[RFC,v3,3/4] fpga: add fake FPGA region

diff --git a/drivers/fpga/tests/fake-fpga-region.c b/drivers/fpga/tests/fake-fpga-region.c
new file mode 100644
index 000000000000..25c0b140c6a7
--- /dev/null
+++ b/drivers/fpga/tests/fake-fpga-region.c
@@ -0,0 +1,259 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for the fake FPGA region
+ *
+ * Copyright (C) 2023 Red Hat, Inc.
+ *
+ * Author: Marco Pagani <marpagan@redhat.com>
+ */
+
+#include <linux/device.h>
+#include <linux/list.h>
+#include <linux/platform_device.h>
+#include <linux/fpga/fpga-mgr.h>
+#include <linux/fpga/fpga-region.h>
+#include <linux/fpga/fpga-bridge.h>
+#include <kunit/test.h>
+
+#include "fake-fpga-region.h"
+
+#define FAKE_FPGA_REGION_DEV_NAME	"fake_fpga_region"
+
+struct fake_region_priv {
+	int id;
+	struct kunit *test;
+	struct list_head bridge_list;
+};
+
+struct bridge_elem {
+	struct fpga_bridge *bridge;
+	struct list_head node;
+};
+
+struct fake_region_data {
+	struct fpga_manager *mgr;
+	struct kunit *test;
+};
+
+/**
+ * fake_fpga_region_register() - register a fake FPGA region.
+ * @mgr: associated FPGA manager.
+ * @parent: parent device.
+ * @test: KUnit test context object.
+ *
+ * Return: pointer to a new fake FPGA region on success, an ERR_PTR() encoded
+ * error code on failure.
+ */
+struct fake_fpga_region *
+fake_fpga_region_register(struct fpga_manager *mgr, struct device *parent,
+			  struct kunit *test)
+{
+	struct fake_fpga_region *region_ctx;
+	struct fake_region_data pdata;
+	struct fake_region_priv *priv;
+	int ret;
+
+	region_ctx = kzalloc(sizeof(*region_ctx), GFP_KERNEL);
+	if (!region_ctx) {
+		ret = -ENOMEM;
+		goto err_mem;
+	}
+
+	region_ctx->pdev = platform_device_alloc(FAKE_FPGA_REGION_DEV_NAME,
+						 PLATFORM_DEVID_AUTO);
+	if (!region_ctx->pdev) {
+		pr_err("Fake FPGA region device allocation failed\n");
+		ret = -ENOMEM;
+		goto err_mem;
+	}
+
+	pdata.mgr = mgr;
+	pdata.test = test;
+	platform_device_add_data(region_ctx->pdev, &pdata, sizeof(pdata));
+
+	region_ctx->pdev->dev.parent = parent;
+	ret = platform_device_add(region_ctx->pdev);
+	if (ret) {
+		pr_err("Fake FPGA region device add failed\n");
+		goto err_pdev;
+	}
+
+	region_ctx->region = platform_get_drvdata(region_ctx->pdev);
+
+	if (test) {
+		priv = region_ctx->region->priv;
+		kunit_info(test, "Fake FPGA region %d registered\n", priv->id);
+	}
+
+	return region_ctx;
+
+err_pdev:
+	platform_device_put(region_ctx->pdev);
+	kfree(region_ctx);
+err_mem:
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(fake_fpga_region_register);
+
+/**
+ * fake_fpga_region_unregister() - unregister a fake FPGA region.
+ * @region_ctx: fake FPGA region context data structure.
+ */
+void fake_fpga_region_unregister(struct fake_fpga_region *region_ctx)
+{
+	struct fake_region_priv *priv;
+	struct kunit *test;
+	int id;
+
+	if (!region_ctx)
+		return;
+
+	priv = region_ctx->region->priv;
+	test = priv->test;
+	id = priv->id;
+
+	if (region_ctx->pdev) {
+		platform_device_unregister(region_ctx->pdev);
+		if (test)
+			kunit_info(test, "Fake FPGA region %d unregistered\n", id);
+	}
+
+	kfree(region_ctx);
+}
+EXPORT_SYMBOL_GPL(fake_fpga_region_unregister);
+
+/**
+ * fake_fpga_region_add_bridge() - add a bridge to a fake FPGA region.
+ * @region_ctx: fake FPGA region context data structure.
+ * @bridge: FPGA bridge.
+ *
+ * Return: 0 if registration succeeded, an error code otherwise.
