platform/x86: Introduce support for Systems Management Driver over WMI for Dell Systems

The Dell WMI Systems Management Driver provides a sysfs
interface for systems management to enable BIOS configuration
capability on certain Dell Systems.

This driver allows user to configure Dell systems with a
uniform common interface. To facilitate this, the patch
introduces a generic way for driver to be able to create
configurable BIOS Attributes available in Setup (F2) screen.

Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: mark gross <mgross@linux.intel.com>
Co-developed-by: Mario Limonciello <mario.limonciello@dell.com>
Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
Co-developed-by: Prasanth KSR <prasanth.ksr@dell.com>
Signed-off-by: Prasanth KSR <prasanth.ksr@dell.com>
Signed-off-by: Divya Bharathi <divya.bharathi@dell.com>
Link: https://lore.kernel.org/r/20201027134944.316730-1-divya.bharathi@dell.comReviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Documentation/ABI/testing/sysfs-class-firmware-attributes

+What:		/sys/class/firmware-attributes/*/attributes/*/
+Date:		February 2021
+KernelVersion:	5.11
+Contact:	Divya Bharathi <Divya.Bharathi@Dell.com>,
+		Mario Limonciello <mario.limonciello@dell.com>,
+		Prasanth KSR <prasanth.ksr@dell.com>
+Description:
+		A sysfs interface for systems management software to enable
+		configuration capability on supported systems.  This directory
+		exposes interfaces for interacting with configuration options.
+
+		Unless otherwise specified in an attribute description all attributes are optional
+		and will accept UTF-8 input.
+
+		type: A file that can be read to obtain the type of attribute.  This attribute is
+			mandatory.
+
+		The following are known types:
+			- enumeration: a set of pre-defined valid values
+			- integer: a range of numerical values
+			- string
+
+		All attribute types support the following values:
+
+		current_value:	A file that can be read to obtain the current
+				value of the <attr>.
+
+				This file can also be written to in order to update the value of a
+				<attr>
+
+				This attribute is mandatory.
+
+		default_value:	A file that can be read to obtain the default
+				value of the <attr>
+
+		display_name:	A file that can be read to obtain a user friendly
+				description of the at <attr>
+
+		display_name_language_code:	A file that can be read to obtain
+						the IETF language tag corresponding to the
+						"display_name" of the <attr>
+
+		"enumeration"-type specific properties:
+
+		possible_values:	A file that can be read to obtain the possible
+					values of the <attr>. Values are separated using
+					semi-colon (``;``).
+
+		"integer"-type specific properties:
+
+		min_value:	A file that can be read to obtain the lower
+				bound value of the <attr>
+
+		max_value:	A file that can be read to obtain the upper
+				bound value of the <attr>
+
+		scalar_increment:	A file that can be read to obtain the scalar value used for
+					increments of current_value this attribute accepts.
+
+		"string"-type specific properties:
+
+		max_length:	A file that can be read to obtain the maximum
+				length value of the <attr>
+
+		min_length:	A file that can be read to obtain the minimum
+				length value of the <attr>
+
+		Dell specific class extensions
+		--------------------------
+
+		On Dell systems the following additional attributes are available:
+
+		dell_modifier:	A file that can be read to obtain attribute-level
+				dependency rule. It says an attribute X will become read-only or
+				suppressed, if/if-not attribute Y is configured.
+
+				modifier rules can be in following format:
+				[ReadOnlyIf:<attribute>=<value>]
+				[ReadOnlyIfNot:<attribute>=<value>]
+				[SuppressIf:<attribute>=<value>]
+				[SuppressIfNot:<attribute>=<value>]
+
+				For example:
+				AutoOnFri/dell_modifier has value,
+					[SuppressIfNot:AutoOn=SelectDays]
+
+				This means AutoOnFri will be suppressed in BIOS setup if AutoOn
+				attribute is not "SelectDays" and its value will not be effective
+				through sysfs until this rule is met.
+
+		Enumeration attributes also support the following:
+
+		dell_value_modifier:	A file that can be read to obtain value-level dependency.
+					This file is similar to dell_modifier but here,	an
+					attribute's current value will be forcefully changed based
+					dependent attributes value.
+
+					dell_value_modifier rules can be in following format:
+					<value>[ForceIf:<attribute>=<value>]
+					<value>[ForceIfNot:<attribute>=<value>]
+
+					For example,
+					LegacyOrom/dell_value_modifier has value:
+						Disabled[ForceIf:SecureBoot=Enabled]
+					This means LegacyOrom's current value will be forced to
+					"Disabled" in BIOS setup if SecureBoot is Enabled and its
+					value will not be effective through sysfs until this rule is
+					met.
+
+What:		/sys/class/firmware-attributes/*/authentication/
+Date:		February 2021
+KernelVersion:	5.11
+Contact:	Divya Bharathi <Divya.Bharathi@Dell.com>,
+		Mario Limonciello <mario.limonciello@dell.com>,
+		Prasanth KSR <prasanth.ksr@dell.com>
+
+		Devices support various authentication mechanisms which can be exposed
+		as a separate configuration object.
+
+		For example a "BIOS Admin" password and "System" Password can be set,
+		reset or cleared using these attributes.
+		- An "Admin" password is used for preventing modification to the BIOS
+		  settings.
+		- A "System" password is required to boot a machine.
+
+		Change in any of these two authentication methods will also generate an
+		uevent KOBJ_CHANGE.
+
+		is_enabled:		A file that can be read to obtain a 0/1 flag to see if
+					<attr> authentication is enabled.
+					This attribute is mandatory.
+
+		role:			The type of authentication used.
+					This attribute is mandatory.
+					Known types:
+						bios-admin: Representing BIOS administrator password
+						power-on: Representing a password required to use
+							  the system
+
+		mechanism:		The means of authentication.  This attribute is mandatory.
+					Only supported type currently is "password".
+
+		max_password_length:	A file that can be read to obtain the
+					maximum length of the Password
+
+		min_password_length:	A file that can be read to obtain the
+					minimum length of the Password
+
+		current_password:	A write only value used for privileged access such as
+					setting	attributes when a system or admin password is set
+					or resetting to a new password
+
+					This attribute is mandatory when mechanism == "password".
+
+		new_password:		A write only value that when used in tandem with
+					current_password will reset a system or admin password.
+
+		Note, password management is session specific. If Admin password is set,
+		same password must be written into current_password file (required for
+		password-validation) and must be cleared once the session is over.
+		For example:
+			echo "password" > current_password
+			echo "disabled" > TouchScreen/current_value
+			echo "" > current_password
+
+		Drivers may emit a CHANGE uevent when a password is set or unset
+		userspace may check it again.
+
+		On Dell systems, if Admin password is set, then all BIOS attributes
+		require password validation.
+
+What:		/sys/class/firmware-attributes/*/attributes/pending_reboot
+Date:		February 2021
+KernelVersion:	5.11
+Contact:	Divya Bharathi <Divya.Bharathi@Dell.com>,
+		Mario Limonciello <mario.limonciello@dell.com>,
+		Prasanth KSR <prasanth.ksr@dell.com>
+Description:
+		A read-only attribute reads 1 if a reboot is necessary to apply
+		pending BIOS attribute changes. Also, an uevent_KOBJ_CHANGE is
+		generated when it changes to 1.
+
+			0:	All BIOS attributes setting are current
+			1:	A reboot is necessary to get pending BIOS attribute changes
+				applied
+
+		Note, userspace applications need to follow below steps for efficient
+		BIOS management,
+		1.	Check if admin password is set. If yes, follow session method for
+			password management as briefed under authentication section above.
+		2.	Before setting any attribute, check if it has any modifiers
+			or value_modifiers. If yes, incorporate them and then modify
+			attribute.
+
+		Drivers may emit a CHANGE uevent when this value changes and userspace
+		may check it again.
+
+What:		/sys/class/firmware-attributes/*/attributes/reset_bios
+Date:		February 2021
+KernelVersion:	5.11
+Contact:	Divya Bharathi <Divya.Bharathi@Dell.com>,
+		Mario Limonciello <mario.limonciello@dell.com>,
+		Prasanth KSR <prasanth.ksr@dell.com>
+Description:
+		This attribute can be used to reset the BIOS Configuration.
+		Specifically, it tells which type of reset BIOS configuration is being
+		requested on the host.
+
+		Reading from it returns a list of supported options encoded as:
+
+			'builtinsafe' (Built in safe configuration profile)
+			'lastknowngood' (Last known good saved configuration profile)
+			'factory' (Default factory settings configuration profile)
+			'custom' (Custom saved configuration profile)
+
+		The currently selected option is printed in square brackets as
+		shown below:
+
+		# echo "factory" > /sys/class/firmware-attributes/*/device/attributes/reset_bios
+		# cat /sys/class/firmware-attributes/*/device/attributes/reset_bios
+		# builtinsafe lastknowngood [factory] custom
+
+		Note that any changes to this attribute requires a reboot
+		for changes to take effect.

