drm/xe/uapi: Align on a common way to return arrays (engines)

The uAPI provides queries which return arrays of elements. As of now
the format used in the struct is different depending on which element
is queried. Fix this for engines by applying the pattern below:

        struct drm_xe_query_Xs {
           __u32 num_Xs;
           struct drm_xe_X Xs[];
           ...
        }

Instead of directly returning an array of struct
drm_xe_query_engine_info, a new struct drm_xe_query_engines is
introduced. It contains itself an array of struct drm_xe_engine
which holds the information about each engine.

v2: Use plural for struct drm_xe_query_engines as multiple engines
    are returned (José Roberto de Souza)
Signed-off-by: Francois Dugast <francois.dugast@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/xe/xe_query.c

@@ -53,7 +53,8 @@ static size_t calc_hw_engine_info_size(struct xe_device *xe)
 			i++;
 		}
 
-	return i * sizeof(struct drm_xe_query_engine_info);
+	return sizeof(struct drm_xe_query_engines) +
+		i * sizeof(struct drm_xe_engine);
 }
 
 typedef u64 (*__ktime_func_t)(void);
@@ -186,9 +187,9 @@ static int query_engines(struct xe_device *xe,
 			 struct drm_xe_device_query *query)
 {
 	size_t size = calc_hw_engine_info_size(xe);
-	struct drm_xe_query_engine_info __user *query_ptr =
+	struct drm_xe_query_engines __user *query_ptr =
 		u64_to_user_ptr(query->data);
-	struct drm_xe_query_engine_info *hw_engine_info;
+	struct drm_xe_query_engines *engines;
 	struct xe_hw_engine *hwe;
 	enum xe_hw_engine_id id;
 	struct xe_gt *gt;
@@ -202,8 +203,8 @@ static int query_engines(struct xe_device *xe,
 		return -EINVAL;
 	}
 
-	hw_engine_info = kmalloc(size, GFP_KERNEL);
-	if (!hw_engine_info)
+	engines = kmalloc(size, GFP_KERNEL);
+	if (!engines)
 		return -ENOMEM;
 
 	for_each_gt(gt, xe, gt_id)
@@ -211,22 +212,26 @@ static int query_engines(struct xe_device *xe,
 			if (xe_hw_engine_is_reserved(hwe))
 				continue;
 
-			hw_engine_info[i].instance.engine_class =
+			engines->engines[i].instance.engine_class =
 				xe_to_user_engine_class[hwe->class];
-			hw_engine_info[i].instance.engine_instance =
+			engines->engines[i].instance.engine_instance =
 				hwe->logical_instance;
-			hw_engine_info[i].instance.gt_id = gt->info.id;
-			hw_engine_info[i].instance.pad = 0;
-			memset(hw_engine_info->reserved, 0, sizeof(hw_engine_info->reserved));
+			engines->engines[i].instance.gt_id = gt->info.id;
+			engines->engines[i].instance.pad = 0;
+			memset(engines->engines[i].reserved, 0,
+			       sizeof(engines->engines[i].reserved));
 
 			i++;
 		}
 
-	if (copy_to_user(query_ptr, hw_engine_info, size)) {
-		kfree(hw_engine_info);
+	engines->pad = 0;
+	engines->num_engines = i;
+
+	if (copy_to_user(query_ptr, engines, size)) {
+		kfree(engines);
 		return -EFAULT;
 	}
-	kfree(hw_engine_info);
+	kfree(engines);
 
 	return 0;
 }

include/uapi/drm/xe_drm.h

@@ -127,9 +127,9 @@ struct xe_user_extension {
 /**
  * struct drm_xe_engine_class_instance - instance of an engine class
  *
- * It is returned as part of the @drm_xe_query_engine_info, but it also is
- * used as the input of engine selection for both @drm_xe_exec_queue_create
- * and @drm_xe_query_engine_cycles
+ * It is returned as part of the @drm_xe_engine, but it also is used as
+ * the input of engine selection for both @drm_xe_exec_queue_create and
+ * @drm_xe_query_engine_cycles
  */
 struct drm_xe_engine_class_instance {
 #define DRM_XE_ENGINE_CLASS_RENDER		0
@@ -154,13 +154,9 @@ struct drm_xe_engine_class_instance {
 };
 
