how glx extension uses the software render

[Wang Baisheng]

Dear Rahaman,

Thank you for answering my questions! Great!

And I have read some docs about dri and aiglx. But Maybe I misunderstand them. 
They all say that when using indirect render, it's the glx module with X 
server will dispatch the request to Mesa. Pls refer :
http://dri.sourceforge.net/doc/dri_data_flow.html
http://dri.sourceforge.net/doc/dri_control_flow.html


And another slide in a ppt named 'Accelerated Indirect GLX' written by 
Kristian Høgsberg on XDevConf , 9 Feb 2006 :
======================
Indirect rendering
 
If the server doesn't support DRI, if part of the DRI setup fails or if the users 
  specifically asks for it, libGL will fall back to indirect rendering.
 
In indirect mode, all OpenGL requests are marshalled to the server and libGL is 
  reduced to just a protocol layer.

In the server, the GLX module maintains an OpenGL context on behalf of the 
  client and forwards the demarshalled requests to the context.
 
The current implementation pulls parts of Mesa into the Glcore module to provide 
  a software backed GL context.

Synonymous with software/slow rendering
=====================

It also said that "The current implementation pulls parts of Mesa into the 
Glcore module to provide a software backed GL context."


But when I look the code of xm_api.c, I found it seems that in indirect mode, 
libGL is not just a protocol layer, and the client use its software render 
functions directly and those software render functions just like a normal  X 
client using xlib api. 

So can I say so that when in software render mode, it's not X server glx 
module dispatch the requests to Mesa, while it's the client using the libGL 
software render functions directly ?

Thanks!
Regards,
Baisheng




On Thursday 05 March 2009 04:56:57 am Mustafizur Rahaman wrote:
> Hi,
>
> I also faced the same problem sometime back , but any how after lot of
> debugging and analyzing the code, i have got some sort of understanding,
> which i am sharing.If anywhere, my understanding is not correct, i
> apologize for that.
>
> Check for these three files  1>glxcmds.c & glxext.c & 2> glxapi.c in
> mesa code. If you see the Makefiles, glxcmds.c & glxext.c is built for
> direct rendering & glxapi.c is built for indirect rendering, not both of
> them are built at the same time with the client program.
>
> So, let's take glxgear.c code for example and track the code flow, e.g.
> following would be the code flow for glXCreateContext for indirect
> rendering case..
>
> glXCreateContext==>Fake_glXCreateContext==>XMesaCreateContext==>_mesa_initi
>alize_context==>_mesa_init_exec_table==>Inside here, you can see all the
> mesa s/w functions are initialized.
>
> For direct rendering case, the following would be the flow...
>
> glXCreateContext==>XF86DRICreateContextWithConfig==> Then it goes to dri
> driver's create context and like this...
>
> I would request you to debug the code for indirect rendering for glxgear
> and see the code flow.And paralelly, try to follow the code flow for
> direct rendering(by code reading if you can't debug)..that's the way i
> followed...
>
> Have patient..because believe me, you will need that.. :-)
>
> Regs,
> Rahaman.
>
> Wang Baisheng wrote:
> > Dear all,
> >
> > Now I am studying the DRI. But I have some questions and I can not get
> > more information from internet. So would you please give me some
> > information for my following questions:
> >
> > How glx extension requests are dispatched to mesa for software render?
> > And how glx extension requests are dispatched to DRI driver ? And I also
> > find in x server 1.3, there is a glcore, but in x server 1.5, the glcore
> > is disappear.
> >
> > Thanks!
> > Regards,
> > Baisheng
> > _______________________________________________
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> > xorg at lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/xorg
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