firmware: dcdbas: Add support for WSMT ACPI table

If the WSMT ACPI table is present and indicates that a fixed communication
buffer should be used, use the firmware-specified buffer instead of
allocating a buffer in memory for communications between the dcdbas driver
and firmare.

Signed-off-by: Stuart Hayes <stuart.w.hayes@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
diff --git a/drivers/firmware/dcdbas.h b/drivers/firmware/dcdbas.h
index ca3cb0a..52729a4 100644
--- a/drivers/firmware/dcdbas.h
+++ b/drivers/firmware/dcdbas.h
@@ -53,6 +53,7 @@
 #define EXPIRED_TIMER				(0)
 
 #define SMI_CMD_MAGIC				(0x534D4931)
+#define SMM_EPS_SIG				"$SCB"
 
 #define DCDBAS_DEV_ATTR_RW(_name) \
 	DEVICE_ATTR(_name,0600,_name##_show,_name##_store);
@@ -103,5 +104,14 @@ struct apm_cmd {
 
 int dcdbas_smi_request(struct smi_cmd *smi_cmd);
 
+struct smm_eps_table {
+	char smm_comm_buff_anchor[4];
+	u8 length;
+	u8 checksum;
+	u8 version;
+	u64 smm_comm_buff_addr;
+	u64 num_of_4k_pages;
+} __packed;
+
 #endif /* _DCDBAS_H_ */