+ */
+int fake_fpga_region_add_bridge(struct fake_fpga_region *region_ctx,
+				struct fpga_bridge *bridge)
+{
+	struct fake_region_priv *priv;
+	struct bridge_elem *elem;
+
+	priv = region_ctx->region->priv;
+
+	elem = devm_kzalloc(&region_ctx->pdev->dev, sizeof(*elem), GFP_KERNEL);
+	if (!elem)
+		return -ENOMEM;
+
+	/* Add bridge to the list of bridges in the private context */
+	elem->bridge = bridge;
+	list_add(&elem->node, &priv->bridge_list);
+
+	if (priv->test)
+		kunit_info(priv->test, "Bridge added to fake FPGA region %d\n",
+			   priv->id);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fake_fpga_region_add_bridge);
+
+int fake_fpga_region_program(struct fake_fpga_region *region_ctx)
+{
+	int ret;
+
+	ret = fpga_region_program_fpga(region_ctx->region);
+
+	/* fpga_region_program_fpga() already puts the bridges in case of errors */
+	if (!ret)
+		fpga_bridges_put(&region_ctx->region->bridge_list);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(fake_fpga_region_program)
+
+static int fake_region_get_bridges(struct fpga_region *region)
+{
+	struct fake_region_priv *priv;
+	struct bridge_elem *elem;
+	int ret;
+
+	priv = region->priv;
+
+	/* Copy the list of bridges from the private context to the region */
+	list_for_each_entry(elem, &priv->bridge_list, node) {
+		ret = fpga_bridge_get_to_list(elem->bridge->dev.parent,
+					      region->info,
+					      &region->bridge_list);
+		if (ret)
+			break;
+	}
+
+	return ret;
+}
+
+static int fake_fpga_region_probe(struct platform_device *pdev)
+{
+	struct device *dev;
+	struct fpga_region *region;
+	struct fpga_manager *mgr;
+	struct fake_region_data *pdata;
+	struct fake_region_priv *priv;
+	struct fpga_region_info info;
+	static int id_count;
+
+	dev = &pdev->dev;
+	pdata = dev_get_platdata(dev);
+
+	if (!pdata) {
+		dev_err(&pdev->dev, "Missing platform data\n");
+		return -EINVAL;
+	}
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	mgr = fpga_mgr_get(pdata->mgr->dev.parent);
+	if (IS_ERR(mgr))
+		return PTR_ERR(mgr);
+
+	INIT_LIST_HEAD(&priv->bridge_list);
+	priv->id = id_count++;
+	priv->test = pdata->test;
+
+	memset(&info, 0, sizeof(info));
+	info.priv = priv;
+	info.mgr = mgr;
+	info.get_bridges = fake_region_get_bridges;
+
+	region = fpga_region_register_full(dev, &info);
+	if (IS_ERR(region)) {
+		fpga_mgr_put(mgr);
+		return PTR_ERR(region);
+	}
+
+	platform_set_drvdata(pdev, region);
+
+	return 0;
+}
+
+static int fake_fpga_region_remove(struct platform_device *pdev)
+{
+	struct fpga_region *region = platform_get_drvdata(pdev);
+	struct fpga_manager *mgr = region->mgr;
+
+	fpga_mgr_put(mgr);
+	fpga_region_unregister(region);
+
+	return 0;
+}
+
+static struct platform_driver fake_fpga_region_drv = {
+	.driver = {
+		.name = FAKE_FPGA_REGION_DEV_NAME
+	},
+	.probe = fake_fpga_region_probe,
+	.remove = fake_fpga_region_remove,
+};
+
+module_platform_driver(fake_fpga_region_drv);
+
+MODULE_AUTHOR("Marco Pagani <marpagan@redhat.com>");
+MODULE_DESCRIPTION("Fake FPGA Bridge");
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/fpga/tests/fake-fpga-region.h b/drivers/fpga/tests/fake-fpga-region.h
new file mode 100644
index 000000000000..976982c192bc
--- /dev/null
+++ b/drivers/fpga/tests/fake-fpga-region.h
@@ -0,0 +1,40 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Header file for the fake FPGA region
+ *
+ * Copyright (C) 2023 Red Hat, Inc.
+ *
+ * Author: Marco Pagani <marpagan@redhat.com>
+ */
+
+#ifndef __FPGA_FAKE_RGN_H
+#define __FPGA_FAKE_RGN_H
+
+#include <linux/platform_device.h>
+#include <kunit/test.h>
+#include <linux/fpga/fpga-mgr.h>
+#include <linux/fpga/fpga-bridge.h>
+
+/**
+ * struct fake_fpga_region - fake FPGA region context data structure
+ *
+ * @region: FPGA region.
+ * @pdev: platform device of the FPGA region.
+ */
+struct fake_fpga_region {
+	struct fpga_region *region;
+	struct platform_device *pdev;
+};
+
+struct fake_fpga_region *
+fake_fpga_region_register(struct fpga_manager *mgr, struct device *parent,
+			  struct kunit *test);
+
+int fake_fpga_region_add_bridge(struct fake_fpga_region *region_ctx,
+				struct fpga_bridge *bridge);
+
+int fake_fpga_region_program(struct fake_fpga_region *region_ctx);
+
+void fake_fpga_region_unregister(struct fake_fpga_region *region_ctx);
+
+#endif /* __FPGA_FAKE_RGN_H */