backend/drm: Simplify object matching code

We originally used match_obj on planes, but this was largely
unnecessary. Instead, this assigns planes statically at startup.

1 files changed, 214 insertions, 308 deletions

diff --git a/backend/drm/drm.c b/backend/drm/drm.c
index 47857df7..7ff8c7f5 100644
--- a/backend/drm/drm.c
+++ b/backend/drm/drm.c
@@ -1,4 +1,4 @@
-#define _POSIX_C_SOURCE 200112L
+#define _XOPEN_SOURCE 700
 #include <assert.h>
 #include <drm_fourcc.h>
 #include <drm_mode.h>
@@ -10,6 +10,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <strings.h>
 #include <time.h>
 #include <wayland-server.h>
 #include <wayland-util.h>
@@ -72,11 +73,86 @@ bool check_drm_features(struct wlr_drm_backend *drm) {
 	return true;
 }
 
-static int cmp_plane(const void *arg1, const void *arg2) {
-	const struct wlr_drm_plane *a = arg1;
-	const struct wlr_drm_plane *b = arg2;
+static bool add_plane(struct wlr_drm_backend *drm,
+		struct wlr_drm_crtc *crtc, drmModePlane *drm_plane,
+		uint32_t type, union wlr_drm_plane_props *props) {
+	assert(!(type == DRM_PLANE_TYPE_PRIMARY && crtc->primary));
 
-	return (int)a->type - (int)b->type;
+	if (type == DRM_PLANE_TYPE_CURSOR && crtc->cursor) {
+		return true;
+	}
+
+	struct wlr_drm_plane *p = calloc(1, sizeof(*p));
+	if (!p) {
+		wlr_log_errno(WLR_ERROR, "Allocation failed");
+		return false;
+	}
+
+	p->type = type;
+	p->id = drm_plane->plane_id;
+	p->props = *props;
+
+	// Choose an RGB format for the plane
+	uint32_t rgb_format = DRM_FORMAT_INVALID;
+	for (size_t j = 0; j < drm_plane->count_formats; ++j) {
+		uint32_t fmt = drm_plane->formats[j];
+		wlr_drm_format_set_add(&p->formats, fmt, DRM_FORMAT_MOD_INVALID);
+
+		if (fmt == DRM_FORMAT_ARGB8888) {
+			// Prefer formats with alpha channel
+			rgb_format = fmt;
+			break;
+		} else if (fmt == DRM_FORMAT_XRGB8888) {
+			rgb_format = fmt;
+		}
+	}
+	p->drm_format = rgb_format;
+
+	if (p->props.in_formats) {
+		uint64_t blob_id;
+		if (!get_drm_prop(drm->fd, p->id, p->props.in_formats, &blob_id)) {
+			wlr_log(WLR_ERROR, "Failed to read IN_FORMATS property");
+			goto error;
+		}
+
+		drmModePropertyBlobRes *blob = drmModeGetPropertyBlob(drm->fd, blob_id);
+		if (!blob) {
+			wlr_log(WLR_ERROR, "Failed to read IN_FORMATS blob");
+			goto error;
+		}
+
+		struct drm_format_modifier_blob *data = blob->data;
+		uint32_t *fmts = (uint32_t *)((char *)data + data->formats_offset);
+		struct drm_format_modifier *mods = (struct drm_format_modifier *)
+			((char *)data + data->modifiers_offset);
+		for (uint32_t i = 0; i < data->count_modifiers; ++i) {
+			for (int j = 0; j < 64; ++j) {
+				if (mods[i].formats & ((uint64_t)1 << j)) {
+					wlr_drm_format_set_add(&p->formats,
+						fmts[j + mods[i].offset], mods[i].modifier);
+				}
+			}
+		}
+
+		drmModeFreePropertyBlob(blob);
+	}
+
+	switch (type) {
+	case DRM_PLANE_TYPE_PRIMARY:
+		crtc->primary = p;
+		break;
+	case DRM_PLANE_TYPE_CURSOR:
+		crtc->cursor = p;
+		break;
+	default:
+		abort();
+	}
+
+	return true;
+
+error:
+	free(p);
+	return false;
 }
 
 static bool init_planes(struct wlr_drm_backend *drm) {
@@ -88,118 +164,72 @@ static bool init_planes(struct wlr_drm_backend *drm) {
 
 	wlr_log(WLR_INFO, "Found %"PRIu32" DRM planes", plane_res->count_planes);
 
-	if (plane_res->count_planes == 0) {
-		drmModeFreePlaneResources(plane_res);
-		return true;
-	}
-
-	drm->num_planes = plane_res->count_planes;
-	drm->planes = calloc(drm->num_planes, sizeof(*drm->planes));
-	if (!drm->planes) {
-		wlr_log_errno(WLR_ERROR, "Allocation failed");
-		goto error_res;
-	}
-
-	for (size_t i = 0; i < drm->num_planes; ++i) {
-		struct wlr_drm_plane *p = &drm->planes[i];
+	for (uint32_t i = 0; i < plane_res->count_planes; ++i) {
+		uint32_t id = plane_res->planes[i];
 
-		drmModePlane *plane = drmModeGetPlane(drm->fd, plane_res->planes[i]);
+		drmModePlane *plane = drmModeGetPlane(drm->fd, id);
 		if (!plane) {
 			wlr_log_errno(WLR_ERROR, "Failed to get DRM plane");
-			goto error_planes;
+			goto error;
 		}
 
-		p->id = plane->plane_id;
-		p->possible_crtcs = plane->possible_crtcs;
+		union wlr_drm_plane_props props = {0};
+		if (!get_drm_plane_props(drm->fd, id, &props)) {
+			drmModeFreePlane(plane);
+			goto error;
+		}
 
 		uint64_t type;
-		if (!get_drm_plane_props(drm->fd, p->id, &p->props) ||
-				!get_drm_prop(drm->fd, p->id, p->props.type, &type)) {
+		if (!get_drm_prop(drm->fd, id, props.type, &type)) {
 			drmModeFreePlane(plane);
-			goto error_planes;
+			goto error;
 		}
 
-		p->type = type;
-		drm->num_type_planes[type]++;
-
-		// Choose an RGB format for the plane
-		uint32_t rgb_format = DRM_FORMAT_INVALID;
-		for (size_t j = 0; j < plane->count_formats; ++j) {
-			uint32_t fmt = plane->formats[j];
-			wlr_drm_format_set_add(&p->formats, fmt, DRM_FORMAT_MOD_INVALID);
-
-			if (fmt == DRM_FORMAT_ARGB8888) {
-				// Prefer formats with alpha channel
-				rgb_format = fmt;
-				break;
-			} else if (fmt == DRM_FORMAT_XRGB8888) {
-				rgb_format = fmt;
+		/*
+		 * This is a very naive implementation of the plane matching
+		 * logic. Primary and cursor planes should only work on a
+		 * single CRTC, and this should be perfectly adequate, but
+		 * overlay planes can potentially work with multiple CRTCs,
+		 * meaning this could return inefficent/skewed results.
+		 *
+		 * However, we don't really care about overlay planes, as we
+		 * don't support them yet. We only bother to keep basic
+		 * tracking of them for DRM lease clients.
+		 *
+		 * possible_crtcs is a bitmask of crtcs, where each bit is an
+		 * index into drmModeRes.crtcs. So if bit 0 is set (ffs starts
+		 * counting from 1), crtc 0 is possible.
+		 */
+		int crtc_bit = ffs(plane->possible_crtcs) - 1;
+
+		// This would be a kernel bug
+		assert(crtc_bit >= 0 && (size_t)crtc_bit < drm->num_crtcs);
+
+		struct wlr_drm_crtc *crtc = &drm->crtcs[crtc_bit];
+
+		if (type == DRM_PLANE_TYPE_OVERLAY) {
+			uint32_t *tmp = realloc(crtc->overlays,
+				sizeof(*crtc->overlays) * (crtc->num_overlays + 1));
+			if (tmp) {
+				crtc->overlays = tmp;
+				crtc->overlays[crtc->num_overlays++] = id;
 			}
-		}
-		// Some overlays exist which don't support XRGB8888/ARGB8888
-		// We aren't even using overlay planes currently, so don't fail
-		// on something unnecessary.
-		if (type != DRM_PLANE_TYPE_OVERLAY && rgb_format == DRM_FORMAT_INVALID) {
-			wlr_log(WLR_ERROR, "Failed to find an RGB format for plane %zu", i);
 			drmModeFreePlane(plane);
-			goto error_planes;
+			continue;
 		}
-		p->drm_format = rgb_format;
-
-		if (p->props.in_formats) {
-			uint64_t blob_id;
-			if (!get_drm_prop(drm->fd, p->id, p->props.in_formats, &blob_id)) {
-				wlr_log(WLR_ERROR, "Failed to read IN_FORMATS property");
-				drmModeFreePlane(plane);
-				goto error_planes;
-			}
-
-			drmModePropertyBlobRes *blob =
-				drmModeGetPropertyBlob(drm->fd, blob_id);
-			if (!blob) {
-				wlr_log(WLR_ERROR, "Failed to read IN_FORMATS blob");
-				drmModeFreePlane(plane);
-				goto error_planes;
-			}
-
-			struct drm_format_modifier_blob *data = blob->data;
-			uint32_t *fmts = (uint32_t *)((char *)data + data->formats_offset);
-			struct drm_format_modifier *mods = (struct drm_format_modifier *)
-				((char *)data + data->modifiers_offset);
-			for (uint32_t i = 0; i < data->count_modifiers; ++i) {
-				for (int j = 0; j < 64; ++j) {
-					if (mods[i].formats & ((uint64_t)1 << j)) {
-						wlr_drm_format_set_add(&p->formats,
-							fmts[j + mods[i].offset], mods[i].modifier);
-					}
-				}
-			}
 
