dmabuf: Remove assumption that all mods are in fallback tranche

According to the spec the compositor should send scanout modifiers in
their respective device tranches, and all other texture modifiers
in the main tranche. Currently wlroots expects all modifiers to be
present in the last (i.e. "fallback") tranche, this removes that assumption
in the feedback compilation stage so that scanout modifiers for secondary
device can be advertised.

"The full-screen feedback parameters have two tranches: one with the
format/modifier pairs supported by the KMS plane, with the scanout flag
set in the tranche_flags event and with tranche_target_device set to the
KMS scan-out device; the other with the rest of the format/modifier
pairs (supported for texturing, but not for scan-out), without the
scanout flag set in the tranche_flags event, an"

types/wlr_linux_dmabuf_v1.c

@@ -502,13 +502,20 @@ static struct wlr_linux_dmabuf_feedback_v1_compiled *feedback_compile(
 	size_t tranches_len = feedback->tranches.size / sizeof(struct wlr_linux_dmabuf_feedback_v1_tranche);
 	assert(tranches_len > 0);
 
-	// Require the last tranche to be the fallback tranche and contain all
-	// formats/modifiers
-	const struct wlr_linux_dmabuf_feedback_v1_tranche *fallback_tranche = &tranches[tranches_len - 1];
+	// Make one big format set that contains all formats across all tranches so that we
+	// can build an index
+	struct wlr_drm_format_set all_formats = {0};
+	for (size_t i = 0; i < tranches_len; i++) {
+		const struct wlr_linux_dmabuf_feedback_v1_tranche *tranche = &tranches[i];
+		if (!wlr_drm_format_set_union(&all_formats, &all_formats, &tranche->formats)) {
+			wlr_log(WLR_ERROR, "Failed to union scanout formats into one tranche");
+			return false;
+		}
+	}
 
 	size_t table_len = 0;
-	for (size_t i = 0; i < fallback_tranche->formats.len; i++) {
-		const struct wlr_drm_format *fmt = &fallback_tranche->formats.formats[i];
+	for (size_t i = 0; i < all_formats.len; i++) {
+		const struct wlr_drm_format *fmt = &all_formats.formats[i];
 		table_len += fmt->len;
 	}
 	assert(table_len > 0);
@@ -533,8 +540,8 @@ static struct wlr_linux_dmabuf_feedback_v1_compiled *feedback_compile(
 	close(rw_fd);
 
 	size_t n = 0;
-	for (size_t i = 0; i < fallback_tranche->formats.len; i++) {
-		const struct wlr_drm_format *fmt = &fallback_tranche->formats.formats[i];
+	for (size_t i = 0; i < all_formats.len; i++) {
+		const struct wlr_drm_format *fmt = &all_formats.formats[i];
 
 		for (size_t k = 0; k < fmt->len; k++) {
 			table[n] = (struct wlr_linux_dmabuf_feedback_v1_table_entry){
@@ -561,8 +568,8 @@ static struct wlr_linux_dmabuf_feedback_v1_compiled *feedback_compile(
 	compiled->table_fd = ro_fd;
 	compiled->table_size = table_size;
 
-	// Build the indices lists for all but the last (fallback) tranches
-	for (size_t i = 0; i < tranches_len - 1; i++) {
+	// Build the indices lists for all tranches
+	for (size_t i = 0; i < tranches_len; i++) {
 		const struct wlr_linux_dmabuf_feedback_v1_tranche *tranche = &tranches[i];
 		struct wlr_linux_dmabuf_feedback_v1_compiled_tranche *compiled_tranche =
 			&compiled->tranches[i];
@@ -582,7 +589,7 @@ static struct wlr_linux_dmabuf_feedback_v1_compiled *feedback_compile(
 			const struct wlr_drm_format *fmt = &tranche->formats.formats[j];
 			for (size_t k = 0; k < fmt->len; k++) {
 				ssize_t index = get_drm_format_set_index(
-					&fallback_tranche->formats, fmt->format, fmt->modifiers[k]);
+					&all_formats, fmt->format, fmt->modifiers[k]);
 				if (index < 0) {
 					wlr_log(WLR_ERROR, "Format 0x%" PRIX32 " and modifier "
 						"0x%" PRIX64 " are in tranche #%zu but are missing "
@@ -597,26 +604,6 @@ static struct wlr_linux_dmabuf_feedback_v1_compiled *feedback_compile(
 		compiled_tranche->indices.size = n * sizeof(uint16_t);
 	}
 
-	struct wlr_linux_dmabuf_feedback_v1_compiled_tranche *fallback_compiled_tranche =
-		&compiled->tranches[compiled->tranches_len - 1];
-	fallback_compiled_tranche->target_device = fallback_tranche->target_device;
-	fallback_compiled_tranche->flags = fallback_tranche->flags;
-
-	// Build the indices list for the last (fallback) tranche
-	wl_array_init(&fallback_compiled_tranche->indices);
-	if (!wl_array_add(&fallback_compiled_tranche->indices,
-			table_len * sizeof(uint16_t))) {
-		wlr_log(WLR_ERROR, "Failed to allocate fallback tranche indices array");
-		goto error_compiled;
-	}
-
-	n = 0;
-	uint16_t *index_ptr;
-	wl_array_for_each(index_ptr, &fallback_compiled_tranche->indices) {
-		*index_ptr = n;
-		n++;
-	}
-
 	return compiled;
 
 error_compiled: