[PATCH 1/1] LinuxPPS core support.

[PATCH 1/1] LinuxPPS core support.

[Rodolfo Giometti]

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>
---
 Documentation/ABI/testing/sysfs-pps  |   73 ++++++++
 Documentation/ioctl/ioctl-number.txt |    2 +
 Documentation/pps/pps.txt            |  172 ++++++++++++++++++
 MAINTAINERS                          |    7 +
 drivers/Kconfig                      |    2 +
 drivers/Makefile                     |    1 +
 drivers/pps/Kconfig                  |   33 ++++
 drivers/pps/Makefile                 |    8 +
 drivers/pps/kapi.c                   |  317 +++++++++++++++++++++++++++++++++
 drivers/pps/pps.c                    |  322 ++++++++++++++++++++++++++++++++++
 drivers/pps/sysfs.c                  |  104 +++++++++++
 include/linux/Kbuild                 |    1 +
 include/linux/pps.h                  |  195 ++++++++++++++++++++
 13 files changed, 1237 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-pps
 create mode 100644 Documentation/pps/pps.txt
 create mode 100644 drivers/pps/Kconfig
 create mode 100644 drivers/pps/Makefile
 create mode 100644 drivers/pps/kapi.c
 create mode 100644 drivers/pps/pps.c
 create mode 100644 drivers/pps/sysfs.c
 create mode 100644 include/linux/pps.h

diff --git a/Documentation/ABI/testing/sysfs-pps b/Documentation/ABI/testing/sysfs-pps
new file mode 100644
index 0000000..25028c7
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-pps
@@ -0,0 +1,73 @@
+What:		/sys/class/pps/
+Date:		February 2008
+Contact:	Rodolfo Giometti <giometti@linux.it>
+Description:
+		The /sys/class/pps/ directory will contain files and
+		directories that will provide a unified interface to
+		the PPS sources.
+
+What:		/sys/class/pps/ppsX/
+Date:		February 2008
+Contact:	Rodolfo Giometti <giometti@linux.it>
+Description:
+		The /sys/class/pps/ppsX/ directory is related to X-th
+		PPS source into the system. Each directory will
+		contain files to manage and control its PPS source.
+
+What:		/sys/class/pps/ppsX/assert
+Date:		February 2008
+Contact:	Rodolfo Giometti <giometti@linux.it>
+Description:
+		The /sys/class/pps/ppsX/assert file reports the assert events
+		and the assert sequence number of the X-th source in the form:
+
+			<secs>.<nsec>#<sequence>
+
+		If the source has no assert events the content of this file
+		is empty.
+
+What:		/sys/class/pps/ppsX/clear
+Date:		February 2008
+Contact:	Rodolfo Giometti <giometti@linux.it>
+Description:
+		The /sys/class/pps/ppsX/clear file reports the clear events
+		and the clear sequence number of the X-th source in the form:
+
+			<secs>.<nsec>#<sequence>
+
+		If the source has no clear events the content of this file
+		is empty.
+
+What:		/sys/class/pps/ppsX/mode
+Date:		February 2008
+Contact:	Rodolfo Giometti <giometti@linux.it>
+Description:
+		The /sys/class/pps/ppsX/mode file reports the functioning
+		mode of the X-th source in hexadecimal encoding.
+
+		Please, refer to linux/include/linux/pps.h for further
+		info.
+
+What:		/sys/class/pps/ppsX/echo
+Date:		February 2008
+Contact:	Rodolfo Giometti <giometti@linux.it>
+Description:
+		The /sys/class/pps/ppsX/echo file reports if the X-th does
+		or does not support an "echo" function.
+
+What:		/sys/class/pps/ppsX/name
+Date:		February 2008
+Contact:	Rodolfo Giometti <giometti@linux.it>
+Description:
+		The /sys/class/pps/ppsX/name file reports the name of the
+		X-th source.
+
+What:		/sys/class/pps/ppsX/path
+Date:		February 2008
+Contact:	Rodolfo Giometti <giometti@linux.it>
+Description:
+		The /sys/class/pps/ppsX/path file reports the path name of
+		the device connected with the X-th source.
+
+		If the source is not connected with any device the content
+		of this file is empty.
diff --git a/Documentation/ioctl/ioctl-number.txt b/Documentation/ioctl/ioctl-number.txt
index f1d6399..eac1a33 100644
--- a/Documentation/ioctl/ioctl-number.txt
+++ b/Documentation/ioctl/ioctl-number.txt
@@ -151,6 +151,8 @@ Code	Seq#	Include File		Comments
 'p'	40-7F	linux/nvram.h
 'p'	80-9F				user-space parport
 					<mailto:tim@cyberelk.net>
+'p'	a0-a4	linux/pps.h		LinuxPPS
+					<mailto:giometti@linux.it>
 'q'	00-1F	linux/serio.h
 'q'	80-FF				Internet PhoneJACK, Internet LineJACK
 					<http://www.quicknet.net>
diff --git a/Documentation/pps/pps.txt b/Documentation/pps/pps.txt
new file mode 100644
index 0000000..125f4ab
--- /dev/null
+++ b/Documentation/pps/pps.txt
@@ -0,0 +1,172 @@
+
+			PPS - Pulse Per Second
+			----------------------
+
+(C) Copyright 2007 Rodolfo Giometti <giometti@enneenne.com>
+
+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.
+
+
+
+Overview
+--------
+
+LinuxPPS provides a programming interface (API) to define in the
+system several PPS sources.
+
+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.
+
+A PPS source can be connected to a serial port (usually to the Data
+Carrier Detect pin) or to a parallel port (ACK-pin) or to a special
+CPU's GPIOs (this is the common case in embedded systems) but in each
+case when a new pulse arrives the system must apply to it a timestamp
+and record it for userland.
+
+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.
+
+
+RFC considerations
+------------------
+
+While implementing a PPS API as RFC 2783 defines and using an embedded
+CPU GPIO-Pin as physical link to the signal, I encountered a deeper
+problem:
+
+   At startup it needs a file descriptor as argument for the function
+   time_pps_create().
+
+This implies that the source has a /dev/... entry. This assumption is
+ok for the serial and parallel port, where you can do something
+useful besides(!) the gathering of timestamps as it is the central
+task for a PPS-API. But this assumption does not work for a single
+purpose GPIO line. In this case even basic file-related functionality
+(like read() and write()) makes no sense at all and should not be a
+precondition for the use of a PPS-API.
+
+The problem can be simply solved if you consider that a PPS source is
+not always connected with a GPS data source.
+
+So your programs should check if the GPS data source (the serial port
+for instance) is a PPS source too, and if not they should provide the
+possibility to open another device as PPS source.
+
+In LinuxPPS the PPS sources are simply char devices usually mapped
+into files /dev/pps0, /dev/pps1, etc..
+
+
+Coding example
+--------------
+
+To register a PPS source into the kernel you should define a struct
+pps_source_info_s as follows:
+
+    static struct pps_source_info pps_ktimer_info = {
+	    .name         = "ktimer",
+	    .path         = "",
+	    .mode         = PPS_CAPTUREASSERT | PPS_OFFSETASSERT | \
+			    PPS_ECHOASSERT | \
+			    PPS_CANWAIT | PPS_TSFMT_TSPEC,
+	    .echo         = pps_ktimer_echo,
+	    .owner        = THIS_MODULE,
+    };
+
+and then calling the function pps_register_source() in your
+intialization routine as follows:
+
+    source = pps_register_source(&pps_ktimer_info,
+			PPS_CAPTUREASSERT | PPS_OFFSETASSERT);
+
+The pps_register_source() prototype is:
+
+  int pps_register_source(struct pps_source_info_s *info, int default_params)
+
+where "info" is a pointer to a structure that describes a particular
+PPS source, "default_params" tells the system what the initial default
+parameters for the device should be (it is obvious that these parameters
+must be a subset of ones defined in the struct
+pps_source_info_s which describe the capabilities of the driver).
+
+Once you have registered a new PPS source into the system you can
+signal an assert event (for example in the interrupt handler routine)
+just using:
+
+    pps_event(source, &ts, PPS_CAPTUREASSERT, ptr)
+
+where "ts" is the event's timestamp.
+
+The same function may also run the defined echo function
+(pps_ktimer_echo(), passing to it the "ptr" pointer) if the user
+asked for that... etc..
+
+Please see the file drivers/pps/clients/ktimer.c for example code.
+
+
+SYSFS support
+-------------
+
+If the SYSFS filesystem is enabled in the kernel it provides a new class:
+
+   $ ls /sys/class/pps/
+   pps0/  pps1/  pps2/
+
+Every directory is the ID of a PPS sources defined in the system and
+inside you find several files:
+
+   $ ls /sys/class/pps/pps0/
+   assert	clear  echo  mode  name  path  subsystem@  uevent
+
+Inside each "assert" and "clear" file you can find the timestamp and a
+sequence number:
+
+   $ cat /sys/class/pps/pps0/assert
+   1170026870.983207967#8
+
+Where before the "#" is the timestamp in seconds; after it is the
+sequence number. Other files are:
+
+* echo: reports if the PPS source has an echo function or not;
+
+* mode: reports available PPS functioning modes;
+
+* name: reports the PPS source's name;
+
+* path: reports the PPS source's device path, that is the device the
+  PPS source is connected to (if it exists).
+
+
+Testing the PPS support
+-----------------------
+
+In order to test the PPS support even without specific hardware you can use
+the ktimer driver (see the client subsection in the PPS configuration menu)
+and the userland tools provided into Documentaion/pps/ directory.
+
+Once you have enabled the compilation of ktimer just modprobe it (if
+not statically compiled):
+
+   # modprobe ktimer
+
+and the run ppstest as follow:
+
+   $ ./ppstest /dev/pps0
+   trying PPS source "/dev/pps1"
+   found PPS source "/dev/pps1"
+   ok, found 1 source(s), now start fetching data...
+   source 0 - assert 1186592699.388832443, sequence: 364 - clear  0.000000000, sequence: 0
+   source 0 - assert 1186592700.388931295, sequence: 365 - clear  0.000000000, sequence: 0
+   source 0 - assert 1186592701.389032765, sequence: 366 - clear  0.000000000, sequence: 0
+
+Please, note that to compile userland programs you need the file timepps.h
+(see Documentation/pps/).
diff --git a/MAINTAINERS b/MAINTAINERS
index d992d40..d2ab232 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3464,6 +3464,13 @@ P:	James Chapman
 M:	jchapman@katalix.com
 S:	Maintained
 
+PPS SUPPORT
+P:	Rodolfo Giometti
+M:	giometti@enneenne.com
+W:	http://wiki.enneenne.com/index.php/LinuxPPS_support
+L:	linuxpps@ml.enneenne.com (subscribers-only)
+S:	Maintained
+
 PREEMPTIBLE KERNEL
 P:	Robert Love
 M:	rml@tech9.net
diff --git a/drivers/Kconfig b/drivers/Kconfig
index 00cf955..e328e5b 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -52,6 +52,8 @@ source "drivers/i2c/Kconfig"
 
 source "drivers/spi/Kconfig"
 
+source "drivers/pps/Kconfig"
+
 source "drivers/gpio/Kconfig"
 
