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From: Gerd Hoffmann <kraxel@redhat.com>
Date: Mon, 18 May 2015 13:17:45 +0200
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Subject: Re: [Qemu-devel] [PATCH 3/8] console: add qemu_alloc_display_format.
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To: Frederic Konrad <fred.konrad@greensocs.com>
Cc: peter.crosthwaite@xilinx.com, mark.burton@greensocs.com, qemu-devel@nongnu.org, hyunk@xilinx.com

On Mo, 2015-05-18 at 09:51 +0200, Frederic Konrad wrote:
> On 18/05/2015 09:34, Gerd Hoffmann wrote:
> > On Mi, 2015-05-13 at 21:12 +0200, fred.konrad@greensocs.com wrote:
> >> From: KONRAD Frederic <fred.konrad@greensocs.com>
> >>
> >> This allows to create a surface with a different format than xrgb8888.
> > What is the use case for this?
> >
> > cheers,
> >    Gerd
> >
> >
> >
> Hi,
> 
> The Display Port introduced in patch 7 and the driver use differents 
> pixel format.
> eg: rgb565, RGB888, etc. see xilinx_dp_change_graphic_fmt in patch 7:

Ah, and dpdma scatterlists (patch 6) suggest the guest framebuffer is
not contiguous in guest phyiscal memory, correct?  So using guest memory
as surface storage using qemu_create_displaysurface_from() doesn't work.

But I think you can simply call qemu_create_displaysurface_from() with
linesize=0 and data=NULL to make pixman allocate storage for you.

cheers,
  Gerd