[RFC,v2,2/4] fpga: add fake FPGA bridge

  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@redhat.com>
---
 drivers/fpga/tests/fake-fpga-bridge.c | 228 ++++++++++++++++++++++++++
 drivers/fpga/tests/fake-fpga-bridge.h |  36 ++++
 2 files changed, 264 insertions(+)
 create mode 100644 drivers/fpga/tests/fake-fpga-bridge.c
 create mode 100644 drivers/fpga/tests/fake-fpga-bridge.h
  

On 2023-03-10 at 18:04:10 +0100, Marco Pagani wrote:
> 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@redhat.com>
> ---
>  drivers/fpga/tests/fake-fpga-bridge.c | 228 ++++++++++++++++++++++++++
>  drivers/fpga/tests/fake-fpga-bridge.h |  36 ++++
>  2 files changed, 264 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..8a2f64fc1bbb
> --- /dev/null
> +++ b/drivers/fpga/tests/fake-fpga-bridge.c
> @@ -0,0 +1,228 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Driver for the fake FPGA bridge
> + *
> + * Copyright (C) 2023 Red Hat, Inc.
> + *
> + * Author: Marco Pagani <marpagan@redhat.com>
> + */
> +
> +#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);

Why check the kunit pointer every time? I remember you mentioned that
the fake fpga modules are expected to be used out of Kunit test, so the
priv->test may be NULL? I suggest you work on these usecases in separate
patchsets. For now just check priv->test on probe is fine.

> +
> +	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.
> + * @bridge_ctx: fake FPGA bridge context data structure.
> + * @parent: parent device.
> + * @test: KUnit test context object.
> + *
> + * Return: 0 if registration succeeded, an error code otherwise.
> + */
> +int fake_fpga_bridge_register(struct fake_fpga_bridge *bridge_ctx,
> +			      struct device *parent, struct kunit *test)

struct fake_fpga_bridge *fake_fpga_bridge_register(struct device *parent, ...)

Is it better?

Thanks,
Yilun

> +{
> +	struct fake_bridge_data pdata;
> +	struct fake_bridge_priv *priv;
> +	int ret;
> +
> +	pdata.test = test;
> +
> +	bridge_ctx->pdev = platform_device_alloc(FAKE_FPGA_BRIDGE_DEV_NAME,
> +						 PLATFORM_DEVID_AUTO);
> +	if (IS_ERR(bridge_ctx->pdev)) {
> +		pr_err("Fake FPGA bridge device allocation failed\n");
> +		return -ENOMEM;
> +	}
> +
> +	bridge_ctx->pdev->dev.parent = parent;
> +	platform_device_add_data(bridge_ctx->pdev, &pdata, sizeof(pdata));
> +
> +	ret = platform_device_add(bridge_ctx->pdev);
> +	if (ret) {
> +		pr_err("Fake FPGA bridge device add failed\n");
> +		platform_device_put(bridge_ctx->pdev);
> +		return ret;
> +	}
> +
> +	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 0;
> +}
> +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);
> +	}
> +}
> +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@redhat.com>");
> +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..ae224b13f284
> --- /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@redhat.com>
> + */
> +
> +#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;
> +};
> +
> +int fake_fpga_bridge_register(struct fake_fpga_bridge *bridge_ctx,
> +			      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
>
  

On 2023-03-17 09:32, Xu Yilun wrote:
> On 2023-03-10 at 18:04:10 +0100, Marco Pagani wrote:
>> 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@redhat.com>
>> ---
>>  drivers/fpga/tests/fake-fpga-bridge.c | 228 ++++++++++++++++++++++++++
>>  drivers/fpga/tests/fake-fpga-bridge.h |  36 ++++
>>  2 files changed, 264 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..8a2f64fc1bbb
>> --- /dev/null
>> +++ b/drivers/fpga/tests/fake-fpga-bridge.c
>> @@ -0,0 +1,228 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Driver for the fake FPGA bridge
>> + *
>> + * Copyright (C) 2023 Red Hat, Inc.
>> + *
>> + * Author: Marco Pagani <marpagan@redhat.com>
>> + */
>> +
>> +#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);
> 
> Why check the kunit pointer every time? I remember you mentioned that
> the fake fpga modules are expected to be used out of Kunit test, so the
> priv->test may be NULL? I suggest you work on these usecases in separate
> patchsets. For now just check priv->test on probe is fine.
> 

The idea was to provide additional info messages, tied with the test, if the
fake bridge is registered with a test instance. If you believe these prints
are unnecessary, I can remove them or replace them with generic dev_info().

