2 files changed, 41 insertions, 0 deletions
diff --git a/include/chardev/char-fe.h b/include/chardev/char-fe.h
index 2cbb262f66..71cd069478 100644
--- a/include/chardev/char-fe.h
+++ b/include/chardev/char-fe.h
@@ -4,6 +4,7 @@
 #include "chardev/char.h"
 
 typedef void IOEventHandler(void *opaque, int event);
+typedef int BackendChangeHandler(void *opaque);
 
 /* This is the backend as seen by frontend, the actual backend is
  * Chardev */
@@ -12,6 +13,7 @@ struct CharBackend {
     IOEventHandler *chr_event;
     IOCanReadHandler *chr_can_read;
     IOReadHandler *chr_read;
+    BackendChangeHandler *chr_be_change;
     void *opaque;
     int tag;
     int fe_open;
@@ -44,16 +46,35 @@ void qemu_chr_fe_deinit(CharBackend *b, bool del);
  *
  * Returns the driver associated with a CharBackend or NULL if no
  * associated Chardev.
+ * Note: avoid this function as the driver should never be accessed directly,
+ *       especially by the frontends that support chardevice hotswap.
+ *       Consider qemu_chr_fe_backend_connected() to check for driver existence
  */
 Chardev *qemu_chr_fe_get_driver(CharBackend *be);
 
 /**
+ * @qemu_chr_fe_backend_connected:
+ *
+ * Returns true if there is a chardevice associated with @be.
+ */
+bool qemu_chr_fe_backend_connected(CharBackend *be);
+
+/**
+ * @qemu_chr_fe_backend_open:
+ *
+ * Returns true if chardevice associated with @be is open.
+ */
+bool qemu_chr_fe_backend_open(CharBackend *be);
+
+/**
  * @qemu_chr_fe_set_handlers:
  * @b: a CharBackend
  * @fd_can_read: callback to get the amount of data the frontend may
  *               receive
  * @fd_read: callback to receive data from char
  * @fd_event: event callback
+ * @be_change: backend change callback; passing NULL means hot backend change
+ *             is not supported and will not be attempted
  * @opaque: an opaque pointer for the callbacks
  * @context: a main loop context or NULL for the default
  * @set_open: whether to call qemu_chr_fe_set_open() implicitely when
@@ -68,6 +89,7 @@ void qemu_chr_fe_set_handlers(CharBackend *b,
                               IOCanReadHandler *fd_can_read,
                               IOReadHandler *fd_read,
                               IOEventHandler *fd_event,
+                              BackendChangeHandler *be_change,
                               void *opaque,
                               GMainContext *context,
                               bool set_open);
diff --git a/include/chardev/char.h b/include/chardev/char.h
index 8a9ade4931..1604ea9143 100644
--- a/include/chardev/char.h
+++ b/include/chardev/char.h
@@ -81,6 +81,16 @@ Chardev *qemu_chr_new_from_opts(QemuOpts *opts,
 void qemu_chr_parse_common(QemuOpts *opts, ChardevCommon *backend);
 
 /**
+ * @qemu_chr_parse_opts:
+ *
+ * Parse the options to the ChardevBackend struct.
+ *
+ * Returns: a new backend or NULL on error
+ */
+ChardevBackend *qemu_chr_parse_opts(QemuOpts *opts,
+                                    Error **errp);
+
+/**
  * @qemu_chr_new:
  *
  * Create a new character backend from a URI.
@@ -93,6 +103,15 @@ void qemu_chr_parse_common(QemuOpts *opts, ChardevCommon *backend);
 Chardev *qemu_chr_new(const char *label, const char *filename);
 
 /**
+ * @qemu_chr_change:
+ *
+ * Change an existing character backend
+ *
+ * @opts the new backend options
+ */
+void qemu_chr_change(QemuOpts *opts, Error **errp);
+
+/**
  * @qemu_chr_cleanup:
  *
  * Delete all chardevs (when leaving qemu)