 source "drivers/w1/Kconfig"
diff --git a/drivers/Makefile b/drivers/Makefile
index c1bf417..ff07ab9 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -71,6 +71,7 @@ obj-$(CONFIG_INPUT)		+= input/
 obj-$(CONFIG_I2O)		+= message/
 obj-$(CONFIG_RTC_LIB)		+= rtc/
 obj-y				+= i2c/
+obj-$(CONFIG_PPS)		+= pps/
 obj-$(CONFIG_W1)		+= w1/
 obj-$(CONFIG_POWER_SUPPLY)	+= power/
 obj-$(CONFIG_HWMON)		+= hwmon/
diff --git a/drivers/pps/Kconfig b/drivers/pps/Kconfig
new file mode 100644
index 0000000..cc2eb8e
--- /dev/null
+++ b/drivers/pps/Kconfig
@@ -0,0 +1,33 @@
+#
+# PPS support configuration
+#
+
+menu "PPS support"
+
+config PPS
+	tristate "PPS support"
+	depends on EXPERIMENTAL
+	---help---
+	  PPS (Pulse Per Second) is a special pulse provided by some GPS
+	  antennae. Userland can use it to get a high-precision time
+	  reference.
+
+	  Some antennae's PPS signals are connected with the CD (Carrier
+	  Detect) pin of the serial line they use to communicate with the
+	  host. In this case use the SERIAL_LINE client support.
+
+	  Some antennae's PPS signals are connected with some special host
+	  inputs so you have to enable the corresponding client support.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pps_core.ko.
+
+config PPS_DEBUG
+	bool "PPS debugging messages"
+	depends on PPS
+	help
+	  Say Y here if you want the PPS support to produce a bunch of debug
+	  messages to the system log.  Select this if you are having a
+	  problem with PPS support and want to see more of what is going on.
+
+endmenu
diff --git a/drivers/pps/Makefile b/drivers/pps/Makefile
new file mode 100644
index 0000000..19ea582
--- /dev/null
+++ b/drivers/pps/Makefile
@@ -0,0 +1,8 @@
+#
+# Makefile for the PPS core.
+#
+
+pps_core-y			:= pps.o kapi.o sysfs.o
+obj-$(CONFIG_PPS)		:= pps_core.o
+
+ccflags-$(CONFIG_PPS_DEBUG) := -DDEBUG
diff --git a/drivers/pps/kapi.c b/drivers/pps/kapi.c
new file mode 100644
index 0000000..917b379
--- /dev/null
+++ b/drivers/pps/kapi.c
@@ -0,0 +1,317 @@
+/*
+ * kernel API
+ *
+ *
+ * Copyright (C) 2005-2009   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/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/time.h>
+#include <linux/spinlock.h>
+#include <linux/idr.h>
+#include <linux/fs.h>
+#include <linux/pps.h>
+
+/*
+ * Global variables
+ */
+
+DEFINE_SPINLOCK(pps_idr_lock);
+DEFINE_IDR(pps_idr);
+
+/*
+ * Local functions
+ */
+
+static void pps_add_offset(struct pps_ktime *ts, struct pps_ktime *offset)
+{
+	ts->nsec += offset->nsec;
+	while (ts->nsec >= NSEC_PER_SEC) {
+		ts->nsec -= NSEC_PER_SEC;
+		ts->sec++;
+	}
+	while (ts->nsec < 0) {
+		ts->nsec += NSEC_PER_SEC;
+		ts->sec--;
+	}
+	ts->sec += offset->sec;
+}
+
+/*
+ * Exported functions
+ */
+
+/* pps_get_source - find a PPS source
+ * @source: the PPS source ID.
+ *
+ * This function is used to find an already registered PPS source into the
+ * system.
+ *
+ * The function returns NULL if found nothing, otherwise it returns a pointer
+ * to the PPS source data struct (the refcounter is incremented by 1).
+ */
+
+struct pps_device *pps_get_source(int source)
+{
+	struct pps_device *pps;
+	unsigned long flags;
+
+	spin_lock_irqsave(&pps_idr_lock, flags);
+
+	pps = idr_find(&pps_idr, source);
+	if (pps != NULL)
+		atomic_inc(&pps->usage);
+
+	spin_unlock_irqrestore(&pps_idr_lock, flags);
+
+	return pps;
+}
+
+/* pps_put_source - free the PPS source data
+ * @pps: a pointer to the PPS source.
+ *
+ * This function is used to free a PPS data struct if its refcount is 0.
+ */
+
+void pps_put_source(struct pps_device *pps)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&pps_idr_lock, flags);
+	BUG_ON(atomic_read(&pps->usage) == 0);
+
+	if (!atomic_dec_and_test(&pps->usage)) {
+		pps = NULL;
+		goto exit;
+	}
+
+	/* No more reference to the PPS source. We can safely remove the
+	 * PPS data struct.
+	 */
+	idr_remove(&pps_idr, pps->id);
+
+exit:
+	spin_unlock_irqrestore(&pps_idr_lock, flags);
+	kfree(pps);
+}
+
+/* pps_register_source - add a PPS source in the system
+ * @info: the PPS info struct
+ * @default_params: the default PPS parameters of the new source
+ *
+ * This function is used to add a new PPS source in the system. The new
+ * source is described by info's fields and it will have, as default PPS
+ * parameters, the ones specified into default_params.
+ *
+ * The function returns, in case of success, the PPS source ID.
+ */
+
+int pps_register_source(struct pps_source_info *info, int default_params)
+{
+	struct pps_device *pps;
+	int id;
+	int err;
+
+	/* Sanity checks */
+	if ((info->mode & default_params) != default_params) {
+		printk(KERN_ERR "pps: %s: unsupported default parameters\n",
+					info->name);
+		err = -EINVAL;
+		goto pps_register_source_exit;
+	}
+	if ((info->mode & (PPS_ECHOASSERT | PPS_ECHOCLEAR)) != 0 &&
+			info->echo == NULL) {
+		printk(KERN_ERR "pps: %s: echo function is not defined\n",
+					info->name);
+		err = -EINVAL;
+		goto pps_register_source_exit;
+	}
+	if ((info->mode & (PPS_TSFMT_TSPEC | PPS_TSFMT_NTPFP)) == 0) {
+		printk(KERN_ERR "pps: %s: unspecified time format\n",
+					info->name);
+		err = -EINVAL;
+		goto pps_register_source_exit;
+	}
+
+	/* Allocate memory for the new PPS source struct */
+	pps = kzalloc(sizeof(struct pps_device), GFP_KERNEL);
+	if (pps == NULL) {
+		err = -ENOMEM;
+		goto pps_register_source_exit;
+	}
+
+	/* Get new ID for the new PPS source */
+	if (idr_pre_get(&pps_idr, GFP_KERNEL) == 0) {
+		err = -ENOMEM;
+		goto kfree_pps;
+	}
+
+	spin_lock_irq(&pps_idr_lock);
+	err = idr_get_new(&pps_idr, pps, &id);
+	spin_unlock_irq(&pps_idr_lock);
+
+	if (err < 0)
+		goto kfree_pps;
+
+	id = id & MAX_ID_MASK;
+	if (id >= PPS_MAX_SOURCES) {
+		printk(KERN_ERR "pps: %s: too many PPS sources in the system\n",
+					info->name);
+		err = -EBUSY;
+		goto free_idr;
+	}
+
+	pps->id = id;
+	pps->params.api_version = PPS_API_VERS;
+	pps->params.mode = default_params;
+	pps->info = *info;
+
+	init_waitqueue_head(&pps->queue);
+	spin_lock_init(&pps->lock);
+	atomic_set(&pps->usage, 1);
+
+	/* Create the char device */
+	err = pps_register_cdev(pps);
+	if (err < 0) {
+		printk(KERN_ERR "pps: %s: unable to create char device\n",
+					info->name);
+		goto free_idr;
+	}
+
+	pr_info("new PPS source %s at ID %d\n", info->name, id);
+
+	return id;
+
+free_idr:
+	spin_lock_irq(&pps_idr_lock);
+	idr_remove(&pps_idr, id);
+	spin_unlock_irq(&pps_idr_lock);
+
+kfree_pps:
+	kfree(pps);
+
+pps_register_source_exit:
+	printk(KERN_ERR "pps: %s: unable to register source\n", info->name);
+
+	return err;
+}
+EXPORT_SYMBOL(pps_register_source);
+
+/* pps_unregister_source - remove a PPS source from the system
+ * @source: the PPS source ID
+ *
+ * This function is used to remove a previously registered PPS source from
+ * the system.
+ */
+
+void pps_unregister_source(int source)
+{
+	struct pps_device *pps;
+
+	spin_lock_irq(&pps_idr_lock);
+	pps = idr_find(&pps_idr, source);
+
+	if (!pps) {
+		BUG();
+		spin_unlock_irq(&pps_idr_lock);
+		return;
+	}
+	spin_unlock_irq(&pps_idr_lock);
+
+	pps_unregister_cdev(pps);
+	pps_put_source(pps);
+}
+EXPORT_SYMBOL(pps_unregister_source);
+
+/* pps_event - register a PPS event into the system
+ * @source: the PPS source ID
+ * @ts: the event timestamp
+ * @event: the event type
+ * @data: userdef pointer
+ *
+ * This function is used by each PPS client in order to register a new
+ * PPS event into the system (it's usually called inside an IRQ handler).
+ *
+ * If an echo function is associated with the PPS source it will be called
+ * as:
+ *	pps->info.echo(source, event, data);
+ */
+
+void pps_event(int source, struct pps_ktime *ts, int event, void *data)
+{
+	struct pps_device *pps;
+	unsigned long flags;
+
+	if ((event & (PPS_CAPTUREASSERT | PPS_CAPTURECLEAR)) == 0) {
+		printk(KERN_ERR "pps: unknown event (%x) for source %d\n",
+			event, source);
+		return;
+	}
+
+	pps = pps_get_source(source);
+	if (!pps)
+		return;
+
+	pr_debug("PPS event on source %d at %llu.%06u\n",
+			pps->id, (unsigned long long) ts->sec, ts->nsec);
+
+	spin_lock_irqsave(&pps->lock, flags);
+
+	/* Must call the echo function? */
+	if ((pps->params.mode & (PPS_ECHOASSERT | PPS_ECHOCLEAR)))
+		pps->info.echo(source, event, data);
+
+	/* Check the event */
+	pps->current_mode = pps->params.mode;
+	if (event & PPS_CAPTUREASSERT) {
+		/* We have to add an offset? */
+		if (pps->params.mode & PPS_OFFSETASSERT)
+			pps_add_offset(ts, &pps->params.assert_off_tu);
+
+		/* Save the time stamp */
+		pps->assert_tu = *ts;
+		pps->assert_sequence++;
+		pr_debug("capture assert seq #%u for source %d\n",
+			pps->assert_sequence, source);
+	}
+	if (event & PPS_CAPTURECLEAR) {
+		/* We have to add an offset? */
+		if (pps->params.mode & PPS_OFFSETCLEAR)
+			pps_add_offset(ts, &pps->params.clear_off_tu);
+
+		/* Save the time stamp */
+		pps->clear_tu = *ts;
+		pps->clear_sequence++;
+		pr_debug("capture clear seq #%u for source %d\n",
+			pps->clear_sequence, source);
+	}
+
+	pps->go = ~0;
+	wake_up_interruptible(&pps->queue);
+
+	kill_fasync(&pps->async_queue, SIGIO, POLL_IN);
+
+	spin_unlock_irqrestore(&pps->lock, flags);
+
+	/* Now we can release the PPS source for (possible) deregistration */
+	pps_put_source(pps);
+}
+EXPORT_SYMBOL(pps_event);
diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
new file mode 100644
index 0000000..aeaa52e
--- /dev/null
+++ b/drivers/pps/pps.c
@@ -0,0 +1,322 @@
+/*
+ * PPS core file
+ *
+ *
+ * Copyright (C) 2005-2009   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/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/uaccess.h>
+#include <linux/idr.h>
+#include <linux/cdev.h>
+#include <linux/poll.h>
+#include <linux/pps.h>
+
+/*
+ * Local variables
+ */
+
+static dev_t pps_devt;
+static struct class *pps_class;
+
+/*
+ * Char device methods
+ */
+
+static unsigned int pps_cdev_poll(struct file *file, poll_table *wait)
+{
+	struct pps_device *pps = file->private_data;
+
+	poll_wait(file, &pps->queue, wait);
+
+	return POLLIN | POLLRDNORM;
+}
+
+static int pps_cdev_fasync(int fd, struct file *file, int on)
+{
+	struct pps_device *pps = file->private_data;
+	return fasync_helper(fd, file, on, &pps->async_queue);
+}
+
+static long pps_cdev_ioctl(struct file *file,
+		unsigned int cmd, unsigned long arg)
+{
+	struct pps_device *pps = file->private_data;
+	struct pps_kparams params;
+	struct pps_fdata fdata;
+	unsigned long ticks;
+	void __user *uarg = (void __user *) arg;
+	int __user *iuarg = (int __user *) arg;
+	int err;
+
+	switch (cmd) {
+	case PPS_CHECK:
+
+		/* This does nothing but signal we are a PPS source... */
+
+		return 0;
+
+	case PPS_GETPARAMS:
+		pr_debug("PPS_GETPARAMS: source %d\n", pps->id);
+
+		/* Return current parameters */
+		err = copy_to_user(uarg, &pps->params,
+						sizeof(struct pps_kparams));
+		if (err)
+			return -EFAULT;
+
+		break;
+
+	case PPS_SETPARAMS:
+		pr_debug("PPS_SETPARAMS: source %d\n", pps->id);
+
+		/* Check the capabilities */
+		if (!capable(CAP_SYS_TIME))
+			return -EPERM;
+
+		err = copy_from_user(&params, uarg, sizeof(struct pps_kparams));
+		if (err)
+			return -EFAULT;
+		if (!(params.mode & (PPS_CAPTUREASSERT | PPS_CAPTURECLEAR))) {
+			pr_debug("capture mode unspecified (%x)\n",
+								params.mode);
+			return -EINVAL;
+		}
+
+		/* Check for supported capabilities */
+		if ((params.mode & ~pps->info.mode) != 0) {
+			pr_debug("unsupported capabilities (%x)\n",
+								params.mode);
+			return -EINVAL;
+		}
+
+		spin_lock_irq(&pps->lock);
+
+		/* Save the new parameters */
+		pps->params = params;
+
+		/* Restore the read only parameters */
+		if ((params.mode & (PPS_TSFMT_TSPEC | PPS_TSFMT_NTPFP)) == 0) {
+			/* section 3.3 of RFC 2783 interpreted */
+			pr_debug("time format unspecified (%x)\n",
+								params.mode);
+			pps->params.mode |= PPS_TSFMT_TSPEC;
+		}
+		if (pps->info.mode & PPS_CANWAIT)
+			pps->params.mode |= PPS_CANWAIT;
+		pps->params.api_version = PPS_API_VERS;
+
+		spin_unlock_irq(&pps->lock);
+
+		break;
+
+	case PPS_GETCAP:
+		pr_debug("PPS_GETCAP: source %d\n", pps->id);
+
+		err = put_user(pps->info.mode, iuarg);
+		if (err)
+			return -EFAULT;
+
+		break;
+
+	case PPS_FETCH:
+		pr_debug("PPS_FETCH: source %d\n", pps->id);
+
+		err = copy_from_user(&fdata, uarg, sizeof(struct pps_fdata));
+		if (err)
+			return -EFAULT;
+
+		pps->go = 0;
+
+		/* Manage the timeout */
+		if (fdata.timeout.flags & PPS_TIME_INVALID)
+			err = wait_event_interruptible(pps->queue, pps->go);
+		else {
+			pr_debug("timeout %lld.%09d\n",
+					(long long) fdata.timeout.sec,
+					fdata.timeout.nsec);
+			ticks = fdata.timeout.sec * HZ;
+			ticks += fdata.timeout.nsec / (NSEC_PER_SEC / HZ);
+
+			if (ticks != 0) {
+				err = wait_event_interruptible_timeout(
+						pps->queue, pps->go, ticks);
+				if (err == 0)
+					return -ETIMEDOUT;
+			}
+		}
+
+		/* Check for pending signals */
+		if (err == -ERESTARTSYS) {
+			pr_debug("pending signal caught\n");
+			return -EINTR;
+		}
+
+		/* Return the fetched timestamp */
+		spin_lock_irq(&pps->lock);
+
+		fdata.info.assert_sequence = pps->assert_sequence;
+		fdata.info.clear_sequence = pps->clear_sequence;
+		fdata.info.assert_tu = pps->assert_tu;
+		fdata.info.clear_tu = pps->clear_tu;
+		fdata.info.current_mode = pps->current_mode;
+
+		spin_unlock_irq(&pps->lock);
+
+		err = copy_to_user(uarg, &fdata, sizeof(struct pps_fdata));
+		if (err)
+			return -EFAULT;
+
+		break;
+
+	default:
+		return -ENOTTY;
+		break;
+	}
+
+	return 0;
+}
+
+static int pps_cdev_open(struct inode *inode, struct file *file)
+{
+	struct pps_device *pps = container_of(inode->i_cdev,
+						struct pps_device, cdev);
+	int found;
+
+	found = pps_get_source(pps->id) != 0;
+	if (!found)
+		return -ENODEV;
+
+	file->private_data = pps;
+
+	return 0;
+}
+
+static int pps_cdev_release(struct inode *inode, struct file *file)
+{
+	struct pps_device *pps = file->private_data;
+
+	/* Free the PPS source and wake up (possible) deregistration */
+	pps_put_source(pps);
+
+	return 0;
+}
+
+/*
+ * Char device stuff
+ */
+
+static const struct file_operations pps_cdev_fops = {
+	.owner		= THIS_MODULE,
+	.llseek		= no_llseek,
+	.poll		= pps_cdev_poll,
+	.fasync		= pps_cdev_fasync,
+	.unlocked_ioctl	= pps_cdev_ioctl,
+	.open		= pps_cdev_open,
+	.release	= pps_cdev_release,
+};
+
+int pps_register_cdev(struct pps_device *pps)
+{
+	int err;
+
+	pps->devno = MKDEV(MAJOR(pps_devt), pps->id);
+	cdev_init(&pps->cdev, &pps_cdev_fops);
+	pps->cdev.owner = pps->info.owner;
+
+	err = cdev_add(&pps->cdev, pps->devno, 1);
+	if (err) {
+		printk(KERN_ERR "pps: %s: failed to add char device %d:%d\n",
+				pps->info.name, MAJOR(pps_devt), pps->id);
+		return err;
+	}
+	pps->dev = device_create(pps_class, pps->info.dev, pps->devno, NULL,
+							"pps%d", pps->id);
+	if (err)
+		goto del_cdev;
+	dev_set_drvdata(pps->dev, pps);
+
+	pr_debug("source %s got cdev (%d:%d)\n", pps->info.name,
+			MAJOR(pps_devt), pps->id);
+
+	return 0;
+
+del_cdev:
+	cdev_del(&pps->cdev);
+
+	return err;
+}
+
+void pps_unregister_cdev(struct pps_device *pps)
+{
+	device_destroy(pps_class, pps->devno);
+	cdev_del(&pps->cdev);
+}
+
+/*
+ * Module stuff
+ */
+
+static void __exit pps_exit(void)
+{
+	class_destroy(pps_class);
+
+	if (pps_devt)
+		unregister_chrdev_region(pps_devt, PPS_MAX_SOURCES);
+
+	pr_info("LinuxPPS API ver. %d removed\n", PPS_API_VERS);
+}
+
+static int __init pps_init(void)
+{
+	int err;
+
+	pps_class = class_create(THIS_MODULE, "pps");
+	if (!pps_class) {
+		printk(KERN_ERR "pps: failed to allocate class\n");
+		return -ENOMEM;
+	}
+	pps_class->dev_attrs = pps_attrs;
+
+	err = alloc_chrdev_region(&pps_devt, 0, PPS_MAX_SOURCES, "pps");
+	if (err < 0) {
+		printk(KERN_ERR "pps: failed to allocate char device region\n");
+		goto remove_class;
+	}
+
+	pr_info("LinuxPPS API ver. %d registered\n", PPS_API_VERS);
+	pr_info("Software ver. %s - Copyright 2005-2007 Rodolfo Giometti "
+		"<giometti@linux.it>\n", PPS_VERSION);
+
+	return 0;
+
+remove_class:
+	class_destroy(pps_class);
+
+	return err;
+}
+
+subsys_initcall(pps_init);
+module_exit(pps_exit);
+
+MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
+MODULE_DESCRIPTION("LinuxPPS support (RFC 2783) - ver. " PPS_VERSION);
+MODULE_LICENSE("GPL");
diff --git a/drivers/pps/sysfs.c b/drivers/pps/sysfs.c
new file mode 100644
index 0000000..43c3b49
--- /dev/null
+++ b/drivers/pps/sysfs.c
@@ -0,0 +1,104 @@
+/*
+ * 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.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);
+}
+DEVICE_ATTR(assert, S_IRUGO, pps_show_assert, NULL);
+
+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);
+}
+DEVICE_ATTR(clear, S_IRUGO, pps_show_clear, NULL);
+
+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);
+}
+DEVICE_ATTR(mode, S_IRUGO, pps_show_mode, NULL);
+
+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);
+}
+DEVICE_ATTR(echo, S_IRUGO, pps_show_echo, NULL);
+
+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);
+}
+DEVICE_ATTR(name, S_IRUGO, pps_show_name, NULL);
+
+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);
+}
+DEVICE_ATTR(path, S_IRUGO, pps_show_path, NULL);
+
+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,
+};
diff --git a/include/linux/Kbuild b/include/linux/Kbuild
index 12e9a29..5df789c 100644
--- a/include/linux/Kbuild
+++ b/include/linux/Kbuild
@@ -304,6 +304,7 @@ unifdef-y += pmu.h
 unifdef-y += poll.h
 unifdef-y += ppp_defs.h
 unifdef-y += ppp-comp.h
+unifdef-y += pps.h
 unifdef-y += ptrace.h
 unifdef-y += qnx4_fs.h
 unifdef-y += quota.h
diff --git a/include/linux/pps.h b/include/linux/pps.h
new file mode 100644
index 0000000..d9079d6
--- /dev/null
+++ b/include/linux/pps.h
@@ -0,0 +1,195 @@
+/*
+ * PPS API kernel header
+ *
+ *
+ * Copyright (C) 2005-2009   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.
+ */
+
+
+#ifndef _PPS_H_
+#define _PPS_H_
+
+#define PPS_VERSION		"5.3.4"
+#define PPS_MAX_SOURCES		16		/* should be enough... */
+
+/* Implementation note: the logical states ``assert'' and ``clear''
+ * are implemented in terms of the chip register, i.e. ``assert''
+ * means the bit is set.  */
+
+/*
+ * 3.2 New data structures
+ */
+
+#define PPS_API_VERS_1		1
+#define PPS_API_VERS		PPS_API_VERS_1	/* we use API version 1 */
+#define PPS_MAX_NAME_LEN	32
+
+/* 32-bit vs. 64-bit compatibility.
+ *
+ * 0n i386, the alignment of a uint64_t is only 4 bytes, while on most other
+ * architectures it's 8 bytes. On i386, there will be no padding between the
+ * two consecutive 'struct pps_ktime' members of struct pps_kinfo and struct
+ * pps_kparams. But on most platforms there will be padding to ensure correct
+ * alignment.
+ *
+ * The simple fix is probably to add an explicit padding.
+ *					 		[David Woodhouse]
+ */
+struct pps_ktime {
+	__s64 sec;
+	__s32 nsec;
+	__u32 flags;
+};
+#define PPS_TIME_INVALID	(1<<0)	/* used to specify timeout==NULL */
+
+struct pps_kinfo {
+	__u32 assert_sequence;		/* seq. num. of assert event */
+	__u32 clear_sequence; 		/* seq. num. of clear event */
+	struct pps_ktime assert_tu;	/* time of assert event */
+	struct pps_ktime clear_tu;	/* time of clear event */
+	int current_mode;		/* current mode bits */
+};
+
+struct pps_kparams {
+	int api_version;		/* API version # */
+	int mode;			/* mode bits */
+	struct pps_ktime assert_off_tu;	/* offset compensation for assert */
+	struct pps_ktime clear_off_tu;	/* offset compensation for clear */
+};
+
+/*
+ * 3.3 Mode bit definitions
+ */
+
+/* Device/implementation parameters */
+#define PPS_CAPTUREASSERT	0x01	/* capture assert events */
+#define PPS_CAPTURECLEAR	0x02	/* capture clear events */
+#define PPS_CAPTUREBOTH		0x03	/* capture assert and clear events */
+
+#define PPS_OFFSETASSERT	0x10	/* apply compensation for assert ev. */
+#define PPS_OFFSETCLEAR		0x20	/* apply compensation for clear ev. */
+
+#define PPS_CANWAIT		0x100	/* can we wait for an event? */
+#define PPS_CANPOLL		0x200	/* bit reserved for future use */
+
+/* Kernel actions */
+#define PPS_ECHOASSERT		0x40	/* feed back assert event to output */
+#define PPS_ECHOCLEAR		0x80	/* feed back clear event to output */
+
+/* Timestamp formats */
+#define PPS_TSFMT_TSPEC		0x1000	/* select timespec format */
+#define PPS_TSFMT_NTPFP		0x2000	/* select NTP format */
+
+/*
+ * 3.4.4 New functions: disciplining the kernel timebase
+ */
+
+/* Kernel consumers */
+#define PPS_KC_HARDPPS		0	/* hardpps() (or equivalent) */
+#define PPS_KC_HARDPPS_PLL	1	/* hardpps() constrained to
+					   use a phase-locked loop */
+#define PPS_KC_HARDPPS_FLL	2	/* hardpps() constrained to
+					   use a frequency-locked loop */
+/*
+ * Here begins the implementation-specific part!
+ */
+
+struct pps_fdata {
+	struct pps_kinfo info;
+	struct pps_ktime timeout;
+};
+
+#include <linux/ioctl.h>
+
+#define PPS_CHECK		_IO('p', 0xa0)
+#define PPS_GETPARAMS		_IOR('p', 0xa1, struct pps_kparams *)
+#define PPS_SETPARAMS		_IOW('p', 0xa2, struct pps_kparams *)
+#define PPS_GETCAP		_IOR('p', 0xa3, int *)
+#define PPS_FETCH		_IOWR('p', 0xa4, struct pps_fdata *)
+
+#ifdef __KERNEL__
+
+#include <linux/cdev.h>
+#include <linux/device.h>
+#include <linux/time.h>
+
+/*
+ * Global defines
+ */
+
+/* The specific PPS source info */
+struct pps_source_info {
+	char name[PPS_MAX_NAME_LEN];		/* simbolic name */
+	char path[PPS_MAX_NAME_LEN];		/* path of connected device */
+	int mode;				/* PPS's allowed mode */
+
+	void (*echo)(int source, int event, void *data); /* PPS echo function */
+
+	struct module *owner;
+	struct device *dev;
+};
+
+/* The main struct */
+struct pps_device {
+	struct pps_source_info info;		/* PSS source info */
+
+	struct pps_kparams params;		/* PPS's current params */
+
+	__u32 assert_sequence;			/* PPS' assert event seq # */
+	__u32 clear_sequence;			/* PPS' clear event seq # */
+	struct pps_ktime assert_tu;
+	struct pps_ktime clear_tu;
+	int current_mode;			/* PPS mode at event time */
+
+	int go;					/* PPS event is arrived? */
+	wait_queue_head_t queue;		/* PPS event queue */
+
+	unsigned int id;			/* PPS source unique ID */
+	struct cdev cdev;
+	struct device *dev;
+	int devno;
+	struct fasync_struct *async_queue;	/* fasync method */
+	spinlock_t lock;
+
+	atomic_t usage;				/* usage count */
+};
+
+/*
+ * Global variables
+ */
+
+extern spinlock_t pps_idr_lock;
+extern struct idr pps_idr;
+
+extern struct device_attribute pps_attrs[];
+
+/*
+ * Exported functions
+ */
+
+struct pps_device *pps_get_source(int source);
+extern void pps_put_source(struct pps_device *pps);
+extern int pps_register_source(struct pps_source_info *info,
+				int default_params);
+extern void pps_unregister_source(int source);
+extern int pps_register_cdev(struct pps_device *pps);
+extern void pps_unregister_cdev(struct pps_device *pps);
+extern void pps_event(int source, struct pps_ktime *ts, int event, void *data);
+
+#endif /* __KERNEL__ */
+
+#endif /* _PPS_H_ */
-- 
1.5.6.3

