Re: [PATCH 3/4] docs/interop/firmware.json: Use full include paths

[Daniel P . Berrangé]

On Fri, Mar 08, 2024 at 04:19:42PM +0100, Markus Armbruster wrote:
> The coupling with the main QAPI schema is unfortunate.
> 
> The purpose of docs/interop/firmware.json is to serve as schema for
> firmware descriptions: a firmware description is a JSON object that
> conforms to this schema's struct Firmware.
> 
> Such a description should be installed along with each firmware binary.
> 
> QAPI tooling can be used to check conformance: parse the firmware
> description JSON object, feed it to the generated visit_type_Firmware().
> Success implies conformance.
> 
> If you find more uses for the C struct Firmware created by
> visit_type_Firmware(), more power to you.
> 
> firmware.json needs machine.json for SysEmuTarget, and block-core.json
> for BlockdevDriver.  The largest and the third-largest QAPI module just
> for two enums.  Almost a quarter Mebibyte of code.

firmware.json can use BlockdevDriver, but we could question
whether it /should/ use BlockdevDriver. Is there really a
compelling reason to support every possible block driver for
readonly firmware and tiny nvram file ? I thin kit would be
totally reasonable to define a "FirmwareFormat" enum which
only permitted 'raw' and 'qcow2'.   If someone wants to
justify why we need another format, I'm all ears...

For SysEmuTarget its a little more useful, as in theory the
firmware could be extended to any QEMU target. In practice
thus far we've only used it todescribe EFI based firmware,
which is relevant for a subset of targets. It doesn't seem
to be a huge downside to define a FirmwareTarget enum with
only the arches we've actually got a use for so far. When
someone comes along with a need for non-EFI we can extend
it, and we'll need to extend libvirt at the same time anyway

> qapi-gen.py generates more than 12kSLOC.  Without the include (and with
> the enums dumbed down to 'str' to enable that), it generates less than
> 800.
> 
> We could use Sphinx to generate a manual from firmware.json's document.
> Except that manual would be useless, because of its 11,000 lines of
> HTML, less than 800 are for firmware.json.
> 
> Options:
> 
> * Live with the mess.
> 
> * Refactor QAPI modules so firmware.json can include just the enums.
> 
>   Drawback: we spread the mess into qapi/.  Ugh.
> 
> * Copy the enums to firmware.json.
> 
>   Drawback: we risk them going stale.

IMHO copy the enum. While the risk exists, I don't think it is a
risk worth worrying about in reality. If someone points out a gap
that's important is a matter of minutes to patch it.

> * Dumb down to 'str'.
> 
>   Drawback: the conformance check no longer enforces the value of
>   FirmwareTarget member @architecture and FirmwareFlashFile member
>   @format is valid.




With regards,
Daniel
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