-			drmModeFreePropertyBlob(blob);
+		if (!add_plane(drm, crtc, plane, type, &props)) {
+			drmModeFreePlane(plane);
+			goto error;
 		}
 
 		drmModeFreePlane(plane);
 	}
 
-	wlr_log(WLR_INFO, "(%zu overlay, %zu primary, %zu cursor)",
-		drm->num_overlay_planes,
-		drm->num_primary_planes,
-		drm->num_cursor_planes);
-
-	qsort(drm->planes, drm->num_planes, sizeof(*drm->planes), cmp_plane);
-
-	drm->overlay_planes = drm->planes;
-	drm->primary_planes = drm->overlay_planes
-		+ drm->num_overlay_planes;
-	drm->cursor_planes = drm->primary_planes
-		+ drm->num_primary_planes;
-
 	drmModeFreePlaneResources(plane_res);
 	return true;
 
-error_planes:
-	free(drm->planes);
-error_res:
+error:
 	drmModeFreePlaneResources(plane_res);
 	return false;
 }
@@ -252,26 +282,33 @@ void finish_drm_resources(struct wlr_drm_backend *drm) {
 		return;
 	}
 
-	for (size_t i = 0; i < drm->num_planes; ++i) {
-		struct wlr_drm_plane *p = &drm->planes[i];
-		wlr_drm_format_set_finish(&p->formats);
-	}
-
 	for (size_t i = 0; i < drm->num_crtcs; ++i) {
 		struct wlr_drm_crtc *crtc = &drm->crtcs[i];
+
 		drmModeAtomicFree(crtc->atomic);
 		drmModeFreeCrtc(crtc->legacy_crtc);
+
 		if (crtc->mode_id) {
 			drmModeDestroyPropertyBlob(drm->fd, crtc->mode_id);
 		}
 		if (crtc->gamma_lut) {
 			drmModeDestroyPropertyBlob(drm->fd, crtc->gamma_lut);
 		}
+
 		free(crtc->gamma_table);
+
+		if (crtc->primary) {
+			wlr_drm_format_set_finish(&crtc->primary->formats);
+			free(crtc->primary);
+		}
+		if (crtc->cursor) {
+			wlr_drm_format_set_finish(&crtc->cursor->formats);
+			free(crtc->cursor);
+		}
+		free(crtc->overlays);
 	}
 
 	free(drm->crtcs);
-	free(drm->planes);
 }
 
 static struct wlr_drm_connector *get_drm_connector_from_output(
@@ -477,7 +514,7 @@ static void drm_connector_start_renderer(struct wlr_drm_connector *conn) {
 	}
 }
 
