linux/drivers/acpi/acpi_cmos_rtc.c
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   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * ACPI support for CMOS RTC Address Space access
   4 *
   5 * Copyright (C) 2013, Intel Corporation
   6 * Authors: Lan Tianyu <tianyu.lan@intel.com>
   7 */
   8
   9#include <linux/acpi.h>
  10#include <linux/device.h>
  11#include <linux/err.h>
  12#include <linux/kernel.h>
  13#include <linux/module.h>
  14#include <linux/mc146818rtc.h>
  15
  16#include "internal.h"
  17
  18static const struct acpi_device_id acpi_cmos_rtc_ids[] = {
  19        { "PNP0B00" },
  20        { "PNP0B01" },
  21        { "PNP0B02" },
  22        {}
  23};
  24
  25static acpi_status
  26acpi_cmos_rtc_space_handler(u32 function, acpi_physical_address address,
  27                      u32 bits, u64 *value64,
  28                      void *handler_context, void *region_context)
  29{
  30        int i;
  31        u8 *value = (u8 *)value64;
  32
  33        if (address > 0xff || !value64)
  34                return AE_BAD_PARAMETER;
  35
  36        if (function != ACPI_WRITE && function != ACPI_READ)
  37                return AE_BAD_PARAMETER;
  38
  39        spin_lock_irq(&rtc_lock);
  40
  41        for (i = 0; i < DIV_ROUND_UP(bits, 8); ++i, ++address, ++value)
  42                if (function == ACPI_READ)
  43                        *value = CMOS_READ(address);
  44                else
  45                        CMOS_WRITE(*value, address);
  46
  47        spin_unlock_irq(&rtc_lock);
  48
  49        return AE_OK;
  50}
  51
  52static int acpi_install_cmos_rtc_space_handler(struct acpi_device *adev,
  53                const struct acpi_device_id *id)
  54{
  55        acpi_status status;
  56
  57        status = acpi_install_address_space_handler(adev->handle,
  58                        ACPI_ADR_SPACE_CMOS,
  59                        &acpi_cmos_rtc_space_handler,
  60                        NULL, NULL);
  61        if (ACPI_FAILURE(status)) {
  62                pr_err(PREFIX "Error installing CMOS-RTC region handler\n");
  63                return -ENODEV;
  64        }
  65
  66        return 1;
  67}
  68
  69static void acpi_remove_cmos_rtc_space_handler(struct acpi_device *adev)
  70{
  71        if (ACPI_FAILURE(acpi_remove_address_space_handler(adev->handle,
  72                        ACPI_ADR_SPACE_CMOS, &acpi_cmos_rtc_space_handler)))
  73                pr_err(PREFIX "Error removing CMOS-RTC region handler\n");
  74}
  75
  76static struct acpi_scan_handler cmos_rtc_handler = {
  77        .ids = acpi_cmos_rtc_ids,
  78        .attach = acpi_install_cmos_rtc_space_handler,
  79        .detach = acpi_remove_cmos_rtc_space_handler,
  80};
  81
  82void __init acpi_cmos_rtc_init(void)
  83{
  84        acpi_scan_add_handler(&cmos_rtc_handler);
  85}
  86