timekeeping: Provide new API to get the current time resolution (6374f912) · Commits · 戴 / test

This patch series introduces a new function u32 ktime_get_resolution_ns(void) which allows to clean up some driver code. In particular the IIO subsystem has a function to provide timestamps for events but no means to get their resolution. So currently the dht11 driver tries to guess the resolution in a rather messy and convoluted way. We can do much better with the new code. This API is not designed to be exposed to user space. This has been tested on i386, sunxi and mxs. Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Signed-off-by:

Harald Geyer <harald@ccbib.org> [jstultz: Tweaked to make it build after upstream changes] Signed-off-by:

John Stultz <john.stultz@linaro.org>

include/linux/timekeeping.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -163,6 +163,7 @@ extern ktime_t ktime_get(void);
		extern ktime_t ktime_get_with_offset(enum tk_offsets offs);
		extern ktime_t ktime_mono_to_any(ktime_t tmono, enum tk_offsets offs);
		extern ktime_t ktime_get_raw(void);
		extern u32 ktime_get_resolution_ns(void);

		/**
		* ktime_get_real - get the real (wall-) time in ktime_t format

kernel/time/timekeeping.c

+17 −0

Original line number	Diff line number	Diff line
		@@ -702,6 +702,23 @@ ktime_t ktime_get(void)
		}
		EXPORT_SYMBOL_GPL(ktime_get);

		u32 ktime_get_resolution_ns(void)
		{
		struct timekeeper *tk = &tk_core.timekeeper;
		unsigned int seq;
		u32 nsecs;

		WARN_ON(timekeeping_suspended);

		do {
		seq = read_seqcount_begin(&tk_core.seq);
		nsecs = tk->tkr_mono.mult >> tk->tkr_mono.shift;
		} while (read_seqcount_retry(&tk_core.seq, seq));

		return nsecs;
		}
		EXPORT_SYMBOL_GPL(ktime_get_resolution_ns);

		static ktime_t *offsets[TK_OFFS_MAX] = {
		[TK_OFFS_REAL] = &tk_core.timekeeper.offs_real,
		[TK_OFFS_BOOT] = &tk_core.timekeeper.offs_boot,

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