lib: add linear ranges helpers

Many devices have control registers which control some measurable
property. Often a register contains control field so that change in
this field causes linear change in the controlled property. It is not
a rare case that user wants to give 'meaningful' control values and
driver needs to convert them to register field values. Even more
often user wants to 'see' the currently set value - again in
meaningful units - and driver needs to convert the values it reads
from register to these meaningful units. Examples of this include:

- regulators, voltage/current configurations
- power, voltage/current configurations
- clk(?) NCOs

and maybe others I can't think of right now.

Provide a linear_range helper which can do conversion from user value
to register value 'selector'.

The idea here is stolen from regulator framework and patches refactoring
the regulator helpers to use this are following.

Current implementation does not support inversely proportional ranges
but it might be useful if we could support also inversely proportional
ranges?

Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/59259bc475e0c800eb4bb163f02528c7c01f7b3a.1588944082.git.matti.vaittinen@fi.rohmeurope.com
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 48 insertions, 0 deletions

diff --git a/include/linux/linear_range.h b/include/linux/linear_range.h
new file mode 100644
index 000000000000..17b5943727d5
--- /dev/null
+++ b/include/linux/linear_range.h
@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2020 ROHM Semiconductors */
+
+#ifndef LINEAR_RANGE_H
+#define LINEAR_RANGE_H
+
+#include <linux/types.h>
+
+/**
+ * struct linear_range - table of selector - value pairs
+ *
+ * Define a lookup-table for range of values. Intended to help when looking
+ * for a register value matching certaing physical measure (like voltage).
+ * Usable when increment of one in register always results a constant increment
+ * of the physical measure (like voltage).
+ *
+ * @min:  Lowest value in range
+ * @min_sel: Lowest selector for range
+ * @max_sel: Highest selector for range
+ * @step: Value step size
+ */
+struct linear_range {
+	unsigned int min;
+	unsigned int min_sel;
+	unsigned int max_sel;
+	unsigned int step;
+};
+
+unsigned int linear_range_values_in_range(const struct linear_range *r);
+unsigned int linear_range_values_in_range_array(const struct linear_range *r,
+						int ranges);
+unsigned int linear_range_get_max_value(const struct linear_range *r);
+
+int linear_range_get_value(const struct linear_range *r, unsigned int selector,
+			   unsigned int *val);
+int linear_range_get_value_array(const struct linear_range *r, int ranges,
+				 unsigned int selector, unsigned int *val);
+int linear_range_get_selector_low(const struct linear_range *r,
+				  unsigned int val, unsigned int *selector,
+				  bool *found);
+int linear_range_get_selector_high(const struct linear_range *r,
+				   unsigned int val, unsigned int *selector,
+				   bool *found);
+int linear_range_get_selector_low_array(const struct linear_range *r,
+					int ranges, unsigned int val,
+					unsigned int *selector, bool *found);
+
+#endif