Re: Questions about fbdriver integration

[Geert Uytterhoeven <geert@linux-m68k.org>]

On Sat, 24 Nov 2007, Ico Doornekamp wrote:
> I have just finished writing a framebuffer driver for a LCD display
> connected to our embedded system (monochrome, 128x64, GPIO driven).
> It's very similar to the hecubafb driver, and uses deferred IO. I've
> included some of the drivers properties at the end of this mail.  Things
> works fine when displaying images by doing write()s to /dev/fb0, so this
> part seems to be ok.
> 
> I hope some of the regulars on this list can clear up some issues
> I've run into when using this driver:
> 
> - My next step as to redirect the linux console to this framebuffer
>   device. I've configured the kernel for framebuffer console, and when
>   loading the fbcon module, the message 
>     
>      Console: switching to mono frame buffer device 16x4" 
>      
>   appears, and
> 
>      cat /sys/class/vtconsole/vtcon1/name -> (M) frame buffer device
>      cat /sys/class/vtconsole/vtcon1/bind -> 1
>   
>   This seems just fine to me, but however, no output appears on the
>   display: just a blank screen. 
> 
>   It seems that the console is doing *something*, since my driver gets
>   triggered by the deferred IO every 200msec (blinking cursor?), problem
>   is that the data arriving in my driver is all zeroes!

Fbcon writes to the memory at fb_info.screen_base.

> - The other question is more a userspace issue: I was hoping to use the
>   xorg fbdev server on my dislay, but unfortunately this does not seem
>   to support 1 bit depth displays :
> 
>     (EE) FBDEV(0): unsupported number of bits per pixel: 1
> 
>   Is there a way to make X work on 1-bit fb devices, or am I out of luck
>   here ?

The old XF86_FBDev (from XFree86 3.x) definitely works with monochrome.
I expect (but never tried) KDrive also to support it.

It's a pity many frame buffer organizations were dropped in Xorg.

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

-------------------------------------------------------------------------
This SF.net email is sponsored by: Microsoft
Defy all challenges. Microsoft(R) Visual Studio 2005.
http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/