drm/format-helper: Add KUnit tests for drm_fb_xrgb8888_to_rgb332()

Test the conversion from XRGB8888 to RGB332.

What is tested?

 - Different values for the X in XRGB8888 to make sure it is ignored
 - Different clip values: Single pixel and full and partial buffer
 - Well known colors: White, black, red, green, blue, magenta, yellow
   and cyan
 - Other colors: Randomly picked
 - Destination pitch

How to run the tests?

 $ ./tools/testing/kunit/kunit.py run --kunitconfig=drivers/gpu/drm/tests \
         --kconfig_add CONFIG_VIRTIO_UML=y \
         --kconfig_add CONFIG_UML_PCI_OVER_VIRTIO=y

Suggested-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: David Gow <davidgow@google.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: José Expósito <jose.exposito89@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220620160640.3790-3-jose.exposito89@gmail.com

drivers/gpu/drm/Kconfig

@@ -70,6 +70,22 @@ config DRM_DEBUG_SELFTEST
 
 	  If in doubt, say "N".
 
+config DRM_KUNIT_TEST
+	tristate "KUnit tests for DRM" if !KUNIT_ALL_TESTS
+	depends on DRM && KUNIT=y
+	select DRM_KMS_HELPER
+	default KUNIT_ALL_TESTS
+	help
+	  This builds unit tests for DRM. This option is not useful for
+	  distributions or general kernels, but only for kernel
+	  developers working on DRM and associated drivers.
+
+	  For more information on KUnit and unit tests in general,
+	  please refer to the KUnit documentation in
+	  Documentation/dev-tools/kunit/.
+
+	  If in doubt, say "N".
+
 config DRM_KMS_HELPER
 	tristate
 	depends on DRM

drivers/gpu/drm/Makefile

@@ -76,6 +76,7 @@ obj-$(CONFIG_DRM_KMS_HELPER) += drm_kms_helper.o
 #
 
 obj-$(CONFIG_DRM_DEBUG_SELFTEST) += selftests/
+obj-$(CONFIG_DRM_KUNIT_TEST) += tests/
 
 obj-$(CONFIG_DRM_MIPI_DBI) += drm_mipi_dbi.o
 obj-$(CONFIG_DRM_MIPI_DSI) += drm_mipi_dsi.o

drivers/gpu/drm/tests/.kunitconfig

@@ -0,0 +1,3 @@
+CONFIG_KUNIT=y
+CONFIG_DRM=y
+CONFIG_DRM_KUNIT_TEST=y

drivers/gpu/drm/tests/Makefile

@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_DRM_KUNIT_TEST) += drm_format_helper_test.o

