boot: Add a shortcut to toggle video/text mode

boot/menu.c

@@ -168,6 +168,11 @@ void show_menu(void) {
 				boot_mode = boot_mode_names[i].index;
 				break;
 			}
+#ifndef EFI_PLATFORM
+		} else if (s == 0x2f) { /* v */
+			void bios_toggle_mode(void);
+			bios_toggle_mode();
+#endif
 		} else if (!timeout) {
 			goto read_again;
 		}

boot/platform.c

@@ -77,12 +77,7 @@ int bios_text_mode(void) {
 	text_reset();
 }
 
-int bios_main(void) {
-	/* Zero BSS */
-	memset(&_bss_start,0,(uintptr_t)&_bss_end-(uintptr_t)&_bss_start);
-
-	text_reset();
-
+int bios_video_mode(void) {
 	int best_match = 0;
 	int match_score = 0;
 
@@ -122,6 +117,23 @@ int bios_main(void) {
 	}
 
 	init_graphics();
+}
+
+void bios_toggle_mode(void) {
+	if (in_graphics_mode) {
+		bios_text_mode();
+	} else {
+		bios_video_mode();
+	}
+}
+
+int bios_main(void) {
+	/* Zero BSS */
+	memset(&_bss_start,0,(uintptr_t)&_bss_end-(uintptr_t)&_bss_start);
+
+	text_reset();
+	bios_video_mode();
+
 
 	return kmain();
 }