1 files changed, 144 insertions, 0 deletions
diff --git a/drivers/platform/x86/intel/wmi/sbl-fw-update.c b/drivers/platform/x86/intel/wmi/sbl-fw-update.c
new file mode 100644
index 000000000000..3c86e0108a24
--- /dev/null
+++ b/drivers/platform/x86/intel/wmi/sbl-fw-update.c
@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Slim Bootloader(SBL) firmware update signaling driver
+ *
+ * Slim Bootloader is a small, open-source, non UEFI compliant, boot firmware
+ * optimized for running on certain Intel platforms.
+ *
+ * SBL exposes an ACPI-WMI device via /sys/bus/wmi/devices/<INTEL_WMI_SBL_GUID>.
+ * This driver further adds "firmware_update_request" device attribute.
+ * This attribute normally has a value of 0 and userspace can signal SBL
+ * to update firmware, on next reboot, by writing a value of 1.
+ *
+ * More details of SBL firmware update process is available at:
+ * https://slimbootloader.github.io/security/firmware-update.html
+ */
+
+#include <linux/acpi.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+#include <linux/wmi.h>
+
+#define INTEL_WMI_SBL_GUID  "44FADEB1-B204-40F2-8581-394BBDC1B651"
+
+static int get_fwu_request(struct device *dev, u32 *out)
+{
+	struct acpi_buffer result = {ACPI_ALLOCATE_BUFFER, NULL};
+	union acpi_object *obj;
+	acpi_status status;
+
+	status = wmi_query_block(INTEL_WMI_SBL_GUID, 0, &result);
+	if (ACPI_FAILURE(status)) {
+		dev_err(dev, "wmi_query_block failed\n");
+		return -ENODEV;
+	}
+
+	obj = (union acpi_object *)result.pointer;
+	if (!obj || obj->type != ACPI_TYPE_INTEGER) {
+		dev_warn(dev, "wmi_query_block returned invalid value\n");
+		kfree(obj);
+		return -EINVAL;
+	}
+
+	*out = obj->integer.value;
+	kfree(obj);
+
+	return 0;
+}
+
+static int set_fwu_request(struct device *dev, u32 in)
+{
+	struct acpi_buffer input;
+	acpi_status status;
+	u32 value;
+
+	value = in;
+	input.length = sizeof(u32);
+	input.pointer = &value;
+
+	status = wmi_set_block(INTEL_WMI_SBL_GUID, 0, &input);
+	if (ACPI_FAILURE(status)) {
+		dev_err(dev, "wmi_set_block failed\n");
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+static ssize_t firmware_update_request_show(struct device *dev,
+					    struct device_attribute *attr,
+					    char *buf)
+{
+	u32 val;
+	int ret;
+
+	ret = get_fwu_request(dev, &val);
+	if (ret)
+		return ret;
+
+	return sprintf(buf, "%d\n", val);
+}
+
+static ssize_t firmware_update_request_store(struct device *dev,
+					     struct device_attribute *attr,
+					     const char *buf, size_t count)
+{
+	unsigned int val;
+	int ret;
+
+	ret = kstrtouint(buf, 0, &val);
+	if (ret)
+		return ret;
+
+	/* May later be extended to support values other than 0 and 1 */
+	if (val > 1)
+		return -ERANGE;
+
+	ret = set_fwu_request(dev, val);
+	if (ret)
+		return ret;
+
+	return count;
+}
+static DEVICE_ATTR_RW(firmware_update_request);
+
+static struct attribute *firmware_update_attrs[] = {
+	&dev_attr_firmware_update_request.attr,
+	NULL
+};
+ATTRIBUTE_GROUPS(firmware_update);
+
+static int intel_wmi_sbl_fw_update_probe(struct wmi_device *wdev,
+					 const void *context)
+{
+	dev_info(&wdev->dev, "Slim Bootloader signaling driver attached\n");
+	return 0;
+}
+
+static void intel_wmi_sbl_fw_update_remove(struct wmi_device *wdev)
+{
+	dev_info(&wdev->dev, "Slim Bootloader signaling driver removed\n");
+}
+
+static const struct wmi_device_id intel_wmi_sbl_id_table[] = {
+	{ .guid_string = INTEL_WMI_SBL_GUID },
+	{}
+};
+MODULE_DEVICE_TABLE(wmi, intel_wmi_sbl_id_table);
+
+static struct wmi_driver intel_wmi_sbl_fw_update_driver = {
+	.driver = {
+		.name = "intel-wmi-sbl-fw-update",
+		.dev_groups = firmware_update_groups,
+	},
+	.probe = intel_wmi_sbl_fw_update_probe,
+	.remove = intel_wmi_sbl_fw_update_remove,
+	.id_table = intel_wmi_sbl_id_table,
+};
+module_wmi_driver(intel_wmi_sbl_fw_update_driver);
+
+MODULE_AUTHOR("Jithu Joseph <jithu.joseph@intel.com>");
+MODULE_DESCRIPTION("Slim Bootloader firmware update signaling driver");
+MODULE_LICENSE("GPL v2");