Re: [Qemu-devel] [RFC PATCH] Allow building without graphics support

[Alexander Graf]

On 13.12.2012, at 08:16, Gerd Hoffmann wrote:

> On 12/13/12 01:57, Scott Wood wrote:
>> On 12/12/2012 01:52:29 AM, Gerd Hoffmann wrote:
>>> On 12/12/12 04:18, Scott Wood wrote:
>>>> QEMU is sometimes used in embedded contexts, where graphical support
>>>> is unnecessary.  The ability to turn off graphics support not only
>>>> saves some space, but it eliminates the dependency on pixman.
>>> 
>>> We have tons of hand-crafted pixel shuffeling code all over the place
>>> which I want replace with pixman library calls.  It's a long road and
>>> will take quite some time.
>>> 
>>> I wanna have pixman as core service in qemu for that, not some optional
>>> add-on.
>> 
>> Why?  Isn't modularity a good thing?  It can still be a core service for
>> any part of QEMU that deals with graphics.
> 
> A pretty central data structure in qemu (DisplayState / DisplaySurface)
> carries a pixman image, not some module which can easily be made
> optional.  Just look at the tons of #ifdef'ery you have to do to get
> this going.

His point is that anything related to DisplayState should be optional.

>> Another thing that is missing on the hardware I'm talking about is a
>> hard drive, so overly large qemu binaries are also not fun.
> 
> Oh, using pixman will actually make the qemu binaries smaller as we can
> replace code with library calls.

That doesn't help for the full system load. We're talking of flash chips in the 
MB range with an embedded initrd here, so you'd have to factor in pixman as 
well, as without QEMU there wouldn't be a pixman in the system in the first 
place.

The same argument really holds true for TCG modularization which nobody tackled 
yet though.

> Independant of that: allow easily stripping down qemu by removing stuff
> you don't want would be a nice (but non-trivial) project.

Yup :).

For the time being, almost none of my boxes can compile QEMU anymore. I have 
pixman versions

  0.12.0
  0.16.0
  0.16.4
  0.26.0

and I really don't want to mess with git submodules. Every time I checked out 
SLOF I ended up with bogus submodule commits in random patches. It's a real 
nightmare.


Alex