eae9d2ba0c
This patch adds the kernel side of the PPS support currently named "LinuxPPS". PPS means "pulse per second" and a PPS source is just a device which provides a high precision signal each second so that an application can use it to adjust system clock time. Common use is the combination of the NTPD as userland program with a GPS receiver as PPS source to obtain a wallclock-time with sub-millisecond synchronisation to UTC. To obtain this goal the userland programs shoud use the PPS API specification (RFC 2783 - Pulse-Per-Second API for UNIX-like Operating Systems, Version 1.0) which in part is implemented by this patch. It provides a set of chars devices, one per PPS source, which can be used to get the time signal. The RFC's functions can be implemented by accessing to these char devices. Signed-off-by: Rodolfo Giometti <giometti@linux.it> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Greg KH <greg@kroah.com> Cc: Randy Dunlap <randy.dunlap@oracle.com> Cc: Kay Sievers <kay.sievers@vrfy.org> Acked-by: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: Michael Kerrisk <mtk.manpages@googlemail.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: Roman Zippel <zippel@linux-m68k.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
98 lines
2.7 KiB
C
98 lines
2.7 KiB
C
/*
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* PPS sysfs support
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*
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*
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* Copyright (C) 2007-2009 Rodolfo Giometti <giometti@linux.it>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <linux/device.h>
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#include <linux/module.h>
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#include <linux/string.h>
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#include <linux/pps_kernel.h>
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/*
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* Attribute functions
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*/
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static ssize_t pps_show_assert(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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struct pps_device *pps = dev_get_drvdata(dev);
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if (!(pps->info.mode & PPS_CAPTUREASSERT))
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return 0;
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return sprintf(buf, "%lld.%09d#%d\n",
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(long long) pps->assert_tu.sec, pps->assert_tu.nsec,
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pps->assert_sequence);
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}
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static ssize_t pps_show_clear(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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struct pps_device *pps = dev_get_drvdata(dev);
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if (!(pps->info.mode & PPS_CAPTURECLEAR))
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return 0;
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return sprintf(buf, "%lld.%09d#%d\n",
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(long long) pps->clear_tu.sec, pps->clear_tu.nsec,
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pps->clear_sequence);
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}
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static ssize_t pps_show_mode(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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struct pps_device *pps = dev_get_drvdata(dev);
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return sprintf(buf, "%4x\n", pps->info.mode);
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}
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static ssize_t pps_show_echo(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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struct pps_device *pps = dev_get_drvdata(dev);
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return sprintf(buf, "%d\n", !!pps->info.echo);
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}
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static ssize_t pps_show_name(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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struct pps_device *pps = dev_get_drvdata(dev);
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return sprintf(buf, "%s\n", pps->info.name);
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}
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static ssize_t pps_show_path(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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struct pps_device *pps = dev_get_drvdata(dev);
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return sprintf(buf, "%s\n", pps->info.path);
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}
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struct device_attribute pps_attrs[] = {
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__ATTR(assert, S_IRUGO, pps_show_assert, NULL),
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__ATTR(clear, S_IRUGO, pps_show_clear, NULL),
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__ATTR(mode, S_IRUGO, pps_show_mode, NULL),
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__ATTR(echo, S_IRUGO, pps_show_echo, NULL),
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__ATTR(name, S_IRUGO, pps_show_name, NULL),
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__ATTR(path, S_IRUGO, pps_show_path, NULL),
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__ATTR_NULL,
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};
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