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SubjectRe: Calm on the GGI waters..


Btw, one last word to clarify my position a bit, and maybe explain why I
have gotten so upset by the GGI discussion.

For example, I've already pointed out that the current kernel already
_has_ a rather limited support for graphics: it can already write text on
various graphics cards (the TGA chip I mention is only one of them, and I
brought it up really only because that's the one I've used personally).

So what is the difference between that kind of graphics support and the
GGI kind?

The difference is really a matter of interface, and tying my hands.

The TGA kind of "make the graphics card work as a text-mode thing" kernel
code does not imply a new interface. The code to do the text rendering may
be simple or complex, buggy or bug-free, but whatever the case is it does
not limit me or the kernel in any way because it really implies only a
very limited interface to user space, and it is also an interface that I'm
more thn happy to provide and that is _obviously_ required, ie a basic
tty-like interface.

Think of it as a very basic kind of driver, but a driver that makes no
policy. The kernel only really guarantees that it can write characters on
the screen.

In contrast, the GGI kind of interface implies a lot _more_ in the way of
support. And by implying that, it ties my hands: I am no longer free to do
what I think is right, because I have to abide by the interface. This is
what makes UNIX so good: the basic interfaces are _really_ well thought
out (whether by chance or good design the basic "fork()" + "execve()" +
"everything is a file" mentality is a very simple but powerful one). That
is why I like UNIX, and why I wanted to write my own.

So while I'm more than happy to have my hands tied in the sense that I, as
the maintainer of Linux, export that kind of fork() + execve() type of
interface to user mode, I am not at all certain what kind of interface I
would feel happy about exporting wrt graphics. I feel confident in
exporting the text-mode things - that one is a no-brainer. But graphics?

As a result, I kick back _very_ strongly because I don't see any
"obviously correct" interface. I'd be happy either with something very
generic (basic DMA and interrupt interfaces to XFree86, for example), or
something very specific (some very limited subset of XAA for example: only
the bare necessities to make XAA easier to do). But anything else is not
"obvious" any more.

And when it is not obvious, I feel that "nothing" is much better than
"something that might not be the right thing". Because it is much easier
to fix up "nothing" than it is to fix something that people depend on.

Linus


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