Re: [Linux-fbdev-devel] vga256fb

[Petr V. <VAN...@vc...>]

On 14 May 01 at 17:58, antirez wrote:
> On Mon, May 14, 2001 at 03:45:51PM +0000, Petr Vandrovec wrote:
> > ftp://platan.vc.cvut.cz/pub/linux/matrox-latest/
> >   vga.gz => vga16fb patch;
> >       fbset -depth 8 -nonstd 0 => up to 320x200/256 colors, linear
> >       fbset -depth 8 -nonstd 1 => up to 360x480/256 colors, planes
> >       fbset -depth 4 -nonstd 0 => up to 720x480/16 colors, planes
> >       fbset -depth 4 -nonstd 1 => up to 720x182/16 (or 320x480/16), linear
> >       (due to some VGA incompatibilites last mode works either on
> >        ATI or on Matrox... you have to change code to switch behavior,
> >        ATI needs 'xoffset--' in vga16fb_pan_var, while Matrox does not,
> >        or vice versa...)
> >   fbset-through-tty.gz => patch to get 'fbset -fb /dev/tty* ...' to work
> >             (not tested with other fbdev than matroxfb)
> >   tabstop.gz => patch for fatal kernel memory corruption and TAB not working
> >             beyond column 160
> 
> I downloaded the patch, it seems your 256 color driver works
> in 360x480 only to provide a graphic console, but not with
> other userspace software that mmap() the video memory.
> Am I right?

It provides mmap. But application must understand FB_AUX_PLANES_CFB8
videomode, not packed pixels.
 
> > fbtv uses busmastering transfers when fbdev reports reasonable values.
> > I have no idea what it checks, but on all my packed_pixels hardware
> > it does busmastering, even on 320x200 VGA.
> 
> I read the source code of fbtv, and it seems to perform a quite
> usual memory mapped I/O. Unfortunatelly I can't test it, I
> lacks a TV-card...

It then passes this address down to bttv, which converts virtual address
back to physical and pushes data directly there.
 
> No I can't use the no-page trick to remap the videoram pages and change
> the hardware state, unfortunatelly: it seems not possible.
> I used it just to mmap the vmalloc()ed "virtual"-fb memory to userspace. There
> is a different kernel timer that updates the video memory and
> switches the registers to write to the proper video plane.

If there is some memory somewhere it will work, as bttv supports
non-continuous data stores due to its ability to write directly to userspace.
                                                 Petr Vandrovec
                                                 van...@vc...