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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 <[email protected]> Cc: Andy Shevchenko <[email protected]> Cc: mark gross <[email protected]> Co-developed-by: Mario Limonciello <[email protected]> Signed-off-by: Mario Limonciello <[email protected]> Co-developed-by: Prasanth KSR <[email protected]> Signed-off-by: Prasanth KSR <[email protected]> Signed-off-by: Divya Bharathi <[email protected]> Link: https://lore.kernel.org/r/[email protected] Reviewed-by: Hans de Goede <[email protected]> Signed-off-by: Hans de Goede <[email protected]>
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‎Documentation/ABI/testing/sysfs-class-firmware-attributes

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

‎MAINTAINERS

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S: Maintained
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F: drivers/platform/x86/dell-wmi-descriptor.c
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DELL WMI SYSMAN DRIVER
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M: Divya Bharathi <[email protected]>
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M: Mario Limonciello <[email protected]>
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M: Prasanth Ksr <[email protected]>
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L: [email protected]
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S: Maintained
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F: drivers/platform/x86/dell-wmi-syman/*
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DELL WMI NOTIFICATIONS DRIVER
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M: Matthew Garrett <[email protected]>
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M: Pali Rohár <[email protected]>

‎drivers/platform/x86/Kconfig

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

‎drivers/platform/x86/Makefile

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

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

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

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