[Qemu-devel] Re: sun framebuffer selection (was option-rom)

[Blue Swirl <blauwirbel@gmail.com>]

On Sat, Jun 5, 2010 at 11:10 PM, Bob Breuer <breuerr@mc.net> wrote:
> Blue Swirl wrote:
>>  but again: should we have a new machine with cg14 or
>> some switch to select TCX vs. cg14?
>>
>> Maybe the recently proposed machine subtype patches could help here.
>>
> Well, let's try to figure out a method of selecting the framebuffer
> type.  I'll try to list some of the options, even if they might be
> ridiculous.
>
> 1) Use the -vga option.  I know TCX and cg14 are not vga, but I think
> it's the closest existing command line option available.
>
> 2) Switch based on the -g WxH option.  At the moment, the TCX emulation
> doesn't really handle anything other than 1024x768, so switch to cg14
> for other resolutions if supported.
>
> 3) Use some other existing command line option, -device, -set or
> -global?  Might work, but the syntax may not be easy to remember.

We don't have an equivalent of -chardev, -netdev and -drive for displays.

> 4) Machine subtype.
>
> 5) New command line option.  Anything above might be better.
>
> 6) New machine type.  Is it a big enough feature to demand it's own
> machine type?  Maybe, but see next option.
>
> 7) Select as default video for SS-20.  The SS-10 and SS-600MP are
> already very similar.  This would allow for some differentiation between
> the machines, but there could still be an option to switch back to TCX.
> Note that TCX was really only available for the SS-4 and SS-5.
>
>
> Is there anything else that I missed?

Combined 7 & 6: make cg14 default for SS-20, add a deprecated
compatibility machine for SS-20 with TCX.

>
> I'm going to go ahead with option 2 in the short term.  I'm inclined to
> narrow it down to options 1, 4, and 7.  I know that 7 would have
> backwards compatibility concerns.  The cg14 seems to have at least the
> same capabilities as TCX so there shouldn't be any loss of
> functionality.  Even though SS-20 is not the default machine, do you
> know of any OS that works with the sun4m implementation today but
> doesn't have a cg14 driver?  Possible downside to cg14 for video is that
> any "acceleration" is handled by the SX pixel processor which has no
> available documentation.  TCX also has some amount of unimplemented
> acceleration.

It would be nice to use some basic device with well defined
acceleration or just a frame buffer as default.