On Mon, 26 Feb 2024 16:10:38 -0500
Harry Wentland wrote:
> 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.
>
> Signed-off-by: Harry Wentland
> ---
> drivers/gpu/drm/tests/Makefile| 3 +-
> drivers/gpu/drm/tests/drm_fixp_test.c | 69 +++
> 2 files changed, 71 insertions(+), 1 deletion(-)
> create mode 100644 drivers/gpu/drm/tests/drm_fixp_test.c
>
> diff --git a/drivers/gpu/drm/tests/Makefile b/drivers/gpu/drm/tests/Makefile
> index d6183b3d7688..98468f7908dd 100644
> --- a/drivers/gpu/drm/tests/Makefile
> +++ b/drivers/gpu/drm/tests/Makefile
> @@ -19,6 +19,7 @@ obj-$(CONFIG_DRM_KUNIT_TEST) += \
> drm_modes_test.o \
> drm_plane_helper_test.o \
> drm_probe_helper_test.o \
> - drm_rect_test.o
> + drm_rect_test.o \
> + drm_fixp_test.o
>
> CFLAGS_drm_mm_test.o := $(DISABLE_STRUCTLEAK_PLUGIN)
> diff --git a/drivers/gpu/drm/tests/drm_fixp_test.c
> b/drivers/gpu/drm/tests/drm_fixp_test.c
> new file mode 100644
> index ..f420f173ff66
> --- /dev/null
> +++ b/drivers/gpu/drm/tests/drm_fixp_test.c
> @@ -0,0 +1,69 @@
> +// SPDX-License-Identifier: MIT
> +/*
> + * Copyright 2022 Advanced Micro Devices, Inc.
> + */
> +
> +#include
> +#include
> +
> +static void drm_test_sm2fixp(struct kunit *test)
> +{
> + KUNIT_EXPECT_EQ(test, 0x7fffll, ((1LL << 63) - 1));
> +
> + /* 1 */
> + KUNIT_EXPECT_EQ(test, drm_int2fixp(1), drm_sm2fixp(1ull <<
> DRM_FIXED_POINT));
This sounds like confusing two different APIs.
DRM_FIXED_POINT is for the two's complement representation, and sm is
not.
It does not look like there is a #define for the signed-magnitude UAPI
construct, otherwise drm_color_ctm_s31_32_to_qm_n() would be using it.
It's just an accident that DRM_FIXED_POINT has the right value for sm.
Hm, drm_color_ctm_s31_32_to_qm_n() produces two's complement. Why not
use that for implementing drm_sm2fixp()?
Thanks,
pq
> +
> + /* -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_rect_test_suite = {
> + .name = "drm_fixp",
> + .test_cases = drm_fixp_tests,
> +};
> +
> +kunit_test_suite(drm_rect_test_suite);
> +
> +MODULE_AUTHOR("AMD");
> +MODULE_LICENSE("GPL and additional rights");
> \ No newline at end of file
pgpieK3eeAbs_.pgp
Description: OpenPGP digital signature
