Documentation/ABI/testing/sysfs-class-firmware-attributes - pub/scm/linux/kernel/git/trace/linux-trace - Git at Google

 What:		/sys/class/firmware-attributes/*/attributes/*/
 Date:		February 2021
 KernelVersion:	5.11
 Contact:	Divya Bharathi <Divya.Bharathi@Dell.com>,
 		Prasanth KSR <prasanth.ksr@dell.com>
 		Dell.Client.Kernel@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

 		HP specific types
 		-----------------
 			- ordered-list - a set of ordered list valid values


 		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.

 		HP specific class extensions
 		------------------------------

 		On HP systems the following additional attributes are available:

 		"ordered-list"-type specific properties:

 		elements:
 					A file that can be read to obtain the possible
 					list of values of the <attr>. Values are separated using
 					semi-colon (``;``) and listed according to their priority.
 					An element listed first has the highest priority. Writing
 					the list in a different order to current_value alters
 					the priority order for the particular attribute.

 What:		/sys/class/firmware-attributes/*/authentication/
 Date:		February 2021
 KernelVersion:	5.11
 Contact:	Divya Bharathi <Divya.Bharathi@Dell.com>,
 		Prasanth KSR <prasanth.ksr@dell.com>
 		Dell.Client.Kernel@dell.com
 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
 					<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
 						system-mgmt:
 							Representing System Management password.
 							See Lenovo extensions section for details
 						HDD:
 							Representing HDD password
 							See Lenovo extensions section for details
 						NVMe:
 							Representing NVMe password
 							See Lenovo extensions section for details

 		mechanism:
 					The means of authentication.  This attribute is mandatory.
 					Supported types are "password" or "certificate".

 		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, Lenovo and HP systems, if Admin password is set, then all BIOS attributes
 		require password validation.
 		On Lenovo systems if you change the Admin password the new password is not active until
 		the next boot.

 		Lenovo specific class extensions
 		--------------------------------

 		On Lenovo systems the following additional settings are available:

 		role: system-mgmt	This gives the same authority as the bios-admin password to control
 					security related features. The authorities allocated can be set via
 					the BIOS menu SMP Access Control Policy

 		role: HDD & NVMe	This password is used to unlock access to the drive at boot. Note see
 					'level' and 'index' extensions below.

 		lenovo_encoding:
 					The encoding method that is used. This can be either "ascii"
 					or "scancode". Default is set to "ascii"

 		lenovo_kbdlang:
 					The keyboard language method that is used. This is generally a
 					two char code (e.g. "us", "fr", "gr") and may vary per platform.
 					Default is set to "us"

 		level:
 					Available for HDD and NVMe authentication to set 'user' or 'master'
 					privilege level.
 					If only the user password is configured then this should be used to
 					unlock the drive at boot. If both master and user passwords are set
 					then either can be used. If a master password is set a user password
 					is required.
 					This attribute defaults to 'user' level

 		index:
 					Used with HDD and NVME authentication to set the drive index
 					that is being referenced (e.g hdd1, hdd2 etc)
 					This attribute defaults to device 1.

 		certificate, signature, save_signature:
 					These attributes are used for certificate based authentication. This is
 					used in conjunction with a signing server as an alternative to password
 					based authentication.
 					The user writes to the attribute(s) with a BASE64 encoded string obtained
 					from the signing server.
 					The attributes can be displayed to check the stored value.

 					Some usage examples:

 						Installing a certificate to enable feature::

 							echo "supervisor password" > authentication/Admin/current_password
 							echo "signed certificate" > authentication/Admin/certificate

 						Updating the installed certificate::

 							echo "signature" > authentication/Admin/signature
 							echo "signed certificate" > authentication/Admin/certificate

 						Removing the installed certificate::

 							echo "signature" > authentication/Admin/signature
 							echo "" > authentication/Admin/certificate

 						Changing a BIOS setting::

 							echo "signature" > authentication/Admin/signature
 							echo "save signature" > authentication/Admin/save_signature
 							echo Enable > attribute/PasswordBeep/current_value

