Re: ACPI locks hardware devices when it doesn't detect vista

From: Maxim Levitsky
Date: Fri Aug 28 2009 - 19:54:13 EST

On Sat, 2009-08-22 at 15:48 +0300, Maxim Levitsky wrote:
> Hi,
> <joke>
> This should be brought to a Microsoft antitrust case...
> </joke>
> Today many notebooks ship with a embedded infrared receiver.
> In Vista there is new subsystem that decodes these signals.
> (of course it works only with Microsoft Certificated Remotes (TM)...)
> The receiver is usually presented to system as a pnp device
> (using acpi tables)
> It turns out that some bioses actually use the OSI, ACPI feature of the
> operation system to detect if running inside Vista. If not they disable
> the infrared receiver.
> Device (MIR)
> {
> Name (_HID, EisaId ("ENE0100"))
> Method (_STA, 0, NotSerialized)
> {
> If (LAnd (MCIR, LEqual (OSYS, 0x07D6)))
> {
> Return (0x0F)
> }
> Else
> {
> Store (Zero, ^^LPCB.IOR2)
> Return (Zero)
> }
> }
> .......

> Scope (_SB)
> {
> Method (_INI, 0, NotSerialized)
> {

> If (CondRefOf (_OSI, Local0))
> {
> If (_OSI ("Linux"))
> {
> Store (One, LINX)
> Store (Zero, ECDY)
> }


> If (_OSI ("Windows 2006"))
> {
> Store (0x07D6, OSYS)
> }

I have finally managed to find root case of this problem.

Indeed the _STA method of infrared receiver is called before the _INI of

The problem lies in acpi_bus_init()
* ACPI 2.0 requires the EC driver to be loaded and work before
* the EC device is found in the namespace (i.e. before acpi_initialize_objects()
* is called).
* This is accomplished by looking for the ECDT table, and getting
* the EC parameters out of that.

status = acpi_ec_ecdt_probe();
/* Ignore result. Not having an ECDT is not fatal. */

status = acpi_initialize_objects(ACPI_FULL_INITIALIZATION);
if (ACPI_FAILURE(status)) {
printk(KERN_ERR PREFIX "Unable to initialize ACPI objects\n");
goto error1;

on Mairo's system (just as well as on mine) there is no ECDT.
Thus, acpi_ec_ecdt_probe() triggers a acpi namespace walk,
which in turn triggers invocation on _STA (which is supposed to be
harmless, but the <beep>, the bios developers produce doesn't seem to
meet this criteria....).

And this is done before running _INI methods, which are run just later,
in acpi_initialize_objects.

I suspect that many systems use _SB._INI to test the OS version, thus
this behavior needs to be revised.

The fact that this (as usual) works in windows suggest that it might be
good to look up the ECDT table before acpi_initialize_objects, but if
not found, look up the EC later.

On my system, although I have tried to reproduce this bug, I couldn't,
and I know now why: It just so happens that on my system CIR device is
listed in acpi tables after the EC, but on Mairo's system EC is just
first device.

Maybe we can add a 'walk only' function, that walks the namespace, but
doesn't touch the _STA, and use it to find the EC there?

Looking for comments,
Best regards,
Maxim Levitsky

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