Re: [PATCH 1/1] LinuxPPS core support.

[Christoph Hellwig]

> +static long pps_cdev_ioctl(struct file *file,
> +		unsigned int cmd, unsigned long arg)
> +{
> +	struct pps_device *pps = file->private_data;
> +	struct pps_kparams params;
> +	struct pps_fdata fdata;
> +	unsigned long ticks;
> +	void __user *uarg = (void __user *) arg;
> +	int __user *iuarg = (int __user *) arg;
> +	int err;
> +
> +	switch (cmd) {
> +	case PPS_CHECK:
> +
> +		/* This does nothing but signal we are a PPS source... */
> +
> +		return 0;

I think this one is superflous.  Just doing a PPS_GETPARAMS: should get
your the same information..

> +	case PPS_GETPARAMS:
> +		pr_debug("PPS_GETPARAMS: source %d\n", pps->id);
> +
> +		/* Return current parameters */
> +		err = copy_to_user(uarg, &pps->params,
> +						sizeof(struct pps_kparams));
> +		if (err)
> +			return -EFAULT;
> +
> +		break;
> +
> +	case PPS_SETPARAMS:
> +		pr_debug("PPS_SETPARAMS: source %d\n", pps->id);
> +
> +		/* Check the capabilities */
> +		if (!capable(CAP_SYS_TIME))
> +			return -EPERM;
> +
> +		err = copy_from_user(&params, uarg, sizeof(struct pps_kparams));
> +		if (err)
> +			return -EFAULT;
> +		if (!(params.mode & (PPS_CAPTUREASSERT | PPS_CAPTURECLEAR))) {
> +			pr_debug("capture mode unspecified (%x)\n",
> +								params.mode);
> +			return -EINVAL;
> +		}

Note that splitting out any non-trivial ioctl into it's own small helper
function gives generally much cleaner code.

> +	if (pps_devt)
> +		unregister_chrdev_region(pps_devt, PPS_MAX_SOURCES);

Given that you have proper error handling in pps_init this can't
ever be zero.

> +
> +	pr_info("LinuxPPS API ver. %d removed\n", PPS_API_VERS);

Printing stuff on exit is rather noisy and should be avoided

[PATCH 1/1] LinuxPPS core support.

[Rodolfo Giometti]

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>
---
 Documentation/ABI/testing/sysfs-pps  |   73 ++++++++
 Documentation/ioctl/ioctl-number.txt |    2 +
 Documentation/pps/pps.txt            |  172 ++++++++++++++++++
 MAINTAINERS                          |    7 +
 drivers/Kconfig                      |    2 +
 drivers/Makefile                     |    1 +
 drivers/pps/Kconfig                  |   33 ++++
 drivers/pps/Makefile                 |    8 +
 drivers/pps/kapi.c                   |  329 ++++++++++++++++++++++++++++++++++
 drivers/pps/pps.c                    |  312 ++++++++++++++++++++++++++++++++
 drivers/pps/sysfs.c                  |  104 +++++++++++
 include/linux/Kbuild                 |    1 +
 include/linux/pps.h                  |  194 ++++++++++++++++++++
 13 files changed, 1238 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-pps
 create mode 100644 Documentation/pps/pps.txt
 create mode 100644 drivers/pps/Kconfig
 create mode 100644 drivers/pps/Makefile
 create mode 100644 drivers/pps/kapi.c
 create mode 100644 drivers/pps/pps.c
 create mode 100644 drivers/pps/sysfs.c
 create mode 100644 include/linux/pps.h

diff --git a/Documentation/ABI/testing/sysfs-pps b/Documentation/ABI/testing/sysfs-pps
new file mode 100644
index 0000000..25028c7
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-pps
@@ -0,0 +1,73 @@
+What:		/sys/class/pps/
+Date:		February 2008
+Contact:	Rodolfo Giometti <giometti@linux.it>
+Description:
+		The /sys/class/pps/ directory will contain files and
+		directories that will provide a unified interface to
+		the PPS sources.
+
+What:		/sys/class/pps/ppsX/
+Date:		February 2008
+Contact:	Rodolfo Giometti <giometti@linux.it>
+Description:
+		The /sys/class/pps/ppsX/ directory is related to X-th
+		PPS source into the system. Each directory will
+		contain files to manage and control its PPS source.
+
+What:		/sys/class/pps/ppsX/assert
+Date:		February 2008
+Contact:	Rodolfo Giometti <giometti@linux.it>
+Description:
+		The /sys/class/pps/ppsX/assert file reports the assert events
+		and the assert sequence number of the X-th source in the form:
+
+			<secs>.<nsec>#<sequence>
+
+		If the source has no assert events the content of this file
+		is empty.
+
+What:		/sys/class/pps/ppsX/clear
+Date:		February 2008
+Contact:	Rodolfo Giometti <giometti@linux.it>
+Description:
+		The /sys/class/pps/ppsX/clear file reports the clear events
+		and the clear sequence number of the X-th source in the form:
+
+			<secs>.<nsec>#<sequence>
+
+		If the source has no clear events the content of this file
+		is empty.
+
+What:		/sys/class/pps/ppsX/mode
+Date:		February 2008
+Contact:	Rodolfo Giometti <giometti@linux.it>
+Description:
+		The /sys/class/pps/ppsX/mode file reports the functioning
+		mode of the X-th source in hexadecimal encoding.
+
+		Please, refer to linux/include/linux/pps.h for further
+		info.
+
+What:		/sys/class/pps/ppsX/echo
+Date:		February 2008
+Contact:	Rodolfo Giometti <giometti@linux.it>
+Description:
+		The /sys/class/pps/ppsX/echo file reports if the X-th does
+		or does not support an "echo" function.
+
+What:		/sys/class/pps/ppsX/name
+Date:		February 2008
+Contact:	Rodolfo Giometti <giometti@linux.it>
+Description:
+		The /sys/class/pps/ppsX/name file reports the name of the
+		X-th source.
+
+What:		/sys/class/pps/ppsX/path
+Date:		February 2008
+Contact:	Rodolfo Giometti <giometti@linux.it>
+Description:
+		The /sys/class/pps/ppsX/path file reports the path name of
+		the device connected with the X-th source.
+
+		If the source is not connected with any device the content
+		of this file is empty.
diff --git a/Documentation/ioctl/ioctl-number.txt b/Documentation/ioctl/ioctl-number.txt
index f1d6399..df7aeca 100644
--- a/Documentation/ioctl/ioctl-number.txt
+++ b/Documentation/ioctl/ioctl-number.txt
@@ -151,6 +151,8 @@ Code	Seq#	Include File		Comments
 'p'	40-7F	linux/nvram.h
 'p'	80-9F				user-space parport
 					<mailto:tim@cyberelk.net>
+'p'	a1-a4	linux/pps.h		LinuxPPS
+					<mailto:giometti@linux.it>
 'q'	00-1F	linux/serio.h
 'q'	80-FF				Internet PhoneJACK, Internet LineJACK
 					<http://www.quicknet.net>
diff --git a/Documentation/pps/pps.txt b/Documentation/pps/pps.txt
new file mode 100644
index 0000000..125f4ab
--- /dev/null
+++ b/Documentation/pps/pps.txt
@@ -0,0 +1,172 @@
+
+			PPS - Pulse Per Second
+			----------------------
+
+(C) Copyright 2007 Rodolfo Giometti <giometti@enneenne.com>
+
+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.
+
+
+
+Overview
+--------
+
+LinuxPPS provides a programming interface (API) to define in the
+system several PPS sources.
+
+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.
+
+A PPS source can be connected to a serial port (usually to the Data
+Carrier Detect pin) or to a parallel port (ACK-pin) or to a special
+CPU's GPIOs (this is the common case in embedded systems) but in each
+case when a new pulse arrives the system must apply to it a timestamp
+and record it for userland.
+
+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.
+
+
+RFC considerations
+------------------
+
+While implementing a PPS API as RFC 2783 defines and using an embedded
+CPU GPIO-Pin as physical link to the signal, I encountered a deeper
+problem:
+
+   At startup it needs a file descriptor as argument for the function
+   time_pps_create().
+
+This implies that the source has a /dev/... entry. This assumption is
+ok for the serial and parallel port, where you can do something
+useful besides(!) the gathering of timestamps as it is the central
+task for a PPS-API. But this assumption does not work for a single
+purpose GPIO line. In this case even basic file-related functionality
+(like read() and write()) makes no sense at all and should not be a
+precondition for the use of a PPS-API.
+
+The problem can be simply solved if you consider that a PPS source is
+not always connected with a GPS data source.
+
+So your programs should check if the GPS data source (the serial port
+for instance) is a PPS source too, and if not they should provide the
+possibility to open another device as PPS source.
+
+In LinuxPPS the PPS sources are simply char devices usually mapped
+into files /dev/pps0, /dev/pps1, etc..
+
+
+Coding example
+--------------
+
+To register a PPS source into the kernel you should define a struct
+pps_source_info_s as follows:
+
+    static struct pps_source_info pps_ktimer_info = {
+	    .name         = "ktimer",
+	    .path         = "",
+	    .mode         = PPS_CAPTUREASSERT | PPS_OFFSETASSERT | \
+			    PPS_ECHOASSERT | \
+			    PPS_CANWAIT | PPS_TSFMT_TSPEC,
+	    .echo         = pps_ktimer_echo,
+	    .owner        = THIS_MODULE,
+    };
+
+and then calling the function pps_register_source() in your
+intialization routine as follows:
+
+    source = pps_register_source(&pps_ktimer_info,
+			PPS_CAPTUREASSERT | PPS_OFFSETASSERT);
+
+The pps_register_source() prototype is:
+
+  int pps_register_source(struct pps_source_info_s *info, int default_params)
+
+where "info" is a pointer to a structure that describes a particular
+PPS source, "default_params" tells the system what the initial default
+parameters for the device should be (it is obvious that these parameters
+must be a subset of ones defined in the struct
+pps_source_info_s which describe the capabilities of the driver).
+
+Once you have registered a new PPS source into the system you can
+signal an assert event (for example in the interrupt handler routine)
+just using:
+
+    pps_event(source, &ts, PPS_CAPTUREASSERT, ptr)
+
+where "ts" is the event's timestamp.
+
+The same function may also run the defined echo function
+(pps_ktimer_echo(), passing to it the "ptr" pointer) if the user
+asked for that... etc..
+
+Please see the file drivers/pps/clients/ktimer.c for example code.
+
+
+SYSFS support
+-------------
+
+If the SYSFS filesystem is enabled in the kernel it provides a new class:
+
+   $ ls /sys/class/pps/
+   pps0/  pps1/  pps2/
+
+Every directory is the ID of a PPS sources defined in the system and
+inside you find several files:
+
+   $ ls /sys/class/pps/pps0/
+   assert	clear  echo  mode  name  path  subsystem@  uevent
+
+Inside each "assert" and "clear" file you can find the timestamp and a
+sequence number:
+
+   $ cat /sys/class/pps/pps0/assert
+   1170026870.983207967#8
+
+Where before the "#" is the timestamp in seconds; after it is the
+sequence number. Other files are:
+
+* echo: reports if the PPS source has an echo function or not;
+
+* mode: reports available PPS functioning modes;
+
+* name: reports the PPS source's name;
+
+* path: reports the PPS source's device path, that is the device the
+  PPS source is connected to (if it exists).
+
+
+Testing the PPS support
+-----------------------
+
+In order to test the PPS support even without specific hardware you can use
+the ktimer driver (see the client subsection in the PPS configuration menu)
+and the userland tools provided into Documentaion/pps/ directory.
+
+Once you have enabled the compilation of ktimer just modprobe it (if
+not statically compiled):
+
+   # modprobe ktimer
+
+and the run ppstest as follow:
+
+   $ ./ppstest /dev/pps0
+   trying PPS source "/dev/pps1"
+   found PPS source "/dev/pps1"
+   ok, found 1 source(s), now start fetching data...
+   source 0 - assert 1186592699.388832443, sequence: 364 - clear  0.000000000, sequence: 0
+   source 0 - assert 1186592700.388931295, sequence: 365 - clear  0.000000000, sequence: 0
+   source 0 - assert 1186592701.389032765, sequence: 366 - clear  0.000000000, sequence: 0
+
+Please, note that to compile userland programs you need the file timepps.h
+(see Documentation/pps/).
diff --git a/MAINTAINERS b/MAINTAINERS
index d992d40..d2ab232 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3464,6 +3464,13 @@ P:	James Chapman
 M:	jchapman@katalix.com
 S:	Maintained
 
