ACPI: improve acpi_extract_package() utility

The current version requires one to know the size of the package
a priori; this is almost impossible if the package is composed of
strings of variable length.  This change allows the utility to
allocate a buffer of the proper size if asked.

Signed-off-by: Al Stone <al.stone@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/utils.c

@@ -169,11 +169,20 @@ acpi_extract_package(union acpi_object *package,
 	/*
 	 * Validate output buffer.
 	 */
-	if (buffer->length < size_required) {
+	if (buffer->length == ACPI_ALLOCATE_BUFFER) {
+		buffer->pointer = ACPI_ALLOCATE(size_required);
+		if (!buffer->pointer)
+			return AE_NO_MEMORY;
 		buffer->length = size_required;
-		return AE_BUFFER_OVERFLOW;
-	} else if (buffer->length != size_required || !buffer->pointer) {
-		return AE_BAD_PARAMETER;
+		memset(buffer->pointer, 0, size_required);
+	} else {
+		if (buffer->length < size_required) {
+			buffer->length = size_required;
+			return AE_BUFFER_OVERFLOW;
+		} else if (buffer->length != size_required ||
+			   !buffer->pointer) {
+			return AE_BAD_PARAMETER;
+		}
 	}
 
 	head = buffer->pointer;