Iñaki Etxebarria wrote:
Hi all, I am working on a system level debugger ( pICE ) and I am giving universal output support to it. I use Linear FrameBuffer by direct writes and it works pretty well.
How are you determining the address of the frame buffer?
The problem is, that by now, calculations for drawing are based on fixed X,Y,BPP(color
depth) resolution, which is a bit annoying...
So I´d like to detect those X,Y and BPP each time the system debugger is fired up (HOTKEY pressed or breakpoint or other ints triggered). I read something about usong CRT regs but I don´t really know how. Also, I have also seen some MMIO stuff, but no idea...
There is simply no generic way to do this. Every graphics card is
different. If you are using the VESA BIOS calls to fetch the address of
the frame buffer, the same interface can be used to fetch the current
mode, but there is no guarantee that the VESA BIOS has the current
information. You could try parsing /var/log/XFree86.0.log, but that's
only accurate if XFree86 happens to be running and in the current VT.
You could try running a process periodically to do the equivalent of
xdpyinfo. That gives you resolution and depth, but not the frame buffer
address. Plus, that doesn't help if a console VT happens to be visible.
One important thing is that -being a system level debugger- it can´t be a call driver or
call kernel approach, I must do direct hardware ( IO ports or memory ) only, since when the
debugger is active, the whole system is frozen and I cant rely on other stuff than my own code or direct
hardware.
Now you know why the best kernel debuggers for Windows use a
--
- Tim Roberts, [EMAIL PROTECTED]
Providenza Boekelheide, Inc.
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