Re: [Qemu-devel] [PATCH 01/17] qidl: add QEMU IDL processor

[Kevin Wolf <kwolf@redhat.com>]

Am 05.06.2012 18:21, schrieb Michael Roth:
> On Tue, Jun 05, 2012 at 11:25:01AM +0200, Kevin Wolf wrote:
>> Am 05.06.2012 03:00, schrieb Michael Roth:
>>> This is an import of Anthony's qidl compiler, with some changes squashed
>>> in to add support for doing the visitor generation via QEMU's qapi code
>>> generators rather than directly.
>>>
>>> Documentation has been imported as well, as is also viewable at:
>>>
>>> https://github.com/aliguori/qidl/blob/master/qc.md
>>>
>>> This will be used to add annotations to device structs to aid in
>>> generating visitors that can be used to serialize/unserialize them.
>>>
>>> Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
>>> ---
>>>  scripts/qc.md |  331 ++++++++++++++++++++++++++++++++++++++
>>>  scripts/qc.py |  494 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>>  2 files changed, 825 insertions(+), 0 deletions(-)
>>>  create mode 100644 scripts/qc.md
>>>  create mode 100755 scripts/qc.py
>>>
>>> diff --git a/scripts/qc.md b/scripts/qc.md
>>> new file mode 100644
>>> index 0000000..4cf4b21
>>> --- /dev/null
>>> +++ b/scripts/qc.md
>>
>> I think docs/ would be a better place than scripts/
>>
>>> +Getting Started
>>> +---------------
>>> +
>>> +The first step is to move your device struct definition to a header file.  This
>>> +header file should only contain the struct definition and any preprocessor
>>> +declarations you need to define the structure.  This header file will act as
>>> +the source for the QC IDL compiler.
>>> +
>>> +Do not include any function declarations in this header file as QC does not
>>> +understand function declarations.
>>
>> Couldn't we use a header file (or even source file) that has some magic
>> markers for the IDL compiler? Like:
>>
>> ... random stuff ...
>>
>> /* QIDL START */
>> struct Foo {
>>     ...
>> };
>> /* QIDL END */
>>
>> ... random stuff ...
>>
>> Adding a new header file for each device really doesn't look like a
>> desirable thing, and this way it could be avoided.
> 
> We could always make the compiler smarter (Anthony has already done
> so apparently), and in the version posted here the compiler actually
> scans line-by-line for the "qc_declaration" annotation before it begins
> processing the annotated structure, so it behaves much like you're
> suggestion.
> 
> The main reason device state needs to be moved to a seperate file is
> because the generated visitors need to access that device state.
> 
> The only way I can think of getting around this is to do nasty things
> like adding an
> 
> #include "qapi-generated/mc146818rtc-qapi-visit.c";
> 
> in hw/mc146818rtc.c.

If the alternative is making private structs public, which is even
nastier IMHO, this might be the lesser evil.

(And I agree with Paolo that Anthony's version is a bit too much magic
and doesn't really make it cleaner)

Kevin