MAINTAINERS

@@ -4991,6 +4991,14 @@ M:	Mario Limonciello <mario.limonciello@dell.com>
 S:	Maintained
 F:	drivers/platform/x86/dell-wmi-descriptor.c
 
+DELL WMI SYSMAN DRIVER
+M:	Divya Bharathi <divya.bharathi@dell.com>
+M:	Mario Limonciello <mario.limonciello@dell.com>
+M:	Prasanth Ksr <prasanth.ksr@dell.com>
+L:	platform-driver-x86@vger.kernel.org
+S:	Maintained
+F:	drivers/platform/x86/dell-wmi-syman/*
+
 DELL WMI NOTIFICATIONS DRIVER
 M:	Matthew Garrett <mjg59@srcf.ucam.org>
 M:	Pali Rohár <pali@kernel.org>

drivers/platform/x86/Kconfig

@@ -430,6 +430,18 @@ config DELL_WMI
 	  To compile this driver as a module, choose M here: the module will
 	  be called dell-wmi.
 
+config DELL_WMI_SYSMAN
+	tristate "Dell WMI-based Systems management driver"
+	depends on ACPI_WMI
+	depends on DMI
+	select NLS
+	help
+	  This driver allows changing BIOS settings on many Dell machines from
+	  2018 and newer without the use of any additional software.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called dell-wmi-sysman.
+
 config DELL_WMI_DESCRIPTOR
 	tristate
 	depends on ACPI_WMI

drivers/platform/x86/Makefile

@@ -47,6 +47,7 @@ obj-$(CONFIG_DELL_WMI)			+= dell-wmi.o
 obj-$(CONFIG_DELL_WMI_DESCRIPTOR)	+= dell-wmi-descriptor.o
 obj-$(CONFIG_DELL_WMI_AIO)		+= dell-wmi-aio.o
 obj-$(CONFIG_DELL_WMI_LED)		+= dell-wmi-led.o
+obj-$(CONFIG_DELL_WMI_SYSMAN)		+= dell-wmi-sysman/
 
 # Fujitsu
 obj-$(CONFIG_AMILO_RFKILL)	+= amilo-rfkill.o

drivers/platform/x86/dell-wmi-sysman/Makefile

+obj-$(CONFIG_DELL_WMI_SYSMAN)  += dell-wmi-sysman.o
+dell-wmi-sysman-objs := 	sysman.o		\
+				enum-attributes.o	\
+				int-attributes.o	\
+				string-attributes.o	\
+				passobj-attributes.o	\
+				biosattr-interface.o	\
+				passwordattr-interface.o