+PPS SUPPORT
+P:	Rodolfo Giometti
+M:	giometti@enneenne.com
+W:	http://wiki.enneenne.com/index.php/LinuxPPS_support
+L:	linuxpps@ml.enneenne.com (subscribers-only)
+S:	Maintained
+
 PREEMPTIBLE KERNEL
 P:	Robert Love
 M:	rml@tech9.net
diff --git a/drivers/Kconfig b/drivers/Kconfig
index 00cf955..e328e5b 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -52,6 +52,8 @@ source "drivers/i2c/Kconfig"
 
 source "drivers/spi/Kconfig"
 
+source "drivers/pps/Kconfig"
+
 source "drivers/gpio/Kconfig"
 
 source "drivers/w1/Kconfig"
diff --git a/drivers/Makefile b/drivers/Makefile
index c1bf417..ff07ab9 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -71,6 +71,7 @@ obj-$(CONFIG_INPUT)		+= input/
 obj-$(CONFIG_I2O)		+= message/
 obj-$(CONFIG_RTC_LIB)		+= rtc/
 obj-y				+= i2c/
+obj-$(CONFIG_PPS)		+= pps/
 obj-$(CONFIG_W1)		+= w1/
 obj-$(CONFIG_POWER_SUPPLY)	+= power/
 obj-$(CONFIG_HWMON)		+= hwmon/
diff --git a/drivers/pps/Kconfig b/drivers/pps/Kconfig
new file mode 100644
index 0000000..cc2eb8e
--- /dev/null
+++ b/drivers/pps/Kconfig
@@ -0,0 +1,33 @@
+#
+# PPS support configuration
+#
+
+menu "PPS support"
+
+config PPS
+	tristate "PPS support"
+	depends on EXPERIMENTAL
+	---help---
+	  PPS (Pulse Per Second) is a special pulse provided by some GPS
+	  antennae. Userland can use it to get a high-precision time
+	  reference.
+
+	  Some antennae's PPS signals are connected with the CD (Carrier
+	  Detect) pin of the serial line they use to communicate with the
+	  host. In this case use the SERIAL_LINE client support.
+
+	  Some antennae's PPS signals are connected with some special host
+	  inputs so you have to enable the corresponding client support.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pps_core.ko.
+
+config PPS_DEBUG
+	bool "PPS debugging messages"
+	depends on PPS
+	help
+	  Say Y here if you want the PPS support to produce a bunch of debug
+	  messages to the system log.  Select this if you are having a
+	  problem with PPS support and want to see more of what is going on.
+
+endmenu
diff --git a/drivers/pps/Makefile b/drivers/pps/Makefile
new file mode 100644
index 0000000..19ea582
--- /dev/null
+++ b/drivers/pps/Makefile
@@ -0,0 +1,8 @@
+#
+# Makefile for the PPS core.
+#
+
+pps_core-y			:= pps.o kapi.o sysfs.o
+obj-$(CONFIG_PPS)		:= pps_core.o
+
+ccflags-$(CONFIG_PPS_DEBUG) := -DDEBUG
diff --git a/drivers/pps/kapi.c b/drivers/pps/kapi.c
new file mode 100644
index 0000000..e0b75ed
--- /dev/null
+++ b/drivers/pps/kapi.c
@@ -0,0 +1,329 @@
+/*
+ * kernel API
+ *
+ *
+ * Copyright (C) 2005-2009   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/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/time.h>
+#include <linux/spinlock.h>
+#include <linux/idr.h>
+#include <linux/fs.h>
+#include <linux/pps.h>
+
+/*
+ * Global variables
+ */
+
+DEFINE_SPINLOCK(pps_idr_lock);
+DEFINE_IDR(pps_idr);
+
+/*
+ * Local functions
+ */
+
+static void pps_add_offset(struct pps_ktime *ts, struct pps_ktime *offset)
+{
+	ts->nsec += offset->nsec;
+	while (ts->nsec >= NSEC_PER_SEC) {
+		ts->nsec -= NSEC_PER_SEC;
+		ts->sec++;
+	}
+	while (ts->nsec < 0) {
+		ts->nsec += NSEC_PER_SEC;
+		ts->sec--;
+	}
+	ts->sec += offset->sec;
+}
+
+/*
+ * Exported functions
+ */
+
+/* pps_get_source - find a PPS source
+ * @source: the PPS source ID.
+ *
+ * This function is used to find an already registered PPS source into the
+ * system.
+ *
+ * The function returns NULL if found nothing, otherwise it returns a pointer
+ * to the PPS source data struct (the refcounter is incremented by 1).
+ */
+
+struct pps_device *pps_get_source(int source)
+{
+	struct pps_device *pps;
+	unsigned long flags;
+
+	spin_lock_irqsave(&pps_idr_lock, flags);
+
+	pps = idr_find(&pps_idr, source);
+	if (pps != NULL)
+		atomic_inc(&pps->usage);
+
+	spin_unlock_irqrestore(&pps_idr_lock, flags);
+
+	return pps;
+}
+
+/* pps_put_source - free the PPS source data
+ * @pps: a pointer to the PPS source.
+ *
+ * This function is used to free a PPS data struct if its refcount is 0.
+ */
+
+void pps_put_source(struct pps_device *pps)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&pps_idr_lock, flags);
+	BUG_ON(atomic_read(&pps->usage) == 0);
+
+	if (!atomic_dec_and_test(&pps->usage)) {
+		pps = NULL;
+		goto exit;
+	}
+
+	/* No more reference to the PPS source. We can safely remove the
+	 * PPS data struct.
+	 */
+	idr_remove(&pps_idr, pps->id);
+
+exit:
+	spin_unlock_irqrestore(&pps_idr_lock, flags);
+	kfree(pps);
+}
+
+/* pps_register_source - add a PPS source in the system
+ * @info: the PPS info struct
+ * @default_params: the default PPS parameters of the new source
+ *
+ * This function is used to add a new PPS source in the system. The new
+ * source is described by info's fields and it will have, as default PPS
+ * parameters, the ones specified into default_params.
+ *
+ * The function returns, in case of success, the PPS source ID.
+ */
+
+int pps_register_source(struct pps_source_info *info, int default_params)
+{
+	struct pps_device *pps;
+	int id;
+	int err;
+
+	/* Sanity checks */
+	if ((info->mode & default_params) != default_params) {
+		printk(KERN_ERR "pps: %s: unsupported default parameters\n",
+					info->name);
+		err = -EINVAL;
+		goto pps_register_source_exit;
+	}
+	if ((info->mode & (PPS_ECHOASSERT | PPS_ECHOCLEAR)) != 0 &&
+			info->echo == NULL) {
+		printk(KERN_ERR "pps: %s: echo function is not defined\n",
+					info->name);
+		err = -EINVAL;
+		goto pps_register_source_exit;
+	}
+	if ((info->mode & (PPS_TSFMT_TSPEC | PPS_TSFMT_NTPFP)) == 0) {
+		printk(KERN_ERR "pps: %s: unspecified time format\n",
+					info->name);
+		err = -EINVAL;
+		goto pps_register_source_exit;
+	}
+
+	/* Allocate memory for the new PPS source struct */
+	pps = kzalloc(sizeof(struct pps_device), GFP_KERNEL);
+	if (pps == NULL) {
+		err = -ENOMEM;
+		goto pps_register_source_exit;
+	}
+
+	/* These initializations must be done before calling idr_get_new()
+	 * in order to avoid reces into pps_event().
+	 */
+	pps->params.api_version = PPS_API_VERS;
+	pps->params.mode = default_params;
+	pps->info = *info;
+
+	init_waitqueue_head(&pps->queue);
+	spin_lock_init(&pps->lock);
+	atomic_set(&pps->usage, 1);
+
+	/* Get new ID for the new PPS source */
+	if (idr_pre_get(&pps_idr, GFP_KERNEL) == 0) {
+		err = -ENOMEM;
+		goto kfree_pps;
+	}
+
+	spin_lock_irq(&pps_idr_lock);
+
+	/* Now really allocate the PPS source.
+	 * After idr_get_new() calling the new source will be freely available
+	 * into the kernel.
+	 */
+	err = idr_get_new(&pps_idr, pps, &id);
+	if (err < 0) {
+		spin_unlock_irq(&pps_idr_lock);
+		goto kfree_pps;
+	}
+
+	id = id & MAX_ID_MASK;
+	if (id >= PPS_MAX_SOURCES) {
+		spin_unlock_irq(&pps_idr_lock);
+
+		printk(KERN_ERR "pps: %s: too many PPS sources in the system\n",
+					info->name);
+		err = -EBUSY;
+		goto free_idr;
+	}
+	pps->id = id;
+
+	spin_unlock_irq(&pps_idr_lock);
+
+	/* Create the char device */
+	err = pps_register_cdev(pps);
+	if (err < 0) {
+		printk(KERN_ERR "pps: %s: unable to create char device\n",
+					info->name);
+		goto free_idr;
+	}
+
+	pr_info("new PPS source %s at ID %d\n", info->name, id);
+
+	return id;
+
+free_idr:
+	spin_lock_irq(&pps_idr_lock);
+	idr_remove(&pps_idr, id);
+	spin_unlock_irq(&pps_idr_lock);
+
+kfree_pps:
+	kfree(pps);
+
+pps_register_source_exit:
+	printk(KERN_ERR "pps: %s: unable to register source\n", info->name);
+
+	return err;
+}
+EXPORT_SYMBOL(pps_register_source);
+
+/* pps_unregister_source - remove a PPS source from the system
+ * @source: the PPS source ID
+ *
+ * This function is used to remove a previously registered PPS source from
+ * the system.
+ */
+
+void pps_unregister_source(int source)
+{
+	struct pps_device *pps;
+
+	spin_lock_irq(&pps_idr_lock);
+	pps = idr_find(&pps_idr, source);
+
+	if (!pps) {
+		BUG();
+		spin_unlock_irq(&pps_idr_lock);
+		return;
+	}
+	spin_unlock_irq(&pps_idr_lock);
+
+	pps_unregister_cdev(pps);
+	pps_put_source(pps);
+}
+EXPORT_SYMBOL(pps_unregister_source);
+
+/* pps_event - register a PPS event into the system
+ * @source: the PPS source ID
+ * @ts: the event timestamp
+ * @event: the event type
+ * @data: userdef pointer
+ *
+ * This function is used by each PPS client in order to register a new
+ * PPS event into the system (it's usually called inside an IRQ handler).
+ *
+ * If an echo function is associated with the PPS source it will be called
+ * as:
+ *	pps->info.echo(source, event, data);
+ */
+
+void pps_event(int source, struct pps_ktime *ts, int event, void *data)
+{
+	struct pps_device *pps;
+	unsigned long flags;
+
+	if ((event & (PPS_CAPTUREASSERT | PPS_CAPTURECLEAR)) == 0) {
+		printk(KERN_ERR "pps: unknown event (%x) for source %d\n",
+			event, source);
+		return;
+	}
+
+	pps = pps_get_source(source);
+	if (!pps)
+		return;
+
+	pr_debug("PPS event on source %d at %llu.%06u\n",
+			pps->id, (unsigned long long) ts->sec, ts->nsec);
+
+	spin_lock_irqsave(&pps->lock, flags);
+
+	/* Must call the echo function? */
+	if ((pps->params.mode & (PPS_ECHOASSERT | PPS_ECHOCLEAR)))
+		pps->info.echo(source, event, data);
+
+	/* Check the event */
+	pps->current_mode = pps->params.mode;
+	if (event & PPS_CAPTUREASSERT) {
+		/* We have to add an offset? */
+		if (pps->params.mode & PPS_OFFSETASSERT)
+			pps_add_offset(ts, &pps->params.assert_off_tu);
+
+		/* Save the time stamp */
+		pps->assert_tu = *ts;
+		pps->assert_sequence++;
+		pr_debug("capture assert seq #%u for source %d\n",
+			pps->assert_sequence, source);
+	}
+	if (event & PPS_CAPTURECLEAR) {
+		/* We have to add an offset? */
+		if (pps->params.mode & PPS_OFFSETCLEAR)
+			pps_add_offset(ts, &pps->params.clear_off_tu);
+
+		/* Save the time stamp */
+		pps->clear_tu = *ts;
+		pps->clear_sequence++;
+		pr_debug("capture clear seq #%u for source %d\n",
+			pps->clear_sequence, source);
+	}
+
+	pps->go = ~0;
+	wake_up_interruptible(&pps->queue);
+
+	kill_fasync(&pps->async_queue, SIGIO, POLL_IN);
+
+	spin_unlock_irqrestore(&pps->lock, flags);
+
+	/* Now we can release the PPS source for (possible) deregistration */
+	pps_put_source(pps);
+}
+EXPORT_SYMBOL(pps_event);
diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
new file mode 100644
index 0000000..23ea070
--- /dev/null
+++ b/drivers/pps/pps.c
@@ -0,0 +1,312 @@
+/*
+ * PPS core file
+ *
+ *
+ * Copyright (C) 2005-2009   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/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/uaccess.h>
+#include <linux/idr.h>
+#include <linux/cdev.h>
+#include <linux/poll.h>
+#include <linux/pps.h>
+
+/*
+ * Local variables
+ */
+
+static dev_t pps_devt;
+static struct class *pps_class;
+
+/*
+ * Char device methods
+ */
+
+static unsigned int pps_cdev_poll(struct file *file, poll_table *wait)
+{
+	struct pps_device *pps = file->private_data;
+
+	poll_wait(file, &pps->queue, wait);
+
+	return POLLIN | POLLRDNORM;
+}
+
+static int pps_cdev_fasync(int fd, struct file *file, int on)
+{
+	struct pps_device *pps = file->private_data;
+	return fasync_helper(fd, file, on, &pps->async_queue);
+}
+
+static long pps_cdev_ioctl(struct file *file,
+		unsigned int cmd, unsigned long arg)
+{
+	struct pps_device *pps = file->private_data;
+	struct pps_kparams params;
+	struct pps_fdata fdata;
+	unsigned long ticks;
+	void __user *uarg = (void __user *) arg;
+	int __user *iuarg = (int __user *) arg;
+	int err;
+
+	switch (cmd) {
+	case PPS_GETPARAMS:
+		pr_debug("PPS_GETPARAMS: source %d\n", pps->id);
+
+		/* Return current parameters */
+		err = copy_to_user(uarg, &pps->params,
+						sizeof(struct pps_kparams));
+		if (err)
+			return -EFAULT;
+
+		break;
+
+	case PPS_SETPARAMS:
+		pr_debug("PPS_SETPARAMS: source %d\n", pps->id);
+
+		/* Check the capabilities */
+		if (!capable(CAP_SYS_TIME))
+			return -EPERM;
+
+		err = copy_from_user(&params, uarg, sizeof(struct pps_kparams));
+		if (err)
+			return -EFAULT;
+		if (!(params.mode & (PPS_CAPTUREASSERT | PPS_CAPTURECLEAR))) {
+			pr_debug("capture mode unspecified (%x)\n",
+								params.mode);
+			return -EINVAL;
+		}
+
+		/* Check for supported capabilities */
+		if ((params.mode & ~pps->info.mode) != 0) {
+			pr_debug("unsupported capabilities (%x)\n",
+								params.mode);
+			return -EINVAL;
+		}
+
+		spin_lock_irq(&pps->lock);
+
+		/* Save the new parameters */
+		pps->params = params;
+
+		/* Restore the read only parameters */
+		if ((params.mode & (PPS_TSFMT_TSPEC | PPS_TSFMT_NTPFP)) == 0) {
+			/* section 3.3 of RFC 2783 interpreted */
+			pr_debug("time format unspecified (%x)\n",
+								params.mode);
+			pps->params.mode |= PPS_TSFMT_TSPEC;
+		}
+		if (pps->info.mode & PPS_CANWAIT)
+			pps->params.mode |= PPS_CANWAIT;
+		pps->params.api_version = PPS_API_VERS;
+
+		spin_unlock_irq(&pps->lock);
+
+		break;
+
+	case PPS_GETCAP:
+		pr_debug("PPS_GETCAP: source %d\n", pps->id);
+
+		err = put_user(pps->info.mode, iuarg);
+		if (err)
+			return -EFAULT;
+
+		break;
+
+	case PPS_FETCH:
+		pr_debug("PPS_FETCH: source %d\n", pps->id);
+
+		err = copy_from_user(&fdata, uarg, sizeof(struct pps_fdata));
+		if (err)
+			return -EFAULT;
+
+		pps->go = 0;
+
+		/* Manage the timeout */
+		if (fdata.timeout.flags & PPS_TIME_INVALID)
+			err = wait_event_interruptible(pps->queue, pps->go);
+		else {
+			pr_debug("timeout %lld.%09d\n",
+					(long long) fdata.timeout.sec,
+					fdata.timeout.nsec);
+			ticks = fdata.timeout.sec * HZ;
+			ticks += fdata.timeout.nsec / (NSEC_PER_SEC / HZ);
+
+			if (ticks != 0) {
+				err = wait_event_interruptible_timeout(
+						pps->queue, pps->go, ticks);
+				if (err == 0)
+					return -ETIMEDOUT;
+			}
+		}
+
+		/* Check for pending signals */
+		if (err == -ERESTARTSYS) {
+			pr_debug("pending signal caught\n");
+			return -EINTR;
+		}
+
+		/* Return the fetched timestamp */
+		spin_lock_irq(&pps->lock);
+
+		fdata.info.assert_sequence = pps->assert_sequence;
+		fdata.info.clear_sequence = pps->clear_sequence;
+		fdata.info.assert_tu = pps->assert_tu;
+		fdata.info.clear_tu = pps->clear_tu;
+		fdata.info.current_mode = pps->current_mode;
+
+		spin_unlock_irq(&pps->lock);
+
+		err = copy_to_user(uarg, &fdata, sizeof(struct pps_fdata));
+		if (err)
+			return -EFAULT;
+
+		break;
+
+	default:
+		return -ENOTTY;
+		break;
+	}
+
+	return 0;
+}
+
+static int pps_cdev_open(struct inode *inode, struct file *file)
+{
+	struct pps_device *pps = container_of(inode->i_cdev,
+						struct pps_device, cdev);
+	int found;
+
+	found = pps_get_source(pps->id) != 0;
+	if (!found)
+		return -ENODEV;
+
+	file->private_data = pps;
+
+	return 0;
+}
+
+static int pps_cdev_release(struct inode *inode, struct file *file)
+{
+	struct pps_device *pps = file->private_data;
+
+	/* Free the PPS source and wake up (possible) deregistration */
+	pps_put_source(pps);
+
+	return 0;
+}
+
+/*
+ * Char device stuff
+ */
+
+static const struct file_operations pps_cdev_fops = {
+	.owner		= THIS_MODULE,
+	.llseek		= no_llseek,
+	.poll		= pps_cdev_poll,
+	.fasync		= pps_cdev_fasync,
+	.unlocked_ioctl	= pps_cdev_ioctl,
+	.open		= pps_cdev_open,
+	.release	= pps_cdev_release,
+};
+
+int pps_register_cdev(struct pps_device *pps)
+{
+	int err;
+
+	pps->devno = MKDEV(MAJOR(pps_devt), pps->id);
+	cdev_init(&pps->cdev, &pps_cdev_fops);
+	pps->cdev.owner = pps->info.owner;
+
+	err = cdev_add(&pps->cdev, pps->devno, 1);
+	if (err) {
+		printk(KERN_ERR "pps: %s: failed to add char device %d:%d\n",
+				pps->info.name, MAJOR(pps_devt), pps->id);
+		return err;
+	}
+	pps->dev = device_create(pps_class, pps->info.dev, pps->devno, NULL,
+							"pps%d", pps->id);
+	if (err)
+		goto del_cdev;
+	dev_set_drvdata(pps->dev, pps);
+
+	pr_debug("source %s got cdev (%d:%d)\n", pps->info.name,
+			MAJOR(pps_devt), pps->id);
+
+	return 0;
+
+del_cdev:
+	cdev_del(&pps->cdev);
+
+	return err;
+}
+
+void pps_unregister_cdev(struct pps_device *pps)
+{
+	device_destroy(pps_class, pps->devno);
+	cdev_del(&pps->cdev);
+}
+
+/*
+ * Module stuff
+ */
+
+static void __exit pps_exit(void)
+{
+	class_destroy(pps_class);
+	unregister_chrdev_region(pps_devt, PPS_MAX_SOURCES);
+}
+
+static int __init pps_init(void)
+{
+	int err;
+
+	pps_class = class_create(THIS_MODULE, "pps");
+	if (!pps_class) {
+		printk(KERN_ERR "pps: failed to allocate class\n");
+		return -ENOMEM;
+	}
+	pps_class->dev_attrs = pps_attrs;
+
+	err = alloc_chrdev_region(&pps_devt, 0, PPS_MAX_SOURCES, "pps");
+	if (err < 0) {
+		printk(KERN_ERR "pps: failed to allocate char device region\n");
+		goto remove_class;
+	}
+
+	pr_info("LinuxPPS API ver. %d registered\n", PPS_API_VERS);
+	pr_info("Software ver. %s - Copyright 2005-2007 Rodolfo Giometti "
+		"<giometti@linux.it>\n", PPS_VERSION);
+
+	return 0;
+
+remove_class:
+	class_destroy(pps_class);
+
+	return err;
+}
+
+subsys_initcall(pps_init);
+module_exit(pps_exit);
+
+MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
+MODULE_DESCRIPTION("LinuxPPS support (RFC 2783) - ver. " PPS_VERSION);
+MODULE_LICENSE("GPL");
diff --git a/drivers/pps/sysfs.c b/drivers/pps/sysfs.c
new file mode 100644
index 0000000..43c3b49
--- /dev/null
+++ b/drivers/pps/sysfs.c
@@ -0,0 +1,104 @@
+/*
+ * 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.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);
+}
+DEVICE_ATTR(assert, S_IRUGO, pps_show_assert, NULL);
+
+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);
+}
+DEVICE_ATTR(clear, S_IRUGO, pps_show_clear, NULL);
+
+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);
+}
+DEVICE_ATTR(mode, S_IRUGO, pps_show_mode, NULL);
+
+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);
+}
+DEVICE_ATTR(echo, S_IRUGO, pps_show_echo, NULL);
+
+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);
+}
+DEVICE_ATTR(name, S_IRUGO, pps_show_name, NULL);
+
+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);
+}
+DEVICE_ATTR(path, S_IRUGO, pps_show_path, NULL);
+
+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,
+};
diff --git a/include/linux/Kbuild b/include/linux/Kbuild
index 12e9a29..5df789c 100644
--- a/include/linux/Kbuild
+++ b/include/linux/Kbuild
@@ -304,6 +304,7 @@ unifdef-y += pmu.h
 unifdef-y += poll.h
 unifdef-y += ppp_defs.h
 unifdef-y += ppp-comp.h
+unifdef-y += pps.h
 unifdef-y += ptrace.h
 unifdef-y += qnx4_fs.h
 unifdef-y += quota.h
diff --git a/include/linux/pps.h b/include/linux/pps.h
new file mode 100644
index 0000000..d00ac05
--- /dev/null
+++ b/include/linux/pps.h
@@ -0,0 +1,194 @@
+/*
+ * PPS API kernel header
+ *
+ *
+ * Copyright (C) 2005-2009   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.
+ */
+
+
+#ifndef _PPS_H_
+#define _PPS_H_
+
+#define PPS_VERSION		"5.3.5"
+#define PPS_MAX_SOURCES		16		/* should be enough... */
+
+/* Implementation note: the logical states ``assert'' and ``clear''
+ * are implemented in terms of the chip register, i.e. ``assert''
+ * means the bit is set.  */
+
+/*
+ * 3.2 New data structures
+ */
+
+#define PPS_API_VERS_1		1
+#define PPS_API_VERS		PPS_API_VERS_1	/* we use API version 1 */
+#define PPS_MAX_NAME_LEN	32
+
+/* 32-bit vs. 64-bit compatibility.
+ *
+ * 0n i386, the alignment of a uint64_t is only 4 bytes, while on most other
+ * architectures it's 8 bytes. On i386, there will be no padding between the
+ * two consecutive 'struct pps_ktime' members of struct pps_kinfo and struct
+ * pps_kparams. But on most platforms there will be padding to ensure correct
+ * alignment.
+ *
+ * The simple fix is probably to add an explicit padding.
+ *					 		[David Woodhouse]
+ */
+struct pps_ktime {
+	__s64 sec;
+	__s32 nsec;
+	__u32 flags;
+};
+#define PPS_TIME_INVALID	(1<<0)	/* used to specify timeout==NULL */
+
+struct pps_kinfo {
+	__u32 assert_sequence;		/* seq. num. of assert event */
+	__u32 clear_sequence; 		/* seq. num. of clear event */
+	struct pps_ktime assert_tu;	/* time of assert event */
+	struct pps_ktime clear_tu;	/* time of clear event */
+	int current_mode;		/* current mode bits */
+};
+
+struct pps_kparams {
+	int api_version;		/* API version # */
+	int mode;			/* mode bits */
+	struct pps_ktime assert_off_tu;	/* offset compensation for assert */
+	struct pps_ktime clear_off_tu;	/* offset compensation for clear */
+};
+
+/*
+ * 3.3 Mode bit definitions
+ */
+
+/* Device/implementation parameters */
+#define PPS_CAPTUREASSERT	0x01	/* capture assert events */
+#define PPS_CAPTURECLEAR	0x02	/* capture clear events */
+#define PPS_CAPTUREBOTH		0x03	/* capture assert and clear events */
+
+#define PPS_OFFSETASSERT	0x10	/* apply compensation for assert ev. */
+#define PPS_OFFSETCLEAR		0x20	/* apply compensation for clear ev. */
+
+#define PPS_CANWAIT		0x100	/* can we wait for an event? */
+#define PPS_CANPOLL		0x200	/* bit reserved for future use */
+
+/* Kernel actions */
+#define PPS_ECHOASSERT		0x40	/* feed back assert event to output */
+#define PPS_ECHOCLEAR		0x80	/* feed back clear event to output */
+
+/* Timestamp formats */
+#define PPS_TSFMT_TSPEC		0x1000	/* select timespec format */
+#define PPS_TSFMT_NTPFP		0x2000	/* select NTP format */
+
+/*
+ * 3.4.4 New functions: disciplining the kernel timebase
+ */
+
+/* Kernel consumers */
+#define PPS_KC_HARDPPS		0	/* hardpps() (or equivalent) */
+#define PPS_KC_HARDPPS_PLL	1	/* hardpps() constrained to
+					   use a phase-locked loop */
+#define PPS_KC_HARDPPS_FLL	2	/* hardpps() constrained to
+					   use a frequency-locked loop */
+/*
+ * Here begins the implementation-specific part!
+ */
+
+struct pps_fdata {
+	struct pps_kinfo info;
+	struct pps_ktime timeout;
+};
+
+#include <linux/ioctl.h>
+
+#define PPS_GETPARAMS		_IOR('p', 0xa1, struct pps_kparams *)
+#define PPS_SETPARAMS		_IOW('p', 0xa2, struct pps_kparams *)
+#define PPS_GETCAP		_IOR('p', 0xa3, int *)
+#define PPS_FETCH		_IOWR('p', 0xa4, struct pps_fdata *)
+
+#ifdef __KERNEL__
+
+#include <linux/cdev.h>
+#include <linux/device.h>
+#include <linux/time.h>
+
+/*
+ * Global defines
+ */
+
+/* The specific PPS source info */
+struct pps_source_info {
+	char name[PPS_MAX_NAME_LEN];		/* simbolic name */
+	char path[PPS_MAX_NAME_LEN];		/* path of connected device */
+	int mode;				/* PPS's allowed mode */
+
+	void (*echo)(int source, int event, void *data); /* PPS echo function */
+
+	struct module *owner;
+	struct device *dev;
+};
+
+/* The main struct */
+struct pps_device {
+	struct pps_source_info info;		/* PSS source info */
+
+	struct pps_kparams params;		/* PPS's current params */
+
+	__u32 assert_sequence;			/* PPS' assert event seq # */
+	__u32 clear_sequence;			/* PPS' clear event seq # */
+	struct pps_ktime assert_tu;
+	struct pps_ktime clear_tu;
+	int current_mode;			/* PPS mode at event time */
+
+	int go;					/* PPS event is arrived? */
+	wait_queue_head_t queue;		/* PPS event queue */
+
+	unsigned int id;			/* PPS source unique ID */
+	struct cdev cdev;
+	struct device *dev;
+	int devno;
+	struct fasync_struct *async_queue;	/* fasync method */
+	spinlock_t lock;
+
+	atomic_t usage;				/* usage count */
+};
+
+/*
+ * Global variables
+ */
+
+extern spinlock_t pps_idr_lock;
+extern struct idr pps_idr;
+
+extern struct device_attribute pps_attrs[];
+
+/*
+ * Exported functions
+ */
+
+struct pps_device *pps_get_source(int source);
+extern void pps_put_source(struct pps_device *pps);
+extern int pps_register_source(struct pps_source_info *info,
+				int default_params);
+extern void pps_unregister_source(int source);
+extern int pps_register_cdev(struct pps_device *pps);
+extern void pps_unregister_cdev(struct pps_device *pps);
+extern void pps_event(int source, struct pps_ktime *ts, int event, void *data);
+
+#endif /* __KERNEL__ */
+
+#endif /* _PPS_H_ */
-- 
1.5.6.3

