[stable PATCH 2.6.22, 2.6.23, 2.6.24, 2.6.25] ACPICA: Ignore ACPI table signature for Load() operator

[stable PATCH 2.6.22, 2.6.23, 2.6.24, 2.6.25] ACPICA: Ignore ACPI table signature for Load() operator

[Len Brown]

From: Bob Moore <robert.moore@intel.com>

upstream bc45b1d39a925b56796bebf8a397a0491489d85c

Without this patch booting with acpi_osi="!Windows 2006" is required
for several machines to function properly with cpufreq
due to failure to load a Vista specific table with a bad signature.

Only "SSDT" is acceptable to the ACPI spec, but tables are
seen with OEMx and null sigs. Therefore, signature validation
is worthless.  Apparently MS ACPI accepts such signatures, ACPICA
must be compatible.

http://bugzilla.kernel.org/show_bug.cgi?id=9919
http://bugzilla.kernel.org/show_bug.cgi?id=10383
http://bugzilla.kernel.org/show_bug.cgi?id=10454
https://bugzilla.novell.com/show_bug.cgi?id=396311

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
---
 drivers/acpi/tables/tbinstal.c |   25 +++++++------------------
 1 files changed, 7 insertions(+), 18 deletions(-)

Index: linux-2.6.25.y/drivers/acpi/tables/tbinstal.c
===================================================================
--- linux-2.6.25.y.orig/drivers/acpi/tables/tbinstal.c
+++ linux-2.6.25.y/drivers/acpi/tables/tbinstal.c
@@ -123,17 +123,13 @@ acpi_tb_add_table(struct acpi_table_desc
 		}
 	}
 
-	/* The table must be either an SSDT or a PSDT or an OEMx */
-
-	if ((!ACPI_COMPARE_NAME(table_desc->pointer->signature, ACPI_SIG_PSDT))
-	    &&
-	    (!ACPI_COMPARE_NAME(table_desc->pointer->signature, ACPI_SIG_SSDT))
-	    && (strncmp(table_desc->pointer->signature, "OEM", 3))) {
-		ACPI_ERROR((AE_INFO,
-			    "Table has invalid signature [%4.4s], must be SSDT, PSDT or OEMx",
-			    table_desc->pointer->signature));
-		return_ACPI_STATUS(AE_BAD_SIGNATURE);
-	}
+	/*
+	 * Originally, we checked the table signature for "SSDT" or "PSDT" here.
+	 * Next, we added support for OEMx tables, signature "OEM".
+	 * Valid tables were encountered with a null signature, so we've just
+	 * given up on validating the signature, since it seems to be a waste
+	 * of code. The original code was removed (05/2008).
+	 */
 
 	(void)acpi_ut_acquire_mutex(ACPI_MTX_TABLES);