linux-kernel - Re: [PATCH v2 15/17] drm/vc4: tests: Introduce a mocking infrastructure

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Date:   Wed, 30 Nov 2022 10:59:37 +0100
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Maxime Ripard <maxime@...no.tech>, Daniel Vetter <daniel@...ll.ch>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        David Airlie <airlied@...il.com>,
        Thomas Zimmermann <tzimmermann@...e.de>
Cc:     dri-devel@...ts.freedesktop.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        kunit-dev@...glegroups.com, linux-media@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linaro-mm-sig@...ts.linaro.org,
        Brendan Higgins <brendan.higgins@...ux.dev>,
        Maíra Canal <mairacanal@...eup.net>,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        linux-kernel@...r.kernel.org, David Gow <davidgow@...gle.com>
Subject: Re: [PATCH v2 15/17] drm/vc4: tests: Introduce a mocking
 infrastructure

On 11/28/22 15:53, Maxime Ripard wrote:
> In order to test the current atomic_check hooks we need to have a DRM
> device that has roughly the same capabilities and layout that the actual
> hardware. We'll also need a bunch of functions to create arbitrary
> atomic states.
> 
> Let's create some helpers to create a device that behaves like the real
> one, and some helpers to maintain the atomic state we want to check.
> 
> Signed-off-by: Maxime Ripard <maxime@...no.tech>
> ---

[...]

> +
> +config DRM_VC4_KUNIT_TEST
> +	bool "KUnit tests for VC4" if !KUNIT_ALL_TESTS
> +	depends on DRM_VC4 && KUNIT

shouldn't this depend on DRM_KUNIT_TEST instead ?

[...]

> +static struct vc4_dev *__mock_device(struct kunit *test, bool is_vc5)
> +{
> +	struct drm_device *drm;
> +	const struct drm_driver *drv = is_vc5 ? &vc5_drm_driver : &vc4_drm_driver;
> +	const struct vc4_mock_desc *desc = is_vc5 ? &vc5_mock : &vc4_mock;
> +	struct vc4_dev *vc4;

Since it could be vc4 or vc5, maybe can be renamed to just struct vc_dev *vc ?

> +struct vc4_dummy_plane *vc4_dummy_plane(struct kunit *test,
> +					struct drm_device *drm,
> +					enum drm_plane_type type)
> +{
> +	struct vc4_dummy_plane *dummy_plane;
> +	struct drm_plane *plane;
> +
> +	dummy_plane = drmm_universal_plane_alloc(drm,
> +						 struct vc4_dummy_plane, plane.base,
> +						 0,
> +						 &vc4_dummy_plane_funcs,
> +						 vc4_dummy_plane_formats,
> +						 ARRAY_SIZE(vc4_dummy_plane_formats),
> +						 NULL,
> +						 DRM_PLANE_TYPE_PRIMARY,
> +						 NULL);
> +	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, dummy_plane);
> +
> +	plane = &dummy_plane->plane.base;
> +	drm_plane_helper_add(plane, &vc4_dummy_plane_helper_funcs);
> +
> +	return dummy_plane;
> +}

I guess many of these helpers could grow to be generic, like this one since
most drivers support the DRM_FORMAT_XRGB8888 format for their primary plane.

[...]

>  
> +extern const struct vc4_pv_data bcm2835_pv0_data;
> +extern const struct vc4_pv_data bcm2835_pv1_data;
> +extern const struct vc4_pv_data bcm2835_pv2_data;
> +extern const struct vc4_pv_data bcm2711_pv0_data;
> +extern const struct vc4_pv_data bcm2711_pv1_data;
> +extern const struct vc4_pv_data bcm2711_pv2_data;
> +extern const struct vc4_pv_data bcm2711_pv3_data;
> +extern const struct vc4_pv_data bcm2711_pv4_data;
> +

Maybe the driver could expose a helper function to get the pixelvalve data
and avoid having to expose all of these variables? For example you could
define an enum vc4_pixelvalve type and have something like the following:

const struct vc4_pv_data *vc4_crtc_get_pixelvalve_data(enum vc4_pixelvalve pv);

All these are small nits though, the patch looks great to me and I think is
awesome to have this level of testing with KUnit. Hope other drivers follow
your lead.

Reviewed-by: Javier Martinez Canillas <javierm@...hat.com>

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat