Require INVALID for implicit format modifiers

See [1] for the motivation.

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

backend/drm/drm.c

@@ -118,9 +118,14 @@ static bool add_plane(struct wlr_drm_backend *drm,
 	p->id = drm_plane->plane_id;
 	p->props = *props;
 
-	for (size_t j = 0; j < drm_plane->count_formats; ++j) {
+	for (size_t i = 0; i < drm_plane->count_formats; ++i) {
-		wlr_drm_format_set_add(&p->formats, drm_plane->formats[j],
+		// Force a LINEAR layout for the cursor if the driver doesn't support
-			DRM_FORMAT_MOD_INVALID);
+		// modifiers
+		uint64_t mod = DRM_FORMAT_MOD_INVALID;
+		if (type == DRM_PLANE_TYPE_CURSOR) {
+			mod = DRM_FORMAT_MOD_LINEAR;
+		}
+		wlr_drm_format_set_add(&p->formats, drm_plane->formats[i], mod);
 	}
 
 	if (p->props.in_formats && drm->addfb2_modifiers) {
@@ -150,13 +155,6 @@ static bool add_plane(struct wlr_drm_backend *drm,
 		}
 
 		drmModeFreePropertyBlob(blob);
-	} else if (type == DRM_PLANE_TYPE_CURSOR) {
-		// Force a LINEAR layout for the cursor if the driver doesn't support
-		// modifiers
-		for (size_t i = 0; i < p->formats.len; ++i) {
-			wlr_drm_format_set_add(&p->formats, p->formats.formats[i]->format,
-				DRM_FORMAT_MOD_LINEAR);
-		}
 	}
 
 	switch (type) {

backend/x11/backend.c

@@ -354,6 +354,7 @@ static bool query_formats(struct wlr_x11_backend *x11) {
 			}
 
 			if (x11->have_dri3) {
+				// X11 always supports implicit modifiers
 				wlr_drm_format_set_add(&x11->dri3_formats, format->drm,
 					DRM_FORMAT_MOD_INVALID);
 				if (!query_dri3_modifiers(x11, format)) {

render/allocator/gbm.c

@@ -7,6 +7,7 @@
 #include <wlr/util/log.h>
 #include <xf86drm.h>
 #include "render/allocator/gbm.h"
+#include "render/drm_format_set.h"
 
 static const struct wlr_buffer_impl buffer_impl;
 
@@ -86,17 +87,20 @@ 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) {
+	struct gbm_bo *bo = gbm_bo_create_with_modifiers(gbm_device, width, height,
-		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;
+		} 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;

render/drm_format_set.c

@@ -43,11 +43,6 @@ bool wlr_drm_format_set_has(const struct wlr_drm_format_set *set,
 	if (!fmt) {
 		return false;
 	}
-
-	if (modifier == DRM_FORMAT_MOD_INVALID) {
-		return true;
-	}
-
 	return wlr_drm_format_has(fmt, modifier);
 }
 
@@ -112,10 +107,6 @@ bool wlr_drm_format_has(const struct wlr_drm_format *fmt, uint64_t modifier) {
 bool wlr_drm_format_add(struct wlr_drm_format **fmt_ptr, uint64_t modifier) {
 	struct wlr_drm_format *fmt = *fmt_ptr;
 
-	if (modifier == DRM_FORMAT_MOD_INVALID) {
-		return true;
-	}
-
 	if (wlr_drm_format_has(fmt, modifier)) {
 		return true;
 	}
@@ -153,15 +144,17 @@ struct wlr_drm_format *wlr_drm_format_intersect(
 		const struct wlr_drm_format *a, const struct wlr_drm_format *b) {
 	assert(a->format == b->format);
 
