[Qemu-devel] [PATCH for-2.1 v2 2/2] char: report frontend open/closed state in 'query-chardev'

[Laszlo Ersek <lersek@redhat.com>]

In addition to the on-line reporting added in the previous patch, allow
libvirt to query frontend state independently of events.

Libvirt's path to identify the guest agent channel it cares about differs
between the event added in the previous patch and the QMP response field
added here. The event identifies the frontend device, by "id". The
'query-chardev' QMP command identifies the backend device (again by "id").
The association is under libvirt's control.

RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1080376
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---

Notes:
    v2:
    - rename "frontend_open" to "frontend-open" in the schema [Eric]
    - "frontend-open" is mandatory [Eric]
    - advertise / target qemu-2.1 with the new field

 qapi-schema.json |  8 +++++++-
 qemu-char.c      |  1 +
 qmp-commands.hx  | 19 ++++++++++++++-----
 3 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/qapi-schema.json b/qapi-schema.json
index d1dc8be..4f968c6 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -210,14 +210,20 @@
 # @label: the label of the character device
 #
 # @filename: the filename of the character device
 #
+# @frontend-open: shows whether the frontend device attached to this backend
+#                 (eg. with the chardev=... option) is in open or closed state
+#                 (since 2.1)
+#
 # Notes: @filename is encoded using the QEMU command line character device
 #        encoding.  See the QEMU man page for details.
 #
 # Since: 0.14.0
 ##
-{ 'type': 'ChardevInfo', 'data': {'label': 'str', 'filename': 'str'} }
+{ 'type': 'ChardevInfo', 'data': {'label': 'str',
+                                  'filename': 'str',
+                                  'frontend-open': 'bool'} }
 
 ##
 # @query-chardev:
 #
diff --git a/qemu-char.c b/qemu-char.c
index 2e50a10..98fb0ab 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -3703,8 +3703,9 @@ ChardevInfoList *qmp_query_chardev(Error **errp)
         ChardevInfoList *info = g_malloc0(sizeof(*info));
         info->value = g_malloc0(sizeof(*info->value));
         info->value->label = g_strdup(chr->label);
         info->value->filename = g_strdup(chr->filename);
+        info->value->frontend_open = chr->fe_open;
 
         info->next = chr_list;
         chr_list = info;
     }
diff --git a/qmp-commands.hx b/qmp-commands.hx
index e4a1c80..35f5146 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -1920,21 +1920,30 @@ of all devices.
 Each json-object contain the following:
 
 - "label": device's label (json-string)
 - "filename": device's file (json-string)
+- "frontend-open": open/closed state of the frontend device attached to this
+                   backend (json-bool)
 
 Example:
 
 -> { "execute": "query-chardev" }
 <- {
-      "return":[
+      "return": [
          {
-            "label":"monitor",
-            "filename":"stdio"
+            "label": "charchannel0",
+            "filename": "unix:/var/lib/libvirt/qemu/seabios.rhel6.agent,server",
+            "frontend-open": false
          },
          {
-            "label":"serial0",
-            "filename":"vc"
+            "label": "charmonitor",
+            "filename": "unix:/var/lib/libvirt/qemu/seabios.rhel6.monitor,server",
+            "frontend-open": true
+         },
+         {
+            "label": "charserial0",
+            "filename": "pty:/dev/pts/2",
+            "frontend-open": true
          }
       ]
    }
 
-- 
1.8.3.1