drivers/platform/x86/dell-wmi-sysman/biosattr-interface.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Functions corresponding to SET methods under BIOS attributes interface GUID for use
+ * with dell-wmi-sysman
+ *
+ *  Copyright (c) 2020 Dell Inc.
+ */
+
+#include <linux/wmi.h>
+#include "dell-wmi-sysman.h"
+
+#define SETDEFAULTVALUES_METHOD_ID					0x02
+#define SETBIOSDEFAULTS_METHOD_ID					0x03
+#define SETATTRIBUTE_METHOD_ID						0x04
+
+static int call_biosattributes_interface(struct wmi_device *wdev, char *in_args, size_t size,
+					int method_id)
+{
+	struct acpi_buffer output = {ACPI_ALLOCATE_BUFFER, NULL};
+	struct acpi_buffer input;
+	union acpi_object *obj;
+	acpi_status status;
+	int ret = -EIO;
+
+	input.length =  (acpi_size) size;
+	input.pointer = in_args;
+	status = wmidev_evaluate_method(wdev, 0, method_id, &input, &output);
+	if (ACPI_FAILURE(status))
+		return -EIO;
+	obj = (union acpi_object *)output.pointer;
+	if (obj->type == ACPI_TYPE_INTEGER)
+		ret = obj->integer.value;
+
+	if (wmi_priv.pending_changes == 0) {
+		wmi_priv.pending_changes = 1;
+		/* let userland know it may need to check reboot pending again */
+		kobject_uevent(&wmi_priv.class_dev->kobj, KOBJ_CHANGE);
+	}
+	kfree(output.pointer);
+	return map_wmi_error(ret);
+}
+
+/**
+ * set_attribute() - Update an attribute value
+ * @a_name: The attribute name
+ * @a_value: The attribute value
+ *
+ * Sets an attribute to new value
+ */
+int set_attribute(const char *a_name, const char *a_value)
+{
+	size_t security_area_size, buffer_size;
+	size_t a_name_size, a_value_size;
+	char *buffer = NULL, *start;
+	int ret;
+
+	mutex_lock(&wmi_priv.mutex);
+	if (!wmi_priv.bios_attr_wdev) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	/* build/calculate buffer */
+	security_area_size = calculate_security_buffer(wmi_priv.current_admin_password);
+	a_name_size = calculate_string_buffer(a_name);
+	a_value_size = calculate_string_buffer(a_value);
+	buffer_size = security_area_size + a_name_size + a_value_size;
+	buffer = kzalloc(buffer_size, GFP_KERNEL);
+	if (!buffer) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	/* build security area */
+	populate_security_buffer(buffer, wmi_priv.current_admin_password);
+
+	/* build variables to set */
+	start = buffer + security_area_size;
+	ret = populate_string_buffer(start, a_name_size, a_name);
+	if (ret < 0)
+		goto out;
+	start += ret;
+	ret = populate_string_buffer(start, a_value_size, a_value);
+	if (ret < 0)
+		goto out;
+
+	print_hex_dump_bytes("set attribute data: ", DUMP_PREFIX_NONE, buffer, buffer_size);
+	ret = call_biosattributes_interface(wmi_priv.bios_attr_wdev,
+					    buffer, buffer_size,
+					    SETATTRIBUTE_METHOD_ID);
+	if (ret == -EOPNOTSUPP)
+		dev_err(&wmi_priv.bios_attr_wdev->dev, "admin password must be configured\n");
+	else if (ret == -EACCES)
+		dev_err(&wmi_priv.bios_attr_wdev->dev, "invalid password\n");
+
+out:
+	kfree(buffer);
+	mutex_unlock(&wmi_priv.mutex);
+	return ret;
+}
+
+/**
+ * set_bios_defaults() - Resets BIOS defaults
+ * @deftype: the type of BIOS value reset to issue.
+ *
+ * Resets BIOS defaults
+ */
+int set_bios_defaults(u8 deftype)
+{
+	size_t security_area_size, buffer_size;
+	size_t integer_area_size = sizeof(u8);
+	char *buffer = NULL;
+	u8 *defaultType;
+	int ret;
+
+	mutex_lock(&wmi_priv.mutex);
+	if (!wmi_priv.bios_attr_wdev) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	security_area_size = calculate_security_buffer(wmi_priv.current_admin_password);
+	buffer_size = security_area_size + integer_area_size;
+	buffer = kzalloc(buffer_size, GFP_KERNEL);
+	if (!buffer) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	/* build security area */
+	populate_security_buffer(buffer, wmi_priv.current_admin_password);
+
+	defaultType = buffer + security_area_size;
+	*defaultType = deftype;
+
+	ret = call_biosattributes_interface(wmi_priv.bios_attr_wdev, buffer, buffer_size,
+					    SETBIOSDEFAULTS_METHOD_ID);
+	if (ret)
+		dev_err(&wmi_priv.bios_attr_wdev->dev, "reset BIOS defaults failed: %d\n", ret);
+
+	kfree(buffer);
+out:
+	mutex_unlock(&wmi_priv.mutex);
+	return ret;
+}
+
+static int bios_attr_set_interface_probe(struct wmi_device *wdev, const void *context)
+{
+	mutex_lock(&wmi_priv.mutex);
+	wmi_priv.bios_attr_wdev = wdev;
+	mutex_unlock(&wmi_priv.mutex);
+	return 0;
+}
+
+static int bios_attr_set_interface_remove(struct wmi_device *wdev)
+{
+	mutex_lock(&wmi_priv.mutex);
+	wmi_priv.bios_attr_wdev = NULL;
+	mutex_unlock(&wmi_priv.mutex);
+	return 0;
+}
+
+static const struct wmi_device_id bios_attr_set_interface_id_table[] = {
+	{ .guid_string = DELL_WMI_BIOS_ATTRIBUTES_INTERFACE_GUID },
+	{ },
+};
+static struct wmi_driver bios_attr_set_interface_driver = {
+	.driver = {
+		.name = DRIVER_NAME
+	},
+	.probe = bios_attr_set_interface_probe,
+	.remove = bios_attr_set_interface_remove,
+	.id_table = bios_attr_set_interface_id_table,
+};
+
+int init_bios_attr_set_interface(void)
+{
+	return wmi_driver_register(&bios_attr_set_interface_driver);
+}
+
+void exit_bios_attr_set_interface(void)
+{
+	wmi_driver_unregister(&bios_attr_set_interface_driver);
+}
+
+MODULE_DEVICE_TABLE(wmi, bios_attr_set_interface_id_table);

