Commit 28aedd7e authored by Mauro Carvalho Chehab's avatar Mauro Carvalho Chehab Committed by Jonathan Corbet
Browse files

docs: pps.txt: convert to ReST and rename to pps.rst 



This file is already in a good shape: just its title and
adding some literal block markups is needed for it to be
part of the document.

While it has a small chapter with sysfs stuff, most of
the document is focused on driver development.

As it describes a kernel API, move it to the driver-api
directory.

In order to avoid conflicts, let's add an :orphan: tag
to it, to be removed when added to the driver-api book.

Signed-off-by: default avatarMauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: default avatarRodolfo Giometti <giometti@enneenne.com>
Signed-off-by: default avatarJonathan Corbet <corbet@lwn.net>
parent 3bdab16c

Documentation/pps/pps.txt→Documentation/driver-api/pps.rst

+35 −32
Original line number Diff line number Diff line 
:orphan:



======================

PPS - Pulse Per Second

			----------------------

======================



(C) Copyright 2007 Rodolfo Giometti <giometti@enneenne.com>

Copyright (C) 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
@@ -88,7 +90,7 @@ Coding example 
--------------



To register a PPS source into the kernel you should define a struct

pps_source_info as follows:

pps_source_info as follows::



    static struct pps_source_info pps_ktimer_info = {

	    .name         = "ktimer",
@@ -101,12 +103,12 @@ pps_source_info as follows: 
    };



and then calling the function pps_register_source() in your

initialization routine as follows:

initialization routine as follows::



    source = pps_register_source(&pps_ktimer_info,

			PPS_CAPTUREASSERT | PPS_OFFSETASSERT);



The pps_register_source() prototype is:

The pps_register_source() prototype is::



  int pps_register_source(struct pps_source_info *info, int default_params)
@@ -118,7 +120,7 @@ pps_source_info 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:

just using::



    pps_event(source, &ts, PPS_CAPTUREASSERT, ptr)
@@ -134,13 +136,13 @@ Please see the file drivers/pps/clients/pps-ktimer.c for example code. 
SYSFS support

-------------



If the SYSFS filesystem is enabled in the kernel it provides a new class:

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:

inside you find several files::



   $ ls -F /sys/class/pps/pps0/

   assert     dev        mode       path       subsystem@
@@ -148,7 +150,7 @@ inside you find several files: 




Inside each "assert" and "clear" file you can find the timestamp and a

sequence number:

sequence number::



   $ cat /sys/class/pps/pps0/assert

   1170026870.983207967#8
@@ -175,11 +177,11 @@ and the userland tools available in your distribution's pps-tools package, 
http://linuxpps.org , or https://github.com/redlab-i/pps-tools.



Once you have enabled the compilation of pps-ktimer just modprobe it (if

not statically compiled):

not statically compiled)::



   # modprobe pps-ktimer



and the run ppstest as follow:

and the run ppstest as follow::



   $ ./ppstest /dev/pps1

   trying PPS source "/dev/pps1"
@@ -204,7 +206,8 @@ nor affordable. The cheap way is to load a PPS generator on one of the 
computers (master) and PPS clients on others (slaves), and use very simple

cables to deliver signals using parallel ports, for example.



Parallel port cable pinout:

Parallel port cable pinout::



	pin	name	master      slave

	1	STROBE	  *------     *

	2	D0	  *     |     *

MAINTAINERS

+1 −1
Original line number Diff line number Diff line
@@ -12659,7 +12659,7 @@ M: Rodolfo Giometti <giometti@enneenne.com> 
W:	http://wiki.enneenne.com/index.php/LinuxPPS_support

L:	linuxpps@ml.enneenne.com (subscribers-only)

S:	Maintained

F:	Documentation/pps/

F:	Documentation/driver-api/pps.rst

F:	Documentation/devicetree/bindings/pps/pps-gpio.txt

F:	Documentation/ABI/testing/sysfs-pps

F:	drivers/pps/

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