-static void realloc_crtcs(struct wlr_drm_backend *drm, bool *changed_outputs);
+static void realloc_crtcs(struct wlr_drm_backend *drm);
 
 static void attempt_enable_needs_modeset(struct wlr_drm_backend *drm) {
 	// Try to modeset any output that has a desired mode and a CRTC (ie. was
@@ -506,7 +543,7 @@ bool enable_drm_connector(struct wlr_output *output, bool enable) {
 
 	if (enable && conn->crtc == NULL) {
 		// Maybe we can steal a CRTC from a disabled output
-		realloc_crtcs(drm, NULL);
+		realloc_crtcs(drm);
 	}
 
 	bool ok = drm->iface->conn_enable(drm, conn, enable);
@@ -517,7 +554,7 @@ bool enable_drm_connector(struct wlr_output *output, bool enable) {
 	if (enable) {
 		drm_connector_start_renderer(conn);
 	} else {
-		realloc_crtcs(drm, NULL);
+		realloc_crtcs(drm);
 
 		attempt_enable_needs_modeset(drm);
 	}
@@ -526,82 +563,6 @@ bool enable_drm_connector(struct wlr_output *output, bool enable) {
 	return true;
 }
 
-static ssize_t connector_index_from_crtc(struct wlr_drm_backend *drm,
-		struct wlr_drm_crtc *crtc) {
-	size_t i = 0;
-	struct wlr_drm_connector *conn;
-	wl_list_for_each(conn, &drm->outputs, link) {
-		if (conn->crtc == crtc) {
-			return i;
-		}
-		++i;
-	}
-	return -1;
-}
-
-static void realloc_planes(struct wlr_drm_backend *drm, const uint32_t *crtc_in,
-		bool *changed_outputs) {
-	wlr_log(WLR_DEBUG, "Reallocating planes");
-
-	// overlay, primary, cursor
-	for (size_t type = 0; type < 3; ++type) {
-		if (drm->num_type_planes[type] == 0) {
-			continue;
-		}
-
-		uint32_t possible[drm->num_type_planes[type] + 1];
-		uint32_t crtc[drm->num_crtcs + 1];
-		uint32_t crtc_res[drm->num_crtcs + 1];
-
-		for (size_t i = 0; i < drm->num_type_planes[type]; ++i) {
-			possible[i] = drm->type_planes[type][i].possible_crtcs;
-		}
-
-		for (size_t i = 0; i < drm->num_crtcs; ++i) {
-			if (crtc_in[i] == UNMATCHED) {
-				crtc[i] = SKIP;
-			} else if (drm->crtcs[i].planes[type]) {
-				crtc[i] = drm->crtcs[i].planes[type]
-					- drm->type_planes[type];
-			} else {
-				crtc[i] = UNMATCHED;
-			}
-		}
-
-		match_obj(drm->num_type_planes[type], possible,
-			drm->num_crtcs, crtc, crtc_res);
-
-		for (size_t i = 0; i < drm->num_crtcs; ++i) {
-			if (crtc_res[i] == UNMATCHED || crtc_res[i] == SKIP) {
-				continue;
-			}
-
-			struct wlr_drm_crtc *c = &drm->crtcs[i];
-			struct wlr_drm_plane **old = &c->planes[type];
-			struct wlr_drm_plane *new = &drm->type_planes[type][crtc_res[i]];
-
-			if (*old != new) {
-				wlr_log(WLR_DEBUG,
-					"Assigning plane %d -> %d (type %zu) to CRTC %d",
-					*old ? (int)(*old)->id : -1,
-					new ? (int)new->id : -1,
-					type,
-					c->id);
-
-				ssize_t conn_idx = connector_index_from_crtc(drm, c);
-				if (conn_idx >= 0) {
-					changed_outputs[conn_idx] = true;
-				}
-				if (*old) {
-					finish_drm_surface(&(*old)->surf);
-				}
-				finish_drm_surface(&new->surf);
-				*old = new;
-			}
-		}
-	}
-}
-
 static void drm_connector_cleanup(struct wlr_drm_connector *conn);
 
