drm/vkms: Add kunit tests for linear and sRGB LUTs

Two tests are added to VKMS LUT handling:
- linear
- inv_srgb

Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Signed-off-by: Simon Ser <contact@emersion.fr>
Link: https://patch.msgid.link/20251115000237.3561250-18-alex.hung@amd.com

Author: Harry Wentland

drivers/gpu/drm/vkms/tests/vkms_color_test.c

@@ -6,6 +6,7 @@
 #include <drm/drm_mode.h>
 #include "../vkms_composer.h"
 #include "../vkms_drv.h"
+#include "../vkms_luts.h"
 
 #define TEST_LUT_SIZE 16
 
@@ -99,6 +100,19 @@ static void vkms_color_test_get_lut_index(struct kunit *test)
 		lut_index = get_lut_index(&test_linear_lut, test_linear_array[i].red);
 		KUNIT_EXPECT_EQ(test, drm_fixp2int_ceil(lut_index), i);
 	}
+
+	KUNIT_EXPECT_EQ(test, drm_fixp2int(get_lut_index(&srgb_eotf, 0x0)), 0x0);
+	KUNIT_EXPECT_EQ(test, drm_fixp2int_ceil(get_lut_index(&srgb_eotf, 0x0)), 0x0);
+	KUNIT_EXPECT_EQ(test, drm_fixp2int_ceil(get_lut_index(&srgb_eotf, 0x101)), 0x1);
+	KUNIT_EXPECT_EQ(test, drm_fixp2int_ceil(get_lut_index(&srgb_eotf, 0x202)), 0x2);
+
+	KUNIT_EXPECT_EQ(test, drm_fixp2int(get_lut_index(&srgb_inv_eotf, 0x0)), 0x0);
+	KUNIT_EXPECT_EQ(test, drm_fixp2int_ceil(get_lut_index(&srgb_inv_eotf, 0x0)), 0x0);
+	KUNIT_EXPECT_EQ(test, drm_fixp2int_ceil(get_lut_index(&srgb_inv_eotf, 0x101)), 0x1);
+	KUNIT_EXPECT_EQ(test, drm_fixp2int_ceil(get_lut_index(&srgb_inv_eotf, 0x202)), 0x2);
+
+	KUNIT_EXPECT_EQ(test, drm_fixp2int_ceil(get_lut_index(&srgb_eotf, 0xfefe)), 0xfe);
+	KUNIT_EXPECT_EQ(test, drm_fixp2int_ceil(get_lut_index(&srgb_eotf, 0xffff)), 0xff);
 }
 
 static void vkms_color_test_lerp(struct kunit *test)
@@ -112,9 +126,33 @@ static void vkms_color_test_lerp(struct kunit *test)
 	}
 }
 
+static void vkms_color_test_linear(struct kunit *test)
+{
+	for (int i = 0; i < LUT_SIZE; i++) {
+		int linear = apply_lut_to_channel_value(&linear_eotf, i * 0x101, LUT_RED);
+
+		KUNIT_EXPECT_EQ(test, DIV_ROUND_CLOSEST(linear, 0x101), i);
+	}
+}
+
+static void vkms_color_srgb_inv_srgb(struct kunit *test)
+{
+	u16 srgb, final;
+
+	for (int i = 0; i < LUT_SIZE; i++) {
+		srgb = apply_lut_to_channel_value(&srgb_eotf, i * 0x101, LUT_RED);
+		final = apply_lut_to_channel_value(&srgb_inv_eotf, srgb, LUT_RED);
+
+		KUNIT_EXPECT_GE(test, final / 0x101, i - 1);
+		KUNIT_EXPECT_LE(test, final / 0x101, i + 1);
+	}
+}
+
 static struct kunit_case vkms_color_test_cases[] = {
 	KUNIT_CASE(vkms_color_test_get_lut_index),
 	KUNIT_CASE(vkms_color_test_lerp),
+	KUNIT_CASE(vkms_color_test_linear),
+	KUNIT_CASE(vkms_color_srgb_inv_srgb),
 	{}
 };
 

drivers/gpu/drm/vkms/vkms_composer.c

@@ -82,19 +82,8 @@ VISIBLE_IF_KUNIT s64 get_lut_index(const struct vkms_color_lut *lut, u16 channel
 }
 EXPORT_SYMBOL_IF_KUNIT(get_lut_index);
 
-/*
- * This enum is related to the positions of the variables inside
- * `struct drm_color_lut`, so the order of both needs to be the same.
- */
-enum lut_channel {
-	LUT_RED = 0,
-	LUT_GREEN,
-	LUT_BLUE,
-	LUT_RESERVED
-};
-
-static u16 apply_lut_to_channel_value(const struct vkms_color_lut *lut, u16 channel_value,
-				      enum lut_channel channel)
+VISIBLE_IF_KUNIT u16 apply_lut_to_channel_value(const struct vkms_color_lut *lut, u16 channel_value,
+						enum lut_channel channel)
 {
 	s64 lut_index = get_lut_index(lut, channel_value);
 	u16 *floor_lut_value, *ceil_lut_value;
@@ -119,6 +108,8 @@ static u16 apply_lut_to_channel_value(const struct vkms_color_lut *lut, u16 chan
 	return lerp_u16(floor_channel_value, ceil_channel_value,
 			lut_index & DRM_FIXED_DECIMAL_MASK);
 }
+EXPORT_SYMBOL_IF_KUNIT(apply_lut_to_channel_value);
+
 
 static void apply_lut(const struct vkms_crtc_state *crtc_state, struct line_buffer *output_buffer)
 {

drivers/gpu/drm/vkms/vkms_composer.h

@@ -6,9 +6,22 @@
 #include <kunit/visibility.h>
 #include "vkms_drv.h"
 
+/*
+ * This enum is related to the positions of the variables inside
+ * `struct drm_color_lut`, so the order of both needs to be the same.
+ */
+enum lut_channel {
+	LUT_RED = 0,
+	LUT_GREEN,
+	LUT_BLUE,
+	LUT_RESERVED
+};
+
 #if IS_ENABLED(CONFIG_KUNIT)
 u16 lerp_u16(u16 a, u16 b, s64 t);
 s64 get_lut_index(const struct vkms_color_lut *lut, u16 channel_value);
+u16 apply_lut_to_channel_value(const struct vkms_color_lut *lut, u16 channel_value,
+			       enum lut_channel channel);
 #endif
 
 #endif /* _VKMS_COMPOSER_H_ */