linux/drivers/pci/pci-label.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Export the firmware instance and label associated with a PCI device to
   4 * sysfs
   5 *
   6 * Copyright (C) 2010 Dell Inc.
   7 * by Narendra K <Narendra_K@dell.com>,
   8 * Jordan Hargrave <Jordan_Hargrave@dell.com>
   9 *
  10 * PCI Firmware Specification Revision 3.1 section 4.6.7 (DSM for Naming a
  11 * PCI or PCI Express Device Under Operating Systems) defines an instance
  12 * number and string name. This code retrieves them and exports them to sysfs.
  13 * If the system firmware does not provide the ACPI _DSM (Device Specific
  14 * Method), then the SMBIOS type 41 instance number and string is exported to
  15 * sysfs.
  16 *
  17 * SMBIOS defines type 41 for onboard pci devices. This code retrieves
  18 * the instance number and string from the type 41 record and exports
  19 * it to sysfs.
  20 *
  21 * Please see https://linux.dell.com/files/biosdevname/ for more
  22 * information.
  23 */
  24
  25#include <linux/dmi.h>
  26#include <linux/sysfs.h>
  27#include <linux/pci.h>
  28#include <linux/pci_ids.h>
  29#include <linux/module.h>
  30#include <linux/device.h>
  31#include <linux/nls.h>
  32#include <linux/acpi.h>
  33#include <linux/pci-acpi.h>
  34#include "pci.h"
  35
  36static bool device_has_acpi_name(struct device *dev)
  37{
  38#ifdef CONFIG_ACPI
  39        acpi_handle handle = ACPI_HANDLE(dev);
  40
  41        if (!handle)
  42                return false;
  43
  44        return acpi_check_dsm(handle, &pci_acpi_dsm_guid, 0x2,
  45                              1 << DSM_PCI_DEVICE_NAME);
  46#else
  47        return false;
  48#endif
  49}
  50
  51#ifdef CONFIG_DMI
  52enum smbios_attr_enum {
  53        SMBIOS_ATTR_NONE = 0,
  54        SMBIOS_ATTR_LABEL_SHOW,
  55        SMBIOS_ATTR_INSTANCE_SHOW,
  56};
  57
  58static size_t find_smbios_instance_string(struct pci_dev *pdev, char *buf,
  59                                          enum smbios_attr_enum attribute)
  60{
  61        const struct dmi_device *dmi;
  62        struct dmi_dev_onboard *donboard;
  63        int domain_nr = pci_domain_nr(pdev->bus);
  64        int bus = pdev->bus->number;
  65        int devfn = pdev->devfn;
  66
  67        dmi = NULL;
  68        while ((dmi = dmi_find_device(DMI_DEV_TYPE_DEV_ONBOARD,
  69                                      NULL, dmi)) != NULL) {
  70                donboard = dmi->device_data;
  71                if (donboard && donboard->segment == domain_nr &&
  72                                donboard->bus == bus &&
  73                                donboard->devfn == devfn) {
  74                        if (buf) {
  75                                if (attribute == SMBIOS_ATTR_INSTANCE_SHOW)
  76                                        return sysfs_emit(buf, "%d\n",
  77                                                          donboard->instance);
  78                                else if (attribute == SMBIOS_ATTR_LABEL_SHOW)
  79                                        return sysfs_emit(buf, "%s\n",
  80                                                          dmi->name);
  81                        }
  82                        return strlen(dmi->name);
  83                }
  84        }
  85        return 0;
  86}
  87
  88static ssize_t smbios_label_show(struct device *dev,
  89                                 struct device_attribute *attr, char *buf)
  90{
  91        struct pci_dev *pdev = to_pci_dev(dev);
  92
  93        return find_smbios_instance_string(pdev, buf,
  94                                           SMBIOS_ATTR_LABEL_SHOW);
  95}
  96static struct device_attribute dev_attr_smbios_label = __ATTR(label, 0444,
  97                                                    smbios_label_show, NULL);
  98
  99static ssize_t index_show(struct device *dev, struct device_attribute *attr,
 100                          char *buf)
 101{
 102        struct pci_dev *pdev = to_pci_dev(dev);
 103
 104        return find_smbios_instance_string(pdev, buf,
 105                                           SMBIOS_ATTR_INSTANCE_SHOW);
 106}
 107static DEVICE_ATTR_RO(index);
 108