 					You cannot enable certificate authentication if a supervisor password
 					has not been set.
 					Clearing the certificate results in no bios-admin authentication method
 					being configured allowing anyone to make changes.
 					After any of these operations the system must reboot for the changes to
 					take effect.
 					Admin and System certificates are supported from 2025 systems onward.

 		certificate_thumbprint:
 					Read only attribute used to display the MD5, SHA1 and SHA256 thumbprints
 					for the certificate installed in the BIOS.

 		certificate_to_password:
 					Write only attribute used to switch from certificate based authentication
 					back to password based.
 					Usage::

 						echo "signature" > authentication/Admin/signature
 						echo "password" > authentication/Admin/certificate_to_password

 		HP specific class extensions
 		--------------------------------

 		On HP systems the following additional settings are available:

 		role: enhanced-bios-auth:
 					This role is specific to Secure Platform Management (SPM) attribute.
 					It requires configuring an endorsement (kek) and signing certificate (sk).


 What:		/sys/class/firmware-attributes/*/attributes/pending_reboot
 Date:		February 2021
 KernelVersion:	5.11
 Contact:	Divya Bharathi <Divya.Bharathi@Dell.com>,
 		Prasanth KSR <prasanth.ksr@dell.com>
 		Dell.Client.Kernel@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>,
 		Prasanth KSR <prasanth.ksr@dell.com>
 		Dell.Client.Kernel@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.

 What:		/sys/class/firmware-attributes/*/attributes/save_settings
 Date:		August 2023
 KernelVersion:	6.6
 Contact:	Mark Pearson <mpearson-lenovo@squebb.ca>
 Description:
 		On Lenovo platforms there is a limitation in the number of times an attribute can be
 		saved. This is an architectural limitation and it limits the number of attributes
 		that can be modified to 48.
 		A solution for this is instead of the attribute being saved after every modification,
 		to allow a user to bulk set the attributes, and then trigger a final save. This allows
 		unlimited attributes.

 		Read the attribute to check what save mode is enabled (single or bulk).
 		E.g:
 		# cat /sys/class/firmware-attributes/thinklmi/attributes/save_settings
 		single

 		Write the attribute with 'bulk' to enable bulk save mode.
 		Write the attribute with 'single' to enable saving, after every attribute set.
 		The default setting is single mode.
 		E.g:
 		# echo bulk > /sys/class/firmware-attributes/thinklmi/attributes/save_settings

 		When in bulk mode write 'save' to trigger a save of all currently modified attributes.
 		Note, once a save has been triggered, in bulk mode, attributes can no longer be set and
 		will return a permissions error. This is to prevent users hitting the 48+ save limitation
 		(which requires entering the BIOS to clear the error condition)
 		E.g:
 		# echo save > /sys/class/firmware-attributes/thinklmi/attributes/save_settings

 What:		/sys/class/firmware-attributes/*/attributes/debug_cmd
 Date:		July 2021
 KernelVersion:	5.14
 Contact:	Mark Pearson <markpearson@lenovo.com>
 Description:
 		This write only attribute can be used to send debug commands to the BIOS.
 		This should only be used when recommended by the BIOS vendor. Vendors may
 		use it to enable extra debug attributes or BIOS features for testing purposes.

 		Note that any changes to this attribute requires a reboot for changes to take effect.


 		HP specific class extensions - Secure Platform Manager (SPM)
 		--------------------------------

 What:		/sys/class/firmware-attributes/*/authentication/SPM/kek
 Date:		March 2023
 KernelVersion:	5.18
 Contact:	"Jorge Lopez" <jorge.lopez2@hp.com>
 Description:
 		'kek' Key-Encryption-Key is a write-only file that can be used to configure the
 		RSA public key that will be used by the BIOS to verify
 		signatures when setting the signing key.  When written,
 		the bytes should correspond to the KEK certificate
 		(x509 .DER format containing an OU).  The size of the
 		certificate must be less than or equal to 4095 bytes.

