Re: [PATCH v5 1/8] drivers: kunit: Generic helpers for test device creation

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Wed, Mar 22, 2023 at 11:05:55AM +0200, Matti Vaittinen wrote:
> --- /dev/null
> +++ b/drivers/base/test/test_kunit_device.c
> @@ -0,0 +1,83 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * These helpers have been extracted from drm test code at
> + * drm_kunit_helpers.c which was authored by
> + * Maxime Ripard <maxime@cerno.tech>
> + */
> +
> +#include <linux/device.h>
> +#include <linux/platform_device.h>
> +
> +#include <kunit/platform_device.h>
> +
> +#define KUNIT_DEVICE_NAME	"test-kunit-mock-device"
> +
> +static int fake_probe(struct platform_device *pdev)

Please do not abuse platform devices and drivers for things that are not
actually platform devices and drivers.

> +{
> +	return 0;
> +}
> +
> +static int fake_remove(struct platform_device *pdev)
> +{
> +	return 0;
> +}
> +
> +static struct platform_driver fake_platform_driver = {
> +	.probe	= fake_probe,
> +	.remove	= fake_remove,
> +	.driver = {
> +		.name	= KUNIT_DEVICE_NAME,
> +	},
> +};

Why do you need this fake platform driver at all?

Why not just use a virtual device?

> +
> +/**
> + * test_kunit_helper_alloc_device - Allocate a mock device for a KUnit test
> + * @test: The test context object
> + *
> + * This allocates a fake struct &device to create a mock for a KUnit
> + * test. The device will also be bound to a fake driver. It will thus be
> + * able to leverage the usual infrastructure and most notably the
> + * device-managed resources just like a "real" device.

What specific "usual infrastructure" are you wanting to access here?

And again, if you want a fake device, make a virtual one, by just
calling device_create().

Or are you wanting to do "more" with that device pointer than
device_create() can give you?

Again, please do not abuse the platform device infrastructure for things
it was never ment to do (i.e. create fake devices that are not really a
platform device.)

thanks,

greg k-h