1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * acpi_lpat.c - LPAT table processing functions
4 *
5 * Copyright (C) 2015 Intel Corporation. All rights reserved.
6 */
7
8#include <linux/export.h>
9#include <linux/acpi.h>
10#include <acpi/acpi_lpat.h>
11
12/**
13 * acpi_lpat_raw_to_temp(): Return temperature from raw value through
14 * LPAT conversion table
15 *
16 * @lpat_table: the temperature_raw mapping table structure
17 * @raw: the raw value, used as a key to get the temperature from the
18 *       above mapping table
19 *
20 * A positive converted temperature value will be returned on success,
21 * a negative errno will be returned in error cases.
22 */
23int acpi_lpat_raw_to_temp(struct acpi_lpat_conversion_table *lpat_table,
24			  int raw)
25{
26	int i, delta_temp, delta_raw, temp;
27	struct acpi_lpat *lpat = lpat_table->lpat;
28
29	for (i = 0; i < lpat_table->lpat_count - 1; i++) {
30		if ((raw >= lpat[i].raw && raw <= lpat[i+1].raw) ||
31		    (raw <= lpat[i].raw && raw >= lpat[i+1].raw))
32			break;
33	}
34
35	if (i == lpat_table->lpat_count - 1)
36		return -ENOENT;
37
38	delta_temp = lpat[i+1].temp - lpat[i].temp;
39	delta_raw = lpat[i+1].raw - lpat[i].raw;
40	temp = lpat[i].temp + (raw - lpat[i].raw) * delta_temp / delta_raw;
41
42	return temp;
43}
44EXPORT_SYMBOL_GPL(acpi_lpat_raw_to_temp);
45
46/**
47 * acpi_lpat_temp_to_raw(): Return raw value from temperature through
48 * LPAT conversion table
49 *
50 * @lpat_table: the temperature_raw mapping table
51 * @temp: the temperature, used as a key to get the raw value from the
52 *        above mapping table
53 *
54 * The raw value will be returned on success,
55 * a negative errno will be returned in error cases.
56 */
57int acpi_lpat_temp_to_raw(struct acpi_lpat_conversion_table *lpat_table,
58			  int temp)
59{
60	int i, delta_temp, delta_raw, raw;
61	struct acpi_lpat *lpat = lpat_table->lpat;
62
63	for (i = 0; i < lpat_table->lpat_count - 1; i++) {
64		if (temp >= lpat[i].temp && temp <= lpat[i+1].temp)
65			break;
66	}
67
68	if (i ==  lpat_table->lpat_count - 1)
69		return -ENOENT;
70
71	delta_temp = lpat[i+1].temp - lpat[i].temp;
72	delta_raw = lpat[i+1].raw - lpat[i].raw;
73	raw = lpat[i].raw + (temp - lpat[i].temp) * delta_raw / delta_temp;
74
75	return raw;
76}
77EXPORT_SYMBOL_GPL(acpi_lpat_temp_to_raw);
78
79/**
80 * acpi_lpat_get_conversion_table(): Parse ACPI LPAT table if present.
81 *
82 * @handle: Handle to acpi device
83 *
84 * Parse LPAT table to a struct of type acpi_lpat_table. On success
85 * it returns a pointer to newly allocated table. This table must
86 * be freed by the caller when finished processing, using a call to
87 * acpi_lpat_free_conversion_table.
88 */
89struct acpi_lpat_conversion_table *acpi_lpat_get_conversion_table(acpi_handle
90								  handle)
91{
92	struct acpi_lpat_conversion_table *lpat_table = NULL;
93	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
94	union acpi_object *obj_p, *obj_e;
95	int *lpat, i;
96	acpi_status status;
97
98	status = acpi_evaluate_object(handle, "LPAT", NULL, &buffer);
99	if (ACPI_FAILURE(status))
100		return NULL;
101
102	obj_p = (union acpi_object *)buffer.pointer;
103	if (!obj_p || (obj_p->type != ACPI_TYPE_PACKAGE) ||
104	    (obj_p->package.count % 2) || (obj_p->package.count < 4))
105		goto out;
106
107	lpat = kcalloc(obj_p->package.count, sizeof(int), GFP_KERNEL);
108	if (!lpat)
109		goto out;
110
111	for (i = 0; i < obj_p->package.count; i++) {
112		obj_e = &obj_p->package.elements[i];
113		if (obj_e->type != ACPI_TYPE_INTEGER) {
114			kfree(lpat);
115			goto out;
116		}
117		lpat[i] = (s64)obj_e->integer.value;
118	}
119
120	lpat_table = kzalloc(sizeof(*lpat_table), GFP_KERNEL);
121	if (!lpat_table) {
122		kfree(lpat);
123		goto out;
124	}
125
126	lpat_table->lpat = (struct acpi_lpat *)lpat;
127	lpat_table->lpat_count = obj_p->package.count / 2;
128
129out:
130	kfree(buffer.pointer);
131	return lpat_table;
132}
133EXPORT_SYMBOL_GPL(acpi_lpat_get_conversion_table);
134
135/**
136 * acpi_lpat_free_conversion_table(): Free LPAT table.
137 *
138 * @lpat_table: the temperature_raw mapping table structure
139 *
140 * Frees the LPAT table previously allocated by a call to
141 * acpi_lpat_get_conversion_table.
142 */
143void acpi_lpat_free_conversion_table(struct acpi_lpat_conversion_table
144				     *lpat_table)
145{
146	if (lpat_table) {
147		kfree(lpat_table->lpat);
148		kfree(lpat_table);
149	}
150}
151EXPORT_SYMBOL_GPL(acpi_lpat_free_conversion_table);
152