 What:		/sys/class/firmware-attributes/*/authentication/SPM/sk
 Date:		March 2023
 KernelVersion:	5.18
 Contact:	"Jorge Lopez" <jorge.lopez2@hp.com>
 Description:
 		'sk' Signature Key is a write-only file that can be used to configure the RSA
 		public key that will be used by the BIOS to verify signatures
 		when configuring BIOS settings and security features.  When
 		written, the bytes should correspond to the modulus of the
 		public key.  The exponent is assumed to be 0x10001.

 What:		/sys/class/firmware-attributes/*/authentication/SPM/status
 Date:		March 2023
 KernelVersion:	5.18
 Contact:	"Jorge Lopez" <jorge.lopez2@hp.com>
 Description:
 		'status' is a read-only file that returns ASCII text in JSON format reporting
 		the status information.

 		  "State": "not provisioned | provisioned | provisioning in progress",
 		  "Version": "Major.Minor",
 		  "Nonce": <16-bit unsigned number display in base 10>,
 		  "FeaturesInUse": <16-bit unsigned number display in base 10>,
 		  "EndorsementKeyMod": "<256 bytes in base64>",
 		  "SigningKeyMod": "<256 bytes in base64>"

 What:		/sys/class/firmware-attributes/*/attributes/Sure_Start/audit_log_entries
 Date:		March 2023
 KernelVersion:	5.18
 Contact:	"Jorge Lopez" <jorge.lopez2@hp.com>
 Description:
 		'audit_log_entries' is a read-only file that returns the events in the log.

 			Audit log entry format

 			Byte 0-15:   Requested Audit Log entry  (Each Audit log is 16 bytes)
 			Byte 16-127: Unused

 What:		/sys/class/firmware-attributes/*/attributes/Sure_Start/audit_log_entry_count
 Date:		March 2023
 KernelVersion:	5.18
 Contact:	"Jorge Lopez" <jorge.lopez2@hp.com>
 Description:
 		'audit_log_entry_count' is a read-only file that returns the number of existing
 		audit log events available to be read. Values are separated using comma. (``,``)

 			[No of entries],[log entry size],[Max number of entries supported]

 		log entry size identifies audit log size for the current BIOS version.
 		The current size is 16 bytes but it can be up to 128 bytes long in future BIOS
 		versions.
	What: /sys/class/firmware-attributes//attributes//
	Date: February 2021
	KernelVersion: 5.11
	Contact: Divya Bharathi <Divya.Bharathi@Dell.com>,
	Prasanth KSR <prasanth.ksr@dell.com>
	Dell.Client.Kernel@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

	HP specific types
	-----------------
	- ordered-list - a set of ordered list valid values


	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.

	HP specific class extensions
	------------------------------

	On HP systems the following additional attributes are available:

	"ordered-list"-type specific properties:

	elements:
	A file that can be read to obtain the possible
	list of values of the <attr>. Values are separated using
	semi-colon (``;``) and listed according to their priority.
	An element listed first has the highest priority. Writing
	the list in a different order to current_value alters
	the priority order for the particular attribute.

	What: /sys/class/firmware-attributes/*/authentication/
	Date: February 2021
	KernelVersion: 5.11
	Contact: Divya Bharathi <Divya.Bharathi@Dell.com>,
	Prasanth KSR <prasanth.ksr@dell.com>
	Dell.Client.Kernel@dell.com
	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
	<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
	system-mgmt:
	Representing System Management password.
	See Lenovo extensions section for details
	HDD:
	Representing HDD password
	See Lenovo extensions section for details
	NVMe:
	Representing NVMe password
	See Lenovo extensions section for details

	mechanism:
	The means of authentication. This attribute is mandatory.
	Supported types are "password" or "certificate".

	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, Lenovo and HP systems, if Admin password is set, then all BIOS attributes
	require password validation.
	On Lenovo systems if you change the Admin password the new password is not active until
	the next boot.

