshua Clayton Subject: [PATCH v3 2/3] rtc: implement a sysfs interface for clock offset Date: Wed, 3 Feb 2016 09:16:43 -0800 Message-Id: <1454519804-13770-2-git-send-email-stillcompiling@gmail.com> X-Mailer: git-send-email 2.5.0 In-Reply-To: <1454519804-13770-1-git-send-email-stillcompiling@gmail.com> References: <1454519804-13770-1-git-send-email-stillcompiling@gmail.com> References: <20160202104111.GU20165@piout.net> In-Reply-To: <20160202104111.GU20165@piout.net> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org clock offset may be set and read in decimal parts per billion attribute is /sys/class/rtc/rtcN/offset The attribute is only visible for rtcs that have set_offset implemented. Signed-off-by: Joshua Clayton --- Documentation/rtc.txt | 6 ++++++ drivers/rtc/rtc-sysfs.c | 35 ++++++++++++++++++++++++++++++++++- 2 files changed, 40 insertions(+), 1 deletion(-) diff --git a/Documentation/rtc.txt b/Documentation/rtc.txt index 8446f1e..ddc3660 100644 --- a/Documentation/rtc.txt +++ b/Documentation/rtc.txt @@ -157,6 +157,12 @@ wakealarm: The time at which the clock will generate a system wakeup the epoch by default, or if there's a leading +, seconds in the future, or if there is a leading +=, seconds ahead of the current alarm. +offset: The amount which the rtc clock has been adjusted in firmware. + Visible only if the driver supports clock offset adjustment. + The unit is parts per billion, i.e. The number of clock ticks + which are added to or removed from the rtc's base clock per + billion ticks. A positive value makes a day pass more slowly, + longer, and a negative value makes a day pass more quickly. IOCTL INTERFACE --------------- diff --git a/drivers/rtc/rtc-sysfs.c b/drivers/rtc/rtc-sysfs.c index 463e286..f8d7f8d 100644 --- a/drivers/rtc/rtc-sysfs.c +++ b/drivers/rtc/rtc-sysfs.c @@ -218,6 +218,34 @@ wakealarm_store(struct device *dev, struct device_attribute *attr, } static DEVICE_ATTR_RW(wakealarm); +static ssize_t +offset_show(struct device *dev, struct device_attribute *attr, char *buf) +{ + ssize_t retval; + long offset; + + retval = rtc_read_offset(to_rtc_device(dev), &offset); + if (retval == 0) + retval = sprintf(buf, "%ld\n", offset); + + return retval; +} + +static ssize_t +offset_store(struct device *dev, struct device_attribute *attr, + const char *buf, size_t n) +{ + ssize_t retval; + long offset; + + retval = kstrtol(buf, 10, &offset); + if (retval == 0) + retval = rtc_set_offset(to_rtc_device(dev), offset); + + return (retval < 0) ? retval : n; +} +static DEVICE_ATTR_RW(offset); + static struct attribute *rtc_attrs[] = { &dev_attr_name.attr, &dev_attr_date.attr, @@ -226,6 +254,7 @@ static struct attribute *rtc_attrs[] = { &dev_attr_max_user_freq.attr, &dev_attr_hctosys.attr, &dev_attr_wakealarm.attr, + &dev_attr_offset.attr, NULL, }; @@ -249,9 +278,13 @@ static umode_t rtc_attr_is_visible(struct kobject *kobj, struct rtc_device *rtc = to_rtc_device(dev); umode_t mode = attr->mode; - if (attr == &dev_attr_wakealarm.attr) + if (attr == &dev_attr_wakealarm.attr) { if (!rtc_does_wakealarm(rtc)) mode = 0; + } else if (attr == &dev_attr_offset.attr) { + if (!rtc->ops->set_offset) + mode = 0; + } return mode; } -- 2.5.0