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ACPI: Add facility to disable all _OSI OS vendor strings

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This patch introduces "acpi_osi=!" command line to force Linux replying
"UNSUPPORTED" to all of the _OSI strings.  This patch is based on an
ACPICA enhancement - the new API acpi_update_interfaces().

The _OSI object provides the platform with the ability to query OSPM
to determine the set of ACPI related interfaces, behaviors, or
features that the operating system supports.  The argument passed to
the _OSI is a string like the followings:
1. Feature Group String, examples include
   Module Device
   Processor Device
   3.0 _SCP Extensions
   Processor Aggregator Device
   ...
2. OS Vendor String, examples include
   Linux
   FreeBSD
   Windows
   ...

There are AML codes provided in the ACPI namespace written in the
following style to determine OSPM interfaces / features:
    Method(OSCK)
    {
        if (CondRefOf(_OSI, Local0))
        {
            if (\_OSI("Windows"))
            {
                Return (One)
            }
            if (\_OSI("Windows 2006"))
            {
                Return (Ones)
            }
            Return (Zero)
        }
        Return (Zero)
    }

There is a debugging facility implemented in Linux.  Users can pass
"acpi_osi=" boot parameters to the kernel to tune the _OSI evaluation
result so that certain AML codes can be executed.  Current
implementation includes:
1. 'acpi_osi=' - this makes CondRefOf(_OSI, Local0) TRUE
2. 'acpi_osi="Windows"' - this makes \_OSI("Windows") TRUE
3. 'acpi_osi="!Windows"' - this makes \_OSI("Windows") FALSE
The function to implement this feature is also used as a quirk mechanism
in the Linux ACPI subystem.

When _OSI is evaluatated by the AML codes, ACPICA replies "SUPPORTED"
to all Windows operating system vendor strings.  This is because
Windows operating systems return "SUPPORTED" if the argument to the
_OSI method specifies an earlier version of Windows.  Please refer to
the following MSDN document:

How to Identify the Windows Version in ACPI by Using _OSI
http://msdn.microsoft.com/en-us/library/hardware/gg463275.aspx

This adds difficulties when developers want to feed specific Windows
operating system vendor string to the BIOS codes for debugging
purpose, multiple acpi_osi="!xxx" have to be specified in the command
line to force Linux replying "UNSUPPORTED" to the Windows OS vendor
strings listed in the AML codes.

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>
This commit is contained in:
Lv Zheng 2013-07-22 16:08:25 +08:00 committed by Rafael J. Wysocki
parent 2cf9f5bcc8
commit 5dc17986fd
2 changed files with 40 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
Documentation/kernel-parameters.txt
View File

@ -235,10 +235,35 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
Format: To spoof as Windows 98: ="Microsoft Windows"
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=! # 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.
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_pm_good [X86]
Override the pmtimer bug detection: force the kernel
to assume that this machine's pmtimer latches its value

14
drivers/acpi/osl.c
View File

@ -140,7 +140,8 @@ static struct osi_linux {
unsigned int enable:1;
unsigned int dmi:1;
unsigned int cmdline:1;
} osi_linux = {0, 0, 0};
unsigned int default_disabling:1;
} osi_linux = {0, 0, 0, 0};
static u32 acpi_osi_handler(acpi_string interface, u32 supported)
{
@ -1376,6 +1377,10 @@ void __init acpi_osi_setup(char *str)
if (*str == '!') {
str++;
if (*str == '\0') {
osi_linux.default_disabling = 1;
return;
}
enable = false;
}
@ -1441,6 +1446,13 @@ static void __init acpi_osi_setup_late(void)
int i;
acpi_status status;
if (osi_linux.default_disabling) {
status = acpi_update_interfaces(ACPI_DISABLE_ALL_VENDOR_STRINGS);
if (ACPI_SUCCESS(status))
printk(KERN_INFO PREFIX "Disabled all _OSI OS vendors\n");
}
for (i = 0; i < OSI_STRING_ENTRIES_MAX; i++) {
osi = &osi_setup_entries[i];
str = osi->string;