backend/drm: add entry for Valve EDID vendor

As found in e.g. the Steam Deck.

README.md

@@ -43,11 +43,11 @@ Install dependencies:
 * meson
 * wayland
 * wayland-protocols
-* EGL
-* GLESv2
+* EGL and GLESv2 (optional, for the GLES2 renderer)
+* Vulkan loader, headers and glslang (optional, for the Vulkan renderer)
 * libdrm
 * GBM
-* libinput
+* libinput (optional, for the libinput backend)
 * xkbcommon
 * udev
 * pixman

backend/drm/util.c

@@ -94,6 +94,7 @@ static const char *get_manufacturer(uint16_t id) {
 	case ID('V', 'E', 'S'): return "Vestel Elektronik Sanayi ve Ticaret A. S.";
 	case ID('V', 'I', 'T'): return "Visitech AS";
 	case ID('V', 'I', 'Z'): return "VIZIO, Inc";
+	case ID('V', 'L', 'V'): return "Valve";
 	case ID('V', 'S', 'C'): return "ViewSonic Corporation";
 	case ID('Y', 'M', 'H'): return "Yamaha Corporation";
 	default:                return "Unknown";

types/output/output.c

@@ -547,6 +547,16 @@ static bool output_basic_test(struct wlr_output *output) {
 		enabled = output->pending.enabled;
 	}
 
+	if (enabled && (output->pending.committed & (WLR_OUTPUT_STATE_ENABLED |
+			WLR_OUTPUT_STATE_MODE))) {
+		int pending_width, pending_height;
+		output_pending_resolution(output, &pending_width, &pending_height);
+		if (pending_width == 0 || pending_height == 0) {
+			wlr_log(WLR_DEBUG, "Tried to enable an output with a zero mode");
+			return false;
+		}
+	}
+
 	if (!enabled && output->pending.committed & WLR_OUTPUT_STATE_BUFFER) {
 		wlr_log(WLR_DEBUG, "Tried to commit a buffer on a disabled output");
 		return false;