lib: add linear range get selector within

Add linear range get selector within for choose closest selector
between minimum and maximum selector.

Signed-off-by: Gene Chen <[e-mail]>
Reviewed-by: Matti Vaittinen <[e-mail]>
Signed-off-by: Sebastian Reichel <[e-mail]>

include/linux/linear_range.h

···
 int linear_range_get_selector_high(const struct linear_range *r,
 				   unsigned int val, unsigned int *selector,
 				   bool *found);
+void linear_range_get_selector_within(const struct linear_range *r,
+				      unsigned int val, unsigned int *selector);
 int linear_range_get_selector_low_array(const struct linear_range *r,
 					int ranges, unsigned int val,
 					unsigned int *selector, bool *found);

lib/linear_ranges.c

···
 }
 EXPORT_SYMBOL_GPL(linear_range_get_selector_high);
 
+/**
+ * linear_range_get_selector_within - 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
+ *
+ * Return selector for which range value is closest match for given
+ * input value. Value is matching if it is equal or lower than given
+ * value. But return maximum selector if given value is higher than
+ * maximum value.
+ */
+void linear_range_get_selector_within(const struct linear_range *r,
+				      unsigned int val, unsigned int *selector)
+{
+	if (r->min > val) {
+		*selector = r->min_sel;
+		return;
+	}
+
+	if (linear_range_get_max_value(r) < val) {
+		*selector = r->max_sel;
+		return;
+	}
+
+	if (r->step == 0)
+		*selector = r->min_sel;
+	else
+		*selector = (val - r->min) / r->step + r->min_sel;
+}
+EXPORT_SYMBOL_GPL(linear_range_get_selector_within);
+
 MODULE_DESCRIPTION("linear-ranges helper");
 MODULE_LICENSE("GPL");