lib/linear_ranges.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * helpers to map values in a linear range to range index
   4  *
   5  * Original idea borrowed from regulator framework
   6  *
   7  * It might be useful if we could support also inversely proportional ranges?
   8  * Copyright 2020 ROHM Semiconductors
   9  */
  10
  11 #include <linux/errno.h>
  12 #include <linux/export.h>
  13 #include <linux/kernel.h>
  14 #include <linux/linear_range.h>
  15 #include <linux/module.h>
  16
  17 /**
  18  * linear_range_values_in_range - return the amount of values in a range
  19  * @r:          pointer to linear range where values are counted
  20  *
  21  * Compute the amount of values in range pointed by @r. Note, values can
  22  * be all equal - range with selectors 0,...,2 with step 0 still contains
  23  * 3 values even though they are all equal.
  24  *
  25  * Return: the amount of values in range pointed by @r
  26  */
  27 unsigned int linear_range_values_in_range(const struct linear_range *r)
  28 {
  29         if (!r)
  30                 return 0;
  31         return r->max_sel - r->min_sel + 1;
  32 }
  33 EXPORT_SYMBOL_GPL(linear_range_values_in_range);
  34
  35 /**
  36  * linear_range_values_in_range_array - return the amount of values in ranges
  37  * @r:          pointer to array of linear ranges where values are counted
  38  * @ranges:     amount of ranges we include in computation.
  39  *
  40  * Compute the amount of values in ranges pointed by @r. Note, values can
  41  * be all equal - range with selectors 0,...,2 with step 0 still contains
  42  * 3 values even though they are all equal.
  43  *
  44  * Return: the amount of values in first @ranges ranges pointed by @r
  45  */
  46 unsigned int linear_range_values_in_range_array(const struct linear_range *r,
  47                                                 int ranges)
  48 {
  49         int i, values_in_range = 0;
  50
  51         for (i = 0; i < ranges; i++) {
  52                 int values;
  53
  54                 values = linear_range_values_in_range(&r[i]);
  55                 if (!values)
  56                         return values;
  57
  58                 values_in_range += values;
  59         }
  60         return values_in_range;
  61 }
  62 EXPORT_SYMBOL_GPL(linear_range_values_in_range_array);
  63
  64 /**
  65  * linear_range_get_max_value - return the largest value in a range
  66  * @r:          pointer to linear range where value is looked from
  67  *
  68  * Return: the largest value in the given range
  69  */
  70 unsigned int linear_range_get_max_value(const struct linear_range *r)
  71 {
  72         return r->min + (r->max_sel - r->min_sel) * r->step;
  73 }
  74 EXPORT_SYMBOL_GPL(linear_range_get_max_value);
  75
  76 /**
  77  * linear_range_get_value - fetch a value from given range
  78  * @r:          pointer to linear range where value is looked from
  79  * @selector:   selector for which the value is searched
  80  * @val:        address where found value is updated
  81  *
  82  * Search given ranges for value which matches given selector.
  83  *
  84  * Return: 0 on success, -EINVAL given selector is not found from any of the
  85  * ranges.
  86  */
  87 int linear_range_get_value(const struct linear_range *r, unsigned int selector,
  88                            unsigned int *val)
  89 {
  90         if (r->min_sel > selector || r->max_sel < selector)
  91                 return -EINVAL;
  92
  93         *val = r->min + (selector - r->min_sel) * r->step;
  94
  95         return 0;
  96 }
  97 EXPORT_SYMBOL_GPL(linear_range_get_value);
  98
  99 /**
 100  * linear_range_get_value_array - fetch a value from array of ranges
 101  * @r:          pointer to array of linear ranges where value is looked from
 102  * @ranges:     amount of ranges in an array
 103  * @selector:   selector for which the value is searched
 104  * @val:        address where found value is updated
 105  *
 106  * Search through an array of ranges for value which matches given selector.
 107  *
 108  * Return: 0 on success, -EINVAL given selector is not found from any of the
 109  * ranges.
