[RFC PATCH v4 2/4] fpga: add fake FPGA bridge

[Marco Pagani]

Add fake FPGA bridge driver with support functions. The driver includes
a counter for the number of switching cycles. This module is part of
the KUnit tests for the FPGA subsystem.

Signed-off-by: Marco Pagani <marpagan@xxxxxxxxxx>
---
 drivers/fpga/tests/fake-fpga-bridge.c | 242 ++++++++++++++++++++++++++
 drivers/fpga/tests/fake-fpga-bridge.h |  36 ++++
 2 files changed, 278 insertions(+)
 create mode 100644 drivers/fpga/tests/fake-fpga-bridge.c
 create mode 100644 drivers/fpga/tests/fake-fpga-bridge.h

diff --git a/drivers/fpga/tests/fake-fpga-bridge.c b/drivers/fpga/tests/fake-fpga-bridge.c
new file mode 100644
index 000000000000..6a62c04a75c0
--- /dev/null
+++ b/drivers/fpga/tests/fake-fpga-bridge.c
@@ -0,0 +1,242 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for the fake FPGA bridge
+ *
+ * Copyright (C) 2023 Red Hat, Inc.
+ *
+ * Author: Marco Pagani <marpagan@xxxxxxxxxx>
+ */
+
+#include <linux/types.h>
+#include <linux/device.h>
+#include <linux/platform_device.h>
+#include <linux/fpga/fpga-bridge.h>
+#include <kunit/test.h>
+
+#include "fake-fpga-bridge.h"
+
+#define FAKE_FPGA_BRIDGE_DEV_NAME	"fake_fpga_bridge"
+
+struct fake_bridge_priv {
+	int id;
+	bool enable;
+	int cycles_count;
+	struct kunit *test;
+};
+
+struct fake_bridge_data {
+	struct kunit *test;
+};
+
+static int op_enable_show(struct fpga_bridge *bridge)
+{
+	struct fake_bridge_priv *priv;
+
+	priv = bridge->priv;
+
+	if (priv->test)
+		kunit_info(priv->test, "Fake FPGA bridge %d: enable_show\n",
+			   priv->id);
+
+	return priv->enable;
+}
+
+static int op_enable_set(struct fpga_bridge *bridge, bool enable)
+{
+	struct fake_bridge_priv *priv;
+
+	priv = bridge->priv;
+
+	if (enable && !priv->enable)
+		priv->cycles_count++;
+
+	priv->enable = enable;
+
+	if (priv->test)
+		kunit_info(priv->test, "Fake FPGA bridge %d: enable_set: %d\n",
+			   priv->id, enable);
+
+	return 0;
+}
+
+static void op_remove(struct fpga_bridge *bridge)
+{
+	struct fake_bridge_priv *priv;
+
+	priv = bridge->priv;
+
+	if (priv->test)
+		kunit_info(priv->test, "Fake FPGA bridge: remove\n");
+}
+
+static const struct fpga_bridge_ops fake_fpga_bridge_ops = {
+	.enable_show = op_enable_show,
+	.enable_set = op_enable_set,
+	.fpga_bridge_remove = op_remove,
+};
+
+/**
+ * fake_fpga_bridge_register() - register a fake FPGA bridge.
+ * @parent: parent device.
+ * @test: KUnit test context object.
+ *
+ * Return: pointer to a new fake FPGA bridge on success, an ERR_PTR()
+ * encoded error code on failure.
+ */
+struct fake_fpga_bridge *
+fake_fpga_bridge_register(struct device *parent, struct kunit *test)
+{
+	struct fake_fpga_bridge *bridge_ctx;
+	struct fake_bridge_data pdata;
+	struct fake_bridge_priv *priv;
+	int ret;
+
+	bridge_ctx = kzalloc(sizeof(*bridge_ctx), GFP_KERNEL);
+	if (!bridge_ctx) {
+		ret = -ENOMEM;
+		goto err_mem;
+	}
+
+	bridge_ctx->pdev = platform_device_alloc(FAKE_FPGA_BRIDGE_DEV_NAME,
+						 PLATFORM_DEVID_AUTO);
+	if (!bridge_ctx->pdev) {
+		pr_err("Fake FPGA bridge device allocation failed\n");
+		ret = -ENOMEM;
+		goto err_mem;
+	}
+
+	pdata.test = test;
+	platform_device_add_data(bridge_ctx->pdev, &pdata, sizeof(pdata));
+
+	bridge_ctx->pdev->dev.parent = parent;
+	ret = platform_device_add(bridge_ctx->pdev);
+	if (ret) {
+		pr_err("Fake FPGA bridge device add failed\n");
+		goto err_pdev;
+	}
+
+	bridge_ctx->bridge = platform_get_drvdata(bridge_ctx->pdev);
+
+	if (test) {
+		priv = bridge_ctx->bridge->priv;
+		kunit_info(test, "Fake FPGA bridge %d registered\n", priv->id);
+	}
+
+	return bridge_ctx;
+
+err_pdev:
+	platform_device_put(bridge_ctx->pdev);
+	kfree(bridge_ctx);
+err_mem:
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(fake_fpga_bridge_register);
