test: emul: Verify backend API operation

Verify backend API is functional with the emulator subsystem.

Signed-off-by: Keith Short <[email protected]>

Author: keith-zephyr

dts/bindings/test/vnd,emul-tester.yaml

@@ -0,0 +1,15 @@
+# Copyright (c) 2023, Google, LLC
+# SPDX-License-Identifier: Apache-2.0
+
+description: VND Emul tester
+
+compatible: "vnd,emul-tester"
+
+include: base.yaml
+
+properties:
+  scale:
+    type: int
+    required: true
+    description: |
+      Integer scale applied to the set action for testing.

tests/subsys/emul/CMakeLists.txt

@@ -8,3 +8,4 @@ find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
 project(emul)
 
 target_sources(app PRIVATE src/main.c)
+target_sources(app PRIVATE src/emul_tester.c)

tests/subsys/emul/app.overlay

@@ -16,4 +16,17 @@
 		reg = <0x68>;
 		status = "okay";
 	};
+
+	emul_tester_a: driver@aa {
+		compatible = "vnd,emul-tester";
+                reg = <0xaa>;
+		status = "okay";
+		scale = <1>;
+	};
+	emul_tester_b: driver@bb {
+		compatible = "vnd,emul-tester";
+                reg = <0xbb>;
+		status = "okay";
+		scale = <10>;
+	};
 };

tests/subsys/emul/src/emul_tester.c

@@ -0,0 +1,82 @@
+/*
+ * Copyright 2023 Google LLC
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include "emul_tester.h"
+
+#include <zephyr/device.h>
+#include <zephyr/drivers/emul.h>
+#include <zephyr/drivers/emul_stub_device.h>
+#include <zephyr/drivers/i2c.h>
+#include <zephyr/drivers/i2c_emul.h>
+
+#define DT_DRV_COMPAT vnd_emul_tester
+
+struct emul_tester_cfg {
+	int scale;
+};
+
+struct emul_tester_data {
+	int action;
+};
+
+static int emul_tester_set_action(const struct emul *target, int action)
+{
+	const struct emul_tester_cfg *cfg = target->cfg;
+	struct emul_tester_data *data = target->data;
+
+	data->action = action * cfg->scale;
+
+	return 0;
+}
+
+static int emul_tester_get_action(const struct emul *target, int *action)
+{
+	struct emul_tester_data *data = target->data;
+
+	*action = data->action;
+
+	return 0;
+}
+
+static int emul_tester_transfer(const struct emul *target, struct i2c_msg *msgs, int num_msgs,
+				int addr)
+{
+	ARG_UNUSED(target);
+	ARG_UNUSED(msgs);
+	ARG_UNUSED(num_msgs);
+	ARG_UNUSED(addr);
+
+	return -ENOTSUP;
+}
+
+static struct i2c_emul_api bus_api = {
+	.transfer = emul_tester_transfer,
+};
+
+static const struct emul_tester_backend_api emul_tester_backend_api = {
+	.set_action = emul_tester_set_action,
+	.get_action = emul_tester_get_action,
+};
+
+static int emul_tester_init(const struct emul *target, const struct device *parent)
+{
+	ARG_UNUSED(target);
+	ARG_UNUSED(parent);
+
+	return 0;
+}
+
+#define EMUL_TESTER(n)                                                                             \
+	static struct emul_tester_data emul_tester_data_##n;                                       \
+	static const struct emul_tester_cfg emul_tester_cfg_##n = {                                \
+		.scale = DT_INST_PROP(n, scale),                                                   \
+	};                                                                                         \
+	EMUL_DT_INST_DEFINE(n, emul_tester_init, &emul_tester_data_##n, &emul_tester_cfg_##n,      \
+			    &bus_api, &emul_tester_backend_api);
+
+DT_INST_FOREACH_STATUS_OKAY(EMUL_TESTER)
+
+DT_INST_FOREACH_STATUS_OKAY(EMUL_STUB_DEVICE)

tests/subsys/emul/src/emul_tester.h

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2023 Google LLC
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef TEST_SUBSYS_EMUL_SRC_EMUL_TESTER_H_
+#define TEST_SUBSYS_EMUL_SRC_EMUL_TESTER_H_
+
+#include <zephyr/drivers/emul.h>
+
+struct emul_tester_backend_api {
+	int (*set_action)(const struct emul *target, int action);
+	int (*get_action)(const struct emul *target, int *action);
+};
+
+static inline int emul_tester_backend_set_action(const struct emul *target, int action)
+{
+	const struct emul_tester_backend_api *api =
+		(const struct emul_tester_backend_api *)target->backend_api;
+
+	return api->set_action(target, action);
+}
+
+static inline int emul_tester_backend_get_action(const struct emul *target, int *action)
+{
+	const struct emul_tester_backend_api *api =
+		(const struct emul_tester_backend_api *)target->backend_api;
+
+	return api->get_action(target, action);
+}
+
+#endif /* TEST_SUBSYS_EMUL_SRC_EMUL_TESTER_H_ */

tests/subsys/emul/src/main.c

@@ -4,6 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
+#include "emul_tester.h"
+
 #include <zephyr/device.h>
 #include <zephyr/devicetree.h>
 #include <zephyr/drivers/emul.h>
@@ -13,6 +15,9 @@
 
 #define TEST_ACCEL DT_NODELABEL(test_bmi)
 
+#define TEST_EMUL_A DT_NODELABEL(emul_tester_a)
+#define TEST_EMUL_B DT_NODELABEL(emul_tester_b)
+
 ZTEST(emul, test_emul_dt_get)
 {
 	/* This variable is static to verify that the result of EMUL_DT_GET is a
@@ -26,4 +31,27 @@ ZTEST(emul, test_emul_dt_get)
 		   "Unexpected device name %s", emul_static->dev->name);
 }
 
+ZTEST(emul, test_emul_backend_api)
+{
+	static const struct emul *emul_a = EMUL_DT_GET(TEST_EMUL_A);
+	static const struct emul *emul_b = EMUL_DT_GET(TEST_EMUL_B);
+	int set_action_value;
+	int scale;
+	int get_action_value;
+
+	set_action_value = 5;
+
+	scale = DT_PROP(TEST_EMUL_A, scale);
+	zassert_not_null(emul_a, "emul_tester_a not found");
+	zassert_ok(emul_tester_backend_set_action(emul_a, set_action_value));
+	zassert_ok(emul_tester_backend_get_action(emul_a, &get_action_value));
+	zassert_equal(get_action_value, set_action_value * scale);
+
+	scale = DT_PROP(TEST_EMUL_B, scale);
+	zassert_not_null(emul_b, "emul_tester_b not found");
+	zassert_ok(emul_tester_backend_set_action(emul_b, set_action_value));
+	zassert_ok(emul_tester_backend_get_action(emul_b, &get_action_value));
+	zassert_equal(get_action_value, set_action_value * scale);
+}
+
 ZTEST_SUITE(emul, NULL, NULL, NULL, NULL, NULL);