drivers/platform/x86/dell-wmi-sysman/dell-wmi-sysman.h

+/* SPDX-License-Identifier: GPL-2.0
+ * Definitions for kernel modules using Dell WMI System Management Driver
+ *
+ *  Copyright (c) 2020 Dell Inc.
+ */
+
+#ifndef _DELL_WMI_BIOS_ATTR_H_
+#define _DELL_WMI_BIOS_ATTR_H_
+
+#include <linux/wmi.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/capability.h>
+
+#define DRIVER_NAME					"dell-wmi-sysman"
+#define MAX_BUFF  512
+
+#define DELL_WMI_BIOS_ENUMERATION_ATTRIBUTE_GUID	"F1DDEE52-063C-4784-A11E-8A06684B9BF5"
+#define DELL_WMI_BIOS_INTEGER_ATTRIBUTE_GUID		"F1DDEE52-063C-4784-A11E-8A06684B9BFA"
+#define DELL_WMI_BIOS_STRING_ATTRIBUTE_GUID		"F1DDEE52-063C-4784-A11E-8A06684B9BF9"
+#define DELL_WMI_BIOS_PASSOBJ_ATTRIBUTE_GUID		"0894B8D6-44A6-4719-97D7-6AD24108BFD4"
+#define DELL_WMI_BIOS_ATTRIBUTES_INTERFACE_GUID		"F1DDEE52-063C-4784-A11E-8A06684B9BF4"
+#define DELL_WMI_BIOS_PASSWORD_INTERFACE_GUID		"70FE8229-D03B-4214-A1C6-1F884B1A892A"
+
+struct enumeration_data {
+	struct kobject *attr_name_kobj;
+	char display_name_language_code[MAX_BUFF];
+	char dell_value_modifier[MAX_BUFF];
+	char possible_values[MAX_BUFF];
+	char attribute_name[MAX_BUFF];
+	char default_value[MAX_BUFF];
+	char dell_modifier[MAX_BUFF];
+	char display_name[MAX_BUFF];
+};
+
+struct integer_data {
+	struct kobject *attr_name_kobj;
+	char display_name_language_code[MAX_BUFF];
+	char attribute_name[MAX_BUFF];
+	char dell_modifier[MAX_BUFF];
+	char display_name[MAX_BUFF];
+	int scalar_increment;
+	int default_value;
+	int min_value;
+	int max_value;
+};
+
+struct str_data {
+	struct kobject *attr_name_kobj;
+	char display_name_language_code[MAX_BUFF];
+	char attribute_name[MAX_BUFF];
+	char display_name[MAX_BUFF];
+	char default_value[MAX_BUFF];
+	char dell_modifier[MAX_BUFF];
+	int min_length;
+	int max_length;
+};
+
+struct po_data {
+	struct kobject *attr_name_kobj;
+	char attribute_name[MAX_BUFF];
+	int min_password_length;
+	int max_password_length;
+};
+
+struct wmi_sysman_priv {
+	char current_admin_password[MAX_BUFF];
+	char current_system_password[MAX_BUFF];
+	struct wmi_device *password_attr_wdev;
+	struct wmi_device *bios_attr_wdev;
+	struct kset *authentication_dir_kset;
+	struct kset *main_dir_kset;
+	struct device *class_dev;
+	struct enumeration_data *enumeration_data;
+	int enumeration_instances_count;
+	struct integer_data *integer_data;
+	int integer_instances_count;
+	struct str_data *str_data;
+	int str_instances_count;
+	struct po_data *po_data;
+	int po_instances_count;
+	bool pending_changes;
+	struct mutex mutex;
+};
+
+/* global structure used by multiple WMI interfaces */
+extern struct wmi_sysman_priv wmi_priv;
+
+enum { ENUM, INT, STR, PO };
+
+enum {
+	ATTR_NAME,
+	DISPL_NAME_LANG_CODE,
+	DISPLAY_NAME,
+	DEFAULT_VAL,
+	CURRENT_VAL,
+	MODIFIER
+};
+
+#define get_instance_id(type)							\
+static int get_##type##_instance_id(struct kobject *kobj)			\
+{										\
+	int i;									\
+	for (i = 0; i <= wmi_priv.type##_instances_count; i++) {		\
+		if (!(strcmp(kobj->name, wmi_priv.type##_data[i].attribute_name)))\
+			return i;						\
+	}									\
+	return -EIO;								\
+}
+
+#define attribute_s_property_show(name, type)					\
+static ssize_t name##_show(struct kobject *kobj, struct kobj_attribute *attr,	\
+			   char *buf)						\
+{										\
+	int i = get_##type##_instance_id(kobj);					\
+	if (i >= 0)								\
+		return sprintf(buf, "%s\n", wmi_priv.type##_data[i].name);	\
+	return 0;								\
+}
+
+#define attribute_n_property_show(name, type)					\
+static ssize_t name##_show(struct kobject *kobj, struct kobj_attribute *attr,	\
+			   char *buf)						\
+{										\
+	int i = get_##type##_instance_id(kobj);					\
+	if (i >= 0)								\
+		return sprintf(buf, "%d\n", wmi_priv.type##_data[i].name);	\
+	return 0;								\
+}
+
+#define attribute_property_store(curr_val, type)				\
+static ssize_t curr_val##_store(struct kobject *kobj,				\
+				struct kobj_attribute *attr,			\
+				const char *buf, size_t count)			\
+{										\
+	char *p, *buf_cp;							\
+	int i, ret = -EIO;							\
+	buf_cp = kstrdup(buf, GFP_KERNEL);					\
+	if (!buf_cp)								\
+		return -ENOMEM;							\
+	p = memchr(buf_cp, '\n', count);					\
+										\
+	if (p != NULL)								\
+		*p = '\0';							\
+	i = get_##type##_instance_id(kobj);					\
+	if (i >= 0)								\
+		ret = validate_##type##_input(i, buf_cp);			\
+	if (!ret)								\
+		ret = set_attribute(kobj->name, buf_cp);			\
+	kfree(buf_cp);								\
+	return ret ? ret : count;						\
+}
+
+union acpi_object *get_wmiobj_pointer(int instance_id, const char *guid_string);
+int get_instance_count(const char *guid_string);
+void strlcpy_attr(char *dest, char *src);
+
+int populate_enum_data(union acpi_object *enumeration_obj, int instance_id,
+			struct kobject *attr_name_kobj);
+int alloc_enum_data(void);
+void exit_enum_attributes(void);
+
+int populate_int_data(union acpi_object *integer_obj, int instance_id,
+			struct kobject *attr_name_kobj);
+int alloc_int_data(void);
+void exit_int_attributes(void);
+
+int populate_str_data(union acpi_object *str_obj, int instance_id, struct kobject *attr_name_kobj);
+int alloc_str_data(void);
+void exit_str_attributes(void);
+
+int populate_po_data(union acpi_object *po_obj, int instance_id, struct kobject *attr_name_kobj);
+int alloc_po_data(void);
+void exit_po_attributes(void);
+
+int set_attribute(const char *a_name, const char *a_value);
+int set_bios_defaults(u8 defType);
+
+void exit_bios_attr_set_interface(void);
+int init_bios_attr_set_interface(void);
+int map_wmi_error(int error_code);
+size_t calculate_string_buffer(const char *str);
+size_t calculate_security_buffer(char *authentication);
+void populate_security_buffer(char *buffer, char *authentication);
+ssize_t populate_string_buffer(char *buffer, size_t buffer_len, const char *str);
+int set_new_password(const char *password_type, const char *new);
+int init_bios_attr_pass_interface(void);
+void exit_bios_attr_pass_interface(void);
+
+#endif

