[patch 16/55] timekeeping: Provide ktime_get_with_offset()

[Thomas Gleixner]

Provide a helper function which lets us implement ktime_t based
interfaces for real, boot and tai clocks.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
 include/linux/timekeeping.h |    9 +++++++++
 kernel/time/timekeeping.c   |   27 +++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

Index: tip/include/linux/timekeeping.h
===================================================================
--- tip.orig/include/linux/timekeeping.h
+++ tip/include/linux/timekeeping.h
@@ -98,7 +98,16 @@ extern void getboottime(struct timespec
 /*
  * ktime_t based interfaces
  */
+
+enum tk_offsets {
+	TK_OFFS_REAL,
+	TK_OFFS_BOOT,
+	TK_OFFS_TAI,
+	TK_OFFS_MAX,
+};
+
 extern ktime_t ktime_get(void);
+extern ktime_t ktime_get_with_offset(enum tk_offsets offs);
 extern ktime_t ktime_get_real(void);
 extern ktime_t ktime_get_boottime(void);
 extern ktime_t ktime_get_monotonic_offset(void);
Index: tip/kernel/time/timekeeping.c
===================================================================
--- tip.orig/kernel/time/timekeeping.c
+++ tip/kernel/time/timekeeping.c
@@ -422,6 +422,33 @@ ktime_t ktime_get(void)
 }
 EXPORT_SYMBOL_GPL(ktime_get);
 
+static ktime_t *offsets[TK_OFFS_MAX] = {
+	[TK_OFFS_REAL]	= &tk_core.timekeeper.offs_real,
+	[TK_OFFS_BOOT]	= &tk_core.timekeeper.offs_boot,
+	[TK_OFFS_TAI]	= &tk_core.timekeeper.offs_tai,
+};
+
+ktime_t ktime_get_with_offset(enum tk_offsets offs)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	unsigned int seq;
+	ktime_t base, *offset = offsets[offs];
+	s64 nsecs;
+
+	WARN_ON(timekeeping_suspended);
+
+	do {
+		seq = read_seqcount_begin(&tk_core.seq);
+		base = ktime_add(tk->base_mono, *offset);
+		nsecs = timekeeping_get_ns(tk);
+
+	} while (read_seqcount_retry(&tk_core.seq, seq));
+
+	return ktime_add_ns(base, nsecs);
+
+}
+EXPORT_SYMBOL_GPL(ktime_get_with_offset);
+
 /**
  * ktime_get_ts64 - get the monotonic clock in timespec64 format
  * @ts:		pointer to timespec variable


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