+
+/**
+ * fake_fpga_bridge_unregister() - unregister a fake FPGA bridge.
+ * @bridge_ctx: fake FPGA bridge context data structure.
+ */
+void fake_fpga_bridge_unregister(struct fake_fpga_bridge *bridge_ctx)
+{
+	struct fake_bridge_priv *priv;
+	struct kunit *test;
+	int id;
+
+	if (!bridge_ctx)
+		return;
+
+	priv = bridge_ctx->bridge->priv;
+	test = priv->test;
+	id = priv->id;
+
+	if (bridge_ctx->pdev) {
+		platform_device_unregister(bridge_ctx->pdev);
+		if (test)
+			kunit_info(test, "Fake FPGA bridge %d unregistered\n", id);
+	}
+
+	kfree(bridge_ctx);
+}
+EXPORT_SYMBOL_GPL(fake_fpga_bridge_unregister);
+
+/**
+ * fake_fpga_bridge_get_state() - get state of a fake FPGA bridge.
+ * @bridge_ctx: fake FPGA bridge context data structure.
+ *
+ * Return: 1 if the bridge is enabled, 0 if disabled.
+ */
+int fake_fpga_bridge_get_state(const struct fake_fpga_bridge *bridge_ctx)
+{
+	return bridge_ctx->bridge->br_ops->enable_show(bridge_ctx->bridge);
+}
+EXPORT_SYMBOL_GPL(fake_fpga_bridge_get_state);
+
+/**
+ * fake_fpga_bridge_get_cycles_count() - get the number of switching cycles.
+ * @bridge_ctx: fake FPGA bridge context data structure.
+ *
+ * Return: number of switching cycles.
+ */
+int fake_fpga_bridge_get_cycles_count(const struct fake_fpga_bridge *bridge_ctx)
+{
+	struct fake_bridge_priv *priv;
+
+	priv = bridge_ctx->bridge->priv;
+
+	return priv->cycles_count;
+}
+EXPORT_SYMBOL_GPL(fake_fpga_bridge_get_cycles_count);
+
+static int fake_fpga_bridge_probe(struct platform_device *pdev)
+{
+	struct device *dev;
+	struct fpga_bridge *bridge;
+	struct fake_bridge_data *pdata;
+	struct fake_bridge_priv *priv;
+	static int id_count;
+
+	dev = &pdev->dev;
+	pdata = dev_get_platdata(dev);
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->id = id_count++;
+	priv->enable = true;
+
+	if (pdata)
+		priv->test = pdata->test;
+
+	bridge = fpga_bridge_register(dev, "Fake FPGA Bridge",
+				      &fake_fpga_bridge_ops, priv);
+	if (IS_ERR(bridge))
+		return PTR_ERR(bridge);
+
+	platform_set_drvdata(pdev, bridge);
+
+	return 0;
+}
+
+static int fake_fpga_bridge_remove(struct platform_device *pdev)
+{
+	struct fpga_bridge *bridge = platform_get_drvdata(pdev);
+
+	fpga_bridge_unregister(bridge);
+
+	return 0;
+}
+
+static struct platform_driver fake_fpga_bridge_drv = {
+	.driver = {
+		.name = FAKE_FPGA_BRIDGE_DEV_NAME
+	},
+	.probe = fake_fpga_bridge_probe,
+	.remove = fake_fpga_bridge_remove,
+};
+
+module_platform_driver(fake_fpga_bridge_drv);
+
+MODULE_AUTHOR("Marco Pagani <marpagan@xxxxxxxxxx>");
+MODULE_DESCRIPTION("Fake FPGA Bridge");
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/fpga/tests/fake-fpga-bridge.h b/drivers/fpga/tests/fake-fpga-bridge.h
new file mode 100644
index 000000000000..a5acfdf18056
--- /dev/null
+++ b/drivers/fpga/tests/fake-fpga-bridge.h
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Header file for the fake FPGA bridge
+ *
+ * Copyright (C) 2023 Red Hat, Inc.
+ *
+ * Author: Marco Pagani <marpagan@xxxxxxxxxx>
+ */
+
+#ifndef __FPGA_FAKE_BRIDGE_H
+#define __FPGA_FAKE_BRIDGE_H
+
+#include <linux/platform_device.h>
+#include <kunit/test.h>
+
+/**
+ * struct fake_fpga_bridge - fake FPGA bridge context data structure
+ *
+ * @bridge: FPGA bridge.
+ * @pdev: platform device of the FPGA bridge.
+ */
+struct fake_fpga_bridge {
+	struct fpga_bridge *bridge;
+	struct platform_device *pdev;
+};
+
+struct fake_fpga_bridge *
+fake_fpga_bridge_register(struct device *parent, struct kunit *test);
+
+void fake_fpga_bridge_unregister(struct fake_fpga_bridge *bridge_ctx);
+
+int fake_fpga_bridge_get_state(const struct fake_fpga_bridge *bridge_ctx);
+
+int fake_fpga_bridge_get_cycles_count(const struct fake_fpga_bridge *bridge_ctx);
+
+#endif /* __FPGA_FAKE_BRIDGE_H */
-- 
2.39.2