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[Ltib] Framebuffer problem with ltib-cf_nommu-20081215


From: Robert S. Grimes
Subject: [Ltib] Framebuffer problem with ltib-cf_nommu-20081215
Date: Wed, 29 Apr 2009 21:32:29 -0400

I've been trying to get Microwindows/Nano-X to work with the BSP from
Freescale, which features a kernel a bit newer than CVS for the mcf5329
processor, and more importantly for me, supports 320 x 240 resolution
LCD screens.  I had thought the hardware and framebuffer were working,
but now I'm not so sure...

Attached is a silly test program that writes directly to the framebuffer
- in other words, I'm not using Microwindows here.  Anyway, in
pseudo-code the program looks like this:

test:
  open framebuffer
  write all zeros to it (i.e. erase the screen)
  sleep(10) to allow inspection
  lseek to beginning
  write all ones to it (i.e. set all pixels white)
  sleep(10)
  lseek to beginning
  write a pattern of 8x8 multi-colored boxes to screen
  sleep(10)
  close framebuffer

Running this shows a nice blank screen for 10 seconds, then a white
screen for 10 seconds, then finally some pretty boxes.  Or at least,
that is what is supposed to happen.

What actually happens, sometimes, is that, sometimes it works, other
times the white screen shows the flicker/tearing/shearing throughout the
entire lower two-thirds of the screen.  Of course, the black looks fine,
but surprisingly, the colored blocks also looks fine.  Well, almost -
when the white shows the shearing, there is usually a small black
rectangle, maybe 3-4 pixels wide by 6-8 high, at the far left of the
screen, centered vertically about the first sheared line; this block is
also present on the white screen, along with an 6-8-pixel long vertical
black line at the same elevation, midway across the screen.  I don't
know if that little line shows up with the colored boxes.

I don't thing there is anything wrong with my code - it's so simple -
but perhaps I'm missing something?  So it seems to be a framebuffer (or
hardware, of course) problem.  Any ideas?

I don't have any familiarity with the framebuffer driver, so just
jumping in is a bit daunting; can anyone point me to a good introduction
on it, or give me a few pointers? 

Thanks,
-Bob

P.S. I've also posted this on the Microwindows mailing list, because I
had been discussing this problem there before, when I thought it was a
Microwindows problem - please forgive me if you've run into this posting
before...

Attachment: hello.c
Description: Text Data


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