fuzzing_engine: Add fuzzing engine uclass

This new class of device will provide fuzzing inputs from a fuzzing
engine.

Signed-off-by: Andrew Scull <ascull@google.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

drivers/fuzz/Kconfig

@@ -0,0 +1,9 @@
+config DM_FUZZING_ENGINE
+	bool "Driver support for fuzzing engine devices"
+	depends on DM
+	help
+	  Enable driver model for fuzzing engine devices. This interface is
+	  used to get successive inputs from a fuzzing engine that aims to
+	  explore different code paths in a fuzz test. The fuzzing engine may
+	  be instrumenting the execution in order to more effectively generate
+	  inputs that explore different code paths.

drivers/fuzz/Makefile

@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Copyright (c) 2022 Google, Inc.
+# Written by Andrew Scull <ascull@google.com>
+#
+
+obj-$(CONFIG_DM_FUZZING_ENGINE) += fuzzing_engine-uclass.o

drivers/fuzz/fuzzing_engine-uclass.c

@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright (c) 2022 Google, Inc.
+ * Written by Andrew Scull <ascull@google.com>
+ */
+
+#define LOG_CATEGORY UCLASS_FUZZING_ENGINE
+
+#include <common.h>
+#include <dm.h>
+#include <fuzzing_engine.h>
+
+int dm_fuzzing_engine_get_input(struct udevice *dev,
+				const uint8_t **data,
+				size_t *size)
+{
+	const struct dm_fuzzing_engine_ops *ops = device_get_ops(dev);
+
+	if (!ops->get_input)
+		return -ENOSYS;
+
+	return ops->get_input(dev, data, size);
+}
+
+UCLASS_DRIVER(fuzzing_engine) = {
+	.name = "fuzzing_engine",
+	.id = UCLASS_FUZZING_ENGINE,
+};