[Mplayer-cvslog] CVS: main/drivers/radeon README,1.14,1.15

[Nick Kurshev]

Hello, Michael!

On Thu, 3 Jan 2002 13:27:25 +0100 you wrote:

> Hi
> 
> On Thursday 03 January 2002 11:17, Nick Kurshev wrote:
> > Hello, Michael!
> >
> > On Wed, 2 Jan 2002 13:11:19 +0100 you wrote:
> > > Hi
> > >
> > > On Wednesday 02 January 2002 12:57, Nick Kurshev wrote:
> > > [...]
> > >
> > > > > what about decreasing hue range to -100..+100, and using sin/cos
> > > > > lookup table?
> > > >
> > > > We'll lose precision.
> > >
> > > do some interpolation (with a table & cubic interpolation it will be more
> > > than precise enough)
> >
> > I already solved this problem with generic_math.h which perform linear
> > interpolation by 1.8 degree step.
> > But there is other BIGGEST problem. This driver violates rule: "No float in
> > the kernel" :( Well there is way to avoid this problem (from
> > linux-kernel at vger.kernel.org):
> [...]
> u could use fixpoint math
> 1<<24 == "1.0"
> int64_t a,b,c
> ADD(a,b) a + b
> MUL(a,b) (a*b + (1<<23))>>24
> DIV(a,b) (a<<24)/b 	//not correctly rounded ...
I never studied bitfield representation of floating types in depth but as I remeber:
-1 = 111111111b for integer
-1.0 == 110000000b for  floats
(roughly)
so probably your a+b won't work propertly.

Currently I already finished library for direct hardware access which is based on gfxdump
utility from GATOS project (This utility printed out video registers even under Win98 - great
hacker's tool). It's already ported under a lot of operating systems:
linux - by default
free(open,net)bsd
Win9x
OS/2
SunOS
SVR4, SCO, ISC, ...
and ported under several arch:
x86
DECAlpha
Sun UltraSparc
PPC
So we can really solve portability request of Alex Beregszaszi and make happy a lots of people.
I plan to implement it in the "X11" way - as dynamically loaded drivers (with help of -libdl).
> 
> Michael
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> 


Best regards! Nick