[Xprint] [Fwd: cfb conversion effort (was Re: Debugging X.org drivers?)]

[Roland Mainz]

Hi!

----

I found the email which said that fb doesn't support some GC operation
overiding...
-- snip --
Intermediate challenge would be something like sunleo or sunffb, where
magic 
GC handling is used to implement primitive acceleration - [...]  This is
pretty
gross and fb doesn't expose the same functionality;
-- snip --
... I didn't checked that in detail but it sounds like there would be a
huge problem with converting the PCL drivers from cfb over to fb (or
not... I didn't investigate that in detail yet... right now I stil don't
dare to touch the PCL drivers in the hope that HP will contribute their
drivers back to Xorg (changing the Xorg drivers may make the merging of
the HP versions more difficult)) ... ;-(

-------- Original Message --------
Subject: cfb conversion effort (was Re: Debugging X.org drivers?)
Date: Sun, 31 Oct 2004 02:07:14 -0400
From: Adam Jackson <ajax at nwnk.net>
To: xorg at freedesktop.org
CC: Roland Mainz <roland.mainz at nrubsig.org>,Jim Gettys
<Jim.Gettys at hp.com>
References: <41826D75.906.4AEE501E at localhost>
<200410301759.49970.ajax at nwnk.net> <418466A8.8AE9401F at nrubsig.org>

On Sunday 31 October 2004 00:14, Roland Mainz wrote:
> Adam Jackson wrote:
> > Kendall, I'm for some reason thinking that the SciTech drivers were based
> > on the cfb framebuffer core.  cfb will not work under dlloader with 6.8
> > without a patch:
> >
> > http://freedesktop.org/bugzilla/show_bug.cgi?id=1114
> >
> > but you may be better off switching to fb.
>
> Do you have any example patch which shows how to turn a driver from cfb
> over to fb ? HP's PCL drivers use cfb extensively and it may be nice to
> switch them over, too...

Sure.  One trivial example is the RealVNC conversion patch Kristian
Høgsberg 
did: http://www.mail-archive.com/vnc-list@realvnc.com/msg14387.html

For drivers that treat the fb layer as something of a black box, this is
all 
you need to do.  Most of the xfree86 ddx drivers are of this sort. 
Until 
fairly recently there was still optional cfb support in six of the
drivers, 
and http://freedesktop.org/bugzilla/show_bug.cgi?id=1192 shows the
changes I 
made to drop that support.  In all but s3virge this support was disabled
at 
compile time, and in s3virge the cfb code was slower and, as with cfb in 
general, didn't support Render (and therefore Composite).

Intermediate challenge would be something like sunleo or sunffb, where
magic 
GC handling is used to implement primitive acceleration - double
entendre on 
"primitive" totally intended.  This is pretty gross and fb doesn't
expose the 
same functionality; I suspect it can be dropped in most cases without
too 
much pain.  There's an experimental patch to convert sunleo to fb: 
http://freedesktop.org/bugzilla/show_bug.cgi?id=1259
which I have received no feedback on as of yet, and I don't have the
hardware 
to verify it.  sunffb is left as an exercise for the reader.

The final step would be converting our overlay support to use fb.  I
don't 
even know where to begin here, largely for lack of hardware.  I see a
couple 
of functions in the fb layer that look like they're intended for overlay 
support.  I've been tempted to just drop our overlay support altogether
to 
see who complains; my guess is, roughly, nobody.

- ajax
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