drivers/platform/x86/intel-wmi-sbl-fw-update.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Slim Bootloader(SBL) firmware update signaling driver
   4  *
   5  * Slim Bootloader is a small, open-source, non UEFI compliant, boot firmware
   6  * optimized for running on certain Intel platforms.
   7  *
   8  * SBL exposes an ACPI-WMI device via /sys/bus/wmi/devices/<INTEL_WMI_SBL_GUID>.
   9  * This driver further adds "firmware_update_request" device attribute.
  10  * This attribute normally has a value of 0 and userspace can signal SBL
  11  * to update firmware, on next reboot, by writing a value of 1.
  12  *
  13  * More details of SBL firmware update process is available at:
  14  * https://slimbootloader.github.io/security/firmware-update.html
  15  */
  16
  17 #include <linux/acpi.h>
  18 #include <linux/device.h>
  19 #include <linux/module.h>
  20 #include <linux/slab.h>
  21 #include <linux/sysfs.h>
  22 #include <linux/wmi.h>
  23
  24 #define INTEL_WMI_SBL_GUID  "44FADEB1-B204-40F2-8581-394BBDC1B651"
  25
  26 static int get_fwu_request(struct device *dev, u32 *out)
  27 {
  28         struct acpi_buffer result = {ACPI_ALLOCATE_BUFFER, NULL};
  29         union acpi_object *obj;
  30         acpi_status status;
  31
  32         status = wmi_query_block(INTEL_WMI_SBL_GUID, 0, &result);
  33         if (ACPI_FAILURE(status)) {
  34                 dev_err(dev, "wmi_query_block failed\n");
  35                 return -ENODEV;
  36         }
  37
  38         obj = (union acpi_object *)result.pointer;
  39         if (!obj || obj->type != ACPI_TYPE_INTEGER) {
  40                 dev_warn(dev, "wmi_query_block returned invalid value\n");
  41                 kfree(obj);
  42                 return -EINVAL;
  43         }
  44
  45         *out = obj->integer.value;
  46         kfree(obj);
  47
  48         return 0;
  49 }
  50
  51 static int set_fwu_request(struct device *dev, u32 in)
  52 {
  53         struct acpi_buffer input;
  54         acpi_status status;
  55         u32 value;
  56
  57         value = in;
  58         input.length = sizeof(u32);
  59         input.pointer = &value;
  60
  61         status = wmi_set_block(INTEL_WMI_SBL_GUID, 0, &input);
  62         if (ACPI_FAILURE(status)) {
  63                 dev_err(dev, "wmi_set_block failed\n");
  64                 return -ENODEV;
  65         }
  66
  67         return 0;
  68 }
  69
  70 static ssize_t firmware_update_request_show(struct device *dev,
  71                                             struct device_attribute *attr,
  72                                             char *buf)
  73 {
  74         u32 val;
  75         int ret;
  76
  77         ret = get_fwu_request(dev, &val);
  78         if (ret)
  79                 return ret;
  80
  81         return sprintf(buf, "%d\n", val);
  82 }
  83
  84 static ssize_t firmware_update_request_store(struct device *dev,
  85                                              struct device_attribute *attr,
  86                                              const char *buf, size_t count)
  87 {
  88         unsigned int val;
  89         int ret;
  90
  91         ret = kstrtouint(buf, 0, &val);
  92         if (ret)
  93                 return ret;
  94
  95         /* May later be extended to support values other than 0 and 1 */
  96         if (val > 1)
  97                 return -ERANGE;
  98
  99         ret = set_fwu_request(dev, val);
 100         if (ret)
 101                 return ret;
 102
 103         return count;
 104 }
 105 static DEVICE_ATTR_RW(firmware_update_request);
 106
 107 static struct attribute *firmware_update_attrs[] = {
 108         &dev_attr_firmware_update_request.attr,
 109         NULL
 110 };
 111 ATTRIBUTE_GROUPS(firmware_update);
 112
 113 static int intel_wmi_sbl_fw_update_probe(struct wmi_device *wdev,
 114                                          const void *context)
 115 {
 116         dev_info(&wdev->dev, "Slim Bootloader signaling driver attached\n");
 117         return 0;
 118 }
 119
 120 static int intel_wmi_sbl_fw_update_remove(struct wmi_device *wdev)
 121 {
 122         dev_info(&wdev->dev, "Slim Bootloader signaling driver removed\n");
 123         return 0;
 124 }
 125
 126 static const struct wmi_device_id intel_wmi_sbl_id_table[] = {
 127         { .guid_string = INTEL_WMI_SBL_GUID },
 128         {}
 129 };
 130 MODULE_DEVICE_TABLE(wmi, intel_wmi_sbl_id_table);
 131
 132 static struct wmi_driver intel_wmi_sbl_fw_update_driver = {
 133         .driver = {
 134                 .name = "intel-wmi-sbl-fw-update",
 135                 .dev_groups = firmware_update_groups,
 136         },
 137         .probe = intel_wmi_sbl_fw_update_probe,
 138         .remove = intel_wmi_sbl_fw_update_remove,
 139         .id_table = intel_wmi_sbl_id_table,
 140 };
 141 module_wmi_driver(intel_wmi_sbl_fw_update_driver);
 142
 143 MODULE_AUTHOR("Jithu Joseph <jithu.joseph@intel.com>");
 144 MODULE_DESCRIPTION("Slim Bootloader firmware update signaling driver");
 145 MODULE_LICENSE("GPL v2");