Message-ID: <988e8e8e-d514-4c69-a384-7d0a70c514c4@redhat.com>
Date:   Tue, 21 Mar 2023 18:33:05 +0100
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Subject: Re: [RFC PATCH v2 2/4] fpga: add fake FPGA bridge
To:     Xu Yilun <yilun.xu@intel.com>
Cc:     Moritz Fischer <mdf@kernel.org>, Wu Hao <hao.wu@intel.com>,
        Tom Rix <trix@redhat.com>, linux-kernel@vger.kernel.org,
        linux-fpga@vger.kernel.org
References: <20230310170412.708363-1-marpagan@redhat.com>
 <20230310170412.708363-3-marpagan@redhat.com>
 <ZBQlnUQWZHJ+ZBu5@yilunxu-OptiPlex-7050>
Content-Language: en-US
From:   Marco Pagani <marpagan@redhat.com>
In-Reply-To: <ZBQlnUQWZHJ+ZBu5@yilunxu-OptiPlex-7050>
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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