On 09/06/2021 15.16, Markus Armbruster wrote:
Thomas Huth <thuth@redhat.com> writes:
Libvirt's "domcapabilities" command has a way to state whether certain graphic frontends are available in QEMU or not. Originally, libvirt looked at the "--help" output of the QEMU binary to determine whether SDL was available or not (by looking for the "-sdl" parameter in the help text), but since libvirt stopped doing this analysis of the help text, the detection of SDL is currently broken, see:
https://bugzilla.redhat.com/show_bug.cgi?id=1790902
QEMU should provide a way via the QMP interface instead. The simplest way, without introducing additional commands, is to make the DisplayType enum entries conditional, so that the enum only contains the entries if the corresponding CONFIG_xxx switches have been set. Unfortunately, this only works for sdl, cocoa and spice, since gtk, egl-headless and curses are hard-wired in the "data" section of the DisplayOptions, and thus unfortunately always have to be defined.
Here:
{ 'union' : 'DisplayOptions', 'base' : { 'type' : 'DisplayType', '*full-screen' : 'bool', '*window-close' : 'bool', '*show-cursor' : 'bool', '*gl' : 'DisplayGLMode' }, 'discriminator' : 'type', 'data' : { 'gtk' : 'DisplayGTK', 'curses' : 'DisplayCurses', 'egl-headless' : 'DisplayEGLHeadless'} }
Flat union branches can be made conditional like so:
'data' : { 'gtk' : { 'type': 'DisplayGTK', 'if': 'defined(CONFIG_GTK)' },
Then you should be able to make the corresponding enum value conditional, too.
Thanks for the hint, I'll give it a try! Thomas