 bool drm_connector_set_mode(struct wlr_output *output,
@@ -610,7 +571,7 @@ bool drm_connector_set_mode(struct wlr_output *output,
 	struct wlr_drm_backend *drm = get_drm_backend_from_backend(output->backend);
 	if (conn->crtc == NULL) {
 		// Maybe we can steal a CRTC from a disabled output
-		realloc_crtcs(drm, NULL);
+		realloc_crtcs(drm);
 	}
 	if (conn->crtc == NULL) {
 		wlr_log(WLR_ERROR, "Cannot modeset '%s': no CRTC for this connector",
@@ -1001,51 +962,37 @@ static void dealloc_crtc(struct wlr_drm_connector *conn) {
 		conn->crtc - drm->crtcs, conn->output.name);
 
 	set_drm_connector_gamma(&conn->output, 0, NULL, NULL, NULL);
-
-	for (size_t type = 0; type < 3; ++type) {
-		struct wlr_drm_plane *plane = conn->crtc->planes[type];
-		if (plane == NULL) {
-			continue;
-		}
-
-		finish_drm_surface(&plane->surf);
-		conn->crtc->planes[type] = NULL;
-	}
+	finish_drm_surface(&conn->crtc->primary->surf);
+	finish_drm_surface(&conn->crtc->cursor->surf);
 
 	drm->iface->conn_enable(drm, conn, false);
 
 	conn->crtc = NULL;
 }
 
-static void realloc_crtcs(struct wlr_drm_backend *drm, bool *changed_outputs) {
-	size_t num_outputs = wl_list_length(&drm->outputs);
-	bool changed_local = changed_outputs ? false : true;
+static void realloc_crtcs(struct wlr_drm_backend *drm) {
+	assert(drm->num_crtcs > 0);
 
-	if (changed_local) {
-		changed_outputs = calloc(num_outputs, sizeof(bool));
-		if (changed_outputs == NULL) {
-			wlr_log(WLR_ERROR, "Allocation failed");
-			return;
-		}
+	size_t num_outputs = wl_list_length(&drm->outputs);
+	if (num_outputs == 0) {
+		return;
 	}
 
 	wlr_log(WLR_DEBUG, "Reallocating CRTCs");
 
-	uint32_t crtc[drm->num_crtcs + 1];
+	struct wlr_drm_connector *connectors[num_outputs];
+	uint32_t connector_constraints[num_outputs];
+	uint32_t previous_match[drm->num_crtcs];
+	uint32_t new_match[drm->num_crtcs];
+
 	for (size_t i = 0; i < drm->num_crtcs; ++i) {
-		crtc[i] = UNMATCHED;
+		previous_match[i] = UNMATCHED;
 	}
 
-	struct wlr_drm_connector *connectors[num_outputs + 1];
-
-	uint32_t possible_crtc[num_outputs + 1];
-	memset(possible_crtc, 0, sizeof(possible_crtc));
-
 	wlr_log(WLR_DEBUG, "State before reallocation:");
-	ssize_t i = -1;
+	size_t i = 0;
 	struct wlr_drm_connector *conn;
 	wl_list_for_each(conn, &drm->outputs, link) {
-		i++;
 		connectors[i] = conn;
 
 		wlr_log(WLR_DEBUG, "  '%s' crtc=%d state=%d desired_enabled=%d",
@@ -1054,7 +1001,7 @@ static void realloc_crtcs(struct wlr_drm_backend *drm, bool *changed_outputs) {
 			conn->state, conn->desired_enabled);
 
 		if (conn->crtc) {
-			crtc[conn->crtc - drm->crtcs] = i;
+			previous_match[conn->crtc - drm->crtcs] = i;
 		}
 
 		// Only search CRTCs for user-enabled outputs (that are already
@@ -1062,86 +1009,84 @@ static void realloc_crtcs(struct wlr_drm_backend *drm, bool *changed_outputs) {
 		if ((conn->state == WLR_DRM_CONN_CONNECTED ||
 				conn->state == WLR_DRM_CONN_NEEDS_MODESET) &&
 				conn->desired_enabled) {
-			possible_crtc[i] = conn->possible_crtc;
+			connector_constraints[i] = conn->possible_crtc;
+		} else {
+			// Will always fail to match anything
+			connector_constraints[i] = 0;
 		}
+
+		++i;
 	}
 
