qapi: Add device ID and head parameters to screendump

QEMU's screendump command can only take dumps from the primary display.
When using multiple VGA cards, there is no way to get a dump from a
secondary card or other display heads yet. So let's add a 'device' and
a 'head' parameter to the HMP and QMP commands to be able to specify
alternative devices and heads with the screendump command, too.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 1520267868-31778-1-git-send-email-thuth@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

hmp-commands.hx

@@ -253,9 +253,10 @@ ETEXI
 
     {
         .name       = "screendump",
-        .args_type  = "filename:F",
-        .params     = "filename",
-        .help       = "save screen into PPM image 'filename'",
+        .args_type  = "filename:F,device:s?,head:i?",
+        .params     = "filename [device [head]]",
+        .help       = "save screen from head 'head' of display device 'device' "
+                      "into PPM image 'filename'",
         .cmd        = hmp_screendump,
     },
 

hmp.c

@@ -2140,9 +2140,11 @@ err_out:
 void hmp_screendump(Monitor *mon, const QDict *qdict)
 {
     const char *filename = qdict_get_str(qdict, "filename");
+    const char *id = qdict_get_try_str(qdict, "device");
+    int64_t head = qdict_get_try_int(qdict, "head", 0);
     Error *err = NULL;
 
-    qmp_screendump(filename, &err);
+    qmp_screendump(filename, id != NULL, id, id != NULL, head, &err);
     hmp_handle_error(mon, &err);
 }
 

qapi/ui.json

@@ -77,6 +77,13 @@
 #
 # @filename: the path of a new PPM file to store the image
 #
+# @device: ID of the display device that should be dumped. If this parameter
+#          is missing, the primary display will be used. (Since 2.12)
+#
+# @head: head to use in case the device supports multiple heads. If this
+#        parameter is missing, head #0 will be used. Also note that the head
+#        can only be specified in conjunction with the device ID. (Since 2.12)
+#
 # Returns: Nothing on success
 #
 # Since: 0.14.0
@@ -88,7 +95,8 @@
 # <- { "return": {} }
 #
 ##
-{ 'command': 'screendump', 'data': {'filename': 'str'} }
+{ 'command': 'screendump',
+  'data': {'filename': 'str', '*device': 'str', '*head': 'int'} }
 
 ##
 # == Spice

ui/console.c

@@ -344,15 +344,29 @@ write_err:
     goto out;
 }
 
-void qmp_screendump(const char *filename, Error **errp)
+void qmp_screendump(const char *filename, bool has_device, const char *device,
+                    bool has_head, int64_t head, Error **errp)
 {
-    QemuConsole *con = qemu_console_lookup_by_index(0);
+    QemuConsole *con;
     DisplaySurface *surface;
 
-    if (con == NULL) {
-        error_setg(errp, "There is no QemuConsole I can screendump from.");
+    if (has_device) {
+        con = qemu_console_lookup_by_device_name(device, has_head ? head : 0,
+                                                 errp);
+        if (!con) {
             return;
         }
+    } else {
+        if (has_head) {
+            error_setg(errp, "'head' must be specified together with 'device'");
+            return;
+        }
+        con = qemu_console_lookup_by_index(0);
+        if (!con) {
+            error_setg(errp, "There is no console to take a screendump from");
+            return;
+        }
+    }
 
     graphic_hw_update(con);
     surface = qemu_console_surface(con);