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.com
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

1 files changed, 224 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-firmware-attributes b/Documentation/ABI/testing/sysfs-class-firmware-attributes
new file mode 100644
index 000000000000..04a15c72e883
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-firmware-attributes
@@ -0,0 +1,224 @@
+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.