ACPI / osi: Add acpi_osi=!! to allow reverting acpi_osi=!

This patch introduces acpi_osi=!! so that quirks may use it to revert
acpi_osi=!.

Tested-by: Lukas Wunner <lukas@wunner.de>
Tested-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

2 files changed, 5 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 0b3de80ec8f6..c48f387109e8 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -312,6 +312,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         acpi_osi=!*             # remove all strings
                         acpi_osi=!              # disable all built-in OS vendor
                                                   strings
+                        acpi_osi=!!             # enable all built-in OS vendor
+                                                  strings
                         acpi_osi=               # disable all strings
 
                         'acpi_osi=!' can be used in combination with single or
diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index 9f59dd1a0af7..f801b59f2a94 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -1763,6 +1763,9 @@ void __init acpi_osi_setup(char *str)
                                 osi->enable = false;
                         }
                         return;
+                } else if (*str == '!') {
+                        osi_config.default_disabling = 0;
+                        return;
                 }
                 enable = false;
         }