Re: -chardev with a JSON argument (was: [PATCH] chardev: introduce 'reconnect-ms' and deprecate 'reconnect')

On Sat, Sep 14, 2024 at 10:42:36 +0200, Markus Armbruster wrote: Yeah, in the meanwhile I had a look and also remembered that we spoke about why this was the case. (All the 'wrapper' objects making the schema of 'chardev-add' extremely unpleasant) So the main motivation is to have just one instance of the code generating the config for qemu. As JSON has type information inside libvirt always generates JSON internally first. This is the case for -object, -device, -netdev, -blockdev, ... For '-chardev' we currently (in tree) have two separate formatters for '-chardev' and QMP 'chardev-add'. I do have a reasonalby looking rework in the works which unifies them (with a few quirky "if (commandline)" blocks). In cases when we need to support the old syntax for any reason we do have a converter that takes JSON and outputs the qemuopts syntax. This is possible for now as we have mostly flat structures and the only difference for now is how the arrays are processed in -device vs -netdev (by callbacks to the converter). For -chardev this will require a bit more logic as we need to avoid the extra wrappers for commandline output and few fields have different names in QMP than on the commandline. My main goal here is to achieve validation against the QMP schema, and it's much easier for us to add test cases via XML than hardcoding them in C. So honestly I don't think we want it too badly. Definitely not so bad that having it with bad design. I reckon that doing the refactor will also simplify things for the future if the QMP design will be changed to e.g. drop the wrappers. Yup, that'll always work :)