drivers/platform/x86/dell-wmi-sysman/enum-attributes.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Functions corresponding to enumeration type attributes under
+ * BIOS Enumeration GUID for use with dell-wmi-sysman
+ *
+ *  Copyright (c) 2020 Dell Inc.
+ */
+
+#include "dell-wmi-sysman.h"
+
+get_instance_id(enumeration);
+
+static ssize_t current_value_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
+{
+	int instance_id = get_enumeration_instance_id(kobj);
+	union acpi_object *obj;
+	ssize_t ret;
+
+	if (instance_id < 0)
+		return instance_id;
+
+	/* need to use specific instance_id and guid combination to get right data */
+	obj = get_wmiobj_pointer(instance_id, DELL_WMI_BIOS_ENUMERATION_ATTRIBUTE_GUID);
+	if (!obj)
+		return -EIO;
+	if (obj->package.elements[CURRENT_VAL].type != ACPI_TYPE_STRING) {
+		kfree(obj);
+		return -EINVAL;
+	}
+	ret = snprintf(buf, PAGE_SIZE, "%s\n", obj->package.elements[CURRENT_VAL].string.pointer);
+	kfree(obj);
+	return ret;
+}
+
+/**
+ * validate_enumeration_input() - Validate input of current_value against possible values
+ * @instance_id: The instance on which input is validated
+ * @buf: Input value
+ */
+static int validate_enumeration_input(int instance_id, const char *buf)
+{
+	char *options, *tmp, *p;
+	int ret = -EINVAL;
+
+	options = tmp = kstrdup(wmi_priv.enumeration_data[instance_id].possible_values,
+				 GFP_KERNEL);
+	if (!options)
+		return -ENOMEM;
+
+	while ((p = strsep(&options, ";")) != NULL) {
+		if (!*p)
+			continue;
+		if (!strcasecmp(p, buf)) {
+			ret = 0;
+			break;
+		}
+	}
+
+	kfree(tmp);
+	return ret;
+}
+
+attribute_s_property_show(display_name_language_code, enumeration);
+static struct kobj_attribute displ_langcode =
+		__ATTR_RO(display_name_language_code);
+
+attribute_s_property_show(display_name, enumeration);
+static struct kobj_attribute displ_name =
+		__ATTR_RO(display_name);
+
+attribute_s_property_show(default_value, enumeration);
+static struct kobj_attribute default_val =
+		__ATTR_RO(default_value);
+
+attribute_property_store(current_value, enumeration);
+static struct kobj_attribute current_val =
+		__ATTR_RW_MODE(current_value, 0600);
+
+attribute_s_property_show(dell_modifier, enumeration);
+static struct kobj_attribute modifier =
+		__ATTR_RO(dell_modifier);
+
+attribute_s_property_show(dell_value_modifier, enumeration);
+static struct kobj_attribute value_modfr =
+		__ATTR_RO(dell_value_modifier);
+
+attribute_s_property_show(possible_values, enumeration);
+static struct kobj_attribute poss_val =
+		__ATTR_RO(possible_values);
+
+static ssize_t type_show(struct kobject *kobj, struct kobj_attribute *attr,
+			 char *buf)
+{
+	return sprintf(buf, "enumeration\n");
+}
+static struct kobj_attribute type =
+		__ATTR_RO(type);
+
+static struct attribute *enumeration_attrs[] = {
+	&displ_langcode.attr,
+	&displ_name.attr,
+	&default_val.attr,
+	&current_val.attr,
+	&modifier.attr,
+	&value_modfr.attr,
+	&poss_val.attr,
+	&type.attr,
+	NULL,
+};
+
+static const struct attribute_group enumeration_attr_group = {
+	.attrs = enumeration_attrs,
+};
+
+int alloc_enum_data(void)
+{
+	int ret = 0;
+
+	wmi_priv.enumeration_instances_count =
+		get_instance_count(DELL_WMI_BIOS_ENUMERATION_ATTRIBUTE_GUID);
+	wmi_priv.enumeration_data = kcalloc(wmi_priv.enumeration_instances_count,
+					sizeof(struct enumeration_data), GFP_KERNEL);
+	if (!wmi_priv.enumeration_data) {
+		wmi_priv.enumeration_instances_count = 0;
+		ret = -ENOMEM;
+	}
+	return ret;
+}
+
+/**
+ * populate_enum_data() - Populate all properties of an instance under enumeration attribute
+ * @enumeration_obj: ACPI object with enumeration data
+ * @instance_id: The instance to enumerate
+ * @attr_name_kobj: The parent kernel object
+ */
+int populate_enum_data(union acpi_object *enumeration_obj, int instance_id,
+			struct kobject *attr_name_kobj)
+{
+	int i, next_obj, value_modifier_count, possible_values_count;
+
+	wmi_priv.enumeration_data[instance_id].attr_name_kobj = attr_name_kobj;
+	strlcpy_attr(wmi_priv.enumeration_data[instance_id].attribute_name,
+		enumeration_obj[ATTR_NAME].string.pointer);
+	strlcpy_attr(wmi_priv.enumeration_data[instance_id].display_name_language_code,
+		enumeration_obj[DISPL_NAME_LANG_CODE].string.pointer);
+	strlcpy_attr(wmi_priv.enumeration_data[instance_id].display_name,
+		enumeration_obj[DISPLAY_NAME].string.pointer);
+	strlcpy_attr(wmi_priv.enumeration_data[instance_id].default_value,
+		enumeration_obj[DEFAULT_VAL].string.pointer);
+	strlcpy_attr(wmi_priv.enumeration_data[instance_id].dell_modifier,
+		enumeration_obj[MODIFIER].string.pointer);
+
+	next_obj = MODIFIER + 1;
+
+	value_modifier_count = (uintptr_t)enumeration_obj[next_obj].string.pointer;
+
+	for (i = 0; i < value_modifier_count; i++) {
+		strcat(wmi_priv.enumeration_data[instance_id].dell_value_modifier,
+			enumeration_obj[++next_obj].string.pointer);
+		strcat(wmi_priv.enumeration_data[instance_id].dell_value_modifier, ";");
+	}
+
+	possible_values_count = (uintptr_t) enumeration_obj[++next_obj].string.pointer;
+
+	for (i = 0; i < possible_values_count; i++) {
+		strcat(wmi_priv.enumeration_data[instance_id].possible_values,
+			enumeration_obj[++next_obj].string.pointer);
+		strcat(wmi_priv.enumeration_data[instance_id].possible_values, ";");
+	}
+
+	return sysfs_create_group(attr_name_kobj, &enumeration_attr_group);
+}
+
+/**
+ * exit_enum_attributes() - Clear all attribute data
+ *
+ * Clears all data allocated for this group of attributes
+ */
+void exit_enum_attributes(void)
+{
+	int instance_id;
+
+	for (instance_id = 0; instance_id < wmi_priv.enumeration_instances_count; instance_id++) {
+		if (wmi_priv.enumeration_data[instance_id].attr_name_kobj)
+			sysfs_remove_group(wmi_priv.enumeration_data[instance_id].attr_name_kobj,
+								&enumeration_attr_group);
+	}
+	kfree(wmi_priv.enumeration_data);
+}

