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

[Michael Roth <mdroth@linux.vnet.ibm.com>]

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.