[...]
>Reallistically we need to do this or something similair (modules?).
The problem with modules is that they'd have to have different code and data
segments. This means that you can't refer to the main kernel code and data
with 16-bit pointers. You could compile in medium, which gives 16-bit data
pointers and 32-bit code pointers, or huge, which gives 32-bit data and code
pointers.
This means you have to change huge amounts of stuff throughout the kernel,
which makes everything bigger, reduces efficiency and decreases stability (a
stray pointer has more chances of pointing at something outside the process'
address space). Also we don't have a medium or huge compiler.
The other solution use a message-passing architecture to pass data back and
forth from the main kernel to a driver (which may or may not live in
userland). This can be slow (this is what kills Minix). We could do a fast
version which doesn't involve the scheduler, but there'd still be overhead.
We've yet to resolve this. It seems easier to keep going the way we are until
we really run out of room in the kernel.
--
+- David Given ---------------McQ-+
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+- http://wired.st-and.ac.uk/~dg -+