	Lenovo specific class extensions
	--------------------------------

	On Lenovo systems the following additional settings are available:

	role: system-mgmt This gives the same authority as the bios-admin password to control
	security related features. The authorities allocated can be set via
	the BIOS menu SMP Access Control Policy

	role: HDD & NVMe This password is used to unlock access to the drive at boot. Note see
	'level' and 'index' extensions below.

	lenovo_encoding:
	The encoding method that is used. This can be either "ascii"
	or "scancode". Default is set to "ascii"

	lenovo_kbdlang:
	The keyboard language method that is used. This is generally a
	two char code (e.g. "us", "fr", "gr") and may vary per platform.
	Default is set to "us"

	level:
	Available for HDD and NVMe authentication to set 'user' or 'master'
	privilege level.
	If only the user password is configured then this should be used to
	unlock the drive at boot. If both master and user passwords are set
	then either can be used. If a master password is set a user password
	is required.
	This attribute defaults to 'user' level

	index:
	Used with HDD and NVME authentication to set the drive index
	that is being referenced (e.g hdd1, hdd2 etc)
	This attribute defaults to device 1.

	certificate, signature, save_signature:
	These attributes are used for certificate based authentication. This is
	used in conjunction with a signing server as an alternative to password
	based authentication.
	The user writes to the attribute(s) with a BASE64 encoded string obtained
	from the signing server.
	The attributes can be displayed to check the stored value.

	Some usage examples:

	Installing a certificate to enable feature::

	echo "supervisor password" > authentication/Admin/current_password
	echo "signed certificate" > authentication/Admin/certificate

	Updating the installed certificate::

	echo "signature" > authentication/Admin/signature
	echo "signed certificate" > authentication/Admin/certificate

	Removing the installed certificate::

	echo "signature" > authentication/Admin/signature
	echo "" > authentication/Admin/certificate

	Changing a BIOS setting::

	echo "signature" > authentication/Admin/signature
	echo "save signature" > authentication/Admin/save_signature
	echo Enable > attribute/PasswordBeep/current_value

	You cannot enable certificate authentication if a supervisor password
	has not been set.
	Clearing the certificate results in no bios-admin authentication method
	being configured allowing anyone to make changes.
	After any of these operations the system must reboot for the changes to
	take effect.
	Admin and System certificates are supported from 2025 systems onward.

	certificate_thumbprint:
	Read only attribute used to display the MD5, SHA1 and SHA256 thumbprints
	for the certificate installed in the BIOS.

	certificate_to_password:
	Write only attribute used to switch from certificate based authentication
	back to password based.
	Usage::

	echo "signature" > authentication/Admin/signature
	echo "password" > authentication/Admin/certificate_to_password

	HP specific class extensions
	--------------------------------

	On HP systems the following additional settings are available:

	role: enhanced-bios-auth:
	This role is specific to Secure Platform Management (SPM) attribute.
	It requires configuring an endorsement (kek) and signing certificate (sk).


	What: /sys/class/firmware-attributes/*/attributes/pending_reboot
	Date: February 2021
	KernelVersion: 5.11
	Contact: Divya Bharathi <Divya.Bharathi@Dell.com>,
	Prasanth KSR <prasanth.ksr@dell.com>
	Dell.Client.Kernel@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>,
	Prasanth KSR <prasanth.ksr@dell.com>
	Dell.Client.Kernel@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.

	What: /sys/class/firmware-attributes/*/attributes/save_settings
	Date: August 2023
	KernelVersion: 6.6
	Contact: Mark Pearson <mpearson-lenovo@squebb.ca>
	Description:
	On Lenovo platforms there is a limitation in the number of times an attribute can be
	saved. This is an architectural limitation and it limits the number of attributes
	that can be modified to 48.
	A solution for this is instead of the attribute being saved after every modification,
	to allow a user to bulk set the attributes, and then trigger a final save. This allows
	unlimited attributes.

