I think this approach is wrong. We're mashing the design of vmstate
with that of visitors and getting something that is not a visitor and
not vmstate.
Instead, I think you should have something like this:
struct VMStateInfo {
const char *name;
// takes a QMPOutputVisitor and a QEMUFile open for reading
int (*load)(QEMUFile *f, const char *name, Visitor *v,
size_t size, Error **err);
// takes a QMPInputVisitor and a QEMUFile open for writing
void (*save)(QEMUFile *f, const char *name, Visitor *v,
size_t size, Error **err);
// takes a QMPOutputVisitor and reads from *pv
int (*get)(Visitor *v, const char *name, void *pv,
size_t size, Error **err);
// takes a QMPInputVisitor and writes into *pv
void (*set)(Visitor *v, const char *name, void *pv,
size_t size, Error **err);
};
that splits the existing callbacks in two steps.
For saving, you would adapt your visitor-based vmstate "put" routines so
that they put things in a dictionary with no regard for integer types (a
bit ugly for uint64, but perfectly fine for everything else). You take
the dictionary from the output visitor and (with an input visitor) you
feed it back to the "save" routines, which convert the dictionary to a
QEMUFile. Both steps keep the types internal to vmstate.
For loading, it's the other way round: you interpret the vmstate with
the QEMUFile reading routines, and create a dictionary. Then make an
input visitor and use the vmstate "set" interpreter to fill in the
struct fields.
I'm sorry for noticing this just now, I was waiting for Anthony's QOM
plans to be committed so that I could understand better how vmstate and
QOM properties would interact. In fact, it would be great and not hard
if the struct<->visitor step (get/set) was also exposed as a QOM property.
qapi-visitor-types.patch