terminal-util: introduce vt_restore() helper

src/basic/terminal-util.c

@@ -1271,3 +1271,37 @@ int vt_reset_keyboard(int fd) {
 
         return 0;
 }
+
+int vt_restore(int fd) {
+        static const struct vt_mode mode = {
+                .mode = VT_AUTO,
+        };
+        int r, q = 0;
+
+        r = ioctl(fd, KDSETMODE, KD_TEXT);
+        if (r < 0)
+                q = log_debug_errno(errno, "Failed to set VT in text mode, ignoring: %m");
+
+        r = vt_reset_keyboard(fd);
+        if (r < 0) {
+                log_debug_errno(r, "Failed to reset keyboard mode, ignoring: %m");
+                if (q >= 0)
+                        q = r;
+        }
+
+        r = ioctl(fd, VT_SETMODE, &mode);
+        if (r < 0) {
+                log_debug_errno(errno, "Failed to set VT_AUTO mode, ignoring: %m");
+                if (q >= 0)
+                        q = -errno;
+        }
+
+        r = fchown(fd, 0, (gid_t) -1);
+        if (r < 0) {
+                log_debug_errno(errno, "Failed to chown VT, ignoring: %m");
+                if (q >= 0)
+                        q = -errno;
+        }
+
+        return q;
+}

src/basic/terminal-util.h

@@ -154,3 +154,4 @@ int open_terminal_in_namespace(pid_t pid, const char *name, int mode);
 
 int vt_default_utf8(void);
 int vt_reset_keyboard(int fd);
+int vt_restore(int fd);