Re: [PATCH 1/1] LinuxPPS core support.

[Ingo Molnar]

* Rodolfo Giometti <giometti@linux.it> wrote:

> 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.

Hm. I was looking at this stuff with the prospect of adding it 
to the timer tree, but i'm really struggling with a few 
fundamental questions.

The most basic one is: why do we need this?

The main purpose of your current patchset seems to be to deliver 
interrupt timestamps to user-space, where it will in essence be 
used to feed new adjtimex adjustments via ntpd.

I.e. the whole thing comes around in a circle in the end, but 
via user-space, where jitter will only increase.

Why not cut out the jittery middle man and add some intelligent 
API to register PPS interrupt sources straight with the NTP 
code, and let those IRQ timestamps be fed _directly_ into our 
time adjustment code?

	Ingo

Re: [PATCH 1/1] LinuxPPS core support.

[H. Peter Anvin]

Ingo Molnar wrote:
>>
>> 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.
> 
> Hm. I was looking at this stuff with the prospect of adding it 
> to the timer tree, but i'm really struggling with a few 
> fundamental questions.
> 
> The most basic one is: why do we need this?
> 
> The main purpose of your current patchset seems to be to deliver 
> interrupt timestamps to user-space, where it will in essence be 
> used to feed new adjtimex adjustments via ntpd.
> 
> I.e. the whole thing comes around in a circle in the end, but 
> via user-space, where jitter will only increase.
> 
> Why not cut out the jittery middle man and add some intelligent 
> API to register PPS interrupt sources straight with the NTP 
> code, and let those IRQ timestamps be fed _directly_ into our 
> time adjustment code?
> 

Well, let's be fair here... the kernel-user space time model involving
ntpd has been very carefully developed over a period of over a decade.
It's known to work.  The userspace involvement isn't just about feeding
the data to the local clock, but also -- or perhaps primarily so -- to
keep the timing inside ntpd calibrated, as that is the time that will be
provided to the outside world.

There is a real benefit to using the model designed for and expected by
ntpd, too.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

Re: [PATCH 1/1] LinuxPPS core support.