	Read the attribute to check what save mode is enabled (single or bulk).
	E.g:
	# cat /sys/class/firmware-attributes/thinklmi/attributes/save_settings
	single

	Write the attribute with 'bulk' to enable bulk save mode.
	Write the attribute with 'single' to enable saving, after every attribute set.
	The default setting is single mode.
	E.g:
	# echo bulk > /sys/class/firmware-attributes/thinklmi/attributes/save_settings

	When in bulk mode write 'save' to trigger a save of all currently modified attributes.
	Note, once a save has been triggered, in bulk mode, attributes can no longer be set and
	will return a permissions error. This is to prevent users hitting the 48+ save limitation
	(which requires entering the BIOS to clear the error condition)
	E.g:
	# echo save > /sys/class/firmware-attributes/thinklmi/attributes/save_settings

	What: /sys/class/firmware-attributes/*/attributes/debug_cmd
	Date: July 2021
	KernelVersion: 5.14
	Contact: Mark Pearson <markpearson@lenovo.com>
	Description:
	This write only attribute can be used to send debug commands to the BIOS.
	This should only be used when recommended by the BIOS vendor. Vendors may
	use it to enable extra debug attributes or BIOS features for testing purposes.

	Note that any changes to this attribute requires a reboot for changes to take effect.


	HP specific class extensions - Secure Platform Manager (SPM)
	--------------------------------

	What: /sys/class/firmware-attributes/*/authentication/SPM/kek
	Date: March 2023
	KernelVersion: 5.18
	Contact: "Jorge Lopez" <jorge.lopez2@hp.com>
	Description:
	'kek' Key-Encryption-Key is a write-only file that can be used to configure the
	RSA public key that will be used by the BIOS to verify
	signatures when setting the signing key. When written,
	the bytes should correspond to the KEK certificate
	(x509 .DER format containing an OU). The size of the
	certificate must be less than or equal to 4095 bytes.

	What: /sys/class/firmware-attributes/*/authentication/SPM/sk
	Date: March 2023
	KernelVersion: 5.18
	Contact: "Jorge Lopez" <jorge.lopez2@hp.com>
	Description:
	'sk' Signature Key is a write-only file that can be used to configure the RSA
	public key that will be used by the BIOS to verify signatures
	when configuring BIOS settings and security features. When
	written, the bytes should correspond to the modulus of the
	public key. The exponent is assumed to be 0x10001.

	What: /sys/class/firmware-attributes/*/authentication/SPM/status
	Date: March 2023
	KernelVersion: 5.18
	Contact: "Jorge Lopez" <jorge.lopez2@hp.com>
	Description:
	'status' is a read-only file that returns ASCII text in JSON format reporting
	the status information.

	"State": "not provisioned \| provisioned \| provisioning in progress",
	"Version": "Major.Minor",
	"Nonce": <16-bit unsigned number display in base 10>,
	"FeaturesInUse": <16-bit unsigned number display in base 10>,
	"EndorsementKeyMod": "<256 bytes in base64>",
	"SigningKeyMod": "<256 bytes in base64>"

	What: /sys/class/firmware-attributes/*/attributes/Sure_Start/audit_log_entries
	Date: March 2023
	KernelVersion: 5.18
	Contact: "Jorge Lopez" <jorge.lopez2@hp.com>
	Description:
	'audit_log_entries' is a read-only file that returns the events in the log.

	Audit log entry format

	Byte 0-15: Requested Audit Log entry (Each Audit log is 16 bytes)
	Byte 16-127: Unused

	What: /sys/class/firmware-attributes/*/attributes/Sure_Start/audit_log_entry_count
	Date: March 2023
	KernelVersion: 5.18
	Contact: "Jorge Lopez" <jorge.lopez2@hp.com>
	Description:
	'audit_log_entry_count' is a read-only file that returns the number of existing
	audit log events available to be read. Values are separated using comma. (``,``)

	[No of entries],[log entry size],[Max number of entries supported]

	log entry size identifies audit log size for the current BIOS version.
	The current size is 16 bytes but it can be up to 128 bytes long in future BIOS
	versions.