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Berrangé wrote: > On Mon, Jan 23, 2023 at 10:20:29AM +0100, Philippe Mathieu-Daudé wrote: >> On 23/1/23 09:39, Thomas Huth wrote: >>> From: Daniel P. Berrangé >>> >>> Way back in QEMU 4.0, the -audiodev command line option was introduced >>> for configuring audio backends. This CLI option does not use QemuOpts >>> so it is not visible for introspection in 'query-command-line-options', >>> instead using the QAPI Audiodev type. Unfortunately there is also no >>> QMP command that uses the Audiodev type, so it is not introspectable >>> with 'query-qmp-schema' either. >>> >>> This introduces a 'query-audiodev' command that simply reflects back >>> the list of configured -audiodev command line options. This alone is >>> maybe not very useful by itself, but it makes Audiodev introspectable >>> via 'query-qmp-schema', so that libvirt (and other upper layer tools) >>> can discover the available audiodevs. >>> >>> Signed-off-by: Daniel P. Berrangé >>> [thuth: Update for upcoming QEMU v8.0, and use QAPI_LIST_PREPEND] >>> Signed-off-by: Thomas Huth >>> --- >>> qapi/audio.json | 13 +++++++++++++ >>> audio/audio.c | 12 ++++++++++++ >>> 2 files changed, 25 insertions(+) >>> >>> diff --git a/qapi/audio.json b/qapi/audio.json >>> index 1e0a24bdfc..c7aafa2763 100644 >>> --- a/qapi/audio.json >>> +++ b/qapi/audio.json >>> @@ -443,3 +443,16 @@ >>> 'sndio': 'AudiodevSndioOptions', >>> 'spice': 'AudiodevGenericOptions', >>> 'wav': 'AudiodevWavOptions' } } >>> + >>> +## >>> +# @query-audiodevs: >>> +# >>> +# Returns information about audiodev configuration >> >> Maybe clearer as 'audio backends'? >> >> So similarly, wouldn't be clearer to name this command >> 'query-audio-backends'? Otherwise we need to go read QEMU >> source to understand what is 'audiodevs'. > > The command line parameter is called '-audiodev' and this > query-audiodevs command reports the same data, so that > looks easy enough to understand IMHO. > >>> +# >>> +# Returns: array of @Audiodev >>> +# >>> +# Since: 8.0 >>> +# >>> +## >>> +{ 'command': 'query-audiodevs', >>> + 'returns': ['Audiodev'] } >>> diff --git a/audio/audio.c b/audio/audio.c >>> index d849a94a81..6f270c07b7 100644 >>> --- a/audio/audio.c >>> +++ b/audio/audio.c >>> @@ -28,8 +28,10 @@ >>> #include "monitor/monitor.h" >>> #include "qemu/timer.h" >>> #include "qapi/error.h" >>> +#include "qapi/clone-visitor.h" >>> #include "qapi/qobject-input-visitor.h" >>> #include "qapi/qapi-visit-audio.h" >>> +#include "qapi/qapi-commands-audio.h" >>> #include "qemu/cutils.h" >>> #include "qemu/module.h" >>> #include "qemu/help_option.h" >>> @@ -2311,3 +2313,13 @@ size_t audio_rate_get_bytes(RateCtl *rate, struct audio_pcm_info *info, >>> return bytes; >>> } >>> + >>> +AudiodevList *qmp_query_audiodevs(Error **errp) >>> +{ >>> + AudiodevList *ret = NULL; >>> + AudiodevListEntry *e; >>> + QSIMPLEQ_FOREACH(e, &audiodevs, next) { >> >> I am a bit confused here, isn't &audiodevs containing what the user provided >> from CLI? How is that useful to libvirt? Maybe the corner case >> of a user hand-modifying the QEMU launch arguments from a XML config? >> >> Wouldn't a list of linked in AudiodevDriver be more useful to libvirt >> so it could pick the best available backend to start a VM? > > On the libvirt side we're never going to need to actually call the > query-audiodevs commands. The mere existance of the command, means > that the QMP schema now exposes information about what audio backends > have been compiled into the binary. This is the same trick we've used > for other aspects of QMP. IOW we don't need a separate command just > for the purpose of listing AudiodevDrivers. I understand having "what audio backends have been compiled into the binary" is useful, but I am missing how you get that from &audiodevs. AFAICT &audiodevs is for the CLI parsed backends, not all the backends linked within a binary. I probably need sugar / coffee and will revisit after lunch. > The idea of a query-audiodevs command is useful in general. When we > later gain support for hotplug/unplug of audio, the set of audiodevs > will no longer be guaranteed to match the original CLI args. > > With regards, > Daniel