>> +
>> +	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.
>> + * @bridge_ctx: fake FPGA bridge context data structure.
>> + * @parent: parent device.
>> + * @test: KUnit test context object.
>> + *
>> + * Return: 0 if registration succeeded, an error code otherwise.
>> + */
>> +int fake_fpga_bridge_register(struct fake_fpga_bridge *bridge_ctx,
>> +			      struct device *parent, struct kunit *test)
> 
> struct fake_fpga_bridge *fake_fpga_bridge_register(struct device *parent, ...)
> 
> Is it better?
> 
> Thanks,
> Yilun

Agreed, it is better. I'll change the registration functions for the fake
bridge, manager, and region in the next version.

> 
>> +{
>> +	struct fake_bridge_data pdata;
>> +	struct fake_bridge_priv *priv;
>> +	int ret;
>> +
>> +	pdata.test = test;
>> +
>> +	bridge_ctx->pdev = platform_device_alloc(FAKE_FPGA_BRIDGE_DEV_NAME,
>> +						 PLATFORM_DEVID_AUTO);
>> +	if (IS_ERR(bridge_ctx->pdev)) {
>> +		pr_err("Fake FPGA bridge device allocation failed\n");
>> +		return -ENOMEM;
>> +	}
>> +
>> +	bridge_ctx->pdev->dev.parent = parent;
>> +	platform_device_add_data(bridge_ctx->pdev, &pdata, sizeof(pdata));
>> +
>> +	ret = platform_device_add(bridge_ctx->pdev);
>> +	if (ret) {
>> +		pr_err("Fake FPGA bridge device add failed\n");
>> +		platform_device_put(bridge_ctx->pdev);
>> +		return ret;
>> +	}
>> +
>> +	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 0;
>> +}
>> +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);
>> +	}
>> +}
>> +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@redhat.com>");
>> +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..ae224b13f284
>> --- /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@redhat.com>
>> + */
>> +
>> +#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;
>> +};
>> +
>> +int fake_fpga_bridge_register(struct fake_fpga_bridge *bridge_ctx,
>> +			      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
>>

Thanks,
Marco
  

On 2023-03-21 at 18:33:05 +0100, Marco Pagani wrote:
> 
> 
> On 2023-03-17 09:32, Xu Yilun wrote:
> > On 2023-03-10 at 18:04:10 +0100, Marco Pagani wrote:
> >> 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@redhat.com>
> >> ---
> >>  drivers/fpga/tests/fake-fpga-bridge.c | 228 ++++++++++++++++++++++++++
> >>  drivers/fpga/tests/fake-fpga-bridge.h |  36 ++++
> >>  2 files changed, 264 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..8a2f64fc1bbb
> >> --- /dev/null
> >> +++ b/drivers/fpga/tests/fake-fpga-bridge.c
> >> @@ -0,0 +1,228 @@
> >> +// SPDX-License-Identifier: GPL-2.0
> >> +/*
> >> + * Driver for the fake FPGA bridge
> >> + *
> >> + * Copyright (C) 2023 Red Hat, Inc.
> >> + *
> >> + * Author: Marco Pagani <marpagan@redhat.com>
> >> + */
> >> +
> >> +#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);
> > 
> > Why check the kunit pointer every time? I remember you mentioned that
> > the fake fpga modules are expected to be used out of Kunit test, so the
> > priv->test may be NULL? I suggest you work on these usecases in separate
> > patchsets. For now just check priv->test on probe is fine.
> > 
> 
> The idea was to provide additional info messages, tied with the test, if the
> fake bridge is registered with a test instance. If you believe these prints
> are unnecessary, I can remove them or replace them with generic dev_info().

OK, on second thought, it's good to me.

Thanks,
Yilun