intel_th: Support Host Debugger mode of operation

This patch adds a 'host_mode' module option to enable host-driven
operational mode in the driver. In this mode, the driver does not
perform trace configuration or enable trace capture, but still
provides all the means necessary for software trace sources to
write their data to the Trace Hub. This means that the debug host
takes care of all the configuration and enabling and we do not
interfere.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>

drivers/hwtracing/intel_th/intel_th.h

@@ -54,6 +54,7 @@ struct intel_th_output {
  * @num_resources:	number of resources in @resource array
  * @type:		INTEL_TH_{SOURCE,OUTPUT,SWITCH}
  * @id:			device instance or -1
+ * @host_mode:		Intel TH is controlled by an external debug host
  * @output:		output descriptor for INTEL_TH_OUTPUT devices
  * @name:		device name to match the driver
  */
@@ -64,6 +65,9 @@ struct intel_th_device {
 	unsigned int	type;
 	int		id;
 
+	/* INTEL_TH_SWITCH specific */
+	bool			host_mode;
+
 	/* INTEL_TH_OUTPUT specific */
 	struct intel_th_output	output;