Re: [Linux-fbdev-devel] Supporting various depth

[Sven L. <lu...@dp...>]

On Wed, Jun 13, 2001 at 08:47:21AM -0700, James Simmons wrote:
> 
> > So i suppose saying fbset -depth 15 could be done to switch the fb to
> > RGBA5551 mode ? 
> > 
> > BTW, what is fbset -depth 24 supposed to do, especially if the chip only
> > support 8, 16, and 32 bpp ?

> > should only fbset -depth 32 be supported ?

mmm, well, the problem is that most current 'millions of color' modes are in
truth depth 24 ones, which are internally either 32bpp (as in the permedia3
case) or 24bpp (saves bandwith, but no alpha channel and you may be forced to
do some shifting).

Now, if a user wants to set a depth of 24, what does he mean ? mostly it is
RGB 888, but for the user the presence of an alpha channel (32bpp) or not
(24bpp) may not be that important. Especially Since X is using per default
depth 24 with bpp 32.

So what should happen if you try to set depth 24 with fbset ? Silently set 32
bpp ? reject it ?

Same goes for depth 15 ? should it silently be set to bpp 16, RGBA 5551, or
rejected ?

> > Also, i am experiencing some (maybe hardware) bugs, and would like to reset
> > the graphic chip. Is there an existing way to do this kind of stuff via ioctl
> > ore such (sure i could do it by hand under root, but i don't think fbcon/fbdev
> > would be really happy with it).
> 
>    Not really. You could make it reset the card when unloading the module.

or when loading it ?

> Log in remotely or use a serial console to do this. 

BTW, if dual head was really working i could do that, wait no, they both would
be using pm3fb. 

Would it be possible to run the vga text console on one head, and a pm3fb on
the other ? (same chip).

>   In theory when you run the program reset. It should reset your console
> back to the default mode. Unfortunely the console system doesn't work that
> way :-(  

Well, the real problem here is not so much to reset to default mode, but to do
a hardware reset on the chip, and initialize it again, to see if the problem
goes away.

The porblem only appears from time to time (but stays if i only do a reboot
:(((), and it seems that either the memory has some problem, or more probably
the accel unit, as this happens only when accel is enabled, and there are
areas where various pixels get some of their bits sets to 1.

Friendly,

Sven Luther
>