On Mon, 21 Oct 2024 at 15:12, Zhao Liu <zhao1....@intel.com> wrote: > > Hi Peter, > > On Mon, Oct 21, 2024 at 10:25:07AM +0100, Peter Maydell wrote: > > Date: Mon, 21 Oct 2024 10:25:07 +0100 > > From: Peter Maydell <peter.mayd...@linaro.org> > > Subject: Re: [Question] What is the definition of “private” fields in > > QOM? > > > > On Sat, 19 Oct 2024 at 16:54, Zhao Liu <zhao1....@intel.com> wrote: > > > > > > Hi maintainers and list, > > > > > > In the QOM structure, the class and object structs have two members: > > > parent_class and parent_obj, which are often marked as "< private >" in > > > the comment. > > > > > > I couldn’t find information on why to define ‘private’ and ‘public’, > > > even in the earliest QOM commits and the patch emails I could find. > > > > This is a rather old thing which I think was originally > > borrowed from glib's commenting convention. > > > > I'm fairly sure that we decided a while back that they were entirely > > unnecessary, so you don't need to add them in new code. (I can't > > actually find anything with a quick list search about that though > > so maybe I'm misremembering.) > > Thanks for your explanation! So I understand that directly accessing > parent_obj/parent_class is actually allowed.
No, you shouldn't do that. You can use a QOM cast of the object pointer to the relevant parent class if you need to treat it as an instance of the parent class. What I mean by "the private/public markers are unnecessary" is that they don't tell the reader anything, because all the fields in a QOM device struct are private. If you're not in the implementation of that class, then you shouldn't really be directly touching any of the fields in the state struct. (In some places we take a shortcut and do it. But really it's almost never necessary.) thanks -- PMM
