chardev: Allow frontends to notify backends of guest open / close

Some frontends know when the guest has opened the "channel" and is actively
listening to it, for example virtio-serial. This patch adds 2 new qemu-chardev
functions which can be used by frontends to signal guest open / close, and
allows interested backends to listen to this.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Alon Levy <alevy@redhat.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/qemu-char.c b/qemu-char.c
index 03858d4..710d98f 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -480,6 +480,9 @@ static CharDriverState *qemu_chr_open_mux(CharDriverState *drv)
     chr->chr_write = mux_chr_write;
     chr->chr_update_read_handler = mux_chr_update_read_handler;
     chr->chr_accept_input = mux_chr_accept_input;
+    /* Frontend guest-open / -close notification is not support with muxes */
+    chr->chr_guest_open = NULL;
+    chr->chr_guest_close = NULL;
 
     /* Muxes are always open on creation */
     qemu_chr_generic_open(chr);
@@ -2579,6 +2582,20 @@ void qemu_chr_set_echo(struct CharDriverState *chr, bool echo)
     }
 }
 
+void qemu_chr_guest_open(struct CharDriverState *chr)
+{
+    if (chr->chr_guest_open) {
+        chr->chr_guest_open(chr);
+    }
+}
+
+void qemu_chr_guest_close(struct CharDriverState *chr)
+{
+    if (chr->chr_guest_close) {
+        chr->chr_guest_close(chr);
+    }
+}
+
 void qemu_chr_close(CharDriverState *chr)
 {
     QTAILQ_REMOVE(&chardevs, chr, next);