-	uint32_t crtc_res[drm->num_crtcs + 1];
-	match_obj(wl_list_length(&drm->outputs), possible_crtc,
-		drm->num_crtcs, crtc, crtc_res);
+	match_obj(num_outputs, connector_constraints,
+		drm->num_crtcs, previous_match, new_match);
 
-	bool matched[num_outputs + 1];
-	memset(matched, false, sizeof(matched));
-	for (size_t i = 0; i < drm->num_crtcs; ++i) {
-		if (crtc_res[i] != UNMATCHED) {
-			matched[crtc_res[i]] = true;
-		}
+	// Converts our crtc=>connector result into a connector=>crtc one.
+	ssize_t connector_match[num_outputs];
+	for (size_t i = 0 ; i < num_outputs; ++i) {
+		connector_match[i] = -1;
 	}
-
 	for (size_t i = 0; i < drm->num_crtcs; ++i) {
-		// We don't want any of the current monitors to be deactivated
-		if (crtc[i] != UNMATCHED && !matched[crtc[i]] &&
-				connectors[crtc[i]]->desired_enabled) {
-			wlr_log(WLR_DEBUG, "Could not match a CRTC for connected output %d",
-				crtc[i]);
-			goto free_changed_outputs;
+		if (new_match[i] != UNMATCHED) {
+			connector_match[new_match[i]] = i;
 		}
 	}
 
-	for (size_t i = 0; i < drm->num_crtcs; ++i) {
-		if (crtc_res[i] == crtc[i]) {
-			continue;
-		}
-
-		// De-allocate this CRTC on previous output
-		if (crtc[i] != UNMATCHED) {
-			changed_outputs[crtc[i]] = true;
-			dealloc_crtc(connectors[crtc[i]]);
-		}
-
-		// Assign this CRTC to next output
-		if (crtc_res[i] != UNMATCHED) {
-			changed_outputs[crtc_res[i]] = true;
-
-			struct wlr_drm_connector *conn = connectors[crtc_res[i]];
-			dealloc_crtc(conn);
-			conn->crtc = &drm->crtcs[i];
-
-			wlr_log(WLR_DEBUG, "Assigning CRTC %zu to output %d -> %d '%s'",
-				i, crtc[i], crtc_res[i], conn->output.name);
+	/*
+	 * In the case that we add a new connector (hotplug) and we fail to
+	 * match everything, we prefer to fail the new connector and keep all
+	 * of the old mappings instead.
+	 */
+	for (size_t i = 0; i < num_outputs; ++i) {
+		struct wlr_drm_connector *conn = connectors[i];
+		if (conn->state == WLR_DRM_CONN_CONNECTED &&
+				conn->desired_enabled &&
+				connector_match[i] == -1) {
+			wlr_log(WLR_DEBUG, "Could not match a CRTC for previously connected output; "
+					"keeping old configuration");
+			return;
 		}
 	}
-
 	wlr_log(WLR_DEBUG, "State after reallocation:");
-	wl_list_for_each(conn, &drm->outputs, link) {
-		wlr_log(WLR_DEBUG, "  '%s' crtc=%d state=%d desired_enabled=%d",
+
+	// Apply new configuration
+	for (size_t i = 0; i < num_outputs; ++i) {
+		struct wlr_drm_connector *conn = connectors[i];
+		bool prev_enabled = conn->crtc;
+
+		wlr_log(WLR_DEBUG, "  '%s' crtc=%zd state=%d desired_enabled=%d",
 			conn->output.name,
-			conn->crtc ? (int)(conn->crtc - drm->crtcs) : -1,
+			connector_match[i],
 			conn->state, conn->desired_enabled);
-	}
 
-	realloc_planes(drm, crtc_res, changed_outputs);
+		// We don't need to change anything.
+		if (prev_enabled && connector_match[i] == conn->crtc - drm->crtcs) {
+			continue;
+		}
 