[Ingo Molnar]

* H. Peter Anvin <hpa@zytor.com> wrote:

> Ingo Molnar wrote:
> >>
> >> 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.
> > 
> > Hm. I was looking at this stuff with the prospect of adding it 
> > to the timer tree, but i'm really struggling with a few 
> > fundamental questions.
> > 
> > The most basic one is: why do we need this?
> > 
> > The main purpose of your current patchset seems to be to deliver 
> > interrupt timestamps to user-space, where it will in essence be 
> > used to feed new adjtimex adjustments via ntpd.
> > 
> > I.e. the whole thing comes around in a circle in the end, but 
> > via user-space, where jitter will only increase.
> > 
> > Why not cut out the jittery middle man and add some intelligent 
> > API to register PPS interrupt sources straight with the NTP 
> > code, and let those IRQ timestamps be fed _directly_ into our 
> > time adjustment code?
> > 
> 
> Well, let's be fair here... the kernel-user space time model 
> involving ntpd has been very carefully developed over a period 
> of over a decade. It's known to work.  The userspace 
> involvement isn't just about feeding the data to the local 
> clock, but also -- or perhaps primarily so -- to keep the 
> timing inside ntpd calibrated, as that is the time that will 
> be provided to the outside world.

Sure thing, the policy bits should still be done by user-space - 
something does have to know that there's a PPS device on the 
serial, parallel or any other port, and has to configure set up 
the actual parameters as well, etc.

What i'm pointing out is that there's no technical benefit from 
passing the _timestamps_ through user-space and from not 
coupling the NTP code with the PPS edges.

Nor has it really been designed into NTP that way. We already 
have all the traditional PPS parameters in the NTP syscall 
interface:

include/linux/timex.h:

struct timex {
[...]
        long ppsfreq;           /* pps frequency (scaled ppm) (ro) */
        long jitter;            /* pps jitter (us) (ro) */
        int shift;              /* interval duration (s) (shift) (ro) */
        long stabil;            /* pps stability (scaled ppm) (ro) */
        long jitcnt;            /* jitter limit exceeded (ro) */
        long calcnt;            /* calibration intervals (ro) */
        long errcnt;            /* calibration errors (ro) */
        long stbcnt;            /* stability limit exceeded (ro) */

(these are the bits to query the state of kernel-side PPS 
support.)

and we have the bits to enable a PPS line disciple, etc., etc. 
We might need some extensions, but since the PPS device will be 
handled by the kernel anyway and the NTP adjustments are done in 
the kernel too, there's no strong reason to route the actual 
timestamps via user-space. In fact, doing so obviously increases 
jitter and slows down NTP convergence.

	Ingo

Re: [PATCH 1/1] LinuxPPS core support.

[Rodolfo Giometti]

On Mon, Feb 23, 2009 at 07:58:01AM +0100, Ingo Molnar wrote:
> 
> * H. Peter Anvin <hpa@zytor.com> wrote:
> 
> > Ingo Molnar wrote:
> > >>
> > >> 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.
> > > 
> > > Hm. I was looking at this stuff with the prospect of adding it 
> > > to the timer tree, but i'm really struggling with a few 
> > > fundamental questions.
> > > 
> > > The most basic one is: why do we need this?
> > > 
> > > The main purpose of your current patchset seems to be to deliver 
> > > interrupt timestamps to user-space, where it will in essence be 
> > > used to feed new adjtimex adjustments via ntpd.
> > > 
> > > I.e. the whole thing comes around in a circle in the end, but 
> > > via user-space, where jitter will only increase.
> > > 
> > > Why not cut out the jittery middle man and add some intelligent 
> > > API to register PPS interrupt sources straight with the NTP 
> > > code, and let those IRQ timestamps be fed _directly_ into our 
> > > time adjustment code?
> > > 
> > 
> > Well, let's be fair here... the kernel-user space time model 
> > involving ntpd has been very carefully developed over a period 
> > of over a decade. It's known to work.  The userspace 
> > involvement isn't just about feeding the data to the local 
> > clock, but also -- or perhaps primarily so -- to keep the 
> > timing inside ntpd calibrated, as that is the time that will 
> > be provided to the outside world.
> 
> Sure thing, the policy bits should still be done by user-space - 
> something does have to know that there's a PPS device on the 
> serial, parallel or any other port, and has to configure set up 
> the actual parameters as well, etc.
> 
> What i'm pointing out is that there's no technical benefit from 
> passing the _timestamps_ through user-space and from not 
> coupling the NTP code with the PPS edges.
> 
> Nor has it really been designed into NTP that way. We already 
> have all the traditional PPS parameters in the NTP syscall 
> interface:
> 
> include/linux/timex.h:
> 
> struct timex {
> [...]
>         long ppsfreq;           /* pps frequency (scaled ppm) (ro) */
>         long jitter;            /* pps jitter (us) (ro) */
>         int shift;              /* interval duration (s) (shift) (ro) */
>         long stabil;            /* pps stability (scaled ppm) (ro) */
>         long jitcnt;            /* jitter limit exceeded (ro) */
>         long calcnt;            /* calibration intervals (ro) */
>         long errcnt;            /* calibration errors (ro) */
>         long stbcnt;            /* stability limit exceeded (ro) */
> 
> (these are the bits to query the state of kernel-side PPS 
> support.)
> 
> and we have the bits to enable a PPS line disciple, etc., etc. 
> We might need some extensions, but since the PPS device will be 
> handled by the kernel anyway and the NTP adjustments are done in 
> the kernel too, there's no strong reason to route the actual 
> timestamps via user-space. In fact, doing so obviously increases 
> jitter and slows down NTP convergence.

Precise time settings can be done in both kernel and user
spaces. RFC2783 specifies an API that can be used to fetch PPS
timestamps from a PPS source, then these timestamps can be processed
by an userland consumer (NTPD in most cases) to set up system time.

Again the RFC2783 specifies a way to manage some kernel consumers
which can do the same jobs in kernel land, but all these stuff are
declared as "optional".

I agree with you that passing timestamps to userland may increase
jitter and slow down NTP convergence but LinuxPPS is a way to have at
least one "precise" time setting tool! :) However, as far as I know,
the NTPD algorith should take in account such jitters (I'm sorry but I
cannot be more precise since I'm not a NTPD guru), in fact if these
timestamps are taken "as soon as" possible inside the IRQ handling
chain the NTP convergence speed up several times.

In any case, if we wish adding a more performance tool in kernel space
we can just do it as RFC2783 says and (maybe) managing it with the
struct above.

Ciao,

Rodolfo

-- 

GNU/Linux Solutions                  e-mail: giometti@enneenne.com
Linux Device Driver                          giometti@linux.it
Embedded Systems                     phone:  +39 349 2432127
UNIX programming                     skype:  rodolfo.giometti

LinuxPPS core (Version 3): the PPS Linux implementation.

[Rodolfo Giometti]

This patch adds the PPS core support into Linux.

Currently I just propose the "core" so after inclusion we can add all
other related stuff as suggested by several people in this list. :)

PPS means "pulse per second" and its API is specified by RFC 2783
(Pulse-Per-Second API for UNIX-like Operating Systems, Version 1.0).

The code has been tested with the NTPD program
(http://www.eecis.udel.edu/~mills/ntp/html/index.html) and several GPS
antennae.


Changelog
=========

Version 2 -> 3
--------------

* include file splitted up.

Version 1 -> 2
--------------

* fix race during PPS source registration.

* PPS_CHECK removed.

* not needed check in pps_exit() removed.

* Printing stuff on exit removed.

Version [full patchset] -> 1
----------------------------

* stupid filenames removed.

* kernel-doc documentation of exported symbols.

* old BKL-locked ioctl removed.

* !uarg checks in the ioctls removed.

* pps.h revisited but not splitted, since several stuff are shared between
  kernel and user land (I hope this will not stop inclusion...)

Rodolfo

--

 Documentation/ABI/testing/sysfs-pps  |   73 +++++++
 Documentation/ioctl/ioctl-number.txt |    2 
 Documentation/pps/pps.txt            |  172 ++++++++++++++++++
 MAINTAINERS                          |    7 
 drivers/Kconfig                      |    2 
 drivers/Makefile                     |    1 
 drivers/pps/Kconfig                  |   33 +++
 drivers/pps/Makefile                 |    8 
 drivers/pps/kapi.c                   |  329 +++++++++++++++++++++++++++++++++++
 drivers/pps/pps.c                    |  312 +++++++++++++++++++++++++++++++++
 drivers/pps/sysfs.c                  |   98 ++++++++++
 include/linux/Kbuild                 |    1 
 include/linux/pps.h                  |  122 ++++++++++++
 include/linux/pps_kernel.h           |   89 +++++++++
 14 files changed, 1249 insertions(+)

[PATCH 1/1] LinuxPPS core support.

[Rodolfo Giometti]

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>
---
 Documentation/ABI/testing/sysfs-pps  |   73 ++++++++
 Documentation/ioctl/ioctl-number.txt |    2 +
 Documentation/pps/pps.txt            |  172 ++++++++++++++++++
 MAINTAINERS                          |    7 +
 drivers/Kconfig                      |    2 +
 drivers/Makefile                     |    1 +
 drivers/pps/Kconfig                  |   33 ++++
 drivers/pps/Makefile                 |    8 +
 drivers/pps/kapi.c                   |  329 ++++++++++++++++++++++++++++++++++
 drivers/pps/pps.c                    |  312 ++++++++++++++++++++++++++++++++
 drivers/pps/sysfs.c                  |   98 ++++++++++
 include/linux/Kbuild                 |    1 +
 include/linux/pps.h                  |  122 +++++++++++++
 include/linux/pps_kernel.h           |   89 +++++++++
 14 files changed, 1249 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-pps
 create mode 100644 Documentation/pps/pps.txt
 create mode 100644 drivers/pps/Kconfig
 create mode 100644 drivers/pps/Makefile
 create mode 100644 drivers/pps/kapi.c
 create mode 100644 drivers/pps/pps.c
 create mode 100644 drivers/pps/sysfs.c
 create mode 100644 include/linux/pps.h
 create mode 100644 include/linux/pps_kernel.h

diff --git a/Documentation/ABI/testing/sysfs-pps b/Documentation/ABI/testing/sysfs-pps
new file mode 100644
index 0000000..25028c7
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-pps
@@ -0,0 +1,73 @@
+What:		/sys/class/pps/
+Date:		February 2008
+Contact:	Rodolfo Giometti <giometti@linux.it>
+Description:
+		The /sys/class/pps/ directory will contain files and
+		directories that will provide a unified interface to
+		the PPS sources.
+
+What:		/sys/class/pps/ppsX/
+Date:		February 2008
+Contact:	Rodolfo Giometti <giometti@linux.it>
+Description:
+		The /sys/class/pps/ppsX/ directory is related to X-th
+		PPS source into the system. Each directory will
+		contain files to manage and control its PPS source.
+
+What:		/sys/class/pps/ppsX/assert
+Date:		February 2008
+Contact:	Rodolfo Giometti <giometti@linux.it>
+Description:
+		The /sys/class/pps/ppsX/assert file reports the assert events
+		and the assert sequence number of the X-th source in the form:
+
+			<secs>.<nsec>#<sequence>
+
+		If the source has no assert events the content of this file
+		is empty.
+
+What:		/sys/class/pps/ppsX/clear
+Date:		February 2008
+Contact:	Rodolfo Giometti <giometti@linux.it>
+Description:
+		The /sys/class/pps/ppsX/clear file reports the clear events
+		and the clear sequence number of the X-th source in the form:
+
+			<secs>.<nsec>#<sequence>
+
+		If the source has no clear events the content of this file
+		is empty.
+
+What:		/sys/class/pps/ppsX/mode
+Date:		February 2008
+Contact:	Rodolfo Giometti <giometti@linux.it>
+Description:
+		The /sys/class/pps/ppsX/mode file reports the functioning
+		mode of the X-th source in hexadecimal encoding.
+
+		Please, refer to linux/include/linux/pps.h for further
+		info.
+
+What:		/sys/class/pps/ppsX/echo
+Date:		February 2008
+Contact:	Rodolfo Giometti <giometti@linux.it>
+Description:
+		The /sys/class/pps/ppsX/echo file reports if the X-th does
+		or does not support an "echo" function.
+
+What:		/sys/class/pps/ppsX/name
+Date:		February 2008
+Contact:	Rodolfo Giometti <giometti@linux.it>
+Description:
+		The /sys/class/pps/ppsX/name file reports the name of the
+		X-th source.
+
+What:		/sys/class/pps/ppsX/path
+Date:		February 2008
+Contact:	Rodolfo Giometti <giometti@linux.it>
+Description:
+		The /sys/class/pps/ppsX/path file reports the path name of
+		the device connected with the X-th source.
+
+		If the source is not connected with any device the content
+		of this file is empty.
diff --git a/Documentation/ioctl/ioctl-number.txt b/Documentation/ioctl/ioctl-number.txt
index 1f779a2..7bb0d93 100644
--- a/Documentation/ioctl/ioctl-number.txt
+++ b/Documentation/ioctl/ioctl-number.txt
@@ -149,6 +149,8 @@ Code	Seq#	Include File		Comments
 'p'	40-7F	linux/nvram.h
 'p'	80-9F				user-space parport
 					<mailto:tim@cyberelk.net>
+'p'	a1-a4	linux/pps.h		LinuxPPS
+					<mailto:giometti@linux.it>
 'q'	00-1F	linux/serio.h
 'q'	80-FF				Internet PhoneJACK, Internet LineJACK
 					<http://www.quicknet.net>
diff --git a/Documentation/pps/pps.txt b/Documentation/pps/pps.txt
new file mode 100644
index 0000000..125f4ab
--- /dev/null
+++ b/Documentation/pps/pps.txt
@@ -0,0 +1,172 @@
+
+			PPS - Pulse Per Second
+			----------------------
+
+(C) Copyright 2007 Rodolfo Giometti <giometti@enneenne.com>
+
+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.
+
+
+
+Overview
+--------
+
+LinuxPPS provides a programming interface (API) to define in the
+system several PPS sources.
+
+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.
+
+A PPS source can be connected to a serial port (usually to the Data
+Carrier Detect pin) or to a parallel port (ACK-pin) or to a special
+CPU's GPIOs (this is the common case in embedded systems) but in each
+case when a new pulse arrives the system must apply to it a timestamp
+and record it for userland.
+
+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.
+
+
+RFC considerations
+------------------
+
+While implementing a PPS API as RFC 2783 defines and using an embedded
+CPU GPIO-Pin as physical link to the signal, I encountered a deeper
+problem:
+
+   At startup it needs a file descriptor as argument for the function
+   time_pps_create().
+
+This implies that the source has a /dev/... entry. This assumption is
+ok for the serial and parallel port, where you can do something
+useful besides(!) the gathering of timestamps as it is the central
+task for a PPS-API. But this assumption does not work for a single
+purpose GPIO line. In this case even basic file-related functionality
+(like read() and write()) makes no sense at all and should not be a
+precondition for the use of a PPS-API.
+
+The problem can be simply solved if you consider that a PPS source is
+not always connected with a GPS data source.
+
+So your programs should check if the GPS data source (the serial port
+for instance) is a PPS source too, and if not they should provide the
+possibility to open another device as PPS source.
+
+In LinuxPPS the PPS sources are simply char devices usually mapped
+into files /dev/pps0, /dev/pps1, etc..
+
+
+Coding example
+--------------
+
+To register a PPS source into the kernel you should define a struct
+pps_source_info_s as follows:
+
+    static struct pps_source_info pps_ktimer_info = {
+	    .name         = "ktimer",
+	    .path         = "",
+	    .mode         = PPS_CAPTUREASSERT | PPS_OFFSETASSERT | \
+			    PPS_ECHOASSERT | \
+			    PPS_CANWAIT | PPS_TSFMT_TSPEC,
+	    .echo         = pps_ktimer_echo,
+	    .owner        = THIS_MODULE,
+    };
+
+and then calling the function pps_register_source() in your
+intialization routine as follows:
+
+    source = pps_register_source(&pps_ktimer_info,
+			PPS_CAPTUREASSERT | PPS_OFFSETASSERT);
+
+The pps_register_source() prototype is:
+
+  int pps_register_source(struct pps_source_info_s *info, int default_params)
+
+where "info" is a pointer to a structure that describes a particular
+PPS source, "default_params" tells the system what the initial default
+parameters for the device should be (it is obvious that these parameters
+must be a subset of ones defined in the struct
+pps_source_info_s which describe the capabilities of the driver).
+
+Once you have registered a new PPS source into the system you can
+signal an assert event (for example in the interrupt handler routine)
+just using:
+
+    pps_event(source, &ts, PPS_CAPTUREASSERT, ptr)
+
+where "ts" is the event's timestamp.
+
+The same function may also run the defined echo function
+(pps_ktimer_echo(), passing to it the "ptr" pointer) if the user
+asked for that... etc..
+
+Please see the file drivers/pps/clients/ktimer.c for example code.
+
+
+SYSFS support
+-------------
+
+If the SYSFS filesystem is enabled in the kernel it provides a new class:
+
+   $ ls /sys/class/pps/
+   pps0/  pps1/  pps2/
+
+Every directory is the ID of a PPS sources defined in the system and
+inside you find several files:
+
+   $ ls /sys/class/pps/pps0/
+   assert	clear  echo  mode  name  path  subsystem@  uevent
+
+Inside each "assert" and "clear" file you can find the timestamp and a
+sequence number:
+
+   $ cat /sys/class/pps/pps0/assert
+   1170026870.983207967#8
+
+Where before the "#" is the timestamp in seconds; after it is the
+sequence number. Other files are:
+
+* echo: reports if the PPS source has an echo function or not;
+
+* mode: reports available PPS functioning modes;
+
+* name: reports the PPS source's name;
+
+* path: reports the PPS source's device path, that is the device the
+  PPS source is connected to (if it exists).
+
+
+Testing the PPS support
+-----------------------
+
+In order to test the PPS support even without specific hardware you can use
+the ktimer driver (see the client subsection in the PPS configuration menu)
+and the userland tools provided into Documentaion/pps/ directory.
+
+Once you have enabled the compilation of ktimer just modprobe it (if
+not statically compiled):
+
+   # modprobe ktimer
+
+and the run ppstest as follow:
+
+   $ ./ppstest /dev/pps0
+   trying PPS source "/dev/pps1"
+   found PPS source "/dev/pps1"
+   ok, found 1 source(s), now start fetching data...
+   source 0 - assert 1186592699.388832443, sequence: 364 - clear  0.000000000, sequence: 0
+   source 0 - assert 1186592700.388931295, sequence: 365 - clear  0.000000000, sequence: 0
+   source 0 - assert 1186592701.389032765, sequence: 366 - clear  0.000000000, sequence: 0
+
+Please, note that to compile userland programs you need the file timepps.h
+(see Documentation/pps/).
diff --git a/MAINTAINERS b/MAINTAINERS
index 2b349ba..c9557c2 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4460,6 +4460,13 @@ S:	Maintained
 F:	drivers/net/pppol2tp.c
 F:	include/linux/if_pppol2tp.h
 
