https://www.kernel.org/diff/diffview.cgi?file=/pub/linux/ker...

         acpi_osi=       [HW,ACPI] Modify list of supported OS interface strings
-                        acpi_osi="string1"      # add string1 -- only one string
-                        acpi_osi="!string2"     # remove built-in string2
+                        acpi_osi="string1"      # add string1
+                        acpi_osi="!string2"     # remove string2
+                        acpi_osi=!*             # remove all strings
+                        acpi_osi=!              # disable all built-in OS vendor
+                                                  strings
                         acpi_osi=               # disable all strings
 
+                        'acpi_osi=!' can be used in combination with single or
+                        multiple 'acpi_osi="string1"' to support specific OS
+                        vendor string(s).  Note that such command can only
+                        affect the default state of the OS vendor strings, thus
+                        it cannot affect the default state of the feature group
+                        strings and the current state of the OS vendor strings,
+                        specifying it multiple times through kernel command line
+                        is meaningless.  This command is useful when one do not
+                        care about the state of the feature group strings which
+                        should be controlled by the OSPM.
+                        Examples:
+                          1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
+                             to 'acpi_osi="Windows 2000" acpi_osi=!', they all
+                             can make '_OSI("Windows 2000")' TRUE.
+
+                        'acpi_osi=' cannot be used in combination with other
+                        'acpi_osi=' command lines, the _OSI method will not
+                        exist in the ACPI namespace.  NOTE that such command can
+                        only affect the _OSI support state, thus specifying it
+                        multiple times through kernel command line is also
+                        meaningless.
+                        Examples:
+                          1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
+                             FALSE.
+
+                        'acpi_osi=!*' can be used in combination with single or
+                        multiple 'acpi_osi="string1"' to support specific
+                        string(s).  Note that such command can affect the
+                        current state of both the OS vendor strings and the
+                        feature group strings, thus specifying it multiple times
+                        through kernel command line is meaningful.  But it may
+                        still not able to affect the final state of a string if
+                        there are quirks related to this string.  This command
+                        is useful when one want to control the state of the
+                        feature group strings to debug BIOS issues related to
+                        the OSPM features.
+                        Examples:
+                          1. 'acpi_osi="Module Device" acpi_osi=!*' can make
+                             '_OSI("Module Device")' FALSE.
+                          2. 'acpi_osi=!* acpi_osi="Module Device"' can make
+                             '_OSI("Module Device")' TRUE.
+                          3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
+                             equivalent to
+                             'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
+                             and
+                             'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
+                             they all will make '_OSI("Windows 2000")' TRUE.