drm/i915: Introduce struct class_instance for engines across the uAPI

SSEU reprogramming of the context introduced the notion of engine class
and instance for a forwards compatible method of describing any engine
beyond the old execbuf interface. We wish to adopt this class:instance
description for more interfaces, so pull it out into a separate type for
userspace convenience.

Fixes: e46c2e99 ("drm/i915: Expose RPCS (SSEU) configuration to userspace (Gen11 only)")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Dmitry Rogozhkin <dmitry.v.rogozhkin@intel.com>
Cc: Tony Ye <tony.ye@intel.com>
Cc: Andi Shyti <andi@etezian.org>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Acked-by: Tony Ye <tony.ye@intel.com>
Reviewed-by: Andi Shyti <andi@etezian.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190412071416.30097-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem_context.c

@@ -1386,8 +1386,8 @@ static int set_sseu(struct i915_gem_context *ctx,
 		return -EINVAL;
 
 	engine = intel_engine_lookup_user(i915,
-					  user_sseu.engine_class,
-					  user_sseu.engine_instance);
+					  user_sseu.engine.engine_class,
+					  user_sseu.engine.engine_instance);
 	if (!engine)
 		return -EINVAL;
 
@@ -1626,8 +1626,8 @@ static int get_sseu(struct i915_gem_context *ctx,
 		return -EINVAL;
 
 	engine = intel_engine_lookup_user(ctx->i915,
-					  user_sseu.engine_class,
-					  user_sseu.engine_instance);
+					  user_sseu.engine.engine_class,
+					  user_sseu.engine.engine_instance);
 	if (!engine)
 		return -EINVAL;
 

include/uapi/drm/i915_drm.h

@@ -126,6 +126,18 @@ enum drm_i915_gem_engine_class {
 	I915_ENGINE_CLASS_INVALID	= -1
 };
 
+/*
+ * There may be more than one engine fulfilling any role within the system.
+ * Each engine of a class is given a unique instance number and therefore
+ * any engine can be specified by its class:instance tuplet. APIs that allow
+ * access to any engine in the system will use struct i915_engine_class_instance
+ * for this identification.
+ */
+struct i915_engine_class_instance {
+	__u16 engine_class; /* see enum drm_i915_gem_engine_class */
+	__u16 engine_instance;
+};
+
 /**
  * DOC: perf_events exposed by i915 through /sys/bus/event_sources/drivers/i915
  *
@@ -1525,8 +1537,7 @@ struct drm_i915_gem_context_param_sseu {
 	/*
 	 * Engine class & instance to be configured or queried.
 	 */
-	__u16 engine_class;
-	__u16 engine_instance;
+	struct i915_engine_class_instance engine;
 
 	/*
 	 * Unused for now. Must be cleared to zero.