lib/math: Move dvb_math.c into lib/math/int_log.c

Some existing and new users may benefit from the intlog2() and
intlog10() APIs, make them wide available.

Reviewed-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Acked-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Link: https://lore.kernel.org/r/20230619172019.21457-2-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20230703135211.87416-2-andriy.shevchenko@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 65 insertions, 0 deletions

diff --git a/include/linux/int_log.h b/include/linux/int_log.h
new file mode 100644
index 000000000000..332306202464
--- /dev/null
+++ b/include/linux/int_log.h
@@ -0,0 +1,65 @@
+/*
+ * Provides fixed-point logarithm operations.
+ *
+ * Copyright (C) 2006 Christoph Pfister (christophpfister@gmail.com)
+ *
+ * This library is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ */
+
+#ifndef __LINUX_INT_LOG_H
+#define __LINUX_INT_LOG_H
+
+#include <linux/types.h>
+
+/**
+ * intlog2 - computes log2 of a value; the result is shifted left by 24 bits
+ *
+ * @value: The value (must be != 0)
+ *
+ * to use rational values you can use the following method:
+ *
+ *   intlog2(value) = intlog2(value * 2^x) - x * 2^24
+ *
+ * Some usecase examples:
+ *
+ *	intlog2(8) will give 3 << 24 = 3 * 2^24
+ *
+ *	intlog2(9) will give 3 << 24 + ... = 3.16... * 2^24
+ *
+ *	intlog2(1.5) = intlog2(3) - 2^24 = 0.584... * 2^24
+ *
+ *
+ * return: log2(value) * 2^24
+ */
+extern unsigned int intlog2(u32 value);
+
+/**
+ * intlog10 - computes log10 of a value; the result is shifted left by 24 bits
+ *
+ * @value: The value (must be != 0)
+ *
+ * to use rational values you can use the following method:
+ *
+ *   intlog10(value) = intlog10(value * 10^x) - x * 2^24
+ *
+ * An usecase example:
+ *
+ *	intlog10(1000) will give 3 << 24 = 3 * 2^24
+ *
+ *   due to the implementation intlog10(1000) might be not exactly 3 * 2^24
+ *
+ * look at intlog2 for similar examples
+ *
+ * return: log10(value) * 2^24
+ */
+extern unsigned int intlog10(u32 value);
+
+#endif