v4.19.13 snapshot.
diff --git a/arch/um/drivers/null.c b/arch/um/drivers/null.c
new file mode 100644
index 0000000..1049574
--- /dev/null
+++ b/arch/um/drivers/null.c
@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com)
+ * Licensed under the GPL
+ */
+
+#include <stddef.h>
+#include <errno.h>
+#include <fcntl.h>
+#include "chan_user.h"
+#include <os.h>
+
+/* This address is used only as a unique identifier */
+static int null_chan;
+
+static void *null_init(char *str, int device, const struct chan_opts *opts)
+{
+ return &null_chan;
+}
+
+static int null_open(int input, int output, int primary, void *d,
+ char **dev_out)
+{
+ int fd;
+
+ *dev_out = NULL;
+
+ fd = open(DEV_NULL, O_RDWR);
+ return (fd < 0) ? -errno : fd;
+}
+
+static int null_read(int fd, char *c_out, void *unused)
+{
+ return -ENODEV;
+}
+
+static void null_free(void *data)
+{
+}
+
+const struct chan_ops null_ops = {
+ .type = "null",
+ .init = null_init,
+ .open = null_open,
+ .close = generic_close,
+ .read = null_read,
+ .write = generic_write,
+ .console_write = generic_console_write,
+ .window_size = generic_window_size,
+ .free = null_free,
+ .winch = 0,
+};