Re: [PATCH 1/2] docs: sbsa: correct graphics card name

[Peter Maydell]

On Thu, 25 May 2023 at 11:32, Thomas Huth <thuth@redhat.com> wrote:
>
> On 25/05/2023 12.05, Peter Maydell wrote:
> > On Tue, 23 May 2023 at 19:41, Thomas Huth <thuth@redhat.com> wrote:
> >>
> >> On 23/05/2023 19.30, Marcin Juszkiewicz wrote:
> >> ...
> >>>> (is there a reason why it can't be disabled with "-vga none" or
> >>>> "-nodefaults"?)
> >>>
> >>> That's something I need to check how it should be done.
> >>
> >> Other boards set mc->default_display in their ...class_init
> >> function and then use pci_vga_init() (or vga_interface_type)
> >> to instantiate their default display adapter ... however, that
> >> does not seem to support the bochs adapter yet (see
> >> vga_interfaces[] in softmmu/vl.c).
> >>
> >> Not sure whether it's worth the effort to extend vga_interfaces[]
> >> in vl.c
> >
> > Isn't that a legacy-command-line-option thing? I feel like
> > the recommended way to select a different graphics card
> > these days would be to use -device my-pci-vga-card ...
>
> "-vga" is kind of legacy, indeed, but currently the sbsa-ref hard-codes the
> graphics card to be always available, so if you add a "-device
> something-vga-card" on the command line, you'd get two graphic cards on your
> machine, even if you use -nodefaults.

At least some boards do "only create the default graphics
type if vga_interface_type != VGA_NONE".

Mostly what I would like here is consistency. But also, we
haven't added a new item to the '-vga' option list since
2014, which makes me strongly suspect it's legacy and we
should only be keeping it for backwards compatibility.

> So there needs to be at least some logic dealing with vga_interface_type if
> we want to be able to select a different graphics card for this machine.
> Then why not go the full way and use pci_vga_init() here, too? ... that's
> certainly the least confusing way for the users.

Is it? From an Arm perspective, having "-vga" do anything
at all is pretty confusing: it's a rather PC-centric option name.
(Also pretty noticeable for the Sparc TCX/CG3 framebuffers,
which are not VGA in any way.)

thanks
-- PMM