This translates legacy command line options that can't be made
compatible with QAPI just by using aliases from the traditional command
line structure into the structure of ChardevOptions.

As a first step, add support for backend name aliases if 'backend' is
given instead of 'type'.

Also add a todo comment for everything that is still incompatible
between the QemuOpts based -chardev and chardev creation by going
through a keyval parser, qemu_chr_translate_legacy_options() and
qemu_chr_new_cli().

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 include/chardev/char.h | 13 +++++++++++++
 chardev/char.c         | 23 +++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/include/chardev/char.h b/include/chardev/char.h
index 54fa2ed8e2..7795e17ca5 100644
--- a/include/chardev/char.h
+++ b/include/chardev/char.h
@@ -94,6 +94,19 @@ Chardev *qemu_chr_new_from_opts(QemuOpts *opts,
  */
 Chardev *qemu_chr_new_cli(ChardevOptions *options, Error **errp);
 
+/**
+ * qemu_chr_translate_legacy_options:
+ * @args: Character device creation options as returned by the keyval parser
+ *
+ * Change @args so that the legacy command line options in it are translated
+ * and @args can be used as the input for a ChardevOptions visitor.
+ *
+ * If @args was not a valid legacy command line, translation may be partially
+ * skipped and the visitor may return an error if @args was not already
+ * suitable for QAPI parsing.
+ */
+void qemu_chr_translate_legacy_options(QDict *args);
+
 /**
  * qemu_chr_parse_common:
  * @opts: the options that still need parsing
diff --git a/chardev/char.c b/chardev/char.c
index 9f00e475d4..40c3f02ec9 100644
--- a/chardev/char.c
+++ b/chardev/char.c
@@ -32,6 +32,7 @@
 #include "chardev/char.h"
 #include "qapi/error.h"
 #include "qapi/qapi-commands-char.h"
+#include "qapi/qmp/qdict.h"
 #include "qapi/qmp/qerror.h"
 #include "sysemu/replay.h"
 #include "qemu/help_option.h"
@@ -717,6 +718,28 @@ out:
     return chr;
 }
 
+void qemu_chr_translate_legacy_options(QDict *args)
+{
+    const char *name;
+
+    /* "backend" instead of "type" enables legacy CLI compatibility */
+    name = qdict_get_try_str(args, "backend");
+    if (!name || qdict_haskey(args, "type")) {
+        return;
+    }
+
+    name = chardev_alias_translate(name);
+    qdict_put_str(args, "type", name);
+    qdict_del(args, "backend");
+
+    /*
+     * TODO:
+     * All backend types: "mux"
+     * socket: "addr.type", "delay", "server", "wait", "fd"
+     * udp: defaults for "host"/"localaddr"/"localport"
+     */
+}
+
 Chardev *qemu_chr_new_noreplay(const char *label, const char *filename,
                                bool permit_mux_mon, GMainContext *context)
 {
-- 
2.28.0