 110  */
 111 int linear_range_get_value_array(const struct linear_range *r, int ranges,
 112                                  unsigned int selector, unsigned int *val)
 113 {
 114         int i;
 115
 116         for (i = 0; i < ranges; i++)
 117                 if (r[i].min_sel <= selector && r[i].max_sel >= selector)
 118                         return linear_range_get_value(&r[i], selector, val);
 119
 120         return -EINVAL;
 121 }
 122 EXPORT_SYMBOL_GPL(linear_range_get_value_array);
 123
 124 /**
 125  * linear_range_get_selector_low - return linear range selector for value
 126  * @r:          pointer to linear range where selector is looked from
 127  * @val:        value for which the selector is searched
 128  * @selector:   address where found selector value is updated
 129  * @found:      flag to indicate that given value was in the range
 130  *
 131  * Return selector which which range value is closest match for given
 132  * input value. Value is matching if it is equal or smaller than given
 133  * value. If given value is in the range, then @found is set true.
 134  *
 135  * Return: 0 on success, -EINVAL if range is invalid or does not contain
 136  * value smaller or equal to given value
 137  */
 138 int linear_range_get_selector_low(const struct linear_range *r,
 139                                   unsigned int val, unsigned int *selector,
 140                                   bool *found)
 141 {
 142         *found = false;
 143
 144         if (r->min > val)
 145                 return -EINVAL;
 146
 147         if (linear_range_get_max_value(r) < val) {
 148                 *selector = r->max_sel;
 149                 return 0;
 150         }
 151
 152         *found = true;
 153
 154         if (r->step == 0)
 155                 *selector = r->min_sel;
 156         else
 157                 *selector = (val - r->min) / r->step + r->min_sel;
 158
 159         return 0;
 160 }
 161 EXPORT_SYMBOL_GPL(linear_range_get_selector_low);
 162
 163 /**
 164  * linear_range_get_selector_low_array - return linear range selector for value
 165  * @r:          pointer to array of linear ranges where selector is looked from
 166  * @ranges:     amount of ranges to scan from array
 167  * @val:        value for which the selector is searched
 168  * @selector:   address where found selector value is updated
 169  * @found:      flag to indicate that given value was in the range
 170  *
 171  * Scan array of ranges for selector which which range value matches given
 172  * input value. Value is matching if it is equal or smaller than given
 173  * value. If given value is found to be in a range scanning is stopped and
 174  * @found is set true. If a range with values smaller than given value is found
 175  * but the range max is being smaller than given value, then the ranges
 176  * biggest selector is updated to @selector but scanning ranges is continued
 177  * and @found is set to false.
 178  *
 179  * Return: 0 on success, -EINVAL if range array is invalid or does not contain
 180  * range with a value smaller or equal to given value
 181  */
 182 int linear_range_get_selector_low_array(const struct linear_range *r,
 183                                         int ranges, unsigned int val,
 184                                         unsigned int *selector, bool *found)
 185 {
 186         int i;
 187         int ret = -EINVAL;
 188
 189         for (i = 0; i < ranges; i++) {
 190                 int tmpret;
 191
 192                 tmpret = linear_range_get_selector_low(&r[i], val, selector,
 193                                                        found);
 194                 if (!tmpret)
 195                         ret = 0;
 196
 197                 if (*found)
 198                         break;
 199         }
 200
 201         return ret;
 202 }
 203 EXPORT_SYMBOL_GPL(linear_range_get_selector_low_array);
 204
 205 /**
 206  * linear_range_get_selector_high - return linear range selector for value
 207  * @r:          pointer to linear range where selector is looked from
 208  * @val:        value for which the selector is searched
 209  * @selector:   address where found selector value is updated
 210  * @found:      flag to indicate that given value was in the range
 211  *
 212  * Return selector which which range value is closest match for given
 213  * input value. Value is matching if it is equal or higher than given
 214  * value. If given value is in the range, then @found is set true.
 215  *
 216  * Return: 0 on success, -EINVAL if range is invalid or does not contain
 217  * value greater or equal to given value
 218  */
 219 int linear_range_get_selector_high(const struct linear_range *r,
 220                                    unsigned int val, unsigned int *selector,
 221                                    bool *found)
 222 {
 223         *found = false;
 224
 225         if (linear_range_get_max_value(r) < val)
 226                 return -EINVAL;
 227
 228         if (r->min > val) {
 229                 *selector = r->min_sel;
 230                 return 0;
 231         }
 232
 233         *found = true;
 234
 235         if (r->step == 0)
 236                 *selector = r->max_sel;
 237         else
 238                 *selector = DIV_ROUND_UP(val - r->min, r->step) + r->min_sel;
 239
 240         return 0;
 241 }
 242 EXPORT_SYMBOL_GPL(linear_range_get_selector_high);
 243
 244 MODULE_DESCRIPTION("linear-ranges helper");
 245 MODULE_LICENSE("GPL");