-	// We need to reinitialize any plane that has changed
-	i = -1;
-	wl_list_for_each(conn, &drm->outputs, link) {
-		i++;
-		struct wlr_output_mode *mode = conn->output.current_mode;
+		dealloc_crtc(conn);
 
-		if (conn->state != WLR_DRM_CONN_CONNECTED || !changed_outputs[i]) {
+		if (connector_match[i] == -1) {
+			if (prev_enabled) {
+				wlr_log(WLR_DEBUG, "Output has %s lost its CRTC",
+					conn->output.name);
+				conn->state = WLR_DRM_CONN_NEEDS_MODESET;
+				wlr_output_update_enabled(&conn->output, false);
+				conn->desired_mode = conn->output.current_mode;
+				wlr_output_update_mode(&conn->output, NULL);
+			}
 			continue;
 		}
 
-		if (conn->crtc == NULL) {
-			wlr_log(WLR_DEBUG, "Output has %s lost its CRTC",
-				conn->output.name);
-			conn->state = WLR_DRM_CONN_NEEDS_MODESET;
-			wlr_output_update_enabled(&conn->output, false);
-			conn->desired_mode = conn->output.current_mode;
-			wlr_output_update_mode(&conn->output, NULL);
+		conn->crtc = &drm->crtcs[connector_match[i]];
+
+		// Only realloc buffers if we have actually been modeset
+		if (conn->state != WLR_DRM_CONN_CONNECTED) {
 			continue;
 		}
 
+		struct wlr_output_mode *mode = conn->output.current_mode;
+
 		if (!init_drm_plane_surfaces(conn->crtc->primary, drm,
 				mode->width, mode->height, drm->renderer.gbm_format)) {
 			wlr_log(WLR_ERROR, "Failed to initialize renderer for plane");
@@ -1153,11 +1098,6 @@ static void realloc_crtcs(struct wlr_drm_backend *drm, bool *changed_outputs) {
 
 		wlr_output_damage_whole(&conn->output);
 	}
-
-free_changed_outputs:
-	if (changed_local) {
-		free(changed_outputs);
-	}
 }
 
 static uint32_t get_possible_crtcs(int fd, drmModeRes *res,
@@ -1392,25 +1332,7 @@ void scan_drm_connectors(struct wlr_drm_backend *drm) {
 		}
 	}
 
-	bool changed_outputs[wl_list_length(&drm->outputs) + 1];
-	memset(changed_outputs, false, sizeof(changed_outputs));
-	for (size_t i = 0; i < new_outputs_len; ++i) {
-		struct wlr_drm_connector *conn = new_outputs[i];
-
-		ssize_t pos = -1;
-		struct wlr_drm_connector *c;
-		wl_list_for_each(c, &drm->outputs, link) {
-			++pos;
-			if (c == conn) {
-				break;
-			}
-		}
-		assert(pos >= 0);
-
-		changed_outputs[pos] = true;
-	}
-
-	realloc_crtcs(drm, changed_outputs);
+	realloc_crtcs(drm);
 
 	for (size_t i = 0; i < new_outputs_len; ++i) {
 		struct wlr_drm_connector *conn = new_outputs[i];
@@ -1536,23 +1458,7 @@ static void drm_connector_cleanup(struct wlr_drm_connector *conn) {
 
 	switch (conn->state) {
 	case WLR_DRM_CONN_CONNECTED:
-	case WLR_DRM_CONN_CLEANUP:;
-		struct wlr_drm_crtc *crtc = conn->crtc;
-		if (crtc != NULL) {
-			for (int i = 0; i < 3; ++i) {
-				if (!crtc->planes[i]) {
-					continue;
-				}
-
-				finish_drm_surface(&crtc->planes[i]->surf);
-				finish_drm_surface(&crtc->planes[i]->mgpu_surf);
-				if (crtc->planes[i]->id == 0) {
-					free(crtc->planes[i]);
-					crtc->planes[i] = NULL;
-				}
-			}
-		}
-
+	case WLR_DRM_CONN_CLEANUP:
 		conn->output.current_mode = NULL;
 		conn->desired_mode = NULL;
 		struct wlr_drm_mode *mode, *tmp;