 /**
- * struct drm_xe_query_engine_info - describe hardware engine
- *
- * If a query is made with a struct @drm_xe_device_query where .query
- * is equal to %DRM_XE_DEVICE_QUERY_ENGINES, then the reply uses an array of
- * struct @drm_xe_query_engine_info in .data.
+ * struct drm_xe_engine - describe hardware engine
  */
-struct drm_xe_query_engine_info {
+struct drm_xe_engine {
 	/** @instance: The @drm_xe_engine_class_instance */
 	struct drm_xe_engine_class_instance instance;
 
@@ -168,6 +164,22 @@ struct drm_xe_query_engine_info {
 	__u64 reserved[3];
 };
 
+/**
+ * struct drm_xe_query_engines - describe engines
+ *
+ * If a query is made with a struct @drm_xe_device_query where .query
+ * is equal to %DRM_XE_DEVICE_QUERY_ENGINES, then the reply uses an array of
+ * struct @drm_xe_query_engines in .data.
+ */
+struct drm_xe_query_engines {
+	/** @num_engines: number of engines returned in @engines */
+	__u32 num_engines;
+	/** @pad: MBZ */
+	__u32 pad;
+	/** @engines: The returned engines for this device */
+	struct drm_xe_engine engines[];
+};
+
 /**
  * enum drm_xe_memory_class - Supported memory classes.
  */
@@ -467,28 +479,32 @@ struct drm_xe_query_topology_mask {
  *
  * .. code-block:: C
  *
- *	struct drm_xe_engine_class_instance *hwe;
- *	struct drm_xe_device_query query = {
- *		.extensions = 0,
- *		.query = DRM_XE_DEVICE_QUERY_ENGINES,
- *		.size = 0,
- *		.data = 0,
- *	};
- *	ioctl(fd, DRM_IOCTL_XE_DEVICE_QUERY, &query);
- *	hwe = malloc(query.size);
- *	query.data = (uintptr_t)hwe;
- *	ioctl(fd, DRM_IOCTL_XE_DEVICE_QUERY, &query);
- *	int num_engines = query.size / sizeof(*hwe);
- *	for (int i = 0; i < num_engines; i++) {
- *		printf("Engine %d: %s\n", i,
- *			hwe[i].engine_class == DRM_XE_ENGINE_CLASS_RENDER ? "RENDER":
- *			hwe[i].engine_class == DRM_XE_ENGINE_CLASS_COPY ? "COPY":
- *			hwe[i].engine_class == DRM_XE_ENGINE_CLASS_VIDEO_DECODE ? "VIDEO_DECODE":
- *			hwe[i].engine_class == DRM_XE_ENGINE_CLASS_VIDEO_ENHANCE ? "VIDEO_ENHANCE":
- *			hwe[i].engine_class == DRM_XE_ENGINE_CLASS_COMPUTE ? "COMPUTE":
- *			"UNKNOWN");
- *	}
- *	free(hwe);
+ *     struct drm_xe_query_engines *engines;
+ *     struct drm_xe_device_query query = {
+ *         .extensions = 0,
+ *         .query = DRM_XE_DEVICE_QUERY_ENGINES,
+ *         .size = 0,
+ *         .data = 0,
+ *     };
+ *     ioctl(fd, DRM_IOCTL_XE_DEVICE_QUERY, &query);
+ *     engines = malloc(query.size);
+ *     query.data = (uintptr_t)engines;
+ *     ioctl(fd, DRM_IOCTL_XE_DEVICE_QUERY, &query);
+ *     for (int i = 0; i < engines->num_engines; i++) {
+ *         printf("Engine %d: %s\n", i,
+ *             engines->engines[i].instance.engine_class ==
+ *                 DRM_XE_ENGINE_CLASS_RENDER ? "RENDER":
+ *             engines->engines[i].instance.engine_class ==
+ *                 DRM_XE_ENGINE_CLASS_COPY ? "COPY":
+ *             engines->engines[i].instance.engine_class ==
+ *                 DRM_XE_ENGINE_CLASS_VIDEO_DECODE ? "VIDEO_DECODE":
+ *             engines->engines[i].instance.engine_class ==
+ *                 DRM_XE_ENGINE_CLASS_VIDEO_ENHANCE ? "VIDEO_ENHANCE":
+ *             engines->engines[i].instance.engine_class ==
+ *                 DRM_XE_ENGINE_CLASS_COMPUTE ? "COMPUTE":
+ *             "UNKNOWN");
+ *     }
+ *     free(engines);
  */
 struct drm_xe_device_query {
 	/** @extensions: Pointer to the first extension struct, if any */