// SPDX-License-Identifier: GPL-2.0-only
/*
 * acpi_lpat.c - LPAT table processing functions
 *
 * Copyright (C) 2015 Intel Corporation. All rights reserved.
 */

#include <linux/export.h>
#include <linux/acpi.h>
#include <acpi/acpi_lpat.h>

/**
 * acpi_lpat_raw_to_temp(): Return temperature from raw value through
 * LPAT conversion table
 *
 * @lpat_table: the temperature_raw mapping table structure
 * @raw: the raw value, used as a key to get the temperature from the
 *       above mapping table
 *
 * A positive converted temperature value will be returned on success,
 * a negative errno will be returned in error cases.
 */
int acpi_lpat_raw_to_temp(struct acpi_lpat_conversion_table *lpat_table,
                          int raw)
{
        int i, delta_temp, delta_raw, temp;
        struct acpi_lpat *lpat = lpat_table->lpat;

        for (i = 0; i < lpat_table->lpat_count - 1; i++) {
                if ((raw >= lpat[i].raw && raw <= lpat[i+1].raw) ||
                    (raw <= lpat[i].raw && raw >= lpat[i+1].raw))
                        break;
        }

        if (i == lpat_table->lpat_count - 1)
                return -ENOENT;

        delta_temp = lpat[i+1].temp - lpat[i].temp;
        delta_raw = lpat[i+1].raw - lpat[i].raw;
        temp = lpat[i].temp + (raw - lpat[i].raw) * delta_temp / delta_raw;

        return temp;
}
EXPORT_SYMBOL_GPL(acpi_lpat_raw_to_temp);

/**
 * acpi_lpat_temp_to_raw(): Return raw value from temperature through
 * LPAT conversion table
 *
 * @lpat_table: the temperature_raw mapping table
 * @temp: the temperature, used as a key to get the raw value from the
 *        above mapping table
 *
 * The raw value will be returned on success,
 * a negative errno will be returned in error cases.
 */
int acpi_lpat_temp_to_raw(struct acpi_lpat_conversion_table *lpat_table,
                          int temp)
{
        int i, delta_temp, delta_raw, raw;
        struct acpi_lpat *lpat = lpat_table->lpat;

        for (i = 0; i < lpat_table->lpat_count - 1; i++) {
                if (temp >= lpat[i].temp && temp <= lpat[i+1].temp)
                        break;
        }

        if (i ==  lpat_table->lpat_count - 1)
                return -ENOENT;

        delta_temp = lpat[i+1].temp - lpat[i].temp;
        delta_raw = lpat[i+1].raw - lpat[i].raw;
        raw = lpat[i].raw + (temp - lpat[i].temp) * delta_raw / delta_temp;

        return raw;
}
EXPORT_SYMBOL_GPL(acpi_lpat_temp_to_raw);

/**
 * acpi_lpat_get_conversion_table(): Parse ACPI LPAT table if present.
 *
 * @handle: Handle to acpi device
 *
 * Parse LPAT table to a struct of type acpi_lpat_table. On success
 * it returns a pointer to newly allocated table. This table must
 * be freed by the caller when finished processing, using a call to
 * acpi_lpat_free_conversion_table.
 */
struct acpi_lpat_conversion_table *acpi_lpat_get_conversion_table(acpi_handle
                                                                  handle)
{
        struct acpi_lpat_conversion_table *lpat_table = NULL;
        struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
        union acpi_object *obj_p, *obj_e;
        int *lpat, i;
        acpi_status status;

        status = acpi_evaluate_object(handle, "LPAT", NULL, &buffer);
        if (ACPI_FAILURE(status))
                return NULL;

        obj_p = (union acpi_object *)buffer.pointer;
        if (!obj_p || (obj_p->type != ACPI_TYPE_PACKAGE) ||
            (obj_p->package.count % 2) || (obj_p->package.count < 4))
                goto out;

        lpat = kzalloc_objs(int, obj_p->package.count);
        if (!lpat)
                goto out;

        for (i = 0; i < obj_p->package.count; i++) {
                obj_e = &obj_p->package.elements[i];
                if (obj_e->type != ACPI_TYPE_INTEGER) {
                        kfree(lpat);
                        goto out;
                }
                lpat[i] = (s64)obj_e->integer.value;
        }

        lpat_table = kzalloc_obj(*lpat_table);
        if (!lpat_table) {
                kfree(lpat);
                goto out;
        }

        lpat_table->lpat = (struct acpi_lpat *)lpat;
        lpat_table->lpat_count = obj_p->package.count / 2;

out:
        kfree(buffer.pointer);
        return lpat_table;
}
EXPORT_SYMBOL_GPL(acpi_lpat_get_conversion_table);

/**
 * acpi_lpat_free_conversion_table(): Free LPAT table.
 *
 * @lpat_table: the temperature_raw mapping table structure
 *
 * Frees the LPAT table previously allocated by a call to
 * acpi_lpat_get_conversion_table.
 */
void acpi_lpat_free_conversion_table(struct acpi_lpat_conversion_table
                                     *lpat_table)
{
        if (lpat_table) {
                kfree(lpat_table->lpat);
                kfree(lpat_table);
        }
}
EXPORT_SYMBOL_GPL(acpi_lpat_free_conversion_table);