Merge branch 'gbm-explicit-upgrade' into 'master'

Draft: `WLR_GBM_EXPLICIT_UPGRADE`

See merge request wlroots/wlroots!5200

docs/env_vars.md

@@ -18,6 +18,9 @@ wlroots reads these environment variables
   and Vulkan
 * *WLR_EGL_NO_MODIFIERS*: set to 1 to disable format modifiers in EGL, this can
   be used to understand and work around driver bugs.
+* *WLR_GBM_EXPLICIT_UPGRADE*: set to 1 to attempt to "upgrade" buffers
+  allocated with implicit modifiers to explicit modifiers. May help when a
+  conservative modifier is required, but may not work with all drivers.
 
 ## DRM backend
 

include/render/allocator/gbm.h

@@ -22,6 +22,10 @@ struct wlr_gbm_allocator {
 	struct gbm_device *gbm_device;
 
 	struct wl_list buffers; // wlr_gbm_buffer.link
+
+	struct {
+		bool explicit_upgrade;
+	} WLR_PRIVATE;
 };
 
 /**

render/allocator/gbm.c

@@ -11,6 +11,7 @@
 
 #include "render/allocator/gbm.h"
 #include "render/drm_format_set.h"
+#include "util/env.h"
 
 static const struct wlr_buffer_impl buffer_impl;
 
@@ -90,6 +91,10 @@ static struct wlr_gbm_buffer *create_buffer(struct wlr_gbm_allocator *alloc,
 		return NULL;
 	}
 
+	if (!has_modifier && alloc->explicit_upgrade) {
+		fallback_modifier = gbm_bo_get_modifier(bo);
+	}
+
 	struct wlr_gbm_buffer *buffer = calloc(1, sizeof(*buffer));
 	if (buffer == NULL) {
 		gbm_bo_destroy(bo);
@@ -174,6 +179,7 @@ struct wlr_allocator *wlr_gbm_allocator_create(int fd) {
 		return NULL;
 	}
 	wlr_allocator_init(&alloc->base, &allocator_impl, WLR_BUFFER_CAP_DMABUF);
+	alloc->explicit_upgrade = env_parse_bool("WLR_GBM_EXPLICIT_UPGRADE");
 
 	alloc->fd = fd;
 	wl_list_init(&alloc->buffers);

types/wlr_output_swapchain_manager.c

@@ -9,6 +9,7 @@
 #include <wlr/util/log.h>
 #include "render/drm_format_set.h"
 #include "types/wlr_output.h"
+#include "util/env.h"
 
 struct wlr_output_swapchain_manager_output {
 	struct wlr_output *output;
@@ -22,6 +23,9 @@ struct wlr_output_swapchain_manager_output {
 	// wlr_output_swapchain_manager_apply() is called. Can be either a pointer
 	// to the newly allocated swapchain, or the old swapchain, or NULL.
 	struct wlr_swapchain *pending_swapchain;
+	// Whether we will trust the allocator to upgrade implicit allocations to
+	// use explicit modifiers.
+	bool explicit_upgrade;
 };
 
 void wlr_output_swapchain_manager_init(struct wlr_output_swapchain_manager *manager,
@@ -55,6 +59,7 @@ static struct wlr_output_swapchain_manager_output *manager_get_or_add_output(
 	}
 	*manager_output = (struct wlr_output_swapchain_manager_output){
 		.output = output,
+		.explicit_upgrade = env_parse_bool("WLR_GBM_EXPLICIT_UPGRADE"),
 	};
 	return manager_output;
 }
@@ -126,7 +131,9 @@ static bool manager_output_prepare(struct wlr_output_swapchain_manager_output *m
 	}
 
 	if (!explicit_modifiers && (format.len != 1 || format.modifiers[0] != DRM_FORMAT_MOD_LINEAR)) {
-		if (!wlr_drm_format_has(&format, DRM_FORMAT_MOD_INVALID)) {
+		if (!wlr_drm_format_has(&format, DRM_FORMAT_MOD_INVALID) &&
+				!(wlr_drm_format_set_has(display_formats, format.format, DRM_FORMAT_MOD_INVALID) &&
+				manager_output->explicit_upgrade)) {
 			wlr_log(WLR_DEBUG, "Implicit modifiers not supported");
 			wlr_drm_format_finish(&format);
 			return false;