directcolor colormap question

["Alexander E. Patrakov" <patrakov@ums.usu.ru>]

Hello,

I am still writing a framebuffer driver for S3 Trio 3D/2X cards. Since 
this card supports (hardware) gamma correction in Windows 98, I decided 
to implement directcolor visuals (Xorg guys: you can set SR1B to 0x18 if 
bpp>8, and then standard VGA PEL registers will alter the hardware 
colormap).

The problem here is that I don't know the proper semantics for colormap 
persistence.

Consider the following scenario:

fbset -depth 16 -rgba 5,5,5,1 -nonstd 1
run some program that sets a colormap, e.g. Xorg with the "fbdev" driver
fbset -depth 16 -rgba 5,6,5,0 -nonstd 1
(oops, the text is all purple!)

The problem is that the program sets the following colormap:

reg 0 -> (0,0,0)
reg 1 -> (8,4,8)
...
reg 31 -> (255,125,255)
reg 32 -> (0,129,0)
reg 33 -> (0,133,0)
...
reg 62 -> (0,250,0)
reg 63 -> (0,255,0)

(i.e. just a linear colormap for 16 bpp). When I switch the framebuffer 
to 15bpp, the colormap persists, but it is no longer a proper colormap 
for that mode! Is this colormap persistence an expected behaviour, or 
should I somehow initialize the colormap to something sane on depth 
switch? If that's a bug in my driver, could you please point me where 
some other driver does this colormap initialization?

-- 
Alexander E. Patrakov


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