Re: [Qemu-devel] [PATCH 2/2] vga: flip qemu 2.2 pc machine types from cirrus to stdvga

[Gerd Hoffmann]

On Di, 2014-10-28 at 10:37 +0000, Dr. David Alan Gilbert wrote:
> * Gerd Hoffmann (address@hidden) wrote:
> > This patch switches the default display from cirrus to vga
> > for the new (qemu 2.2+) machine types.  Old machines types
> > stay as-is for compatibility reasons.
> > 
> > Signed-off-by: Gerd Hoffmann <address@hidden>
> > ---
> >  hw/i386/pc_piix.c | 7 +++++--
> >  hw/i386/pc_q35.c  | 7 +++++--
> >  2 files changed, 10 insertions(+), 4 deletions(-)
> > 
> > diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
> > index 91a20cb..8637246 100644
> > --- a/hw/i386/pc_piix.c
> > +++ b/hw/i386/pc_piix.c
> > @@ -456,7 +456,8 @@ static void pc_xen_hvm_init(MachineState *machine)
> >  
> >  #define PC_I440FX_2_2_MACHINE_OPTIONS                           \
> >      PC_I440FX_MACHINE_OPTIONS,                                  \
> > -    .default_machine_opts = "firmware=bios-256k.bin"
> > +    .default_machine_opts = "firmware=bios-256k.bin",           \
> > +    .default_display = "std"
> >  
> >  static QEMUMachine pc_i440fx_machine_v2_2 = {
> >      PC_I440FX_2_2_MACHINE_OPTIONS,
> > @@ -466,7 +467,9 @@ static QEMUMachine pc_i440fx_machine_v2_2 = {
> >      .is_default = 1,
> >  };
> >  
> > -#define PC_I440FX_2_1_MACHINE_OPTIONS PC_I440FX_2_2_MACHINE_OPTIONS
> > +#define PC_I440FX_2_1_MACHINE_OPTIONS                           \
> > +    PC_I440FX_MACHINE_OPTIONS,                                  \
> > +    .default_machine_opts = "firmware=bios-256k.bin"
> 
> I think the normal way to do this is the opposite of this; i.e.
> make the display defaults be the new behaviour, then add the .default_display 
> = "cirrus"
> to the v2_1 machine type, and everything below it will automatically inherit
> it, and everything newer will just use the new default.

That is indeed the case for (device) compat properties,
but not for QEMUMachine entries.  default_display logic follows the way
default_machine_opts works.

cheers,
  Gerd