Re: geodefb issues, possible patch

[Knut Petersen <Knut_Petersen@t-online.de>]

>i have a patch if someone is interested. the problem is that i dont
>know what else to do, as i cant debug (with printf's) the driver as i
>dont have a screen, how does a fb driver gets debugged? 
>
First of all, it´s a good idea to allow the driver to be compiled either 
as a
module or as a permanent part of the kernel. If it´s a module, it is really
helpfull if it can be unloaded / reloaded.  Allow your driver to be loaded
with vesafb or vesafb-tng compiled into the kernel, normally that should
be possible if you do not fail if you cannot get exclusive access to some
resources vesafb reserves. That way you might start with vesafb, load 
version
1 of your driver, map consoles to either one, do some testing, map all
consoles to vesafb, unload your module and load a new version. That helped
a lot in debugging cyblafb.

If you do loop for some conditions, always include a timeout.

Use printks, and have a look at the system log after a reboot.

Use a serial console or another computer connected via network.

Let the driver display some status information at a fixed location of
the screen.

First of all: write a userspace program that does a complete register dump.
Boot with vesafb and all vga=??? parameters supported by the bios and store
those register dump.  Include a register dump function in the driver and 
compare
the register values to those found for vesafb.

Don´t believe documentation that indexed registers end at index x if x is
less than the highest possible value. If bits of a value are stored in 
several
places (e.g. vga screen start address), don´t assume that the documentation
documents all high bits.

Get it right unaccelerated first.

cu,
 knut



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