Commit b7f51380 authored by Harry Wentland's avatar Harry Wentland Committed by Simon Ser
Browse files

drm/tests: Add a few tests around drm_fixed.h 



While working on the CTM implementation of VKMS I had to ascertain
myself of a few assumptions. One of those is whether drm_fixed.h
treats its numbers using signed-magnitude or twos-complement. It is
twos-complement.

In order to make someone else's day easier I am adding the
drm_test_int2fixp test that validates the above assumption.

I am also adding a test for the new sm2fixp function that converts
from a signed-magnitude fixed point to the twos-complement fixed
point.

Reviewed-by: default avatarLouis Chauvet <louis.chauvet@bootlin.com>
Signed-off-by: default avatarAlex Hung <alex.hung@amd.com>
Signed-off-by: default avatarHarry Wentland <harry.wentland@amd.com>
Reviewed-by: default avatarDaniel Stone <daniels@collabora.com>
Signed-off-by: default avatarSimon Ser <contact@emersion.fr>
Link: https://patch.msgid.link/20251115000237.3561250-22-alex.hung@amd.com
parent ea3f6baf

drivers/gpu/drm/tests/Makefile

+2 −1
Original line number Diff line number Diff line
@@ -24,6 +24,7 @@ obj-$(CONFIG_DRM_KUNIT_TEST) += \ 
	drm_plane_helper_test.o \

	drm_probe_helper_test.o \

	drm_rect_test.o \

	drm_sysfb_modeset_test.o

	drm_sysfb_modeset_test.o \

	drm_fixp_test.o



CFLAGS_drm_mm_test.o := $(DISABLE_STRUCTLEAK_PLUGIN)

drivers/gpu/drm/tests/drm_fixp_test.c

0 → 100644
+71 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: MIT

/*

 * Copyright 2022 Advanced Micro Devices, Inc.

 */



#include <kunit/test.h>

#include <drm/drm_fixed.h>



static void drm_test_sm2fixp(struct kunit *test)

{

	KUNIT_EXPECT_EQ(test, 0x7fffffffffffffffll, ((1ull << 63) - 1));



	/* 1 */

	KUNIT_EXPECT_EQ(test, drm_int2fixp(1), drm_sm2fixp(1ull << DRM_FIXED_POINT));



	/* -1 */

	KUNIT_EXPECT_EQ(test, drm_int2fixp(-1),

			drm_sm2fixp((1ull << 63) | (1ull << DRM_FIXED_POINT)));



	/* 0.5 */

	KUNIT_EXPECT_EQ(test, drm_fixp_from_fraction(1, 2),

			drm_sm2fixp(1ull << (DRM_FIXED_POINT - 1)));



	/* -0.5 */

	KUNIT_EXPECT_EQ(test, drm_fixp_from_fraction(-1, 2),

			drm_sm2fixp((1ull << 63) | (1ull << (DRM_FIXED_POINT - 1))));

}



static void drm_test_int2fixp(struct kunit *test)

{

	/* 1 */

	KUNIT_EXPECT_EQ(test, 1ll << 32, drm_int2fixp(1));



	/* -1 */

	KUNIT_EXPECT_EQ(test, -(1ll << 32), drm_int2fixp(-1));



	/* 1 + (-1) = 0 */

	KUNIT_EXPECT_EQ(test, 0, drm_int2fixp(1) + drm_int2fixp(-1));



	/* 1 / 2 */

	KUNIT_EXPECT_EQ(test, 1ll << 31, drm_fixp_from_fraction(1, 2));



	/* -0.5 */

	KUNIT_EXPECT_EQ(test, -(1ll << 31), drm_fixp_from_fraction(-1, 2));



	/* (1 / 2) + (-1) = 0.5 */

	KUNIT_EXPECT_EQ(test, 1ll << 31, drm_fixp_from_fraction(-1, 2) + drm_int2fixp(1));



	/* (1 / 2) - 1) = 0.5 */

	KUNIT_EXPECT_EQ(test, -(1ll << 31), drm_fixp_from_fraction(1, 2) + drm_int2fixp(-1));



	/* (1 / 2) - 1) = 0.5 */

	KUNIT_EXPECT_EQ(test, -(1ll << 31), drm_fixp_from_fraction(1, 2) - drm_int2fixp(1));

}



static struct kunit_case drm_fixp_tests[] = {

	KUNIT_CASE(drm_test_int2fixp),

	KUNIT_CASE(drm_test_sm2fixp),

	{ }

};



static struct kunit_suite drm_fixp_test_suite = {

	.name = "drm_fixp",

	.test_cases = drm_fixp_tests,

};



kunit_test_suite(drm_fixp_test_suite);



MODULE_AUTHOR("AMD");

MODULE_LICENSE("Dual MIT/GPL");

MODULE_DESCRIPTION("Unit tests for drm_fixed.h");