drivers/acpi/acpi_lpat.c

   1 /*
   2  * acpi_lpat.c - LPAT table processing functions
   3  *
   4  * Copyright (C) 2015 Intel Corporation. All rights reserved.
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License version
   8  * 2 as published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  */
  15
  16 #include <linux/export.h>
  17 #include <linux/acpi.h>
  18 #include <acpi/acpi_lpat.h>
  19
  20 /**
  21  * acpi_lpat_raw_to_temp(): Return temperature from raw value through
  22  * LPAT conversion table
  23  *
  24  * @lpat_table: the temperature_raw mapping table structure
  25  * @raw: the raw value, used as a key to get the temerature from the
  26  *       above mapping table
  27  *
  28  * A positive converted temperarure value will be returned on success,
  29  * a negative errno will be returned in error cases.
  30  */
  31 int acpi_lpat_raw_to_temp(struct acpi_lpat_conversion_table *lpat_table,
  32                           int raw)
  33 {
  34         int i, delta_temp, delta_raw, temp;
  35         struct acpi_lpat *lpat = lpat_table->lpat;
  36
  37         for (i = 0; i < lpat_table->lpat_count - 1; i++) {
  38                 if ((raw >= lpat[i].raw && raw <= lpat[i+1].raw) ||
  39                     (raw <= lpat[i].raw && raw >= lpat[i+1].raw))
  40                         break;
  41         }
  42
  43         if (i == lpat_table->lpat_count - 1)
  44                 return -ENOENT;
  45
  46         delta_temp = lpat[i+1].temp - lpat[i].temp;
  47         delta_raw = lpat[i+1].raw - lpat[i].raw;
  48         temp = lpat[i].temp + (raw - lpat[i].raw) * delta_temp / delta_raw;
  49
  50         return temp;
  51 }
  52 EXPORT_SYMBOL_GPL(acpi_lpat_raw_to_temp);
  53
  54 /**
  55  * acpi_lpat_temp_to_raw(): Return raw value from temperature through
  56  * LPAT conversion table
  57  *
  58  * @lpat: the temperature_raw mapping table
  59  * @temp: the temperature, used as a key to get the raw value from the
  60  *        above mapping table
  61  *
  62  * A positive converted temperature value will be returned on success,
  63  * a negative errno will be returned in error cases.
  64  */
  65 int acpi_lpat_temp_to_raw(struct acpi_lpat_conversion_table *lpat_table,
  66                           int temp)
  67 {
  68         int i, delta_temp, delta_raw, raw;
  69         struct acpi_lpat *lpat = lpat_table->lpat;
  70
  71         for (i = 0; i < lpat_table->lpat_count - 1; i++) {
  72                 if (temp >= lpat[i].temp && temp <= lpat[i+1].temp)
  73                         break;
  74         }
  75
  76         if (i ==  lpat_table->lpat_count - 1)
  77                 return -ENOENT;
  78
  79         delta_temp = lpat[i+1].temp - lpat[i].temp;
  80         delta_raw = lpat[i+1].raw - lpat[i].raw;
  81         raw = lpat[i].raw + (temp - lpat[i].temp) * delta_raw / delta_temp;
  82
  83         return raw;
  84 }
  85 EXPORT_SYMBOL_GPL(acpi_lpat_temp_to_raw);
  86
  87 /**
  88  * acpi_lpat_get_conversion_table(): Parse ACPI LPAT table if present.
  89  *
  90  * @handle: Handle to acpi device
  91  *
  92  * Parse LPAT table to a struct of type acpi_lpat_table. On success
  93  * it returns a pointer to newly allocated table. This table must
  94  * be freed by the caller when finished processing, using a call to
  95  * acpi_lpat_free_conversion_table.
  96  */
  97 struct acpi_lpat_conversion_table *acpi_lpat_get_conversion_table(acpi_handle
  98                                                                   handle)
  99 {
 100         struct acpi_lpat_conversion_table *lpat_table = NULL;
 101         struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
 102         union acpi_object *obj_p, *obj_e;
 103         int *lpat, i;
 104         acpi_status status;
 105
 106         status = acpi_evaluate_object(handle, "LPAT", NULL, &buffer);
 107         if (ACPI_FAILURE(status))
 108                 return NULL;
 109
 110         obj_p = (union acpi_object *)buffer.pointer;
 111         if (!obj_p || (obj_p->type != ACPI_TYPE_PACKAGE) ||
 112             (obj_p->package.count % 2) || (obj_p->package.count < 4))
 113                 goto out;
 114
 115         lpat = kcalloc(obj_p->package.count, sizeof(int), GFP_KERNEL);
 116         if (!lpat)
 117                 goto out;
 118
 119         for (i = 0; i < obj_p->package.count; i++) {
 120                 obj_e = &obj_p->package.elements[i];
 121                 if (obj_e->type != ACPI_TYPE_INTEGER) {
 122                         kfree(lpat);
 123                         goto out;
 124                 }
 125                 lpat[i] = (s64)obj_e->integer.value;
 126         }
 127
 128         lpat_table = kzalloc(sizeof(*lpat_table), GFP_KERNEL);
 129         if (!lpat_table) {
 130                 kfree(lpat);
 131                 goto out;
 132         }
 133
 134         lpat_table->lpat = (struct acpi_lpat *)lpat;
 135         lpat_table->lpat_count = obj_p->package.count / 2;
 136
 137 out:
 138         kfree(buffer.pointer);
 139         return lpat_table;
 140 }
 141 EXPORT_SYMBOL_GPL(acpi_lpat_get_conversion_table);
 142
 143 /**
 144  * acpi_lpat_free_conversion_table(): Free LPAT table.
 145  *
 146  * @lpat_table: the temperature_raw mapping table structure
 147  *
 148  * Frees the LPAT table previously allocated by a call to
 149  * acpi_lpat_get_conversion_table.
 150  */
 151 void acpi_lpat_free_conversion_table(struct acpi_lpat_conversion_table
 152                                      *lpat_table)
 153 {
 154         if (lpat_table) {
 155                 kfree(lpat_table->lpat);
 156                 kfree(lpat_table);
 157         }
 158 }
 159 EXPORT_SYMBOL_GPL(acpi_lpat_free_conversion_table);