4 files changed, 30 insertions, 0 deletions

diff --git a/drivers/acpi/acpica/acglobal.h b/drivers/acpi/acpica/acglobal.h
index 9070f1fe8f17..899d68afc3c5 100644
--- a/drivers/acpi/acpica/acglobal.h
+++ b/drivers/acpi/acpica/acglobal.h
@@ -125,6 +125,14 @@ u8 ACPI_INIT_GLOBAL(acpi_gbl_enable_aml_debug_object, FALSE);
  */
 u8 ACPI_INIT_GLOBAL(acpi_gbl_copy_dsdt_locally, FALSE);
 
+/*
+ * Optionally truncate I/O addresses to 16 bits. Provides compatibility
+ * with other ACPI implementations. NOTE: During ACPICA initialization,
+ * this value is set to TRUE if any Windows OSI strings have been
+ * requested by the BIOS.
+ */
+u8 ACPI_INIT_GLOBAL(acpi_gbl_truncate_io_addresses, FALSE);
+
 /* acpi_gbl_FADT is a local copy of the FADT, converted to a common format. */
 
 struct acpi_table_fadt acpi_gbl_FADT;
diff --git a/drivers/acpi/acpica/hwvalid.c b/drivers/acpi/acpica/hwvalid.c
index c10d587c1641..e1d9c777b213 100644
--- a/drivers/acpi/acpica/hwvalid.c
+++ b/drivers/acpi/acpica/hwvalid.c
@@ -222,6 +222,12 @@ acpi_status acpi_hw_read_port(acpi_io_address address, u32 *value, u32 width)
         u32 one_byte;
         u32 i;
 
+        /* Truncate address to 16 bits if requested */
+
+        if (acpi_gbl_truncate_io_addresses) {
+                address &= ACPI_UINT16_MAX;
+        }
+
         /* Validate the entire request and perform the I/O */
 
         status = acpi_hw_validate_io_request(address, width);
@@ -279,6 +285,12 @@ acpi_status acpi_hw_write_port(acpi_io_address address, u32 value, u32 width)
         acpi_status status;
         u32 i;
 
+        /* Truncate address to 16 bits if requested */
+
+        if (acpi_gbl_truncate_io_addresses) {
+                address &= ACPI_UINT16_MAX;
+        }
+
         /* Validate the entire request and perform the I/O */
 
         status = acpi_hw_validate_io_request(address, width);
diff --git a/drivers/acpi/acpica/nsinit.c b/drivers/acpi/acpica/nsinit.c
index 9bd6f050f299..4e5272c313e0 100644
--- a/drivers/acpi/acpica/nsinit.c
+++ b/drivers/acpi/acpica/nsinit.c
@@ -193,6 +193,15 @@ acpi_status acpi_ns_initialize_devices(void)
                                         acpi_ns_init_one_device, NULL, &info,
                                         NULL);
 
+        /*
+         * Any _OSI requests should be completed by now. If the BIOS has
+         * requested any Windows OSI strings, we will always truncate
+         * I/O addresses to 16 bits -- for Windows compatibility.
+         */
+        if (acpi_gbl_osi_data >= ACPI_OSI_WIN_2000) {
+                acpi_gbl_truncate_io_addresses = TRUE;
+        }
+
         ACPI_FREE(info.evaluate_info);
         if (ACPI_FAILURE(status)) {
                 goto error_exit;
diff --git a/include/acpi/acpixf.h b/include/acpi/acpixf.h
index 0e4ab1fe5966..1371cc997393 100644
--- a/include/acpi/acpixf.h
+++ b/include/acpi/acpixf.h
@@ -69,6 +69,7 @@ extern acpi_name acpi_gbl_trace_method_name;
 extern u32 acpi_gbl_trace_flags;
 extern u8 acpi_gbl_enable_aml_debug_object;
 extern u8 acpi_gbl_copy_dsdt_locally;
+extern u8 acpi_gbl_truncate_io_addresses;
 
 extern u32 acpi_current_gpe_count;
 extern struct acpi_table_fadt acpi_gbl_FADT;