drivers/gpu/drm/tests/drm_format_helper_test.c

@@ -0,0 +1,161 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+#include <kunit/test.h>
+
+#include <drm/drm_device.h>
+#include <drm/drm_file.h>
+#include <drm/drm_format_helper.h>
+#include <drm/drm_fourcc.h>
+#include <drm/drm_framebuffer.h>
+#include <drm/drm_gem_framebuffer_helper.h>
+#include <drm/drm_mode.h>
+#include <drm/drm_print.h>
+#include <drm/drm_rect.h>
+
+#include "../drm_crtc_internal.h"
+
+#define TEST_BUF_SIZE 50
+
+struct xrgb8888_to_rgb332_case {
+	const char *name;
+	unsigned int pitch;
+	unsigned int dst_pitch;
+	struct drm_rect clip;
+	const u32 xrgb8888[TEST_BUF_SIZE];
+	const u8 expected[4 * TEST_BUF_SIZE];
+};
+
+static struct xrgb8888_to_rgb332_case xrgb8888_to_rgb332_cases[] = {
+	{
+		.name = "single_pixel_source_buffer",
+		.pitch = 1 * 4,
+		.dst_pitch = 0,
+		.clip = DRM_RECT_INIT(0, 0, 1, 1),
+		.xrgb8888 = { 0x01FF0000 },
+		.expected = { 0xE0 },
+	},
+	{
+		.name = "single_pixel_clip_rectangle",
+		.pitch = 2 * 4,
+		.dst_pitch = 0,
+		.clip = DRM_RECT_INIT(1, 1, 1, 1),
+		.xrgb8888 = {
+			0x00000000, 0x00000000,
+			0x00000000, 0x10FF0000,
+		},
+		.expected = { 0xE0 },
+	},
+	{
+		/* Well known colors: White, black, red, green, blue, magenta,
+		 * yellow and cyan. Different values for the X in XRGB8888 to
+		 * make sure it is ignored. Partial clip area.
+		 */
+		.name = "well_known_colors",
+		.pitch = 4 * 4,
+		.dst_pitch = 0,
+		.clip = DRM_RECT_INIT(1, 1, 2, 4),
+		.xrgb8888 = {
+			0x00000000, 0x00000000, 0x00000000, 0x00000000,
+			0x00000000, 0x11FFFFFF, 0x22000000, 0x00000000,
+			0x00000000, 0x33FF0000, 0x4400FF00, 0x00000000,
+			0x00000000, 0x550000FF, 0x66FF00FF, 0x00000000,
+			0x00000000, 0x77FFFF00, 0x8800FFFF, 0x00000000,
+		},
+		.expected = {
+			0xFF, 0x00,
+			0xE0, 0x1C,
+			0x03, 0xE3,
+			0xFC, 0x1F,
+		},
+	},
+	{
+		/* Randomly picked colors. Full buffer within the clip area. */
+		.name = "destination_pitch",
+		.pitch = 3 * 4,
+		.dst_pitch = 5,
+		.clip = DRM_RECT_INIT(0, 0, 3, 3),
+		.xrgb8888 = {
+			0xA10E449C, 0xB1114D05, 0xC1A80303,
+			0xD16C7073, 0xA20E449C, 0xB2114D05,
+			0xC2A80303, 0xD26C7073, 0xA30E449C,
+		},
+		.expected = {
+			0x0A, 0x08, 0xA0, 0x00, 0x00,
+			0x6D, 0x0A, 0x08, 0x00, 0x00,
+			0xA0, 0x6D, 0x0A, 0x00, 0x00,
+		},
+	},
+};
+
+/*
+ * conversion_buf_size - Return the destination buffer size required to convert
+ * between formats.
+ * @dst_format: destination buffer pixel format (DRM_FORMAT_*)
+ * @dst_pitch: Number of bytes between two consecutive scanlines within dst
+ * @clip: Clip rectangle area to convert
+ *
+ * Returns:
+ * The size of the destination buffer or negative value on error.
+ */
+static size_t conversion_buf_size(u32 dst_format, unsigned int dst_pitch,
+				  const struct drm_rect *clip)
+{
+	const struct drm_format_info *dst_fi = drm_format_info(dst_format);
+
+	if (!dst_fi)
+		return -EINVAL;
+
+	if (!dst_pitch)
+		dst_pitch = drm_rect_width(clip) * dst_fi->cpp[0];
+
+	return dst_pitch * drm_rect_height(clip);
+}
+
+static void xrgb8888_to_rgb332_case_desc(struct xrgb8888_to_rgb332_case *t,
+					 char *desc)
+{
+	strscpy(desc, t->name, KUNIT_PARAM_DESC_SIZE);
+}
+
+KUNIT_ARRAY_PARAM(xrgb8888_to_rgb332, xrgb8888_to_rgb332_cases,
+		  xrgb8888_to_rgb332_case_desc);
+
+static void xrgb8888_to_rgb332_test(struct kunit *test)
+{
+	const struct xrgb8888_to_rgb332_case *params = test->param_value;
+	size_t dst_size;
+	__u8 *dst = NULL;
+
+	struct drm_framebuffer fb = {
+		.format = drm_format_info(DRM_FORMAT_XRGB8888),
+		.pitches = { params->pitch, 0, 0 },
+	};
+
+	dst_size = conversion_buf_size(DRM_FORMAT_RGB332, params->dst_pitch,
+				       &params->clip);
+	KUNIT_ASSERT_GT(test, dst_size, 0);
+
+	dst = kunit_kzalloc(test, dst_size, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, dst);
+
+	drm_fb_xrgb8888_to_rgb332(dst, params->dst_pitch, params->xrgb8888,
+				  &fb, &params->clip);
+	KUNIT_EXPECT_EQ(test, memcmp(dst, params->expected, dst_size), 0);
+}
+
+static struct kunit_case drm_format_helper_test_cases[] = {
+	KUNIT_CASE_PARAM(xrgb8888_to_rgb332_test,
+			 xrgb8888_to_rgb332_gen_params),
+	{}
+};
+
+static struct kunit_suite drm_format_helper_test_suite = {
+	.name = "drm_format_helper_test",
+	.test_cases = drm_format_helper_test_cases,
+};
+
+kunit_test_suite(drm_format_helper_test_suite);
+
+MODULE_DESCRIPTION("KUnit tests for the drm_format_helper APIs");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("José Expósito <jose.exposito89@gmail.com>");