lib: isolate rational fractions helper function

Provide a helper function to determine optimum numerator
denominator value pairs taking into account restricted
register size. Useful especially with PLL and other clock
configurations.

Signed-off-by: Oskar Schirmer <os@emlix.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/include/linux/rational.h b/include/linux/rational.h
new file mode 100644
index 000000000000..4f532fcd9eea
--- /dev/null
+++ b/include/linux/rational.h
@@ -0,0 +1,19 @@
+/*
+ * rational fractions
+ *
+ * Copyright (C) 2009 emlix GmbH, Oskar Schirmer <os@emlix.com>
+ *
+ * helper functions when coping with rational numbers,
+ * e.g. when calculating optimum numerator/denominator pairs for
+ * pll configuration taking into account restricted register size
+ */
+
+#ifndef _LINUX_RATIONAL_H
+#define _LINUX_RATIONAL_H
+
+void rational_best_approximation(
+        unsigned long given_numerator, unsigned long given_denominator,
+        unsigned long max_numerator, unsigned long max_denominator,
+        unsigned long *best_numerator, unsigned long *best_denominator);
+
+#endif /* _LINUX_RATIONAL_H */