+PPS SUPPORT
+P:	Rodolfo Giometti
+M:	giometti@enneenne.com
+W:	http://wiki.enneenne.com/index.php/LinuxPPS_support
+L:	linuxpps@ml.enneenne.com (subscribers-only)
+S:	Maintained
+
 PREEMPTIBLE KERNEL
 P:	Robert Love
 M:	rml@tech9.net
diff --git a/drivers/Kconfig b/drivers/Kconfig
index 00cf955..e328e5b 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -52,6 +52,8 @@ source "drivers/i2c/Kconfig"
 
 source "drivers/spi/Kconfig"
 
+source "drivers/pps/Kconfig"
+
 source "drivers/gpio/Kconfig"
 
 source "drivers/w1/Kconfig"
diff --git a/drivers/Makefile b/drivers/Makefile
index 1266ead..61536b9 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -72,6 +72,7 @@ obj-$(CONFIG_INPUT)		+= input/
 obj-$(CONFIG_I2O)		+= message/
 obj-$(CONFIG_RTC_LIB)		+= rtc/
 obj-y				+= i2c/ media/
+obj-$(CONFIG_PPS)		+= pps/
 obj-$(CONFIG_W1)		+= w1/
 obj-$(CONFIG_POWER_SUPPLY)	+= power/
 obj-$(CONFIG_HWMON)		+= hwmon/
diff --git a/drivers/pps/Kconfig b/drivers/pps/Kconfig
new file mode 100644
index 0000000..cc2eb8e
--- /dev/null
+++ b/drivers/pps/Kconfig
@@ -0,0 +1,33 @@
+#
+# PPS support configuration
+#
+
+menu "PPS support"
+
+config PPS
+	tristate "PPS support"
+	depends on EXPERIMENTAL
+	---help---
+	  PPS (Pulse Per Second) is a special pulse provided by some GPS
+	  antennae. Userland can use it to get a high-precision time
+	  reference.
+
+	  Some antennae's PPS signals are connected with the CD (Carrier
+	  Detect) pin of the serial line they use to communicate with the
+	  host. In this case use the SERIAL_LINE client support.
+
+	  Some antennae's PPS signals are connected with some special host
+	  inputs so you have to enable the corresponding client support.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pps_core.ko.
+
+config PPS_DEBUG
+	bool "PPS debugging messages"
+	depends on PPS
+	help
+	  Say Y here if you want the PPS support to produce a bunch of debug
+	  messages to the system log.  Select this if you are having a
+	  problem with PPS support and want to see more of what is going on.
+
+endmenu
diff --git a/drivers/pps/Makefile b/drivers/pps/Makefile
new file mode 100644
index 0000000..19ea582
--- /dev/null
+++ b/drivers/pps/Makefile
@@ -0,0 +1,8 @@
+#
+# Makefile for the PPS core.
+#
+
+pps_core-y			:= pps.o kapi.o sysfs.o
+obj-$(CONFIG_PPS)		:= pps_core.o
+
+ccflags-$(CONFIG_PPS_DEBUG) := -DDEBUG
diff --git a/drivers/pps/kapi.c b/drivers/pps/kapi.c
new file mode 100644
index 0000000..35a0b19
--- /dev/null
+++ b/drivers/pps/kapi.c
@@ -0,0 +1,329 @@
+/*
+ * kernel API
+ *
+ *
+ * Copyright (C) 2005-2009   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/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/time.h>
+#include <linux/spinlock.h>
+#include <linux/idr.h>
+#include <linux/fs.h>
+#include <linux/pps_kernel.h>
+
+/*
+ * Global variables
+ */
+
+DEFINE_SPINLOCK(pps_idr_lock);
+DEFINE_IDR(pps_idr);
+
+/*
+ * Local functions
+ */
+
+static void pps_add_offset(struct pps_ktime *ts, struct pps_ktime *offset)
+{
+	ts->nsec += offset->nsec;
+	while (ts->nsec >= NSEC_PER_SEC) {
+		ts->nsec -= NSEC_PER_SEC;
+		ts->sec++;
+	}
+	while (ts->nsec < 0) {
+		ts->nsec += NSEC_PER_SEC;
+		ts->sec--;
+	}
+	ts->sec += offset->sec;
+}
+
+/*
+ * Exported functions
+ */
+
+/* pps_get_source - find a PPS source
+ * @source: the PPS source ID.
+ *
+ * This function is used to find an already registered PPS source into the
+ * system.
+ *
+ * The function returns NULL if found nothing, otherwise it returns a pointer
+ * to the PPS source data struct (the refcounter is incremented by 1).
+ */
+
+struct pps_device *pps_get_source(int source)
+{
+	struct pps_device *pps;
+	unsigned long flags;
+
+	spin_lock_irqsave(&pps_idr_lock, flags);
+
+	pps = idr_find(&pps_idr, source);
+	if (pps != NULL)
+		atomic_inc(&pps->usage);
+
+	spin_unlock_irqrestore(&pps_idr_lock, flags);
+
+	return pps;
+}
+
+/* pps_put_source - free the PPS source data
+ * @pps: a pointer to the PPS source.
+ *
+ * This function is used to free a PPS data struct if its refcount is 0.
+ */
+
+void pps_put_source(struct pps_device *pps)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&pps_idr_lock, flags);
+	BUG_ON(atomic_read(&pps->usage) == 0);
+
+	if (!atomic_dec_and_test(&pps->usage)) {
+		pps = NULL;
+		goto exit;
+	}
+
+	/* No more reference to the PPS source. We can safely remove the
+	 * PPS data struct.
+	 */
+	idr_remove(&pps_idr, pps->id);
+
+exit:
+	spin_unlock_irqrestore(&pps_idr_lock, flags);
+	kfree(pps);
+}
+
+/* pps_register_source - add a PPS source in the system
+ * @info: the PPS info struct
+ * @default_params: the default PPS parameters of the new source
+ *
+ * This function is used to add a new PPS source in the system. The new
+ * source is described by info's fields and it will have, as default PPS
+ * parameters, the ones specified into default_params.
+ *
+ * The function returns, in case of success, the PPS source ID.
+ */
+
+int pps_register_source(struct pps_source_info *info, int default_params)
+{
+	struct pps_device *pps;
+	int id;
+	int err;
+
+	/* Sanity checks */
+	if ((info->mode & default_params) != default_params) {
+		printk(KERN_ERR "pps: %s: unsupported default parameters\n",
+					info->name);
+		err = -EINVAL;
+		goto pps_register_source_exit;
+	}
+	if ((info->mode & (PPS_ECHOASSERT | PPS_ECHOCLEAR)) != 0 &&
+			info->echo == NULL) {
+		printk(KERN_ERR "pps: %s: echo function is not defined\n",
+					info->name);
+		err = -EINVAL;
+		goto pps_register_source_exit;
+	}
+	if ((info->mode & (PPS_TSFMT_TSPEC | PPS_TSFMT_NTPFP)) == 0) {
+		printk(KERN_ERR "pps: %s: unspecified time format\n",
+					info->name);
+		err = -EINVAL;
+		goto pps_register_source_exit;
+	}
+
+	/* Allocate memory for the new PPS source struct */
+	pps = kzalloc(sizeof(struct pps_device), GFP_KERNEL);
+	if (pps == NULL) {
+		err = -ENOMEM;
+		goto pps_register_source_exit;
+	}
+
+	/* These initializations must be done before calling idr_get_new()
+	 * in order to avoid reces into pps_event().
+	 */
+	pps->params.api_version = PPS_API_VERS;
+	pps->params.mode = default_params;
+	pps->info = *info;
+
+	init_waitqueue_head(&pps->queue);
+	spin_lock_init(&pps->lock);
+	atomic_set(&pps->usage, 1);
+
+	/* Get new ID for the new PPS source */
+	if (idr_pre_get(&pps_idr, GFP_KERNEL) == 0) {
+		err = -ENOMEM;
+		goto kfree_pps;
+	}
+
+	spin_lock_irq(&pps_idr_lock);
+
+	/* Now really allocate the PPS source.
+	 * After idr_get_new() calling the new source will be freely available
+	 * into the kernel.
+	 */
+	err = idr_get_new(&pps_idr, pps, &id);
+	if (err < 0) {
+		spin_unlock_irq(&pps_idr_lock);
+		goto kfree_pps;
+	}
+
+	id = id & MAX_ID_MASK;
+	if (id >= PPS_MAX_SOURCES) {
+		spin_unlock_irq(&pps_idr_lock);
+
+		printk(KERN_ERR "pps: %s: too many PPS sources in the system\n",
+					info->name);
+		err = -EBUSY;
+		goto free_idr;
+	}
+	pps->id = id;
+
+	spin_unlock_irq(&pps_idr_lock);
+
+	/* Create the char device */
+	err = pps_register_cdev(pps);
+	if (err < 0) {
+		printk(KERN_ERR "pps: %s: unable to create char device\n",
+					info->name);
+		goto free_idr;
+	}
+
+	pr_info("new PPS source %s at ID %d\n", info->name, id);
+
+	return id;
+
+free_idr:
+	spin_lock_irq(&pps_idr_lock);
+	idr_remove(&pps_idr, id);
+	spin_unlock_irq(&pps_idr_lock);
+
+kfree_pps:
+	kfree(pps);
+
+pps_register_source_exit:
+	printk(KERN_ERR "pps: %s: unable to register source\n", info->name);
+
+	return err;
+}
+EXPORT_SYMBOL(pps_register_source);
+
+/* pps_unregister_source - remove a PPS source from the system
+ * @source: the PPS source ID
+ *
+ * This function is used to remove a previously registered PPS source from
+ * the system.
+ */
+
+void pps_unregister_source(int source)
+{
+	struct pps_device *pps;
+
+	spin_lock_irq(&pps_idr_lock);
+	pps = idr_find(&pps_idr, source);
+
+	if (!pps) {
+		BUG();
+		spin_unlock_irq(&pps_idr_lock);
+		return;
+	}
+	spin_unlock_irq(&pps_idr_lock);
+
+	pps_unregister_cdev(pps);
+	pps_put_source(pps);
+}
+EXPORT_SYMBOL(pps_unregister_source);
+
+/* pps_event - register a PPS event into the system
+ * @source: the PPS source ID
+ * @ts: the event timestamp
+ * @event: the event type
+ * @data: userdef pointer
+ *
+ * This function is used by each PPS client in order to register a new
+ * PPS event into the system (it's usually called inside an IRQ handler).
+ *
+ * If an echo function is associated with the PPS source it will be called
+ * as:
+ *	pps->info.echo(source, event, data);
+ */
+
+void pps_event(int source, struct pps_ktime *ts, int event, void *data)
+{
+	struct pps_device *pps;
+	unsigned long flags;
+
+	if ((event & (PPS_CAPTUREASSERT | PPS_CAPTURECLEAR)) == 0) {
+		printk(KERN_ERR "pps: unknown event (%x) for source %d\n",
+			event, source);
+		return;
+	}
+
+	pps = pps_get_source(source);
+	if (!pps)
+		return;
+
+	pr_debug("PPS event on source %d at %llu.%06u\n",
+			pps->id, (unsigned long long) ts->sec, ts->nsec);
+
+	spin_lock_irqsave(&pps->lock, flags);
+
+	/* Must call the echo function? */
+	if ((pps->params.mode & (PPS_ECHOASSERT | PPS_ECHOCLEAR)))
+		pps->info.echo(source, event, data);
+
+	/* Check the event */
+	pps->current_mode = pps->params.mode;
+	if (event & PPS_CAPTUREASSERT) {
+		/* We have to add an offset? */
+		if (pps->params.mode & PPS_OFFSETASSERT)
+			pps_add_offset(ts, &pps->params.assert_off_tu);
+
+		/* Save the time stamp */
+		pps->assert_tu = *ts;
+		pps->assert_sequence++;
+		pr_debug("capture assert seq #%u for source %d\n",
+			pps->assert_sequence, source);
+	}
+	if (event & PPS_CAPTURECLEAR) {
+		/* We have to add an offset? */
+		if (pps->params.mode & PPS_OFFSETCLEAR)
+			pps_add_offset(ts, &pps->params.clear_off_tu);
+
+		/* Save the time stamp */
+		pps->clear_tu = *ts;
+		pps->clear_sequence++;
+		pr_debug("capture clear seq #%u for source %d\n",
+			pps->clear_sequence, source);
+	}
+
+	pps->go = ~0;
+	wake_up_interruptible(&pps->queue);
+
+	kill_fasync(&pps->async_queue, SIGIO, POLL_IN);
+
+	spin_unlock_irqrestore(&pps->lock, flags);
+
+	/* Now we can release the PPS source for (possible) deregistration */
+	pps_put_source(pps);
+}
+EXPORT_SYMBOL(pps_event);
diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
new file mode 100644
index 0000000..ac8cc8c
--- /dev/null
+++ b/drivers/pps/pps.c
@@ -0,0 +1,312 @@
+/*
+ * PPS core file
+ *
+ *
+ * Copyright (C) 2005-2009   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/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/uaccess.h>
+#include <linux/idr.h>
+#include <linux/cdev.h>
+#include <linux/poll.h>
+#include <linux/pps_kernel.h>
+
+/*
+ * Local variables
+ */
+
+static dev_t pps_devt;
+static struct class *pps_class;
+
+/*
+ * Char device methods
+ */
+
+static unsigned int pps_cdev_poll(struct file *file, poll_table *wait)
+{
+	struct pps_device *pps = file->private_data;
+
+	poll_wait(file, &pps->queue, wait);
+
+	return POLLIN | POLLRDNORM;
+}
+
+static int pps_cdev_fasync(int fd, struct file *file, int on)
+{
+	struct pps_device *pps = file->private_data;
+	return fasync_helper(fd, file, on, &pps->async_queue);
+}
+
+static long pps_cdev_ioctl(struct file *file,
+		unsigned int cmd, unsigned long arg)
+{
+	struct pps_device *pps = file->private_data;
+	struct pps_kparams params;
+	struct pps_fdata fdata;
+	unsigned long ticks;
+	void __user *uarg = (void __user *) arg;
+	int __user *iuarg = (int __user *) arg;
+	int err;
+
+	switch (cmd) {
+	case PPS_GETPARAMS:
+		pr_debug("PPS_GETPARAMS: source %d\n", pps->id);
+
+		/* Return current parameters */
+		err = copy_to_user(uarg, &pps->params,
+						sizeof(struct pps_kparams));
+		if (err)
+			return -EFAULT;
+
+		break;
+
+	case PPS_SETPARAMS:
+		pr_debug("PPS_SETPARAMS: source %d\n", pps->id);
+
+		/* Check the capabilities */
+		if (!capable(CAP_SYS_TIME))
+			return -EPERM;
+
+		err = copy_from_user(&params, uarg, sizeof(struct pps_kparams));
+		if (err)
+			return -EFAULT;
+		if (!(params.mode & (PPS_CAPTUREASSERT | PPS_CAPTURECLEAR))) {
+			pr_debug("capture mode unspecified (%x)\n",
+								params.mode);
+			return -EINVAL;
+		}
+
+		/* Check for supported capabilities */
+		if ((params.mode & ~pps->info.mode) != 0) {
+			pr_debug("unsupported capabilities (%x)\n",
+								params.mode);
+			return -EINVAL;
+		}
+
+		spin_lock_irq(&pps->lock);
+
+		/* Save the new parameters */
+		pps->params = params;
+
+		/* Restore the read only parameters */
+		if ((params.mode & (PPS_TSFMT_TSPEC | PPS_TSFMT_NTPFP)) == 0) {
+			/* section 3.3 of RFC 2783 interpreted */
+			pr_debug("time format unspecified (%x)\n",
+								params.mode);
+			pps->params.mode |= PPS_TSFMT_TSPEC;
+		}
+		if (pps->info.mode & PPS_CANWAIT)
+			pps->params.mode |= PPS_CANWAIT;
+		pps->params.api_version = PPS_API_VERS;
+
+		spin_unlock_irq(&pps->lock);
+
+		break;
+
+	case PPS_GETCAP:
+		pr_debug("PPS_GETCAP: source %d\n", pps->id);
+
+		err = put_user(pps->info.mode, iuarg);
+		if (err)
+			return -EFAULT;
+
+		break;
+
+	case PPS_FETCH:
+		pr_debug("PPS_FETCH: source %d\n", pps->id);
+
+		err = copy_from_user(&fdata, uarg, sizeof(struct pps_fdata));
+		if (err)
+			return -EFAULT;
+
+		pps->go = 0;
+
+		/* Manage the timeout */
+		if (fdata.timeout.flags & PPS_TIME_INVALID)
+			err = wait_event_interruptible(pps->queue, pps->go);
+		else {
+			pr_debug("timeout %lld.%09d\n",
+					(long long) fdata.timeout.sec,
+					fdata.timeout.nsec);
+			ticks = fdata.timeout.sec * HZ;
+			ticks += fdata.timeout.nsec / (NSEC_PER_SEC / HZ);
+
+			if (ticks != 0) {
+				err = wait_event_interruptible_timeout(
+						pps->queue, pps->go, ticks);
+				if (err == 0)
+					return -ETIMEDOUT;
+			}
+		}
+
+		/* Check for pending signals */
+		if (err == -ERESTARTSYS) {
+			pr_debug("pending signal caught\n");
+			return -EINTR;
+		}
+
+		/* Return the fetched timestamp */
+		spin_lock_irq(&pps->lock);
+
+		fdata.info.assert_sequence = pps->assert_sequence;
+		fdata.info.clear_sequence = pps->clear_sequence;
+		fdata.info.assert_tu = pps->assert_tu;
+		fdata.info.clear_tu = pps->clear_tu;
+		fdata.info.current_mode = pps->current_mode;
+
+		spin_unlock_irq(&pps->lock);
+
+		err = copy_to_user(uarg, &fdata, sizeof(struct pps_fdata));
+		if (err)
+			return -EFAULT;
+
+		break;
+
+	default:
+		return -ENOTTY;
+		break;
+	}
+
+	return 0;
+}
+
+static int pps_cdev_open(struct inode *inode, struct file *file)
+{
+	struct pps_device *pps = container_of(inode->i_cdev,
+						struct pps_device, cdev);
+	int found;
+
+	found = pps_get_source(pps->id) != 0;
+	if (!found)
+		return -ENODEV;
+
+	file->private_data = pps;
+
+	return 0;
+}
+
+static int pps_cdev_release(struct inode *inode, struct file *file)
+{
+	struct pps_device *pps = file->private_data;
+
+	/* Free the PPS source and wake up (possible) deregistration */
+	pps_put_source(pps);
+
+	return 0;
+}
+
+/*
+ * Char device stuff
+ */
+
+static const struct file_operations pps_cdev_fops = {
+	.owner		= THIS_MODULE,
+	.llseek		= no_llseek,
+	.poll		= pps_cdev_poll,
+	.fasync		= pps_cdev_fasync,
+	.unlocked_ioctl	= pps_cdev_ioctl,
+	.open		= pps_cdev_open,
+	.release	= pps_cdev_release,
+};
+
+int pps_register_cdev(struct pps_device *pps)
+{
+	int err;
+
+	pps->devno = MKDEV(MAJOR(pps_devt), pps->id);
+	cdev_init(&pps->cdev, &pps_cdev_fops);
+	pps->cdev.owner = pps->info.owner;
+
+	err = cdev_add(&pps->cdev, pps->devno, 1);
+	if (err) {
+		printk(KERN_ERR "pps: %s: failed to add char device %d:%d\n",
+				pps->info.name, MAJOR(pps_devt), pps->id);
+		return err;
+	}
+	pps->dev = device_create(pps_class, pps->info.dev, pps->devno, NULL,
+							"pps%d", pps->id);
+	if (err)
+		goto del_cdev;
+	dev_set_drvdata(pps->dev, pps);
+
+	pr_debug("source %s got cdev (%d:%d)\n", pps->info.name,
+			MAJOR(pps_devt), pps->id);
+
+	return 0;
+
+del_cdev:
+	cdev_del(&pps->cdev);
+
+	return err;
+}
+
+void pps_unregister_cdev(struct pps_device *pps)
+{
+	device_destroy(pps_class, pps->devno);
+	cdev_del(&pps->cdev);
+}
+
+/*
+ * Module stuff
+ */
+
+static void __exit pps_exit(void)
+{
+	class_destroy(pps_class);
+	unregister_chrdev_region(pps_devt, PPS_MAX_SOURCES);
+}
+
+static int __init pps_init(void)
+{
+	int err;
+
+	pps_class = class_create(THIS_MODULE, "pps");
+	if (!pps_class) {
+		printk(KERN_ERR "pps: failed to allocate class\n");
+		return -ENOMEM;
+	}
+	pps_class->dev_attrs = pps_attrs;
+
+	err = alloc_chrdev_region(&pps_devt, 0, PPS_MAX_SOURCES, "pps");
+	if (err < 0) {
+		printk(KERN_ERR "pps: failed to allocate char device region\n");
+		goto remove_class;
+	}
+
+	pr_info("LinuxPPS API ver. %d registered\n", PPS_API_VERS);
+	pr_info("Software ver. %s - Copyright 2005-2007 Rodolfo Giometti "
+		"<giometti@linux.it>\n", PPS_VERSION);
+
+	return 0;
+
+remove_class:
+	class_destroy(pps_class);
+
+	return err;
+}
+
+subsys_initcall(pps_init);
+module_exit(pps_exit);
+
+MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
+MODULE_DESCRIPTION("LinuxPPS support (RFC 2783) - ver. " PPS_VERSION);
+MODULE_LICENSE("GPL");
diff --git a/drivers/pps/sysfs.c b/drivers/pps/sysfs.c
new file mode 100644
index 0000000..ef0978c
--- /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,
+};
diff --git a/include/linux/Kbuild b/include/linux/Kbuild
index 3f0eaa3..3547c61 100644
--- a/include/linux/Kbuild
+++ b/include/linux/Kbuild
@@ -307,6 +307,7 @@ unifdef-y += pmu.h
 unifdef-y += poll.h
 unifdef-y += ppp_defs.h
 unifdef-y += ppp-comp.h
+unifdef-y += pps.h
 unifdef-y += ptrace.h
 unifdef-y += qnx4_fs.h
 unifdef-y += quota.h
diff --git a/include/linux/pps.h b/include/linux/pps.h
new file mode 100644
index 0000000..cfe5c72
--- /dev/null
+++ b/include/linux/pps.h
@@ -0,0 +1,122 @@
+/*
+ * PPS API header
+ *
+ * Copyright (C) 2005-2009   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.
+ */
+
+
+#ifndef _PPS_H_
+#define _PPS_H_
+
+#define PPS_VERSION		"5.3.6"
+#define PPS_MAX_SOURCES		16		/* should be enough... */
+
+/* Implementation note: the logical states ``assert'' and ``clear''
+ * are implemented in terms of the chip register, i.e. ``assert''
+ * means the bit is set.  */
+
+/*
+ * 3.2 New data structures
+ */
+
+#define PPS_API_VERS_1		1
+#define PPS_API_VERS		PPS_API_VERS_1	/* we use API version 1 */
+#define PPS_MAX_NAME_LEN	32
+
+/* 32-bit vs. 64-bit compatibility.
+ *
+ * 0n i386, the alignment of a uint64_t is only 4 bytes, while on most other
+ * architectures it's 8 bytes. On i386, there will be no padding between the
+ * two consecutive 'struct pps_ktime' members of struct pps_kinfo and struct
+ * pps_kparams. But on most platforms there will be padding to ensure correct
+ * alignment.
+ *
+ * The simple fix is probably to add an explicit padding.
+ *					 		[David Woodhouse]
+ */
+struct pps_ktime {
+	__s64 sec;
+	__s32 nsec;
+	__u32 flags;
+};
+#define PPS_TIME_INVALID	(1<<0)	/* used to specify timeout==NULL */
+
+struct pps_kinfo {
+	__u32 assert_sequence;		/* seq. num. of assert event */
+	__u32 clear_sequence; 		/* seq. num. of clear event */
+	struct pps_ktime assert_tu;	/* time of assert event */
+	struct pps_ktime clear_tu;	/* time of clear event */
+	int current_mode;		/* current mode bits */
+};
+
+struct pps_kparams {
+	int api_version;		/* API version # */
+	int mode;			/* mode bits */
+	struct pps_ktime assert_off_tu;	/* offset compensation for assert */
+	struct pps_ktime clear_off_tu;	/* offset compensation for clear */
+};
+
+/*
+ * 3.3 Mode bit definitions
+ */
+
+/* Device/implementation parameters */
+#define PPS_CAPTUREASSERT	0x01	/* capture assert events */
+#define PPS_CAPTURECLEAR	0x02	/* capture clear events */
+#define PPS_CAPTUREBOTH		0x03	/* capture assert and clear events */
+
+#define PPS_OFFSETASSERT	0x10	/* apply compensation for assert ev. */
+#define PPS_OFFSETCLEAR		0x20	/* apply compensation for clear ev. */
+
+#define PPS_CANWAIT		0x100	/* can we wait for an event? */
+#define PPS_CANPOLL		0x200	/* bit reserved for future use */
+
+/* Kernel actions */
+#define PPS_ECHOASSERT		0x40	/* feed back assert event to output */
+#define PPS_ECHOCLEAR		0x80	/* feed back clear event to output */
+
+/* Timestamp formats */
+#define PPS_TSFMT_TSPEC		0x1000	/* select timespec format */
+#define PPS_TSFMT_NTPFP		0x2000	/* select NTP format */
+
+/*
+ * 3.4.4 New functions: disciplining the kernel timebase
+ */
+
+/* Kernel consumers */
+#define PPS_KC_HARDPPS		0	/* hardpps() (or equivalent) */
+#define PPS_KC_HARDPPS_PLL	1	/* hardpps() constrained to
+					   use a phase-locked loop */
+#define PPS_KC_HARDPPS_FLL	2	/* hardpps() constrained to
+					   use a frequency-locked loop */
+/*
+ * Here begins the implementation-specific part!
+ */
+
+struct pps_fdata {
+	struct pps_kinfo info;
+	struct pps_ktime timeout;
+};
+
+#include <linux/ioctl.h>
+
+#define PPS_GETPARAMS		_IOR('p', 0xa1, struct pps_kparams *)
+#define PPS_SETPARAMS		_IOW('p', 0xa2, struct pps_kparams *)
+#define PPS_GETCAP		_IOR('p', 0xa3, int *)
+#define PPS_FETCH		_IOWR('p', 0xa4, struct pps_fdata *)
+
+#endif /* _PPS_H_ */
diff --git a/include/linux/pps_kernel.h b/include/linux/pps_kernel.h
new file mode 100644
index 0000000..e0a193f
--- /dev/null
+++ b/include/linux/pps_kernel.h
@@ -0,0 +1,89 @@
+/*
+ * PPS API kernel header
+ *
+ * Copyright (C) 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/pps.h>
+
+#include <linux/cdev.h>
+#include <linux/device.h>
+#include <linux/time.h>
+
+/*
+ * Global defines
+ */
+
+/* The specific PPS source info */
+struct pps_source_info {
+	char name[PPS_MAX_NAME_LEN];		/* simbolic name */
+	char path[PPS_MAX_NAME_LEN];		/* path of connected device */
+	int mode;				/* PPS's allowed mode */
+
+	void (*echo)(int source, int event, void *data); /* PPS echo function */
+
+	struct module *owner;
+	struct device *dev;
+};
+
+/* The main struct */
+struct pps_device {
+	struct pps_source_info info;		/* PSS source info */
+
+	struct pps_kparams params;		/* PPS's current params */
+
+	__u32 assert_sequence;			/* PPS' assert event seq # */
+	__u32 clear_sequence;			/* PPS' clear event seq # */
+	struct pps_ktime assert_tu;
+	struct pps_ktime clear_tu;
+	int current_mode;			/* PPS mode at event time */
+
+	int go;					/* PPS event is arrived? */
+	wait_queue_head_t queue;		/* PPS event queue */
+
+	unsigned int id;			/* PPS source unique ID */
+	struct cdev cdev;
+	struct device *dev;
+	int devno;
+	struct fasync_struct *async_queue;	/* fasync method */
+	spinlock_t lock;
+
+	atomic_t usage;				/* usage count */
+};
+
+/*
+ * Global variables
+ */
+
+extern spinlock_t pps_idr_lock;
+extern struct idr pps_idr;
+extern struct timespec pps_irq_ts[];
+
+extern struct device_attribute pps_attrs[];
+
+/*
+ * Exported functions
+ */
+
+struct pps_device *pps_get_source(int source);
+extern void pps_put_source(struct pps_device *pps);
+extern int pps_register_source(struct pps_source_info *info,
+				int default_params);
+extern void pps_unregister_source(int source);
+extern int pps_register_cdev(struct pps_device *pps);
+extern void pps_unregister_cdev(struct pps_device *pps);
+extern void pps_event(int source, struct pps_ktime *ts, int event, void *data);
-- 
1.5.6.3

