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

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

[John Hunter]

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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.


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

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

[Gerd Hoffmann]

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.
 * 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



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

[John Hunter]

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On Tue, Apr 7, 2015 at 2:56 PM, Gerd Hoffmann <kraxel@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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Re: Is CIRRUS a suitable driver to convert to atomic mode-setting

[Gerd Hoffmann]

  Hi,
 
> 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.

Feel free to try.  I don't mind being proven wrong ;)

> 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.

I'd suggest to start with bochs, I'm sure it is easier that cirrus.

cheers,
  Gerd



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

[John Hunter]

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Hi Gerd,
Thanks for the suggestion.
I will try my best :)

On Tue, Apr 7, 2015 at 4:55 PM, Gerd Hoffmann <kraxel@redhat.com> wrote:

>   Hi,
>
> > 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.
>
> Feel free to try.  I don't mind being proven wrong ;)
>
> > 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.
>
> I'd suggest to start with bochs, I'm sure it is easier that cirrus.
>
> 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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