-	// Special case: if a format only supports LINEAR and the other doesn't
+	// Special case: if a format only supports LINEAR and the other supports
-	// support any modifier, force LINEAR. This will force the allocator to
+	// implicit modifiers, force LINEAR. This will force the allocator to
-	// create a buffer with a LINEAR layout instead of an implicit modifier.
+	// create a buffer with a linear layout instead of an implicit modifier.
-	if (a->len == 0 && b->len == 1 && b->modifiers[0] == DRM_FORMAT_MOD_LINEAR) {
+	if (a->len == 1 && a->modifiers[0] == DRM_FORMAT_MOD_LINEAR &&
-		return wlr_drm_format_dup(b);
+			wlr_drm_format_has(b, DRM_FORMAT_MOD_INVALID)) {
-	}
-	if (b->len == 0 && a->len == 1 && a->modifiers[0] == DRM_FORMAT_MOD_LINEAR) {
 		return wlr_drm_format_dup(a);
 	}
+	if (b->len == 1 && b->modifiers[0] == DRM_FORMAT_MOD_LINEAR &&
+			wlr_drm_format_has(a, DRM_FORMAT_MOD_INVALID)) {
+		return wlr_drm_format_dup(b);
+	}
 
 	size_t format_cap = a->len < b->len ? a->len : b->len;
 	size_t format_size = sizeof(struct wlr_drm_format) +
@@ -185,9 +178,9 @@ struct wlr_drm_format *wlr_drm_format_intersect(
 		}
 	}
 
-	// If both formats support modifiers, but the intersection is empty, then
+	// If the intersection is empty, then the formats aren't compatible with
-	// the formats aren't compatible with each other
+	// each other.
-	if (format->len == 0 && a->len > 0 && b->len > 0) {
+	if (format->len == 0) {
 		free(format);
 		return NULL;
 	}

render/egl.c

@@ -119,12 +119,11 @@ static void init_dmabuf_formats(struct wlr_egl *egl) {
 
 		has_modifiers = has_modifiers || modifiers_len > 0;
 
-		if (modifiers_len == 0) {
+		// EGL always supports implicit modifiers
 		wlr_drm_format_set_add(&egl->dmabuf_texture_formats, fmt,
 			DRM_FORMAT_MOD_INVALID);
 		wlr_drm_format_set_add(&egl->dmabuf_render_formats, fmt,
 			DRM_FORMAT_MOD_INVALID);
-		}
 
 		for (int j = 0; j < modifiers_len; j++) {
 			wlr_drm_format_set_add(&egl->dmabuf_texture_formats, fmt,

types/wlr_linux_dmabuf_v1.c

@@ -9,6 +9,7 @@
 #include <wlr/types/wlr_linux_dmabuf_v1.h>
 #include <wlr/util/log.h>
 #include "linux-dmabuf-unstable-v1-protocol.h"
+#include "render/drm_format_set.h"
 #include "util/signal.h"
 
 #define LINUX_DMABUF_VERSION 3
@@ -413,7 +414,9 @@ static const struct zwp_linux_dmabuf_v1_interface linux_dmabuf_impl = {
 static void linux_dmabuf_send_modifiers(struct wl_resource *resource,
 		const struct wlr_drm_format *fmt) {
 	if (wl_resource_get_version(resource) < ZWP_LINUX_DMABUF_V1_MODIFIER_SINCE_VERSION) {
+		if (wlr_drm_format_has(fmt, DRM_FORMAT_MOD_INVALID)) {
 			zwp_linux_dmabuf_v1_send_format(resource, fmt->format);
+		}
 		return;
 	}
 
@@ -422,10 +425,6 @@ static void linux_dmabuf_send_modifiers(struct wl_resource *resource,
 		zwp_linux_dmabuf_v1_send_modifier(resource, fmt->format,
 			mod >> 32, mod & 0xFFFFFFFF);
 	}
-
-	// We always support buffers with an implicit modifier
-	zwp_linux_dmabuf_v1_send_modifier(resource, fmt->format,
-		DRM_FORMAT_MOD_INVALID >> 32, DRM_FORMAT_MOD_INVALID & 0xFFFFFFFF);
 }
 
 static void linux_dmabuf_send_formats(struct wlr_linux_dmabuf_v1 *linux_dmabuf,