Re: [PATCH 1/1] LinuxPPS core support.

[Andrew Morton]

On Fri, 22 May 2009 08:12:33 +0200
Rodolfo Giometti <giometti@linux.it> wrote:

> 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.
>
> ...
>
>  Documentation/ABI/testing/sysfs-pps  |   73 ++++++++
>  Documentation/ioctl/ioctl-number.txt |    2 +
>  Documentation/pps/pps.txt            |  172 ++++++++++++++++++
>  MAINTAINERS                          |    7 +
>  drivers/Kconfig                      |    2 +
>  drivers/Makefile                     |    1 +
>  drivers/pps/Kconfig                  |   33 ++++
>  drivers/pps/Makefile                 |    8 +
>  drivers/pps/kapi.c                   |  329 ++++++++++++++++++++++++++++++++++
>  drivers/pps/pps.c                    |  312 ++++++++++++++++++++++++++++++++
>  drivers/pps/sysfs.c                  |   98 ++++++++++
>  include/linux/Kbuild                 |    1 +
>  include/linux/pps.h                  |  122 +++++++++++++
>  include/linux/pps_kernel.h           |   89 +++++++++

Well it seems that Christoph's header file suggestion was addressed.

It's been a long time and there have been many reviews and comments. 
Have you been keeping track of them all?

If so, can you please let us know which review comments remain
unaddressed, or were deliberately not addressed because you disagreed
with them?

Thanks.

Re: [PATCH 1/1] LinuxPPS core support.

[Alan Cox]

I'm happy with this now certainly

Re: [PATCH 1/1] LinuxPPS core support.

[Rodolfo Giometti]

On Tue, May 26, 2009 at 04:33:33PM -0700, Andrew Morton wrote:

> Well it seems that Christoph's header file suggestion was addressed.

Yes, I fixed it.

> It's been a long time and there have been many reviews and comments. 
> Have you been keeping track of them all?
> 
> If so, can you please let us know which review comments remain
> unaddressed, or were deliberately not addressed because you disagreed
> with them?

I fixed everything but didn't include George Spelvin
<linux@horizon.com>'s pathes (see them here
http://ml.enneenne.com/pipermail/linuxpps/2009-February/002788.html)
because after a (very) long discussion (please, refer also to some
private messages to you from myself and George) we agree to wait for a
new patchset from him but, after several weeks, I still receive
nothing so I decided to addres the header file issue and repropose my
implementation which is currenlty used into several systems.

Ciao,

Rodolfo

-- 

GNU/Linux Solutions                  e-mail: giometti@enneenne.com
Linux Device Driver                          giometti@linux.it
Embedded Systems                     phone:  +39 349 2432127
UNIX programming                     skype:  rodolfo.giometti

Re: [PATCH 1/1] LinuxPPS core support.

[Folkert van Heusden]

> I'm happy with this now certainly

Great to hear! So it will now be merged? For 2.6.31?


Thanks,

Folkert van Heusden

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