drm/i915: Define an engine class enum for the uABI

We want to be able to report back to userspace details about an engine's
class, and in return for userspace to be able to request actions
regarding certain classes of engines. To isolate the uABI from any
variations between hw generations, we define an abstract class for the
engines and internally map onto the hw.

v2: Remove MAX from the uABI; keep it internal if we need it, but don't
let userspace make the mistake of using it themselves.
v3: s/OTHER/INVALID/
  The use of OTHER is ill-defined, so remove it from the uABI as any
  future new type of engine can define a class to suit it. But keep a
  reserved value for an invalid class, so that we can always
  unambiguously express when something doesn't belong to the
  classification.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> #v2
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171110142634.10551-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/intel_engine_cs.c

@@ -50,6 +50,8 @@ struct engine_class_info {
 	const char *name;
 	int (*init_legacy)(struct intel_engine_cs *engine);
 	int (*init_execlists)(struct intel_engine_cs *engine);
+
+	u8 uabi_class;
 };
 
 static const struct engine_class_info intel_engine_classes[] = {
@@ -57,21 +59,25 @@ static const struct engine_class_info intel_engine_classes[] = {
 		.name = "rcs",
 		.init_execlists = logical_render_ring_init,
 		.init_legacy = intel_init_render_ring_buffer,
+		.uabi_class = I915_ENGINE_CLASS_RENDER,
 	},
 	[COPY_ENGINE_CLASS] = {
 		.name = "bcs",
 		.init_execlists = logical_xcs_ring_init,
 		.init_legacy = intel_init_blt_ring_buffer,
+		.uabi_class = I915_ENGINE_CLASS_COPY,
 	},
 	[VIDEO_DECODE_CLASS] = {
 		.name = "vcs",
 		.init_execlists = logical_xcs_ring_init,
 		.init_legacy = intel_init_bsd_ring_buffer,
+		.uabi_class = I915_ENGINE_CLASS_VIDEO,
 	},
 	[VIDEO_ENHANCEMENT_CLASS] = {
 		.name = "vecs",
 		.init_execlists = logical_xcs_ring_init,
 		.init_legacy = intel_init_vebox_ring_buffer,
+		.uabi_class = I915_ENGINE_CLASS_VIDEO_ENHANCE,
 	},
 };
 
@@ -213,13 +219,15 @@ intel_engine_setup(struct drm_i915_private *dev_priv,
 	WARN_ON(snprintf(engine->name, sizeof(engine->name), "%s%u",
 			 class_info->name, info->instance) >=
 		sizeof(engine->name));
-	engine->uabi_id = info->uabi_id;
 	engine->hw_id = engine->guc_id = info->hw_id;
 	engine->mmio_base = info->mmio_base;
 	engine->irq_shift = info->irq_shift;
 	engine->class = info->class;
 	engine->instance = info->instance;
 
+	engine->uabi_id = info->uabi_id;
+	engine->uabi_class = class_info->uabi_class;
+
 	engine->context_size = __intel_engine_context_size(dev_priv,
 							   engine->class);
 	if (WARN_ON(engine->context_size > BIT(20)))

drivers/gpu/drm/i915/intel_ringbuffer.h

@@ -289,11 +289,14 @@ struct intel_engine_execlists {
 struct intel_engine_cs {
 	struct drm_i915_private *i915;
 	char name[INTEL_ENGINE_CS_MAX_NAME];
+
 	enum intel_engine_id id;
-	unsigned int uabi_id;
 	unsigned int hw_id;
 	unsigned int guc_id;
 
+	u8 uabi_id;
+	u8 uabi_class;
+
 	u8 class;
 	u8 instance;
 	u32 context_size;

include/uapi/drm/i915_drm.h

@@ -86,6 +86,22 @@ enum i915_mocs_table_index {
 	I915_MOCS_CACHED,
 };
 
+/*
+ * Different engines serve different roles, and there may be more than one
+ * engine serving each role. enum drm_i915_gem_engine_class provides a
+ * classification of the role of the engine, which may be used when requesting
+ * operations to be performed on a certain subset of engines, or for providing
+ * information about that group.
+ */
+enum drm_i915_gem_engine_class {
+	I915_ENGINE_CLASS_RENDER	= 0,
+	I915_ENGINE_CLASS_COPY		= 1,
+	I915_ENGINE_CLASS_VIDEO		= 2,
+	I915_ENGINE_CLASS_VIDEO_ENHANCE	= 3,
+
+	I915_ENGINE_CLASS_INVALID	= -1
+};
+
 /* Each region is a minimum of 16k, and there are at most 255 of them.
  */
 #define I915_NR_TEX_REGIONS 255	/* table size 2k - maximum due to use