linux-kernel - [V2 2/4] drivers pps/generators: add dummy PPS generator

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Message-Id: <20241031163508.259522-3-giometti@enneenne.com>
Date: Thu, 31 Oct 2024 17:35:06 +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 2/4] drivers pps/generators: add dummy PPS generator

This dummy PPS generator can be used for debugging and documentation
purposes.

Signed-off-by: Rodolfo Giometti <giometti@...eenne.com>
---
 drivers/pps/generators/Kconfig         |  9 +++
 drivers/pps/generators/Makefile        |  1 +
 drivers/pps/generators/pps_gen-dummy.c | 96 ++++++++++++++++++++++++++
 3 files changed, 106 insertions(+)
 create mode 100644 drivers/pps/generators/pps_gen-dummy.c

diff --git a/drivers/pps/generators/Kconfig b/drivers/pps/generators/Kconfig
index 5edbfdb8bd92..51c05b090d94 100644
--- a/drivers/pps/generators/Kconfig
+++ b/drivers/pps/generators/Kconfig
@@ -14,6 +14,15 @@ menuconfig PPS_GENERATOR
 
 if PPS_GENERATOR
 
+config PPS_GENERATOR_DUMMY
+        tristate "Dummy PPS generator (Testing generator, use for debug)"
+        help
+          If you say yes here you get support for a PPS debugging generator
+          (which generates no PPS signal at all).
+
+          This driver can also be built as a module.  If so, the module
+          will be called pps_gen-dummy.
+
 config PPS_GENERATOR_PARPORT
 	tristate "Parallel port PPS signal generator"
 	depends on PARPORT && BROKEN
diff --git a/drivers/pps/generators/Makefile b/drivers/pps/generators/Makefile
index 034a78edfa26..dc1aa5a4688b 100644
--- a/drivers/pps/generators/Makefile
+++ b/drivers/pps/generators/Makefile
@@ -6,6 +6,7 @@
 pps_gen_core-y			:= pps_gen.o sysfs.o
 obj-$(CONFIG_PPS_GENERATOR)	:= pps_gen_core.o
 
+obj-$(CONFIG_PPS_GENERATOR_DUMMY)   += pps_gen-dummy.o
 obj-$(CONFIG_PPS_GENERATOR_PARPORT) += pps_gen_parport.o
 
 ccflags-$(CONFIG_PPS_DEBUG) := -DDEBUG
diff --git a/drivers/pps/generators/pps_gen-dummy.c b/drivers/pps/generators/pps_gen-dummy.c
new file mode 100644
index 000000000000..b284c200cbe5
--- /dev/null
+++ b/drivers/pps/generators/pps_gen-dummy.c
@@ -0,0 +1,96 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * PPS dummy generator
+ *
+ * Copyright (C) 2024 Rodolfo Giometti <giometti@...eenne.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/time.h>
+#include <linux/timer.h>
+#include <linux/random.h>
+#include <linux/pps_gen_kernel.h>
+
+static struct pps_gen_device *pps_gen;
+static struct timer_list ktimer;
+
+static unsigned int get_random_delay(void)
+{
+	unsigned int delay = get_random_u8() & 0x0f;
+
+	return (delay + 1) * HZ;
+}
+
+/*
+ * The kernel timer
+ */
+
+static void pps_gen_ktimer_event(struct timer_list *unused)
+{
+	pps_gen_event(pps_gen, PPS_GEN_EVENT_MISSEDPULSE, NULL);
+}
+
+/*
+ * PPS Generator methods
+ */
+
+static int pps_gen_dummy_get_time(struct pps_gen_device *pps_gen,
+					struct timespec64 *time)
+{
+	struct system_time_snapshot snap;
+
+	ktime_get_snapshot(&snap);
+	*time = ktime_to_timespec64(snap.real);
+
+	return 0;
+}
+
+static int pps_gen_dummy_enable(struct pps_gen_device *pps_gen, bool enable)
+{
+	if (enable)
+		mod_timer(&ktimer, jiffies + get_random_delay());
+	else
+		del_timer_sync(&ktimer);
+
+	return 0;
+}
+
+/*
+ * The PPS info struct
+ */
+
+static struct pps_gen_source_info pps_gen_dummy_info = {
+	.use_system_clock	= true,
+	.get_time		= pps_gen_dummy_get_time,
+	.enable			= pps_gen_dummy_enable,
+};
+
+/*
+ * Module staff
+ */
+
+static void __exit pps_gen_dummy_exit(void)
+{
+	del_timer_sync(&ktimer);
+	pps_gen_unregister_source(pps_gen);
+}
+
+static int __init pps_gen_dummy_init(void)
+{
+	pps_gen = pps_gen_register_source(&pps_gen_dummy_info);
+	if (IS_ERR(pps_gen))
+		return PTR_ERR(pps_gen);
+
+	timer_setup(&ktimer, pps_gen_ktimer_event, 0);
+
+	return 0;
+}
+
+module_init(pps_gen_dummy_init);
+module_exit(pps_gen_dummy_exit);
+
+MODULE_AUTHOR("Rodolfo Giometti <giometti@...eenne.com>");
+MODULE_DESCRIPTION("LinuxPPS dummy generator");
+MODULE_LICENSE("GPL");
-- 
2.34.1