Re: [Qemu-devel] [PATCH 4 of 5] [UPDATE] DisplayState interface change

[Anthony Liguori <anthony@codemonkey.ws>]

Stefano Stabellini wrote:
> This patch changes the DisplayState interface adding support for
> multiple frontends at the same time (sdl and vnc) and implements most
> of the benefit of the shared_buf patch without the added complexity.
>
> Currently DisplayState is managed by sdl (or vnc) and sdl (or vnc) is
> also responsible for allocating the data and setting the depth.
> Vga.c (or another backend) will do any necessary conversion.
>
> The idea is to change it so that is vga.c (or another backend) together
> with console.c that fully manage the DisplayState interface allocating
> data and setting the depth (either 16 or 32 bit, if the guest uses a
> different resolution or is in text mode, vga.c (or another backend) is
> in charge of doing the conversion seamlessly).
>
> The other idea is that DisplayState supports *multiple* frontends
> like sdl and vnc; each of them can register some callbacks to be called
> when a display event occurs.
>
> The interesting changes are:
>
> - the new structures and related functions in console.h and console.c
>
> in particular the following functions are very helpful to manage a
> DisplaySurface:
>
> qemu_createDisplaySurface
> qemu_resizeDisplaySurface
> qemu_createDisplaySurfaceFrom
> qemu_freeDisplaySurface
>
> - console_select and qemu_console_resize in console.c
> this two functions manage multiple consoles on a single host display
>
> - moving code around in hw/vga.c
> as for the shared_buf patch this is necessary to be able to handle a dynamic
> DisplaySurface bpp
>
> - changes to vga_draw_graphic in hw/vga.c
> this is the place where the DisplaySurface buffer is shared with the
> videoram, when possible;
>
> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
>   

I think we need another intermediate step here.

Right now, we have a pretty poor abstraction wrt QEMUConsole and 
DisplayState.  QEMUConsole is known to much of the hardware emulation 
but DisplayState is too.

I think we need a step that replaces all notions of QEMUConsole in 
hw/*.c with DisplayState including an appropriate creation functions.  
There's really no point in passing a DisplayState to the hardware 
devices, instead they should be allocating it and returning it to be 
passed to the SDL/VNC front-ends.

Regards,

Anthony Liguori