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xen-devel
Re: [Xen-devel][RFC] Dynamic modes support for PV xenfb (included)
> The attached files allow the PV framebuffer to be dynamically resized from
> 800x600 to 1024x768 and back.
>
> xen-fbfront-resize.patch is applied to tip of linux-2.6.18-xen
> xen-fbback-resize.patch is applied to tip of unstable-xen
> I am NOT requesting commit to xen- unstable. This is just a posting
> for code review and feedback.
>
> After the patches are applied to dom0 and your domU
> PV guest you will need to properly configure the domU X
> server for display modes 800x600 and 1024x768.
Nice.
I took a quite look through the code and was impressed by how small a patch
was actually required.
A few general comments:
1) I think it would be preferable to be able to dynamically size the memory
allocated to the framebuffer according to the resolution, rather than
statically allocating it and then potentially not using all of it.
Presumably this would require more extensive changes to the backend, since it
would need to map and unmap the framebuffer memory during a resize operation.
How complicated do you think this would be?
2) Dynamically allocating the memory would make it practical to support a
larger range of resultions than currently possible, without wasting lots of
memory for potential higher resolutions (e.g. to suit users with very big
monitors connected to dom0).
I think that this is nice support to have available. Other VMM user
interfaces even allow resizing of the guest display resolution simply by
resizing the viewer window on the host - this would require a little more
software running in the guest to support it but would be cool to support. Of
course, that's just me getting excited - simply supporting resize from within
the guest is a major win in practicality.
Do you have any further plans for xenfb? It's not got as much love as it
could have done and it definitely seems like there are things that can be
done to improve it still further.
Cheers,
Mark
> For testing I used "xrandr" to dynamically resize the domU
> GUI session.
>
> >$ xrandr // show capabilities
>
> SZ: Pixels Physical Refresh
> *0 1024 x 768 ( 361mm x 291mm ) *73
> 1 800 x 600 ( 361mm x 291mm ) 73
> Current rotation - normal
> Current reflection - none
> Rotations possible - normal
> Reflections possible - none
>
> >$ xrandr --size 800x600 //change to 800x600
> >$ xrandr --size 1024x768
>
> domU xorg.conf :
> SuSE sax2 is not able to configure a PV framebuffer properly
> so I hand crafted a new xorg.conf file for the PV guest. Below
> are the sections I changed.
>
> Section "Monitor"
> HorizSync 30-65
> Identifier "Monitor[0]"
> ModelName "XEN PVFB"
> Option "DPMS"
> VendorName "XEN"
> VertRefresh 43-75
> UseModes "Modes[0]"
> EndSection
>
> Section "Modes"
> Identifier "Modes[0]"
> Modeline "1024x768" 77.25 1024 1080 1192 1360 768 769 772 800
> Modeline "800x600" 46.15 800 840 920 1040 600 601 604 625
> EndSection
>
> Section "Screen"
> SubSection "Display"
> Depth 24
> Modes "1024x768" "800x600"
> EndSubSection
> Device "Device[0]"
> Identifier "Screen[0]"
> Monitor "Monitor[0]"
> EndSection
>
> Pat
--
Dave: Just a question. What use is a unicyle with no seat? And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!
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