drivers pps: add PPS generators support

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.

This patch adds PPS generators class in order to have a well-defined
interface for these devices.

Signed-off-by: Rodolfo Giometti <giometti@enneenne.com>
Link: https://lore.kernel.org/r/20241108073115.759039-2-giometti@enneenne.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 37 insertions, 0 deletions

diff --git a/include/uapi/linux/pps_gen.h b/include/uapi/linux/pps_gen.h
new file mode 100644
index 000000000000..60a5d0fcfa68
--- /dev/null
+++ b/include/uapi/linux/pps_gen.h
@@ -0,0 +1,37 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * PPS generator API header
+ *
+ * Copyright (C) 2024 Rodolfo Giometti <giometti@enneenne.com>
+ */
+
+#ifndef _PPS_GEN_H_
+#define _PPS_GEN_H_
+
+#include <linux/types.h>
+#include <linux/ioctl.h>
+
+/**
+ * struct pps_gen_event - the PPS generator events
+ * @event: the event type
+ * @sequence: the event sequence number
+ *
+ * Userspace can get the last PPS generator event by using the
+ * ioctl(pps_gen, PPS_GEN_FETCHEVENT, ...) syscall.
+ * The sequence field can be used to save the last event ID, while in the
+ * event field is stored the last event type. Currently known event is:
+ *
+ *     PPS_GEN_EVENT_MISSEDPULSE	: last pulse was not generated
+ */
+struct pps_gen_event {
+	unsigned int event;
+	unsigned int sequence;
+};
+
+#define PPS_GEN_EVENT_MISSEDPULSE	1
+
+#define PPS_GEN_SETENABLE		_IOW('p', 0xb1, unsigned int *)
+#define PPS_GEN_USESYSTEMCLOCK		_IOR('p', 0xb2, unsigned int *)
+#define PPS_GEN_FETCHEVENT		_IOR('p', 0xb3, struct pps_gen_event *)
+
+#endif /* _PPS_GEN_H_ */