mxm/wmi: add MXMX interface entry point.

The MXMX method appears to be a mutex of some sort.
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/nouveau/nouveau_acpi.c

@@ -150,6 +150,7 @@ static int nouveau_dsm(acpi_handle handle, int func, int arg, uint32_t *result)
 
 static int nouveau_dsm_switch_mux(acpi_handle handle, int mux_id)
 {
+	mxm_wmi_call_mxmx(mux_id == NOUVEAU_DSM_LED_STAMINA ? MXM_MXDS_ADAPTER_IGD : MXM_MXDS_ADAPTER_0);
 	mxm_wmi_call_mxds(mux_id == NOUVEAU_DSM_LED_STAMINA ? MXM_MXDS_ADAPTER_IGD : MXM_MXDS_ADAPTER_0);
 	return nouveau_dsm(handle, NOUVEAU_DSM_LED, mux_id, NULL);
 }

drivers/platform/x86/mxm-wmi.c

@@ -32,6 +32,7 @@ MODULE_LICENSE("GPL");
 MODULE_ALIAS("wmi:"MXM_WMMX_GUID);
 
 #define MXM_WMMX_FUNC_MXDS 0x5344584D /* "MXDS" */
+#define MXM_WMMX_FUNC_MXMX 0x53445344 /* "MXMX" */
 
 struct mxds_args {
 	u32 func;
@@ -64,6 +65,31 @@ int mxm_wmi_call_mxds(int adapter)
 }
 EXPORT_SYMBOL_GPL(mxm_wmi_call_mxds);
 
+int mxm_wmi_call_mxmx(int adapter)
+{
+	struct mxds_args args = {
+		.func = MXM_WMMX_FUNC_MXMX,
+		.args = 0,
+		.xarg = 1,
+	};
+	struct acpi_buffer input = { (acpi_size)sizeof(args), &args };
+	struct acpi_buffer output = { ACPI_ALLOCATE_BUFFER, NULL };
+	acpi_status status;
+
+	printk("calling mux switch %d\n", adapter);
+
+	status = wmi_evaluate_method(MXM_WMMX_GUID, 0x1, adapter, &input,
+				     &output);
+
+	if (ACPI_FAILURE(status))
+		return status;
+
+	printk("mux mutex set switched %d\n", status);
+	return 0;
+			    
+}
+EXPORT_SYMBOL_GPL(mxm_wmi_call_mxmx);
+
 bool mxm_wmi_supported(void)
 {
 	bool guid_valid;

include/linux/mxm-wmi.h

@@ -27,6 +27,7 @@
 /* integrated adapter */
 #define MXM_MXDS_ADAPTER_IGD 0x10
 int mxm_wmi_call_mxds(int adapter);
+int mxm_wmi_call_mxmx(int adapter);
 bool mxm_wmi_supported(void);
 
 #endif