What: /sys/class/firmware-attributes/*/attributes/*/ Date: February 2021 KernelVersion: 5.11 Contact: Divya Bharathi , Mario Limonciello , Prasanth KSR 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 . This file can also be written to in order to update the value of a This attribute is mandatory. default_value: A file that can be read to obtain the default value of the display_name: A file that can be read to obtain a user friendly description of the at display_name_language_code: A file that can be read to obtain the IETF language tag corresponding to the "display_name" of the "enumeration"-type specific properties: possible_values: A file that can be read to obtain the possible values of the . 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 max_value: A file that can be read to obtain the upper bound value of the 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 min_length: A file that can be read to obtain the minimum length value of the 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:=] [ReadOnlyIfNot:=] [SuppressIf:=] [SuppressIfNot:=] 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:: [ForceIf:=] [ForceIfNot:=] 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 , Mario Limonciello , Prasanth KSR Description: 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 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 , Mario Limonciello , Prasanth KSR 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 , Mario Limonciello , Prasanth KSR 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.