Re: [Linux-fbdev-devel] Mirrored Display?

[Michael K. <kau...@so...>]

On Saturday 14 December 2002 23:29, you wrote:
> On Fri, 2002-12-13 at 23:33, Michael Kaufmann wrote:
> > Hello,
> >
> > i would like to use a mono LCD with a framebuffer driver.
> >
> > I've modified existing drivers, and after a lot of work i now have a
> > clear picture on my display. Unfortunately, the complete picture is
> > mirrored. The Bootlogo is top/right instead of top/left and the ascii
> > output starts from right to left.
> >
> > Where is the right place to modify this behaviour?
> > I'm also looking for a possibility to rotate the picture.
> > Because my videocontroller can emulate 15 grayscales, i'm useing 4bpp=
=2E
> >
> > It would be very nice, if someone can guide me in the right direction=
=2E
>
> Are you using fbcon-cfb4.c to draw the characters?  Is the whole displa=
y
> mirrored, including individual characters?  If you run an fb-based app
> (like fbtest for instance), is the display also mirrored?

Yes,  i'm using fbon-cfb4.c. The console is on my display, i see the boot=
 logo=20
and the kernel messages in the display mirrored. I never used fbtest. By =
the=20
way, where can i find fbtest? But i already startet nanox/microwindows on=
 top=20
of the fb, and the picture is also mirrored. =20

> If it's the whole display, maybe your hardware supports mirroring (some
> hardware with video overlay need this to support YUV formats that are
> either vertically or horizontally mirrored).  Maybe it has something
> like that.  Otherwise, it will be difficult to correct this without
> rewriting practically everything.

No, i don't think so. It is a simple video controller. Nevertheless, i ha=
ve=20
just looked in the datasheet, and do not found such a feature.=20

I don't think that this is a bug or something like this in the framebuffe=
r.=20
Because everthing works like i exect it, but i have to mirror the picture=
=2E
I have also measured with a scope all signals to the display, and the=20
generated output looks like i expect it. The datastream starts with the f=
irst=20
pixel (in the picture top/left) and continues with the second pixel (on t=
he=20
right of the first pixel) and so on.
But my display is mapping this datastream from the right to the left.
Please take a look on the attached picture, i think it explains the behav=
iour.
I can reproduce it without Linux with a simple monitor programm

At the moment i have two explanations:
1) I have a display witch must be accessed unusual, and the LINUX FB does=
n't
    support this kind of access (not yet).
2) There is a hardware problem with the signals to the display (changed=20
   signals like frame-pulse, and line-pulse, or something like this.

I don't think that it is a hardware problem, but i will check the connect=
ion=20
again. Is there really no way in the framebuffer to mirror and/or rotate =
the=20
picture data?
When i have to fix it in software, what kind of code do i have to rewrite=
?=20

And, thank's for your reply!
=20
Bye
Michael