Re: [Qemu-devel] [PATCH 22/23] gtk: show a window for each graphical QemuConsole

[Peter Maydell]

On 21 March 2013 18:25, Anthony Liguori <address@hidden> wrote:
> Gerd Hoffmann <address@hidden> writes:
>> I think the most sensible way to handle this is to implement the output
>> routing device, make it own the (single) QemuConsole, and depending on
>> the router state the one or the other display device is allowed to
>> render to the QemuConsole.
>
> Where does the switching happen in hardware?  Is this two devices with a
> DVI port with a switch on it to have a single output port or it is
> something more sophisticated where there are two memory regions and a
> register is used to select which one is written out?

The motherboard has a DVI multiplexer, which selects between the
two video+audio output streams (actually it selects between three
sources but we don't model the second daughterboard at all). I think
these streams are not actually DVI but they are certainly video
with pixel clock and S/PDIF audio already. There's a config register
in the motherboard which selects which source should go out to the
DVI connector. Conceptually I think it should look like this:

                             /-----\
   [ PL111 ] ===(video)====> |     |
                             | MUX | ===(video)===> [display]
   [ PL111 ] ===(video)====> |     |
                             \-----/
                                ^
   [arm_sysregs]---(qemu_irq)---/

(where [] means a device and () a kind of connection.)

If we supported routing of audio output we could in theory run
the audio through the mux in the same way.

-- PMM