On 1/20/20 1:29 PM, Philippe Mathieu-Daudé wrote:
Commit c388f408b5 added the possibility to list the display
backends using '-display help'. Since the 'none' backend is
is not implemented as a DisplayChangeListenerOps, it is not
registered to the dpys[] array with qemu_display_register(),
and is not listed in the help output.

This might be confusing, as we list it in the man page:

   -display type
       Select type of display to use. This option is a replacement for
       the old style -sdl/-curses/... options. Valid values for type are

       none
           Do not display video output. The guest will still see an
           emulated graphics card, but its output will not be displayed
           to the QEMU user. This option differs from the -nographic
           option in that it only affects what is done with video
           output; -nographic also changes the destination of the serial
           and parallel port data.

Fix by manually listing the special 'none' backend in the help.

Suggested-by: Thomas Huth <th...@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <phi...@redhat.com>
---
  ui/console.c | 1 +
  1 file changed, 1 insertion(+)

Reviewed-by: Eric Blake <ebl...@redhat.com>


diff --git a/ui/console.c b/ui/console.c
index 69339b028b..179901c35e 100644
--- a/ui/console.c
+++ b/ui/console.c
@@ -2338,6 +2338,7 @@ void qemu_display_help(void)
      int idx;
printf("Available display backend types:\n");
+    printf("none\n");
      for (idx = DISPLAY_TYPE_NONE; idx < DISPLAY_TYPE__MAX; idx++) {
          if (!dpys[idx]) {
              ui_module_load_one(DisplayType_str(idx));


--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org


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