drm/i915/mtl: don't expose GSC command streamer to the user

There is no userspace user for this CS yet, we only need it for internal
kernel ops (e.g. HuC, PXP), so don't expose it.

v2: even if it's not exposed, rename the engine so it is easier to
identify in the debug logs (Matt)

Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221102171047.2787951-6-daniele.ceraolospurio@intel.com

drivers/gpu/drm/i915/gt/intel_engine_user.c

@@ -191,6 +191,15 @@ static void add_legacy_ring(struct legacy_ring *ring,
 		ring->instance++;
 }
 
+static void engine_rename(struct intel_engine_cs *engine, const char *name, u16 instance)
+{
+	char old[sizeof(engine->name)];
+
+	memcpy(old, engine->name, sizeof(engine->name));
+	scnprintf(engine->name, sizeof(engine->name), "%s%u", name, instance);
+	drm_dbg(&engine->i915->drm, "renamed %s to %s\n", old, engine->name);
+}
+
 void intel_engines_driver_register(struct drm_i915_private *i915)
 {
 	struct legacy_ring ring = {};
@@ -206,11 +215,19 @@ void intel_engines_driver_register(struct drm_i915_private *i915)
 		struct intel_engine_cs *engine =
 			container_of((struct rb_node *)it, typeof(*engine),
 				     uabi_node);
-		char old[sizeof(engine->name)];
 
 		if (intel_gt_has_unrecoverable_error(engine->gt))
 			continue; /* ignore incomplete engines */
 
+		/*
+		 * We don't want to expose the GSC engine to the users, but we
+		 * still rename it so it is easier to identify in the debug logs
+		 */
+		if (engine->id == GSC0) {
+			engine_rename(engine, "gsc", 0);
+			continue;
+		}
+
 		GEM_BUG_ON(engine->class >= ARRAY_SIZE(uabi_classes));
 		engine->uabi_class = uabi_classes[engine->class];
 
@@ -220,11 +237,9 @@ void intel_engines_driver_register(struct drm_i915_private *i915)
 			i915->engine_uabi_class_count[engine->uabi_class]++;
 
 		/* Replace the internal name with the final user facing name */
-		memcpy(old, engine->name, sizeof(engine->name));
-		scnprintf(engine->name, sizeof(engine->name), "%s%u",
-			  intel_engine_class_repr(engine->class),
-			  engine->uabi_instance);
-		DRM_DEBUG_DRIVER("renamed %s to %s\n", old, engine->name);
+		engine_rename(engine,
+			      intel_engine_class_repr(engine->class),
+			      engine->uabi_instance);
 
 		rb_link_node(&engine->uabi_node, prev, p);
 		rb_insert_color(&engine->uabi_node, &i915->uabi_engines);