new file mode 100644
@@ -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
@@ -19,6 +19,9 @@ config RAID6_PQ_BENCHMARK
Benchmark all available RAID6 PQ functions on init and choose the
fastest one.
+config LINEAR_RANGES
+ tristate
+
config PACKING
bool "Generic bitfield packing and unpacking"
default n
@@ -125,6 +125,7 @@ obj-$(CONFIG_DEBUG_LIST) += list_debug.o
obj-$(CONFIG_DEBUG_OBJECTS) += debugobjects.o
obj-$(CONFIG_BITREVERSE) += bitrev.o
+obj-$(CONFIG_LINEAR_RANGES) += linear_ranges.o
obj-$(CONFIG_PACKING) += packing.o
obj-$(CONFIG_CRC_CCITT) += crc-ccitt.o
obj-$(CONFIG_CRC16) += crc16.o
new file mode 100644
@@ -0,0 +1,241 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * helpers to map values in a linear range to range index
+ *
+ * Original idea borrowed from regulator framework
+ *
+ * It might be useful if we could support also inversely proportional ranges?
+ * Copyright 2020 ROHM Semiconductors
+ */
+
+#include <linux/errno.h>
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/linear_range.h>
+
+/**
+ * linear_range_values_in_range - return the amount of values in a range
+ * @r: pointer to linear range where values are counted
+ *
+ * Compute the amount of values in range pointed by @r. Note, values can
+ * be all equal - range with selectors 0,...,2 with step 0 still contains
+ * 3 values even though they are all equal.
+ *
+ * Return: the amount of values in range pointed by @r
+ */
+unsigned int linear_range_values_in_range(const struct linear_range *r)
+{
+ if (!r)
+ return 0;
+ return r->max_sel - r->min_sel + 1;
+}
+EXPORT_SYMBOL_GPL(linear_range_values_in_range);
+
+/**
+ * linear_range_values_in_range_array - return the amount of values in ranges
+ * @r: pointer to array of linear ranges where values are counted
+ * @ranges: amount of ranges we include in computation.
+ *
+ * Compute the amount of values in ranges pointed by @r. Note, values can
+ * be all equal - range with selectors 0,...,2 with step 0 still contains
+ * 3 values even though they are all equal.
+ *
+ * Return: the amount of values in first @ranges ranges pointed by @r
+ */
+unsigned int linear_range_values_in_range_array(const struct linear_range *r,
+ int ranges)
+{
+ int i, values_in_range = 0;
+
+ for (i = 0; i < ranges; i++) {
+ int values;
+
+ values = linear_range_values_in_range(&r[i]);
+ if (!values)
+ return values;
+
+ values_in_range += values;
+ }
+ return values_in_range;
+}
+EXPORT_SYMBOL_GPL(linear_range_values_in_range_array);
+
+/**
+ * linear_range_get_max_value - return the largest value in a range
+ * @r: pointer to linear range where value is looked from
+ *
+ * Return: the largest value in the given range
+ */
+unsigned int linear_range_get_max_value(const struct linear_range *r)
+{
+ return r->min + (r->max_sel - r->min_sel) * r->step;
+}
+EXPORT_SYMBOL_GPL(linear_range_get_max_value);
+
+/**
+ * linear_range_get_value - fetch a value from given range
+ * @r: pointer to linear range where value is looked from
+ * @selector: selector for which the value is searched
+ * @val: address where found value is updated
+ *
+ * Search given ranges for value which matches given selector.
+ *
+ * Return: 0 on success, -EINVAL given selector is not found from any of the
+ * ranges.
+ */
+int linear_range_get_value(const struct linear_range *r, unsigned int selector,
+ unsigned int *val)
+{
+ if (r->min_sel > selector || r->max_sel < selector)
+ return -EINVAL;
+
+ *val = r->min + (selector - r->min_sel) * r->step;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(linear_range_get_value);
+
+/**
+ * linear_range_get_value_array - fetch a value from array of ranges
+ * @r: pointer to array of linear ranges where value is looked from
+ * @ranges: amount of ranges in an array
+ * @selector: selector for which the value is searched
+ * @val: address where found value is updated
+ *
+ * Search through an array of ranges for value which matches given selector.
