Re: vesafb scrolling weirdness

Geert Uytterhoeven (Geert.Uytterhoeven@cs.kuleuven.ac.be)
Sat, 11 Jul 1998 14:39:35 +0200 (MET DST)

On Fri, 10 Jul 1998, Gerd Knorr wrote:
> In lists.linux.kernel you write:
>
> >It seems there is definately something weird going on in the screen
> >redraw routines when using vesafb. I've looked through the code, but
> >not being familiar with it I haven't found any likely cause. The
> >problem looks like there is always one line of text _underneath_ the
> >one containing the cursor, when the cursor it at the bottom of the
> >screen.
>
> >This line of text becomes visible (in the right place) when the screen
> >scrolls one line. The line after that one is then hidden, and so
> >on. There are also similar weirdnesses in ncurses-based programs.
>
> Have this one here to with the new 108b patches. Older versions work
> fine.
>
> vesafb does scrolling by redrawing the the whole screen from the
> shadow screen. Becauce most of the time the whole screen is scrolled
> and reading from video memory is slow, this works faster than memmove.
>
> It is possible to switch to memmove with "video=vesa:memmove" on the
> kernel command line. This fixes the problem, but slows down the console.
>
> The release notes for the patch list some "smart redraw scrolling",
> which probably does something like vesafb too. Seems these two
> optimations don't like each other...
>
> Maybe the generic fbcon code calles driver's scroll first and updates
> the shadow screen later on sometimes? Just a guess, hav'nt checked
> the code yet.

That may explain it. There changed a lot in drivers/char/console.c. Can you try
enabling the SCROLL_YREDRAW flag, as is done for creatorfb on SPARC? Then you
won't have to do redraw yourself.

Greetings,

Geert

--
Geert Uytterhoeven                     Geert.Uytterhoeven@cs.kuleuven.ac.be
Wavelets, Linux/{m68k~Amiga,PPC~CHRP}  http://www.cs.kuleuven.ac.be/~geert/
Department of Computer Science -- Katholieke Universiteit Leuven -- Belgium




-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.altern.org/andrebalsa/doc/lkml-faq.html