[PATCH 1/1] acpi_get_sleep_type_data(): accept package with one element

[Laszlo Ersek <lersek@redhat.com>]

Citation from "ACPIspec50.pdf":

  7.3.4 System \_Sx states

    [...]

    Return Value:

    A Package containing an Integer containing register values for
    sleeping

Hence accept one-element packages as well when parsing sleep states, in
addition to the currently accepted multi-element packages.

See the ACPICA upstream posting under [1].

This change is prompted by OVMF svn rev 14003 [2] that creates the \_S3
and \_S4 packages with a single DWORD in each:

  Name (\_S3, Package (0x01)
  {
      0x00000001
  })
  Name (\_S4, Package (0x01)
  {
      0x00000002
  })

Tested with a RHEL-6 kernel (patch applies verbatim) in virtual machines.
Without the patch,
- on OVMF, errors like

  ACPI Error: Sleep State return package does not have at least two
              elements (20120711/hwxface-511)
  ACPI Exception: AE_AML_NO_OPERAND, While evaluating SleepState [\_S3_],
                  bad Sleep object ffff880119a33cf0 type Package
                  (20120711/hwxface-543)

  are logged and suspend doesn't work,

- on SeaBIOS, which provides multi-element packages, suspend works.

With the patch, the messages are gone on OVMF, and the VM can be suspended
with both boot firmwares.

[1] http://lists.acpica.org/pipermail/devel/2012-December/000405.html
[2] http://tianocore.git.sourceforge.net/git/gitweb.cgi?p=tianocore/edk2;a=commitdiff;h=14430c55c8d0e9a8487c2c74155e63299632ef5e

Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---
 drivers/acpi/acpica/hwxface.c |   60 ++++++++++++++++++++++-------------------
 1 files changed, 32 insertions(+), 28 deletions(-)

diff --git a/drivers/acpi/acpica/hwxface.c b/drivers/acpi/acpica/hwxface.c
index 05a154c..6cd5bb0 100644
--- a/drivers/acpi/acpica/hwxface.c
+++ b/drivers/acpi/acpica/hwxface.c
@@ -499,39 +499,43 @@ acpi_get_sleep_type_data(u8 sleep_state, u8 *sleep_type_a, u8 *sleep_type_b)
 	}
 
 	/*
-	 * The package must have at least two elements. NOTE (March 2005): This
-	 * goes against the current ACPI spec which defines this object as a
-	 * package with one encoded DWORD element. However, existing practice
-	 * by BIOS vendors seems to be to have 2 or more elements, at least
-	 * one per sleep type (A/B).
+	 * The current ACPI spec (v 5.0) defines this object as a package with
+	 * one encoded DWORD element.
+	 *
+	 * Existing practice by BIOS vendors seems to be to have 2 or more
+	 * elements, at least one per sleep type (A/B).
 	 */
-	else if (info->return_object->package.count < 2) {
+	else if (info->return_object->package.count == 0) {
 		ACPI_ERROR((AE_INFO,
-			    "Sleep State return package does not have at least two elements"));
+			    "Sleep State return package does not have elements"));
 		status = AE_AML_NO_OPERAND;
-	}
-
-	/* The first two elements must both be of type Integer */
-
-	else if (((info->return_object->package.elements[0])->common.type
-		  != ACPI_TYPE_INTEGER) ||
-		 ((info->return_object->package.elements[1])->common.type
-		  != ACPI_TYPE_INTEGER)) {
-		ACPI_ERROR((AE_INFO,
-			    "Sleep State return package elements are not both Integers "
-			    "(%s, %s)",
-			    acpi_ut_get_object_type_name(info->return_object->
-							 package.elements[0]),
-			    acpi_ut_get_object_type_name(info->return_object->
-							 package.elements[1])));
-		status = AE_AML_OPERAND_TYPE;
 	} else {
-		/* Valid _Sx_ package size, type, and value */
+		union acpi_operand_object **elements;
 
-		*sleep_type_a = (u8)
-		    (info->return_object->package.elements[0])->integer.value;
-		*sleep_type_b = (u8)
-		    (info->return_object->package.elements[1])->integer.value;
+		elements = info->return_object->package.elements;
+
+		if (elements[0]->common.type != ACPI_TYPE_INTEGER) {
+			ACPI_ERROR((AE_INFO,
+				    "1st element in Sleep State return package is not Integer "
+				    "(%s)",
+				    acpi_ut_get_object_type_name(elements[0])));
+			status = AE_AML_OPERAND_TYPE;
+		}
+		else if (info->return_object->package.count == 1) {
+			*sleep_type_a = (u8) elements[0]->integer.value;
+			*sleep_type_b = (u8)(elements[0]->integer.value >> 8);
+		}
+		else if (elements[1]->common.type != ACPI_TYPE_INTEGER) {
+			ACPI_ERROR((AE_INFO,
+				    "2nd element in Sleep State return package is not Integer "
+				    "(%s)",
+				    acpi_ut_get_object_type_name(elements[1])));
+			status = AE_AML_OPERAND_TYPE;
+		}
+		else {
+			*sleep_type_a = (u8)elements[0]->integer.value;
+			*sleep_type_b = (u8)elements[1]->integer.value;
+		}
 	}
 
 	if (ACPI_FAILURE(status)) {
-- 
1.7.1