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authorChris Wilson <chris@chris-wilson.co.uk>2016-12-22 14:45:14 +0000
committerDaniel Vetter <daniel.vetter@ffwll.ch>2016-12-27 12:30:56 +0100
commitcf4a7207b1cb4a3c3fe3aa11a83c9d673722a7f5 (patch)
tree664430c374186b63e808e08f65bca635747e14c9 /include/linux/prime_numbers.h
parentb3ee963fe41d0034cf8b6aff1f0cc9c91bf8d478 (diff)
lib: Add a simple prime number generator
Prime numbers are interesting for testing components that use multiplies and divides, such as testing DRM's struct drm_mm alignment computations. v2: Move to lib/, add selftest v3: Fix initial constants (exclude 0/1 from being primes) v4: More RCU markup to keep 0day/sparse happy v5: Fix RCU unwind on module exit, add to kselftests v6: Tidy computation of bitmap size v7: for_each_prime_number_from() v8: Compose small-primes using BIT() for easier verification v9: Move rcu dance entirely into callers. v10: Improve quote for Betrand's Postulate (aka Chebyshev's theorem) Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Lukas Wunner <lukas@wunner.de> Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: http://patchwork.freedesktop.org/patch/msgid/20161222144514.3911-1-chris@chris-wilson.co.uk
Diffstat (limited to 'include/linux/prime_numbers.h')
-rw-r--r--include/linux/prime_numbers.h37
1 files changed, 37 insertions, 0 deletions
diff --git a/include/linux/prime_numbers.h b/include/linux/prime_numbers.h
new file mode 100644
index 000000000000..14ec4f567342
--- /dev/null
+++ b/include/linux/prime_numbers.h
@@ -0,0 +1,37 @@
+#ifndef __LINUX_PRIME_NUMBERS_H
+#define __LINUX_PRIME_NUMBERS_H
+
+#include <linux/types.h>
+
+bool is_prime_number(unsigned long x);
+unsigned long next_prime_number(unsigned long x);
+
+/**
+ * for_each_prime_number - iterate over each prime upto a value
+ * @prime: the current prime number in this iteration
+ * @max: the upper limit
+ *
+ * Starting from the first prime number 2 iterate over each prime number up to
+ * the @max value. On each iteration, @prime is set to the current prime number.
+ * @max should be less than ULONG_MAX to ensure termination. To begin with
+ * @prime set to 1 on the first iteration use for_each_prime_number_from()
+ * instead.
+ */
+#define for_each_prime_number(prime, max) \
+ for_each_prime_number_from((prime), 2, (max))
+
+/**
+ * for_each_prime_number_from - iterate over each prime upto a value
+ * @prime: the current prime number in this iteration
+ * @from: the initial value
+ * @max: the upper limit
+ *
+ * Starting from @from iterate over each successive prime number up to the
+ * @max value. On each iteration, @prime is set to the current prime number.
+ * @max should be less than ULONG_MAX, and @from less than @max, to ensure
+ * termination.
+ */
+#define for_each_prime_number_from(prime, from, max) \
+ for (prime = (from); prime <= (max); prime = next_prime_number(prime))
+
+#endif /* !__LINUX_PRIME_NUMBERS_H */