 109static struct attribute *smbios_attrs[] = {
 110        &dev_attr_smbios_label.attr,
 111        &dev_attr_index.attr,
 112        NULL,
 113};
 114
 115static umode_t smbios_attr_is_visible(struct kobject *kobj, struct attribute *a,
 116                                      int n)
 117{
 118        struct device *dev = kobj_to_dev(kobj);
 119        struct pci_dev *pdev = to_pci_dev(dev);
 120
 121        if (device_has_acpi_name(dev))
 122                return 0;
 123
 124        if (!find_smbios_instance_string(pdev, NULL, SMBIOS_ATTR_NONE))
 125                return 0;
 126
 127        return a->mode;
 128}
 129
 130const struct attribute_group pci_dev_smbios_attr_group = {
 131        .attrs = smbios_attrs,
 132        .is_visible = smbios_attr_is_visible,
 133};
 134#endif
 135
 136#ifdef CONFIG_ACPI
 137enum acpi_attr_enum {
 138        ACPI_ATTR_LABEL_SHOW,
 139        ACPI_ATTR_INDEX_SHOW,
 140};
 141
 142static void dsm_label_utf16s_to_utf8s(union acpi_object *obj, char *buf)
 143{
 144        int len;
 145        len = utf16s_to_utf8s((const wchar_t *)obj->buffer.pointer,
 146                              obj->buffer.length,
 147                              UTF16_LITTLE_ENDIAN,
 148                              buf, PAGE_SIZE - 1);
 149        buf[len] = '\n';
 150}
 151
 152static int dsm_get_label(struct device *dev, char *buf,
 153                         enum acpi_attr_enum attr)
 154{
 155        acpi_handle handle = ACPI_HANDLE(dev);
 156        union acpi_object *obj, *tmp;
 157        int len = -1;
 158
 159        if (!handle)
 160                return -1;
 161
 162        obj = acpi_evaluate_dsm(handle, &pci_acpi_dsm_guid, 0x2,
 163                                DSM_PCI_DEVICE_NAME, NULL);
 164        if (!obj)
 165                return -1;
 166
 167        tmp = obj->package.elements;
 168        if (obj->type == ACPI_TYPE_PACKAGE && obj->package.count == 2 &&
 169            tmp[0].type == ACPI_TYPE_INTEGER &&
 170            (tmp[1].type == ACPI_TYPE_STRING ||
 171             tmp[1].type == ACPI_TYPE_BUFFER)) {
 172                /*
 173                 * The second string element is optional even when
 174                 * this _DSM is implemented; when not implemented,
 175                 * this entry must return a null string.
 176                 */
 177                if (attr == ACPI_ATTR_INDEX_SHOW) {
 178                        scnprintf(buf, PAGE_SIZE, "%llu\n", tmp->integer.value);
 179                } else if (attr == ACPI_ATTR_LABEL_SHOW) {
 180                        if (tmp[1].type == ACPI_TYPE_STRING)
 181                                scnprintf(buf, PAGE_SIZE, "%s\n",
 182                                          tmp[1].string.pointer);
 183                        else if (tmp[1].type == ACPI_TYPE_BUFFER)
 184                                dsm_label_utf16s_to_utf8s(tmp + 1, buf);
 185                }
 186                len = strlen(buf) > 0 ? strlen(buf) : -1;
 187        }
 188
 189        ACPI_FREE(obj);
 190
 191        return len;
 192}
 193
 194static ssize_t label_show(struct device *dev, struct device_attribute *attr,
 195                          char *buf)
 196{
 197        return dsm_get_label(dev, buf, ACPI_ATTR_LABEL_SHOW);
 198}
 199static DEVICE_ATTR_RO(label);
 200
 201static ssize_t acpi_index_show(struct device *dev,
 202                              struct device_attribute *attr, char *buf)
 203{
 204        return dsm_get_label(dev, buf, ACPI_ATTR_INDEX_SHOW);
 205}
 206static DEVICE_ATTR_RO(acpi_index);
 207
 208static struct attribute *acpi_attrs[] = {
 209        &dev_attr_label.attr,
 210        &dev_attr_acpi_index.attr,
 211        NULL,
 212};
 213
 214static umode_t acpi_attr_is_visible(struct kobject *kobj, struct attribute *a,
 215                                    int n)
 216{
 217        struct device *dev = kobj_to_dev(kobj);
 218
 219        if (!device_has_acpi_name(dev))
 220                return 0;
 221
 222        return a->mode;
 223}
 224
 225const struct attribute_group pci_dev_acpi_attr_group = {
 226        .attrs = acpi_attrs,
 227        .is_visible = acpi_attr_is_visible,
 228};
 229#endif
 230