LinuxPPS: core support

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>

1 files changed, 98 insertions, 0 deletions

diff --git a/drivers/pps/sysfs.c b/drivers/pps/sysfs.c
new file mode 100644
index 000000000000..ef0978c71eee
--- /dev/null
+++ b/drivers/pps/sysfs.c
@@ -0,0 +1,98 @@
+/*
+ * PPS sysfs support
+ *
+ *
+ * Copyright (C) 2007-2009   Rodolfo Giometti <giometti@linux.it>
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program; if not, write to the Free Software
+ *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/pps_kernel.h>
+
+/*
+ * Attribute functions
+ */
+
+static ssize_t pps_show_assert(struct device *dev,
+                                struct device_attribute *attr, char *buf)
+{
+        struct pps_device *pps = dev_get_drvdata(dev);
+
+        if (!(pps->info.mode & PPS_CAPTUREASSERT))
+                return 0;
+
+        return sprintf(buf, "%lld.%09d#%d\n",
+                        (long long) pps->assert_tu.sec, pps->assert_tu.nsec,
+                        pps->assert_sequence);
+}
+
+static ssize_t pps_show_clear(struct device *dev,
+                                struct device_attribute *attr, char *buf)
+{
+        struct pps_device *pps = dev_get_drvdata(dev);
+
+        if (!(pps->info.mode & PPS_CAPTURECLEAR))
+                return 0;
+
+        return sprintf(buf, "%lld.%09d#%d\n",
+                        (long long) pps->clear_tu.sec, pps->clear_tu.nsec,
+                        pps->clear_sequence);
+}
+
+static ssize_t pps_show_mode(struct device *dev,
+                                struct device_attribute *attr, char *buf)
+{
+        struct pps_device *pps = dev_get_drvdata(dev);
+
+        return sprintf(buf, "%4x\n", pps->info.mode);
+}
+
+static ssize_t pps_show_echo(struct device *dev,
+                                struct device_attribute *attr, char *buf)
+{
+        struct pps_device *pps = dev_get_drvdata(dev);
+
+        return sprintf(buf, "%d\n", !!pps->info.echo);
+}
+
+static ssize_t pps_show_name(struct device *dev,
+                                struct device_attribute *attr, char *buf)
+{
+        struct pps_device *pps = dev_get_drvdata(dev);
+
+        return sprintf(buf, "%s\n", pps->info.name);
+}
+
+static ssize_t pps_show_path(struct device *dev,
+                                struct device_attribute *attr, char *buf)
+{
+        struct pps_device *pps = dev_get_drvdata(dev);
+
+        return sprintf(buf, "%s\n", pps->info.path);
+}
+
+struct device_attribute pps_attrs[] = {
+        __ATTR(assert, S_IRUGO, pps_show_assert, NULL),
+        __ATTR(clear, S_IRUGO, pps_show_clear, NULL),
+        __ATTR(mode, S_IRUGO, pps_show_mode, NULL),
+        __ATTR(echo, S_IRUGO, pps_show_echo, NULL),
+        __ATTR(name, S_IRUGO, pps_show_name, NULL),
+        __ATTR(path, S_IRUGO, pps_show_path, NULL),
+        __ATTR_NULL,
+};