ACPICA: Clarify ACPI_FREE_BUFFER usage.

Add a comment to clarify reason for using ACPI_FREE_BUFFER directly
instead of ACPI_FREE.

In addition to that, change one instance in which ACPI_FREE_BUFFER()
should be used instead of ACPI_FREE().

[rjw: Subject and changelog]
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/acpica/nsxfeval.c

@@ -139,7 +139,7 @@ acpi_evaluate_object_typed(acpi_handle handle,
 
 		/* Caller used ACPI_ALLOCATE_BUFFER, free the return buffer */
 
-		ACPI_FREE(return_buffer->pointer);
+		ACPI_FREE_BUFFER(*return_buffer);
 		return_buffer->pointer = NULL;
 	}
 

include/acpi/actypes.h

@@ -919,9 +919,13 @@ struct acpi_buffer {
 	void *pointer;		/* pointer to buffer */
 };
 
-/* Free a buffer created in an struct acpi_buffer via ACPI_ALLOCATE_LOCAL_BUFFER */
-
-#define ACPI_FREE_BUFFER(b)         ACPI_FREE(b.pointer)
+/*
+ * Free a buffer created in an struct acpi_buffer via ACPI_ALLOCATE_BUFFER.
+ * Note: We use acpi_os_free here because acpi_os_allocate was used to allocate
+ * the buffer. This purposefully bypasses the internal allocation tracking
+ * mechanism (if it is enabled).
+ */
+#define ACPI_FREE_BUFFER(b)         acpi_os_free((b).pointer)
 
 /*
  * name_type for acpi_get_name