ACPI: Add facility to remove all _OSI strings

This patch changes the "acpi_osi=" boot parameter implementation so
that:
1. "acpi_osi=!" can be used to disable all _OSI OS vendor strings by
   default.  It is meaningless to specify "acpi_osi=!" multiple
   times as it can only affect the default state of the target _OSI
   strings.
2. "acpi_osi=!*" can be used to remove all _OSI OS vendor strings
   and all _OSI feature group strings.  It is useful to specify
   "acpi_osi=!*" multiple times through kernel command line to
   override the current state of the target _OSI strings.

Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Reviewed-by: Zhang Rui <rui.zhang@intel.com>
Acked-by: Len Brown <len.brown@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 27 insertions, 1 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index d0d9cf278ae3..5ec77aad1773 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -237,6 +237,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
         acpi_osi=       [HW,ACPI] Modify list of supported OS interface strings
                         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
@@ -248,7 +249,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         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.
+                        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
@@ -264,6 +267,29 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                           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.
+
         acpi_pm_good    [X86]
                         Override the pmtimer bug detection: force the kernel
                         to assume that this machine's pmtimer latches its value