Re: Mirrored Display?

[Michael Kaufmann <kaufmann@sohard.de>]

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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.
> >
> > It would be very nice, if someone can guide me in the right direction.
>
> Are you using fbcon-cfb4.c to draw the characters?  Is the whole display
> 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 
and the kernel messages in the display mirrored. I never used fbtest. By the 
way, where can i find fbtest? But i already startet nanox/microwindows on top 
of the fb, and the picture is also mirrored.  

> 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 have 
just looked in the datasheet, and do not found such a feature. 

I don't think that this is a bug or something like this in the framebuffer. 
Because everthing works like i exect it, but i have to mirror the picture.
I have also measured with a scope all signals to the display, and the 
generated output looks like i expect it. The datastream starts with the first 
pixel (in the picture top/left) and continues with the second pixel (on the 
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 behaviour.
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 doesn't
    support this kind of access (not yet).
2) There is a hardware problem with the signals to the display (changed 
   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 connection 
again. Is there really no way in the framebuffer to mirror and/or rotate the 
picture data?
When i have to fix it in software, what kind of code do i have to rewrite? 

And, thank's for your reply!
 
Bye
Michael

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