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Message-Id: <20241031163508.259522-4-giometti@enneenne.com>
Date: Thu, 31 Oct 2024 17:35:07 +0100
From: Rodolfo Giometti <giometti@...eenne.com>
To: linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Greg KH <greg@...ah.com>,
corbet@....net,
Hall Christopher S <christopher.s.hall@...el.com>,
Mohan Subramanian <subramanian.mohan@...el.com>,
tglx@...utronix.de,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Dong Eddie <eddie.dong@...el.com>,
N Pandith <pandith.n@...el.com>,
T R Thejesh Reddy <thejesh.reddy.t.r@...el.com>,
Zage David <david.zage@...el.com>,
Chinnadurai Srinivasan <srinivasan.chinnadurai@...el.com>,
Randy Dunlap <rdunlap@...radead.org>,
Rodolfo Giometti <giometti@...eenne.com>
Subject: [V2 3/4] Documentation pps.rst: add PPS generators documentation
This patch adds some examples about how to register a new PPS
generator in the system, and how to manage it.
Signed-off-by: Rodolfo Giometti <giometti@...eenne.com>
---
Documentation/driver-api/pps.rst | 40 ++++++++++++++++++++++++++++++++
1 file changed, 40 insertions(+)
diff --git a/Documentation/driver-api/pps.rst b/Documentation/driver-api/pps.rst
index 78dded03e5d8..dffa06ed919f 100644
--- a/Documentation/driver-api/pps.rst
+++ b/Documentation/driver-api/pps.rst
@@ -202,6 +202,46 @@ Sometimes one needs to be able not only to catch PPS signals but to produce
them also. For example, running a distributed simulation, which requires
computers' clock to be synchronized very tightly.
+To do so the class pps-gen has been added. PPS generators can be
+registered in the kernel by defining a struct pps_gen_source_info as
+follows::
+
+ static struct pps_gen_source_info pps_gen_dummy_info = {
+ .name = "dummy",
+ .use_system_clock = true,
+ .get_time = pps_gen_dummy_get_time,
+ .enable = pps_gen_dummy_enable,
+ };
+
+Where the use_system_clock states if the generator uses the system
+clock to generate its pulses, or from a peripheral device
+clock. Method get_time() is used to query the time stored into the
+generator clock, while the method enable() is used to enable or
+disable the PPS pulse generation.
+
+Then calling the function pps_gen_register_source() in your
+initialization routine as follows creates a new generator in the
+system::
+
+ pps_gen = pps_gen_register_source(&pps_gen_dummy_info);
+
+Generators SYSFS support
+------------------------
+
+If the SYSFS filesystem is enabled in the kernel it provides a new class::
+
+ $ ls /sys/class/pps-gen/
+ pps-gen0/ pps-gen1/ pps-gen2/
+
+Every directory is the ID of a PPS generator defined in the system and
+inside you find several files::
+
+ $ ls -F /sys/class/pps-gen/pps-gen0/
+ dev enable name power/ subsystem@ system time uevent
+
+To enable the PPS signal generation you can use the command below::
+
+ $ echo 1 > /sys/class/pps-gen/pps-gen0/enable
Parallel port generator
------------------------
--
2.34.1
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