Re: [PATCH 1/2] meson: introduce modules_arch

[Jose R. Ziviani]

Hello!

On Fri, Sep 17, 2021 at 09:14:04AM +0200, Gerd Hoffmann wrote:
>   Hi,
> 
> > This variable keeps track of all modules enabled for a target
> > architecture. This will be used in modinfo to refine the
> > architectures that can really load the .so to avoid errors.
> 
> I think this is the wrong approach.  The reason why modules are
> not loading is typically *not* the architecture, but a feature
> or subsystem the device needs not being compiled in.  Often the
> subsystem is a bus (pci, usb, ccw), but there are also other
> cases (virtio, vga).
> 
> We can stick that into modinfo, simliar to module_dep() but for bits
> provided by core qemu instead of other modules.  i.e. add something
> along the lines of ...

Yes, I really like your approach, makes more sense indeed. But, how do I
get the core modules that other modules depend on?

I see that Kconfig already has something in this line:

config VGA  (from hw/display)
    bool

config PCI  (from hw/pci)
    bool

config QXL  (from hw/display)
    bool
    depends on SPICE && PCI
    select VGA

I assume that independent entries (like VGA and PCI) are core and that I
can rely on it to add
  module_need(PCI)
  module_need(VGA)
for hw-display-qxl. Am I right?

Thanks for reviewing it!!

> 
>       module_need(BUS_PCI);
> 
> ... to the modules, store that in modinfo and check it before trying
> to load.
> 
> That would also allow to remove hacks like commit 2dd9d8cfb4f3 ("s390x:
> add have_virtio_ccw")
> 
> take care,
>   Gerd
>

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