drm/i915/gsc: Mark internal GSC engine with reserved uabi class

The GSC CS is not exposed to the user, so we skipped assigning a uabi
class number for it. However, the trace logs use the uabi class and
instance to identify the engine, so leaving uabi class unset makes the
GSC CS show up as the RCS in those logs.

Given that the engine is not exposed to the user, we can't add a new
case in the uabi enum, so we insted internally define a kernel
internal class as -1.

At the same time remove special handling for the name and complete
the uabi_classes array so internal class is automatically correctly
assigned.

Engine will show as 65535:0 other0 in the logs/traces which should
be unique enough.

v2:
 * Fix uabi class u8 vs u16 type confusion.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Fixes: 194babe2 ("drm/i915/mtl: don't expose GSC command streamer to the user")
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Alan Previn <alan.previn.teres.alexis@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231116084456.291533-1-tvrtko.ursulin@linux.intel.com

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

@@ -41,12 +41,15 @@ void intel_engine_add_user(struct intel_engine_cs *engine)
 	llist_add(&engine->uabi_llist, &engine->i915->uabi_engines_llist);
 }
 
-static const u8 uabi_classes[] = {
+#define I915_NO_UABI_CLASS ((u16)(-1))
+
+static const u16 uabi_classes[] = {
 	[RENDER_CLASS] = I915_ENGINE_CLASS_RENDER,
 	[COPY_ENGINE_CLASS] = I915_ENGINE_CLASS_COPY,
 	[VIDEO_DECODE_CLASS] = I915_ENGINE_CLASS_VIDEO,
 	[VIDEO_ENHANCEMENT_CLASS] = I915_ENGINE_CLASS_VIDEO_ENHANCE,
 	[COMPUTE_CLASS] = I915_ENGINE_CLASS_COMPUTE,
+	[OTHER_CLASS] = I915_NO_UABI_CLASS, /* Not exposed to users, no uabi class. */
 };
 
 static int engine_cmp(void *priv, const struct list_head *A,
@@ -200,6 +203,7 @@ static void engine_rename(struct intel_engine_cs *engine, const char *name, u16
 
 void intel_engines_driver_register(struct drm_i915_private *i915)
 {
+	u16 name_instance, other_instance = 0;
 	struct legacy_ring ring = {};
 	struct list_head *it, *next;
 	struct rb_node **p, *prev;
@@ -216,27 +220,28 @@ void intel_engines_driver_register(struct drm_i915_private *i915)
 		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];
-
+		if (engine->uabi_class == I915_NO_UABI_CLASS) {
+			name_instance = other_instance++;
+		} else {
 			GEM_BUG_ON(engine->uabi_class >=
 				   ARRAY_SIZE(i915->engine_uabi_class_count));
-		engine->uabi_instance =
+			name_instance =
 				i915->engine_uabi_class_count[engine->uabi_class]++;
+		}
+		engine->uabi_instance = name_instance;
 
-		/* Replace the internal name with the final user facing name */
+		/*
+		 * Replace the internal name with the final user and log facing
+		 * name.
+		 */
 		engine_rename(engine,
 			      intel_engine_class_repr(engine->class),
-			      engine->uabi_instance);
+			      name_instance);
+
+		if (engine->uabi_class == I915_NO_UABI_CLASS)
+			continue;
 
 		rb_link_node(&engine->uabi_node, prev, p);
 		rb_insert_color(&engine->uabi_node, &i915->uabi_engines);