Is CIRRUS a suitable driver to convert to atomic mode-setting

[John Hunter]

On Tue, Apr 7, 2015 at 2:56 PM, Gerd Hoffmann <kraxel at redhat.com> wrote:

> On Do, 2015-04-02 at 09:57 +0800, John Hunter wrote:
> > Hi Daniel,
> > Sorry to disturb you, I realized you are a busy man of the community.
> > So I did some work before I email you.
> >
> >
> > I submit my proposal as you suggest, convert the two virtual driver
> > (CIRRUS
> > and BOCHS, if I remember it right) to atomic mode-setting.
> >
> >
> > After talked with Martin Peres(the administrator of xorg on gsoc) and
> > Gerd Hoffmann (the author of VirtIO gpu driver), we got this question,
> > is CIRRUS suitable to convert, as qemu using cirrus considered
> > harmful.
>
> Short background summary on the later for everybody involved:
>
> cirrus emulates hardware from the 90ies which simply isn't up to todays
> needs.  The two major issues:
>
>  * It has very limited video memory.  The cirrus driver does swap
>    framebuffers in and out of video memory because of that.  I suspect
>    converting the driver to atomic modesetting will be either impossible
>    or at least pretty difficult because of that.  The limited video
>    memory also limits the available resolutions, cirrus can't do FullHD
>    for example.
>

I think at least I should give it a try. If it is really impossible to
convert, then
we should talk about whether we should deprecate it in the future.
And I hope to treat cirrus as an test filed, it's a easier driver, so I can
get into
the drm kernel hacking quickly.

 * cirrus can run 1024x768 only at 24bpp (not 32bpp).  Which is rather
>    unusual these days and cirrus has display issues in xorg because it
>    takes code paths which are not really maintained & tested any more.
>
> cirrus isn't the default vga any more in qemu version 2.2 & newer
> because of these problems.
>
> cheers,
>   Gerd
>
>
>
>


-- 
Best regards
Junwang Zhao
Microprocessor Research and Develop Center
Department of Computer Science &Technology
Peking University
Beijing, 100871, PRC
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