Require INVALID for implicit format modifiers

See [1] for the motivation.

[1]: https://gitlab.freedesktop.org/wayland/wayland-protocols/-/merge_requests/75

1 files changed, 12 insertions, 6 deletions

diff --git a/render/allocator/gbm.c b/render/allocator/gbm.c
index b546e412..8f73862a 100644
--- a/render/allocator/gbm.c
+++ b/render/allocator/gbm.c
@@ -10,6 +10,7 @@
 #include <xf86drm.h>
 
 #include "render/allocator/gbm.h"
+#include "render/drm_format_set.h"
 
 static const struct wlr_buffer_impl buffer_impl;
 
@@ -89,17 +90,22 @@ static struct wlr_gbm_buffer *create_buffer(struct wlr_gbm_allocator *alloc,
 		int width, int height, const struct wlr_drm_format *format) {
 	struct gbm_device *gbm_device = alloc->gbm_device;
 
-	struct gbm_bo *bo = NULL;
+	assert(format->len > 0);
+
 	bool has_modifier = true;
-	if (format->len > 0) {
-		bo = gbm_bo_create_with_modifiers(gbm_device, width, height,
-			format->format, format->modifiers, format->len);
-	}
+	uint64_t fallback_modifier = DRM_FORMAT_MOD_INVALID;
+	struct gbm_bo *bo = gbm_bo_create_with_modifiers(gbm_device, width, height,
+		format->format, format->modifiers, format->len);
 	if (bo == NULL) {
 		uint32_t usage = GBM_BO_USE_SCANOUT | GBM_BO_USE_RENDERING;
 		if (format->len == 1 &&
 				format->modifiers[0] == DRM_FORMAT_MOD_LINEAR) {
 			usage |= GBM_BO_USE_LINEAR;
+			fallback_modifier = DRM_FORMAT_MOD_LINEAR;
+		} else if (!wlr_drm_format_has(format, DRM_FORMAT_MOD_INVALID)) {
+			// If the format doesn't accept an implicit modifier, bail out.
+			wlr_log(WLR_ERROR, "gbm_bo_create_with_modifiers failed");
+			return NULL;
 		}
 		bo = gbm_bo_create(gbm_device, width, height, format->format, usage);
 		has_modifier = false;
@@ -128,7 +134,7 @@ static struct wlr_gbm_buffer *create_buffer(struct wlr_gbm_allocator *alloc,
 	// don't populate the modifier field: other parts of the stack may not
 	// understand modifiers, and they can't strip the modifier.
 	if (!has_modifier) {
-		buffer->dmabuf.modifier = DRM_FORMAT_MOD_INVALID;
+		buffer->dmabuf.modifier = fallback_modifier;
 	}
 
 	wlr_log(WLR_DEBUG, "Allocated %dx%d GBM buffer (format 0x%"PRIX32", "