drivers/platform/x86/dell-wmi-sysman/int-attributes.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Functions corresponding to integer type attributes under BIOS Integer GUID for use with
+ * dell-wmi-sysman
+ *
+ *  Copyright (c) 2020 Dell Inc.
+ */
+
+#include "dell-wmi-sysman.h"
+
+enum int_properties {MIN_VALUE = 6, MAX_VALUE, SCALAR_INCR};
+
+get_instance_id(integer);
+
+static ssize_t current_value_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
+{
+	int instance_id = get_integer_instance_id(kobj);
+	union acpi_object *obj;
+	ssize_t ret;
+
+	if (instance_id < 0)
+		return instance_id;
+
+	/* need to use specific instance_id and guid combination to get right data */
+	obj = get_wmiobj_pointer(instance_id, DELL_WMI_BIOS_INTEGER_ATTRIBUTE_GUID);
+	if (!obj)
+		return -EIO;
+	if (obj->package.elements[CURRENT_VAL].type != ACPI_TYPE_INTEGER) {
+		kfree(obj);
+		return -EINVAL;
+	}
+	ret = snprintf(buf, PAGE_SIZE, "%lld\n", obj->package.elements[CURRENT_VAL].integer.value);
+	kfree(obj);
+	return ret;
+}
+
+/**
+ * validate_integer_input() - Validate input of current_value against lower and upper bound
+ * @instance_id: The instance on which input is validated
+ * @buf: Input value
+ */
+static int validate_integer_input(int instance_id, const char *buf)
+{
+	int in_val;
+	int ret;
+
+	ret = kstrtoint(buf, 0, &in_val);
+	if (ret)
+		return ret;
+	if (in_val < wmi_priv.integer_data[instance_id].min_value ||
+			in_val > wmi_priv.integer_data[instance_id].max_value)
+		return -EINVAL;
+
+	return ret;
+}
+
+attribute_s_property_show(display_name_language_code, integer);
+static struct kobj_attribute integer_displ_langcode =
+	__ATTR_RO(display_name_language_code);
+
+attribute_s_property_show(display_name, integer);
+static struct kobj_attribute integer_displ_name =
+	__ATTR_RO(display_name);
+
+attribute_n_property_show(default_value, integer);
+static struct kobj_attribute integer_default_val =
+	__ATTR_RO(default_value);
+
+attribute_property_store(current_value, integer);
+static struct kobj_attribute integer_current_val =
+	__ATTR_RW_MODE(current_value, 0600);
+
+attribute_s_property_show(dell_modifier, integer);
+static struct kobj_attribute integer_modifier =
+	__ATTR_RO(dell_modifier);
+
+attribute_n_property_show(min_value, integer);
+static struct kobj_attribute integer_lower_bound =
+	__ATTR_RO(min_value);
+
+attribute_n_property_show(max_value, integer);
+static struct kobj_attribute integer_upper_bound =
+	__ATTR_RO(max_value);
+
+attribute_n_property_show(scalar_increment, integer);
+static struct kobj_attribute integer_scalar_increment =
+	__ATTR_RO(scalar_increment);
+
+static ssize_t type_show(struct kobject *kobj, struct kobj_attribute *attr,
+			 char *buf)
+{
+	return sprintf(buf, "integer\n");
+}
+static struct kobj_attribute integer_type =
+	__ATTR_RO(type);
+
+static struct attribute *integer_attrs[] = {
+	&integer_displ_langcode.attr,
+	&integer_displ_name.attr,
+	&integer_default_val.attr,
+	&integer_current_val.attr,
+	&integer_modifier.attr,
+	&integer_lower_bound.attr,
+	&integer_upper_bound.attr,
+	&integer_scalar_increment.attr,
+	&integer_type.attr,
+	NULL,
+};
+
+static const struct attribute_group integer_attr_group = {
+	.attrs = integer_attrs,
+};
+
+int alloc_int_data(void)
+{
+	int ret = 0;
+
+	wmi_priv.integer_instances_count = get_instance_count(DELL_WMI_BIOS_INTEGER_ATTRIBUTE_GUID);
+	wmi_priv.integer_data = kcalloc(wmi_priv.integer_instances_count,
+					sizeof(struct integer_data), GFP_KERNEL);
+	if (!wmi_priv.integer_data) {
+		wmi_priv.integer_instances_count = 0;
+		ret = -ENOMEM;
+	}
+	return ret;
+}
+
+/**
+ * populate_int_data() - Populate all properties of an instance under integer attribute
+ * @integer_obj: ACPI object with integer data
+ * @instance_id: The instance to enumerate
+ * @attr_name_kobj: The parent kernel object
+ */
+int populate_int_data(union acpi_object *integer_obj, int instance_id,
+			struct kobject *attr_name_kobj)
+{
+	wmi_priv.integer_data[instance_id].attr_name_kobj = attr_name_kobj;
+	strlcpy_attr(wmi_priv.integer_data[instance_id].attribute_name,
+		integer_obj[ATTR_NAME].string.pointer);
+	strlcpy_attr(wmi_priv.integer_data[instance_id].display_name_language_code,
+		integer_obj[DISPL_NAME_LANG_CODE].string.pointer);
+	strlcpy_attr(wmi_priv.integer_data[instance_id].display_name,
+		integer_obj[DISPLAY_NAME].string.pointer);
+	wmi_priv.integer_data[instance_id].default_value =
+		(uintptr_t)integer_obj[DEFAULT_VAL].string.pointer;
+	strlcpy_attr(wmi_priv.integer_data[instance_id].dell_modifier,
+		integer_obj[MODIFIER].string.pointer);
+	wmi_priv.integer_data[instance_id].min_value =
+		(uintptr_t)integer_obj[MIN_VALUE].string.pointer;
+	wmi_priv.integer_data[instance_id].max_value =
+		(uintptr_t)integer_obj[MAX_VALUE].string.pointer;
+	wmi_priv.integer_data[instance_id].scalar_increment =
+		(uintptr_t)integer_obj[SCALAR_INCR].string.pointer;
+
+	return sysfs_create_group(attr_name_kobj, &integer_attr_group);
+}
+
+/**
+ * exit_int_attributes() - Clear all attribute data
+ *
+ * Clears all data allocated for this group of attributes
+ */
+void exit_int_attributes(void)
+{
+	int instance_id;
+
+	for (instance_id = 0; instance_id < wmi_priv.integer_instances_count; instance_id++) {
+		if (wmi_priv.integer_data[instance_id].attr_name_kobj)
+			sysfs_remove_group(wmi_priv.integer_data[instance_id].attr_name_kobj,
+								&integer_attr_group);
+	}
+	kfree(wmi_priv.integer_data);
+}

drivers/platform/x86/dell-wmi-sysman/passobj-attributes.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Functions corresponding to password object type attributes under BIOS Password Object GUID for
+ * use with dell-wmi-sysman
+ *
+ *  Copyright (c) 2020 Dell Inc.
+ */
+
+#include "dell-wmi-sysman.h"
+
+enum po_properties {IS_PASS_SET = 1, MIN_PASS_LEN, MAX_PASS_LEN};
+
+get_instance_id(po);
+
+static ssize_t is_enabled_show(struct kobject *kobj, struct kobj_attribute *attr,
+					  char *buf)
+{
+	int instance_id = get_po_instance_id(kobj);
+	union acpi_object *obj;
+	ssize_t ret;
+
+	if (instance_id < 0)
+		return instance_id;
+
+	/* need to use specific instance_id and guid combination to get right data */
+	obj = get_wmiobj_pointer(instance_id, DELL_WMI_BIOS_PASSOBJ_ATTRIBUTE_GUID);
+	if (!obj)
+		return -EIO;
+	if (obj->package.elements[IS_PASS_SET].type != ACPI_TYPE_INTEGER) {
+		kfree(obj);
+		return -EINVAL;
+	}
+	ret = snprintf(buf, PAGE_SIZE, "%lld\n", obj->package.elements[IS_PASS_SET].integer.value);
+	kfree(obj);
+	return ret;
+}
+
+struct kobj_attribute po_is_pass_set =
+		__ATTR_RO(is_enabled);
+
+static ssize_t current_password_store(struct kobject *kobj,
+				      struct kobj_attribute *attr,
+				      const char *buf, size_t count)
+{
+	char *target = NULL;
+	int length;
+
+	length = strlen(buf);
+	if (buf[length-1] == '\n')
+		length--;
+
+	/* firmware does verifiation of min/max password length,
+	 * hence only check for not exceeding MAX_BUFF here.
+	 */
+	if (length >= MAX_BUFF)
+		return -EINVAL;
+
+	if (strcmp(kobj->name, "Admin") == 0)
+		target = wmi_priv.current_admin_password;
+	else if (strcmp(kobj->name, "System") == 0)
+		target = wmi_priv.current_system_password;
+	if (!target)
+		return -EIO;
+	memcpy(target, buf, length);
+	target[length] = '\0';
+
+	return count;
+}
+
+struct kobj_attribute po_current_password =
+		__ATTR_WO(current_password);
+
+static ssize_t new_password_store(struct kobject *kobj,
+				  struct kobj_attribute *attr,
+				  const char *buf, size_t count)
+{
+	char *p, *buf_cp;
+	int ret;
+
+	buf_cp = kstrdup(buf, GFP_KERNEL);
+	if (!buf_cp)
+		return -ENOMEM;
+	p = memchr(buf_cp, '\n', count);
+
+	if (p != NULL)
+		*p = '\0';
+	if (strlen(buf_cp) > MAX_BUFF) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	ret = set_new_password(kobj->name, buf_cp);
+
+out:
+	kfree(buf_cp);
+	return ret ? ret : count;
+}
+
+struct kobj_attribute po_new_password =
+		__ATTR_WO(new_password);
+
+attribute_n_property_show(min_password_length, po);
+struct kobj_attribute po_min_pass_length =
+		__ATTR_RO(min_password_length);
+
+attribute_n_property_show(max_password_length, po);
+struct kobj_attribute po_max_pass_length =
+		__ATTR_RO(max_password_length);
+
+static ssize_t mechanism_show(struct kobject *kobj, struct kobj_attribute *attr,
+			 char *buf)
+{
+	return sprintf(buf, "password\n");
+}
+
+struct kobj_attribute po_mechanism =
+	__ATTR_RO(mechanism);
+
+static ssize_t role_show(struct kobject *kobj, struct kobj_attribute *attr,
+			 char *buf)
+{
+	if (strcmp(kobj->name, "Admin") == 0)
+		return sprintf(buf, "bios-admin\n");
+	else if (strcmp(kobj->name, "System") == 0)
+		return sprintf(buf, "power-on\n");
+	return -EIO;
+}
+
+struct kobj_attribute po_role =
+	__ATTR_RO(role);
+
+static struct attribute *po_attrs[] = {
+	&po_is_pass_set.attr,
+	&po_min_pass_length.attr,
+	&po_max_pass_length.attr,
+	&po_current_password.attr,
+	&po_new_password.attr,
+	&po_role.attr,
+	&po_mechanism.attr,
+	NULL,
+};
+
+static const struct attribute_group po_attr_group = {
+	.attrs = po_attrs,
+};
+
+int alloc_po_data(void)
+{
+	int ret = 0;
+
+	wmi_priv.po_instances_count = get_instance_count(DELL_WMI_BIOS_PASSOBJ_ATTRIBUTE_GUID);
+	wmi_priv.po_data = kcalloc(wmi_priv.po_instances_count, sizeof(struct po_data), GFP_KERNEL);
+	if (!wmi_priv.po_data) {
+		wmi_priv.po_instances_count = 0;
+		ret = -ENOMEM;
+	}
+	return ret;
+}
+
+/**
+ * populate_po_data() - Populate all properties of an instance under password object attribute
+ * @po_obj: ACPI object with password object data
+ * @instance_id: The instance to enumerate
+ * @attr_name_kobj: The parent kernel object
+ */
+int populate_po_data(union acpi_object *po_obj, int instance_id, struct kobject *attr_name_kobj)
+{
+	wmi_priv.po_data[instance_id].attr_name_kobj = attr_name_kobj;
+	strlcpy_attr(wmi_priv.po_data[instance_id].attribute_name,
+		     po_obj[ATTR_NAME].string.pointer);
+	wmi_priv.po_data[instance_id].min_password_length =
+		(uintptr_t)po_obj[MIN_PASS_LEN].string.pointer;
+	wmi_priv.po_data[instance_id].max_password_length =
+		(uintptr_t) po_obj[MAX_PASS_LEN].string.pointer;
+
+	return sysfs_create_group(attr_name_kobj, &po_attr_group);
+}
+
+/**
+ * exit_po_attributes() - Clear all attribute data
+ *
+ * Clears all data allocated for this group of attributes
+ */
+void exit_po_attributes(void)
+{
+	int instance_id;
+
+	for (instance_id = 0; instance_id < wmi_priv.po_instances_count; instance_id++) {
+		if (wmi_priv.po_data[instance_id].attr_name_kobj)
+			sysfs_remove_group(wmi_priv.po_data[instance_id].attr_name_kobj,
+								&po_attr_group);
+	}
+	kfree(wmi_priv.po_data);
+}

drivers/platform/x86/dell-wmi-sysman/passwordattr-interface.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Functions corresponding to SET password methods under BIOS attributes interface GUID
+ *
+ *  Copyright (c) 2020 Dell Inc.
+ */
+
+#include <linux/wmi.h>
+#include "dell-wmi-sysman.h"
+
+static int call_password_interface(struct wmi_device *wdev, char *in_args, size_t size)
+{
+	struct acpi_buffer output = {ACPI_ALLOCATE_BUFFER, NULL};
+	struct acpi_buffer input;
+	union acpi_object *obj;
+	acpi_status status;
+	int ret = -EIO;
+
+	input.length =  (acpi_size) size;
+	input.pointer = in_args;
+	status = wmidev_evaluate_method(wdev, 0, 1, &input, &output);
+	if (ACPI_FAILURE(status))
+		return -EIO;
+	obj = (union acpi_object *)output.pointer;
+	if (obj->type == ACPI_TYPE_INTEGER)
+		ret = obj->integer.value;
+
+	kfree(output.pointer);
+	/* let userland know it may need to check is_password_set again */
+	kobject_uevent(&wmi_priv.class_dev->kobj, KOBJ_CHANGE);
+	return map_wmi_error(ret);
+}
+
+/**
+ * set_new_password() - Sets a system admin password
+ * @password_type: The type of password to set
+ * @new: The new password
+ *
+ * Sets the password using plaintext interface
+ */
+int set_new_password(const char *password_type, const char *new)
+{
+	size_t password_type_size, current_password_size, new_size;
+	size_t security_area_size, buffer_size;
+	char *buffer = NULL, *start;
+	char *current_password;
+	int ret;
+
+	mutex_lock(&wmi_priv.mutex);
+	if (!wmi_priv.password_attr_wdev) {
+		ret = -ENODEV;
+		goto out;
+	}
+	if (strcmp(password_type, "Admin") == 0) {
+		current_password = wmi_priv.current_admin_password;
+	} else if (strcmp(password_type, "System") == 0) {
+		current_password = wmi_priv.current_system_password;
+	} else {
+		ret = -EINVAL;
+		dev_err(&wmi_priv.password_attr_wdev->dev, "unknown password type %s\n",
+			password_type);
+		goto out;
+	}
+
+	/* build/calculate buffer */
+	security_area_size = calculate_security_buffer(wmi_priv.current_admin_password);
+	password_type_size = calculate_string_buffer(password_type);
+	current_password_size = calculate_string_buffer(current_password);
+	new_size = calculate_string_buffer(new);
+	buffer_size = security_area_size + password_type_size + current_password_size + new_size;
+	buffer = kzalloc(buffer_size, GFP_KERNEL);
+	if (!buffer) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	/* build security area */
+	populate_security_buffer(buffer, wmi_priv.current_admin_password);
+
+	/* build variables to set */
+	start = buffer + security_area_size;
+	ret = populate_string_buffer(start, password_type_size, password_type);
+	if (ret < 0)
+		goto out;
+
+	start += ret;
+	ret = populate_string_buffer(start, current_password_size, current_password);
+	if (ret < 0)
+		goto out;
+
+	start += ret;
+	ret = populate_string_buffer(start, new_size, new);
+	if (ret < 0)
+		goto out;
+
+	print_hex_dump_bytes("set new password data: ", DUMP_PREFIX_NONE, buffer, buffer_size);
+	ret = call_password_interface(wmi_priv.password_attr_wdev, buffer, buffer_size);
+	/* clear current_password here and use user input from wmi_priv.current_password */
+	if (!ret)
+		memset(current_password, 0, MAX_BUFF);
+	/* explain to user the detailed failure reason */
+	else if (ret == -EOPNOTSUPP)
+		dev_err(&wmi_priv.password_attr_wdev->dev, "admin password must be configured\n");
+	else if (ret == -EACCES)
+		dev_err(&wmi_priv.password_attr_wdev->dev, "invalid password\n");
+
+out:
+	kfree(buffer);
+	mutex_unlock(&wmi_priv.mutex);
+
+	return ret;
+}
+
+static int bios_attr_pass_interface_probe(struct wmi_device *wdev, const void *context)
+{
+	mutex_lock(&wmi_priv.mutex);
+	wmi_priv.password_attr_wdev = wdev;
+	mutex_unlock(&wmi_priv.mutex);
+	return 0;
+}
+
+static int bios_attr_pass_interface_remove(struct wmi_device *wdev)
+{
+	mutex_lock(&wmi_priv.mutex);
+	wmi_priv.password_attr_wdev = NULL;
+	mutex_unlock(&wmi_priv.mutex);
+	return 0;
+}
+
+static const struct wmi_device_id bios_attr_pass_interface_id_table[] = {
+	{ .guid_string = DELL_WMI_BIOS_PASSWORD_INTERFACE_GUID },
+	{ },
+};
+static struct wmi_driver bios_attr_pass_interface_driver = {
+	.driver = {
+		.name = DRIVER_NAME"-password"
+	},
+	.probe = bios_attr_pass_interface_probe,
+	.remove = bios_attr_pass_interface_remove,
+	.id_table = bios_attr_pass_interface_id_table,
+};
+
+int init_bios_attr_pass_interface(void)
+{
+	return wmi_driver_register(&bios_attr_pass_interface_driver);
+}
+
+void exit_bios_attr_pass_interface(void)
+{
+	wmi_driver_unregister(&bios_attr_pass_interface_driver);
+}
+
+MODULE_DEVICE_TABLE(wmi, bios_attr_pass_interface_id_table);

