Xgl server

[Jerome Glisse]

Jon Smirl wrote:

>On Sun, 07 Nov 2004 08:33:33 +1100, Benjamin Herrenschmidt
><benh at kernel.crashing.org> wrote:
>  
>
>>Where are you of your work on dual head fbdev ? I'm working on radeonfb
>>a bit lately, mostly power management stuff, but I want to add support
>>for mirroring using the second CRTC and may dual head. The problem with
>>the later is the fbdev API itself isn't very good at it. Userland need
>>to know what head is "linked" to what head, among others, plus the need
>>to dynamically add/remove the second head when user enables mirroring
>>for example.
>>    
>>
>
>If you start from the end result of wanting XGL as the desktop X
>server, you then figure out that you need a standalone OpenGL
>implementation to run it on. We have that in mesa-solo. Currently
>mesa-solo does not include mode setting and cursor support. To get
>mode setting and cursor support mesa-solo uses fbdev.
>
>Next you want both heads to work. Since mode setting and cursor
>support is coming from fbdev I started looking at fbdev to add second
>head support. At this point you will come to realize that the fbinfo
>structure is not designed to support more that one head. DRM also did
>not have the correct structure for supporting multiple heads, but that
>is fixed now.
>
>At OLS Alan Cox and I discussed several solutions for controlling
>modes for multiple heads. The best solution we came up with is via
>sysfs. The code at  bk://mesa3d@bkbits.net/drm-fb starts to implement
>this. The code is also a start at integrating fbdev/DRM.
>
>/sys/class/dri/card0
>      modes
>      mode
>      monitor
>/sys/class/dri/card1
>      modes
>      mode
>      monitor
>
>modes is the list of legal modes. It includes merged fbmodes. You set
>a mode by taking a string from modes and sett it to mode. displaying
>mode gives the current mode. If either card0/1 sets a merged fbmode
>the other device will disappear. The same effect could be done for
>clone. If you don't own both devices you can't set merged fb or clone.
>
>I have code in there for setting the mode on the second head but I
>can't figure out why it isn't working.
>
>The initial list of modes is set by a hotplug event from the driver
>executing a root user space program. The user space program reads the
>EDID and sets the modes by assigning them to modes. I used the fbmode
>structure. The hotplug event is not hooked up yet.
>
>There is a lot more coding and design work that needs to be done to
>get all of this working. I treat fbdev and drm as core libraries. Some
>drivers will load and only use the fbdev libraries. Other drivers,
>like the radeon one, use both libraries. Multi-head just isn't going
>to work unless the DRM/fbdev drivers are merged so that they can sort
>out memory management.
>
>Another project I need to finish is the little VGA driver that resets
>secondary video cards at boot.
>
>I would really like to encourage more people to help design and code a
>set of video drivers capable of supporting mesa-solo and XGL. I'm only
>about 5% of the way through this problem and I use all the help and I
>can get. There are many more aspects to this this design that I can
>explain further if people are interested.
>  
>
Do you plan to use EGL specification or stay with miniglx ? I'm willing 
to help but i fear to not
have enought time to do much.  Anyway if you have a more developed plan 
& | to do list thus
i can check if i can help in a way.

I will give a try at the drm-fb stuff next week.

best
Jerome Glisse