Re: Mirrored Display?

[Michael Kaufmann <kaufmann@sohard.de>]

Dear James,

thanks for your reply.

On Friday 20 December 2002 18:49, you wrote:
> > 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.
>
> Some hardware supports mirroring. Sounds like you turned it on by mistake.

No, there is nothing i could turn on/off in my hardware. 
I have checked the hardware and the datasheets again, and i'm now sure. The 
display i'm using is a LCD monochrom display. And this type of display writes 
the picture date from right to left (mirrored). There is nothing i can do 
against it. My videocontroller has no feature to output every line mirrored.
The videocontroller start sending the picture datastream to the display from
videobuffer address 0. The first pixel from the picture datastream will be 
displayed on the right/top edge on my LCD and the second pixel left to the 
first and so on. 

First i thought that this behaviour of my display is extremly unusal. After 
looking to other display datasheets i now know, that it is unusal but far not 
sooo unusual i thought the first time.  

> > 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.
>
> The latest 2.5.X kernels have hardware hooks for rotation. I haven't added
> it yet to the software accel functions. I plan to a soon as I get time.
> Thank you.

Antonino has also answered to my question. And he said that there is nothing 
i can do, because user apps will directly acces the framebuffer via read/write 
or nmap. I can only patch the console and the show _logo to write the data 
mirrored to the videobuffer (a lot of work).
So my user apps (like nanoX or directfb/GTK+) must know about the mirrored 
display and should write the picturedata mirrored in the framebuffer. 

I'm know a litte bit amazed about a rotation feature in next versions. Does 
this mean, that the buffer where user apps (or also the console) are writing 
there picture data is not directly the videobuffer anymore? Or how does this 
rotation feature works?

I think it would be a good feature to have 'something' between the framebuffer 
and the physical videobuffer to be able to manipulate the picture data (like 
rotation, mirroring, etc.). But i don't know how this peace of software 
should detect, changed data in the 'framebuffer' to e.g. mirror in the 
videobuffer? Writing the whole buffers from time to time whould be a very
bad solution (performance).

At the moment i plan to do the manipulation in the directfb layer on top of 
the framebuffer device. I 'only' need to run some GTK+ applications. I need 
to mirror the picture, and i also want to rotate the picture from landcape to 
portrait.

Bye
Michael 


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