qemu-char: Automatically do fe_open / fe_close on qemu_chr_add_handlers

Most frontends can't really determine if the guest actually has the frontend
side open. So lets automatically generate fe_open / fe_close as soon as a
frontend becomes ready (as signalled by calling qemu_chr_add_handlers) /
becomes non ready (as signalled by setting all handlers to NULL).

And allow frontends which can actually determine if the guest is listening to
opt-out of this.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Message-id: 1364292483-16564-5-git-send-email-hdegoede@redhat.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

4 files changed, 15 insertions, 2 deletions

diff --git a/hw/usb/redirect.c b/hw/usb/redirect.c
index 9734e426ec..d02a7b94c4 100644
--- a/hw/usb/redirect.c
+++ b/hw/usb/redirect.c
@@ -1282,7 +1282,6 @@ static int usbredir_initfn(USBDevice *udev)
     dev->compatible_speedmask = USB_SPEED_MASK_FULL | USB_SPEED_MASK_HIGH;
 
     /* Let the backend know we are ready */
-    qemu_chr_fe_open(dev->cs);
     qemu_chr_add_handlers(dev->cs, usbredir_chardev_can_read,
                           usbredir_chardev_read, usbredir_chardev_event, dev);
 
@@ -1306,7 +1305,6 @@ static void usbredir_handle_destroy(USBDevice *udev)
 {
     USBRedirDevice *dev = DO_UPCAST(USBRedirDevice, dev, udev);
 
-    qemu_chr_fe_close(dev->cs);
     qemu_chr_delete(dev->cs);
     /* Note must be done after qemu_chr_close, as that causes a close event */
     qemu_bh_delete(dev->chardev_close_bh);
diff --git a/hw/virtio-console.c b/hw/virtio-console.c
index e2d1c58d9d..2f7c3dfe9e 100644
--- a/hw/virtio-console.c
+++ b/hw/virtio-console.c
@@ -131,6 +131,7 @@ static int virtconsole_initfn(VirtIOSerialPort *port)
     }
 
     if (vcon->chr) {
+        vcon->chr->explicit_fe_open = 1;
         qemu_chr_add_handlers(vcon->chr, chr_can_read, chr_read, chr_event,
                               vcon);
     }
diff --git a/include/char/char.h b/include/char/char.h
index dbb1b89f8c..3cd2aef77d 100644
--- a/include/char/char.h
+++ b/include/char/char.h
@@ -76,6 +76,7 @@ struct CharDriverState {
     char *filename;
     int be_open;
     int fe_open;
+    int explicit_fe_open;
     int avail_connections;
     QemuOpts *opts;
     QTAILQ_ENTRY(CharDriverState) next;
diff --git a/qemu-char.c b/qemu-char.c
index c9890ad20f..947541a559 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -221,9 +221,14 @@ void qemu_chr_add_handlers(CharDriverState *s,
                            IOEventHandler *fd_event,
                            void *opaque)
 {
+    int fe_open;
+
     if (!opaque && !fd_can_read && !fd_read && !fd_event) {
         /* chr driver being released. */
         ++s->avail_connections;
+        fe_open = 0;
+    } else {
+        fe_open = 1;
     }
     s->chr_can_read = fd_can_read;
     s->chr_read = fd_read;
@@ -232,6 +237,14 @@ void qemu_chr_add_handlers(CharDriverState *s,
     if (s->chr_update_read_handler)
         s->chr_update_read_handler(s);
 
+    if (!s->explicit_fe_open) {
+        if (fe_open) {
+            qemu_chr_fe_open(s);
+        } else {
+            qemu_chr_fe_close(s);
+        }
+    }
+
     /* We're connecting to an already opened device, so let's make sure we
        also get the open event */
     if (s->be_open) {