Re: [PATCH] tpm: add backend for mssim

[Markus Armbruster <armbru@redhat.com>]

James Bottomley <jejb@linux.ibm.com> writes:

> On Wed, 2022-12-14 at 11:31 +0000, Daniel P. Berrangé wrote:

[...]

>> These days, we have a policy of not tyring to map nested data onto
>> the flat QemuOpts. This has been done in several areas and we've
>> ended up with a mess of ever so slightly different impls each with
>> their own flaws. This is why our preferred approach these days is to
>> add support for JSON syntax to enable non-flat config.
>
> Well, OK, but I've got to say on behalf of shell script writers
> everywhere that using json for command line arguments is a textbook
> definition of cruel and unusual punishment.

For new code, use qobject_input_visitor_new_str().  Parses both JSON and
dotted keys.  Example: case QEMU_OPTION_blockdev in qemu_init().  Dotted
keys can fall apart for corner cases.  See util/keyval.c if you're
curious.

Sometimes we bend over backwards for backward compatibility, and do
something like

    if (optarg[0] == '{') {
        QObject *obj = qobject_from_json(optarg, &error_fatal);

        v = qobject_input_visitor_new(obj);
        qobject_unref(obj);
    } else {
        ... old parser ...
    }

This parses both JSON and whatever old crap.  Example:
object_option_parse().

Questions?