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1// SPDX-License-Identifier: GPL-2.02/*3 * Slim Bootloader(SBL) firmware update signaling driver4 *5 * Slim Bootloader is a small, open-source, non UEFI compliant, boot firmware6 * 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 SBL11 * 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.html15 */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 26static int get_fwu_request(struct device *dev, u32 *out)27{28 union acpi_object *obj;29 30 obj = wmidev_block_query(to_wmi_device(dev), 0);31 if (!obj)32 return -ENODEV;33 34 if (obj->type != ACPI_TYPE_INTEGER) {35 dev_warn(dev, "wmidev_block_query returned invalid value\n");36 kfree(obj);37 return -EINVAL;38 }39 40 *out = obj->integer.value;41 kfree(obj);42 43 return 0;44}45 46static int set_fwu_request(struct device *dev, u32 in)47{48 struct acpi_buffer input;49 acpi_status status;50 u32 value;51 52 value = in;53 input.length = sizeof(u32);54 input.pointer = &value;55 56 status = wmidev_block_set(to_wmi_device(dev), 0, &input);57 if (ACPI_FAILURE(status)) {58 dev_err(dev, "wmidev_block_set failed\n");59 return -ENODEV;60 }61 62 return 0;63}64 65static ssize_t firmware_update_request_show(struct device *dev,66 struct device_attribute *attr,67 char *buf)68{69 u32 val;70 int ret;71 72 ret = get_fwu_request(dev, &val);73 if (ret)74 return ret;75 76 return sprintf(buf, "%d\n", val);77}78 79static ssize_t firmware_update_request_store(struct device *dev,80 struct device_attribute *attr,81 const char *buf, size_t count)82{83 unsigned int val;84 int ret;85 86 ret = kstrtouint(buf, 0, &val);87 if (ret)88 return ret;89 90 /* May later be extended to support values other than 0 and 1 */91 if (val > 1)92 return -ERANGE;93 94 ret = set_fwu_request(dev, val);95 if (ret)96 return ret;97 98 return count;99}100static DEVICE_ATTR_RW(firmware_update_request);101 102static struct attribute *firmware_update_attrs[] = {103 &dev_attr_firmware_update_request.attr,104 NULL105};106ATTRIBUTE_GROUPS(firmware_update);107 108static int intel_wmi_sbl_fw_update_probe(struct wmi_device *wdev,109 const void *context)110{111 dev_info(&wdev->dev, "Slim Bootloader signaling driver attached\n");112 return 0;113}114 115static void intel_wmi_sbl_fw_update_remove(struct wmi_device *wdev)116{117 dev_info(&wdev->dev, "Slim Bootloader signaling driver removed\n");118}119 120static const struct wmi_device_id intel_wmi_sbl_id_table[] = {121 { .guid_string = INTEL_WMI_SBL_GUID },122 {}123};124MODULE_DEVICE_TABLE(wmi, intel_wmi_sbl_id_table);125 126static struct wmi_driver intel_wmi_sbl_fw_update_driver = {127 .driver = {128 .name = "intel-wmi-sbl-fw-update",129 .dev_groups = firmware_update_groups,130 },131 .probe = intel_wmi_sbl_fw_update_probe,132 .remove = intel_wmi_sbl_fw_update_remove,133 .id_table = intel_wmi_sbl_id_table,134 .no_singleton = true,135};136module_wmi_driver(intel_wmi_sbl_fw_update_driver);137 138MODULE_AUTHOR("Jithu Joseph <jithu.joseph@intel.com>");139MODULE_DESCRIPTION("Slim Bootloader firmware update signaling driver");140MODULE_LICENSE("GPL v2");141