+ *
+ * Return: 0 on success, -EINVAL given selector is not found from any of the
+ * ranges.
+ */
+int linear_range_get_value_array(const struct linear_range *r, int ranges,
+ unsigned int selector, unsigned int *val)
+{
+ int i;
+
+ for (i = 0; i < ranges; i++)
+ if (r[i].min_sel <= selector && r[i].max_sel >= selector)
+ return linear_range_get_value(&r[i], selector, val);
+
+ return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(linear_range_get_value_array);
+
+/**
+ * linear_range_get_selector_low - return linear range selector for value
+ * @r: pointer to linear range where selector is looked from
+ * @val: value for which the selector is searched
+ * @selector: address where found selector value is updated
+ * @found: flag to indicate that given value was in the range
+ *
+ * Return selector which which range value is closest match for given
+ * input value. Value is matching if it is equal or smaller than given
+ * value. If given value is in the range, then @found is set true.
+ *
+ * Return: 0 on success, -EINVAL if range is invalid or does not contain
+ * value smaller or equal to given value
+ */
+int linear_range_get_selector_low(const struct linear_range *r,
+ unsigned int val, unsigned int *selector,
+ bool *found)
+{
+ *found = false;
+
+ if (r->min > val)
+ return -EINVAL;
+
+ if (linear_range_get_max_value(r) < val) {
+ *selector = r->max_sel;
+ return 0;
+ }
+
+ *found = true;
+
+ if (r->step == 0)
+ *selector = r->min_sel;
+ else
+ *selector = (val - r->min) / r->step + r->min_sel;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(linear_range_get_selector_low);
+
+/**
+ * linear_range_get_selector_low_array - return linear range selector for value
+ * @r: pointer to array of linear ranges where selector is looked from
+ * @ranges: amount of ranges to scan from array
+ * @val: value for which the selector is searched
+ * @selector: address where found selector value is updated
+ * @found: flag to indicate that given value was in the range
+ *
+ * Scan array of ranges for selector which which range value matches given
+ * input value. Value is matching if it is equal or smaller than given
+ * value. If given value is found to be in a range scanning is stopped and
+ * @found is set true. If a range with values smaller than given value is found
+ * but the range max is being smaller than given value, then the ranges
+ * biggest selector is updated to @selector but scanning ranges is continued
+ * and @found is set to false.
+ *
+ * Return: 0 on success, -EINVAL if range array is invalid or does not contain
+ * range with a value smaller or equal to given value
+ */
+int linear_range_get_selector_low_array(const struct linear_range *r,
+ int ranges, unsigned int val,
+ unsigned int *selector, bool *found)
+{
+ int i;
+ int ret = -EINVAL;
+
+ for (i = 0; i < ranges; i++) {
+ int tmpret;
+
+ tmpret = linear_range_get_selector_low(&r[i], val, selector,
+ found);
+ if (!tmpret)
+ ret = 0;
+
+ if (*found)
+ break;
+ }
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(linear_range_get_selector_low_array);
+
+/**
+ * linear_range_get_selector_high - return linear range selector for value
+ * @r: pointer to linear range where selector is looked from
+ * @val: value for which the selector is searched
+ * @selector: address where found selector value is updated
+ * @found: flag to indicate that given value was in the range
+ *
+ * Return selector which which range value is closest match for given
+ * input value. Value is matching if it is equal or higher than given
+ * value. If given value is in the range, then @found is set true.
+ *
+ * Return: 0 on success, -EINVAL if range is invalid or does not contain
+ * value greater or equal to given value
+ */
+int linear_range_get_selector_high(const struct linear_range *r,
+ unsigned int val, unsigned int *selector,
+ bool *found)
+{
+ *found = false;
+
+ if (linear_range_get_max_value(r) < val)
+ return -EINVAL;
+
+ if (r->min > val) {
+ *selector = r->min_sel;
+ return 0;
+ }
+
+ *found = true;
+
+ if (r->step == 0)
+ *selector = r->max_sel;
+ else
+ *selector = DIV_ROUND_UP(val - r->min, r->step) + r->min_sel;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(linear_range_get_selector_high);