handle fadt->si_cmd == 0

In reading the spec, it looks like if a particular ACPI implementation leaves fadt->si_cmd equal to 0, that means the platform doesn't support system management mode, which seems legal. I needed this patch for my system. With the patch applied, I'm able to see /proc/acpi and the interpreter appears to start. Is this legal?

Thanks,
Jesse

@@ -180,6 +180,10 @@
 
 	ACPI_FUNCTION_TRACE ("Hw_get_mode");
 
+	/* If there's no smi_cmd port, then it's ACPI only hw */
+	if (!acpi_gbl_FADT->smi_cmd)
+		return_VALUE (ACPI_SYS_MODE_ACPI);
+
 	status = acpi_get_register (ACPI_BITREG_SCI_ENABLE, &value, ACPI_MTX_LOCK);
 	if (ACPI_FAILURE (status)) {
 		return_VALUE (ACPI_SYS_MODE_LEGACY);

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Hi Jesse,

From: jbarnes-sJ/[email protected] (Jesse Barnes)
Subject: [ACPI] [PATCH] handle fadt->si_cmd == 0
Date: Fri, 6 Jun 2003 10:17:30 -0700
Message-ID: <20030606171730.GD1349-sJ/[email protected]>

Once there was an exactly same discussion, and the current implementation is correct. As you wrote, the meaning of value 0 in smi_cmd field in the FADT is clarified in the ACPI spec 2.0 and this is implemented in acpi_hw_set_mode().

But in any case, SCI_ENABLE bit in PM1 control register should be set correctly, reflecting the system state. If your platform specifies smi_cmd is 0 and SCI_ENABLE is 'enabled', the ACPI subsystem won't try to call acpi_hw_set_mode() to enable ACPI mode (as it's already in ACPI mode).

IIRC, once there was the same workaround in the ia64 patch for some (prototype?) HP machines.

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