aboutsummaryrefslogtreecommitdiff
path: root/lib
diff options
context:
space:
mode:
authorLinus Torvalds <torvalds@linux-foundation.org>2009-06-11 08:57:47 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-11 08:57:47 -0700
commit49c355617f603b8e71ec117c1f940152a998528a (patch)
tree6b5e373003371bbe8c587a9fdda7bc4f0e791b03 /lib
parent991ec02cdca33b03a132a0cacfe6f0aa0be9aa8d (diff)
parentf0e8527726b9e56649b9eafde3bc0fbc4dd2dd47 (diff)
downloadvexpress-lsk-49c355617f603b8e71ec117c1f940152a998528a.tar.gz
Merge branch 'serial-from-alan'
* serial-from-alan: (79 commits) moxa: prevent opening unavailable ports imx: serial: use tty_encode_baud_rate to set true rate imx: serial: add IrDA support to serial driver imx: serial: use rational library function lib: isolate rational fractions helper function imx: serial: handle initialisation failure correctly imx: serial: be sure to stop xmit upon shutdown imx: serial: notify higher layers in case xmit IRQ was not called imx: serial: fix one bit field type imx: serial: fix whitespaces (no changes in functionality) tty: use prepare/finish_wait tty: remove sleep_on sierra: driver interface blacklisting sierra: driver urb handling improvements tty: resolve some sierra breakage timbuart: Fix the termios logic serial: Added Timberdale UART driver tty: Add URL for ttydev queue devpts: unregister the file system on error tty: Untangle termios and mm mutex dependencies ...
Diffstat (limited to 'lib')
-rw-r--r--lib/Kconfig3
-rw-r--r--lib/Makefile1
-rw-r--r--lib/rational.c62
3 files changed, 66 insertions, 0 deletions
diff --git a/lib/Kconfig b/lib/Kconfig
index 8ade0a7a91e..9960be04cbb 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -10,6 +10,9 @@ menu "Library routines"
config BITREVERSE
tristate
+config RATIONAL
+ boolean
+
config GENERIC_FIND_FIRST_BIT
bool
diff --git a/lib/Makefile b/lib/Makefile
index 33a40e40e3e..1f6edefebff 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -50,6 +50,7 @@ ifneq ($(CONFIG_HAVE_DEC_LOCK),y)
endif
obj-$(CONFIG_BITREVERSE) += bitrev.o
+obj-$(CONFIG_RATIONAL) += rational.o
obj-$(CONFIG_CRC_CCITT) += crc-ccitt.o
obj-$(CONFIG_CRC16) += crc16.o
obj-$(CONFIG_CRC_T10DIF)+= crc-t10dif.o
diff --git a/lib/rational.c b/lib/rational.c
new file mode 100644
index 00000000000..b3c099b5478
--- /dev/null
+++ b/lib/rational.c
@@ -0,0 +1,62 @@
+/*
+ * rational fractions
+ *
+ * Copyright (C) 2009 emlix GmbH, Oskar Schirmer <os@emlix.com>
+ *
+ * helper functions when coping with rational numbers
+ */
+
+#include <linux/rational.h>
+
+/*
+ * calculate best rational approximation for a given fraction
+ * taking into account restricted register size, e.g. to find
+ * appropriate values for a pll with 5 bit denominator and
+ * 8 bit numerator register fields, trying to set up with a
+ * frequency ratio of 3.1415, one would say:
+ *
+ * rational_best_approximation(31415, 10000,
+ * (1 << 8) - 1, (1 << 5) - 1, &n, &d);
+ *
+ * you may look at given_numerator as a fixed point number,
+ * with the fractional part size described in given_denominator.
+ *
+ * for theoretical background, see:
+ * http://en.wikipedia.org/wiki/Continued_fraction
+ */
+
+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)
+{
+ unsigned long n, d, n0, d0, n1, d1;
+ n = given_numerator;
+ d = given_denominator;
+ n0 = d1 = 0;
+ n1 = d0 = 1;
+ for (;;) {
+ unsigned long t, a;
+ if ((n1 > max_numerator) || (d1 > max_denominator)) {
+ n1 = n0;
+ d1 = d0;
+ break;
+ }
+ if (d == 0)
+ break;
+ t = d;
+ a = n / d;
+ d = n % d;
+ n = t;
+ t = n0 + a * n1;
+ n0 = n1;
+ n1 = t;
+ t = d0 + a * d1;
+ d0 = d1;
+ d1 = t;
+ }
+ *best_numerator = n1;
+ *best_denominator = d1;
+}
+
+EXPORT_SYMBOL(rational_best_approximation);