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