drivers/platform/x86/dell-wmi-sysman/string-attributes.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Functions corresponding to string type attributes under BIOS String GUID for use with
+ * dell-wmi-sysman
+ *
+ *  Copyright (c) 2020 Dell Inc.
+ */
+
+#include "dell-wmi-sysman.h"
+
+enum string_properties {MIN_LEN = 6, MAX_LEN};
+
+get_instance_id(str);
+
+static ssize_t current_value_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
+{
+	int instance_id = get_str_instance_id(kobj);
+	union acpi_object *obj;
+	ssize_t ret;
+
+	if (instance_id < 0)
+		return -EIO;
+
+	/* need to use specific instance_id and guid combination to get right data */
+	obj = get_wmiobj_pointer(instance_id, DELL_WMI_BIOS_STRING_ATTRIBUTE_GUID);
+	if (!obj)
+		return -EIO;
+	if (obj->package.elements[CURRENT_VAL].type != ACPI_TYPE_STRING) {
+		kfree(obj);
+		return -EINVAL;
+	}
+	ret = snprintf(buf, PAGE_SIZE, "%s\n", obj->package.elements[CURRENT_VAL].string.pointer);
+	kfree(obj);
+	return ret;
+}
+
+/**
+ * validate_str_input() - Validate input of current_value against min and max lengths
+ * @instance_id: The instance on which input is validated
+ * @buf: Input value
+ */
+static int validate_str_input(int instance_id, const char *buf)
+{
+	int in_len = strlen(buf);
+
+	if ((in_len < wmi_priv.str_data[instance_id].min_length) ||
+			(in_len > wmi_priv.str_data[instance_id].max_length))
+		return -EINVAL;
+
+	return 0;
+}
+
+attribute_s_property_show(display_name_language_code, str);
+static struct kobj_attribute str_displ_langcode =
+		__ATTR_RO(display_name_language_code);
+
+attribute_s_property_show(display_name, str);
+static struct kobj_attribute str_displ_name =
+		__ATTR_RO(display_name);
+
+attribute_s_property_show(default_value, str);
+static struct kobj_attribute str_default_val =
+		__ATTR_RO(default_value);
+
+attribute_property_store(current_value, str);
+static struct kobj_attribute str_current_val =
+		__ATTR_RW_MODE(current_value, 0600);
+
+attribute_s_property_show(dell_modifier, str);
+static struct kobj_attribute str_modifier =
+		__ATTR_RO(dell_modifier);
+
+attribute_n_property_show(min_length, str);
+static struct kobj_attribute str_min_length =
+		__ATTR_RO(min_length);
+
+attribute_n_property_show(max_length, str);
+static struct kobj_attribute str_max_length =
+		__ATTR_RO(max_length);
+
+static ssize_t type_show(struct kobject *kobj, struct kobj_attribute *attr,
+			 char *buf)
+{
+	return sprintf(buf, "string\n");
+}
+static struct kobj_attribute str_type =
+	__ATTR_RO(type);
+
+static struct attribute *str_attrs[] = {
+	&str_displ_langcode.attr,
+	&str_displ_name.attr,
+	&str_default_val.attr,
+	&str_current_val.attr,
+	&str_modifier.attr,
+	&str_min_length.attr,
+	&str_max_length.attr,
+	&str_type.attr,
+	NULL,
+};
+
+static const struct attribute_group str_attr_group = {
+	.attrs = str_attrs,
+};
+
+int alloc_str_data(void)
+{
+	int ret = 0;
+
+	wmi_priv.str_instances_count = get_instance_count(DELL_WMI_BIOS_STRING_ATTRIBUTE_GUID);
+	wmi_priv.str_data = kcalloc(wmi_priv.str_instances_count,
+					sizeof(struct str_data), GFP_KERNEL);
+	if (!wmi_priv.str_data) {
+		wmi_priv.str_instances_count = 0;
+		ret = -ENOMEM;
+	}
+	return ret;
+}
+
+/**
+ * populate_str_data() - Populate all properties of an instance under string attribute
+ * @str_obj: ACPI object with integer data
+ * @instance_id: The instance to enumerate
+ * @attr_name_kobj: The parent kernel object
+ */
+int populate_str_data(union acpi_object *str_obj, int instance_id, struct kobject *attr_name_kobj)
+{
+	wmi_priv.str_data[instance_id].attr_name_kobj = attr_name_kobj;
+	strlcpy_attr(wmi_priv.str_data[instance_id].attribute_name,
+		     str_obj[ATTR_NAME].string.pointer);
+	strlcpy_attr(wmi_priv.str_data[instance_id].display_name_language_code,
+		     str_obj[DISPL_NAME_LANG_CODE].string.pointer);
+	strlcpy_attr(wmi_priv.str_data[instance_id].display_name,
+		     str_obj[DISPLAY_NAME].string.pointer);
+	strlcpy_attr(wmi_priv.str_data[instance_id].default_value,
+		     str_obj[DEFAULT_VAL].string.pointer);
+	strlcpy_attr(wmi_priv.str_data[instance_id].dell_modifier,
+		     str_obj[MODIFIER].string.pointer);
+	wmi_priv.str_data[instance_id].min_length = (uintptr_t)str_obj[MIN_LEN].string.pointer;
+	wmi_priv.str_data[instance_id].max_length = (uintptr_t) str_obj[MAX_LEN].string.pointer;
+
+	return sysfs_create_group(attr_name_kobj, &str_attr_group);
+}
+
+/**
+ * exit_str_attributes() - Clear all attribute data
+ *
+ * Clears all data allocated for this group of attributes
+ */
+void exit_str_attributes(void)
+{
+	int instance_id;
+
+	for (instance_id = 0; instance_id < wmi_priv.str_instances_count; instance_id++) {
+		if (wmi_priv.str_data[instance_id].attr_name_kobj)
+			sysfs_remove_group(wmi_priv.str_data[instance_id].attr_name_kobj,
+								&str_attr_group);
+	}
+	kfree(wmi_priv.str_data);
+}