drm: Add Enhanced LUT precision structure

Existing LUT precision structure drm_color_lut has only 16 bit
precision. This is not enough for upcoming enhanced hardwares
and advance usecases like HDR processing. Hence added a new
structure with 32 bit precision values.

Signed-off-by: Alex Hung <[e-mail]>
Signed-off-by: Uma Shankar <[e-mail]>
Signed-off-by: Chaitanya Kumar Borah <[e-mail]>
Reviewed-by: Sebastian Wick <[e-mail]>
Signed-off-by: Simon Ser <[e-mail]>
Link: https://patch.msgid.link/[e-mail]

drivers/gpu/drm/drm_color_mgmt.c

···
 		fill_palette_8(crtc, i, set_palette);
 }
 EXPORT_SYMBOL(drm_crtc_fill_palette_8);
+
+/**
+ * drm_color_lut32_check - check validity of extended lookup table
+ * @lut: property blob containing extended LUT to check
+ * @tests: bitmask of tests to run
+ *
+ * Helper to check whether a userspace-provided extended lookup table is valid and
+ * satisfies hardware requirements.  Drivers pass a bitmask indicating which of
+ * the tests in &drm_color_lut_tests should be performed.
+ *
+ * Returns 0 on success, -EINVAL on failure.
+ */
+int drm_color_lut32_check(const struct drm_property_blob *lut, u32 tests)
+{
+	const struct drm_color_lut32 *entry;
+	int i;
+
+	if (!lut || !tests)
+		return 0;
+
+	entry = lut->data;
+	for (i = 0; i < drm_color_lut32_size(lut); i++) {
+		if (tests & DRM_COLOR_LUT_EQUAL_CHANNELS) {
+			if (entry[i].red != entry[i].blue ||
+			    entry[i].red != entry[i].green) {
+				DRM_DEBUG_KMS("All LUT entries must have equal r/g/b\n");
+				return -EINVAL;
+			}
+		}
+
+		if (i > 0 && tests & DRM_COLOR_LUT_NON_DECREASING) {
+			if (entry[i].red < entry[i - 1].red ||
+			    entry[i].green < entry[i - 1].green ||
+			    entry[i].blue < entry[i - 1].blue) {
+				DRM_DEBUG_KMS("LUT entries must never decrease.\n");
+				return -EINVAL;
+			}
+		}
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_color_lut32_check);

include/drm/drm_color_mgmt.h

···
 	return blob->length / sizeof(struct drm_color_lut);
 }
 
+/**
+ * drm_color_lut32_size - calculate the number of entries in the extended LUT
+ * @blob: blob containing the LUT
+ *
+ * Returns:
+ * The number of entries in the color LUT stored in @blob.
+ */
+static inline int drm_color_lut32_size(const struct drm_property_blob *blob)
+{
+	return blob->length / sizeof(struct drm_color_lut32);
+}
+
 enum drm_color_encoding {
 	DRM_COLOR_YCBCR_BT601,
 	DRM_COLOR_YCBCR_BT709,
···
 void drm_crtc_fill_palette_332(struct drm_crtc *crtc, drm_crtc_set_lut_func set_palette);
 void drm_crtc_fill_palette_8(struct drm_crtc *crtc, drm_crtc_set_lut_func set_palette);
 
+int drm_color_lut32_check(const struct drm_property_blob *lut, u32 tests);
 #endif

include/uapi/drm/drm_mode.h

···
 	__u16 reserved;
 };
 
+/*
+ * struct drm_color_lut32
+ *
+ * 32-bit per channel color LUT entry, similar to drm_color_lut.
+ */
+struct drm_color_lut32 {
+	__u32 red;
+	__u32 green;
+	__u32 blue;
+	__u32 reserved;
+};
+
 /**
  * enum drm_colorop_type - Type of color operation
  *