From: Marko Mäkelä (marko.makela_at_iki.fi)
Date: 2007-09-20 15:26:50
On Thu, Sep 20, 2007 at 12:35:28PM +0200, Gábor Lénárt wrote:
> On Thu, Sep 20, 2007 at 10:38:41AM +0300, Marko Mäkelä wrote:
> > The "fault" of GNU/Linux, if you like to call it that, is changing
> > software interfaces. Microsoft has often managed to keep the ABI
> > (application binary interface) backward-compatible, so that you can
> > still run very old binaries.
> >
> > Linux is not too bad either: for the fun of it, I was able to fire up
> > one of the first graphical web browsers (NCSA Mosaic, last updated
> > in 1994 or so) a couple of years ago.
> >
> > While the user interfaces of the Linux kernel and the GNU libc have
> > remained pretty compatible, the Linux kernel interfaces do change
> > even between minor versions. That is why it would be best to have
> > drivers inside the official Linux kernel tree. However, that could
> > be hard nowadays for projects like OpenCBM, given that the kernel
> > development is dominated by commercial companies.
>
> This is a common misunderstanding about the Linux kernel. It has got an API
> and even ABI towards the user space called syscall interface, and it's quite
> stable and compatible since almost the beginings. The problem here is not
> the module/drive "ABI", since there is no such thing for real at all
Based on our private follow-up, Gábor must have misunderstood my post.
Nevertheless, Gábor explains well why it is so hard to compile and
install third-party Linux kernel modules.
I am not suggesting that the Linux kernel should have a stable module
API or ABI. I did not claim that there would have been incompatible changes
to the user space application program or binary interfaces (which I
meant by "user interfaces"). I only implied that out-of-tree modules
(such as OpenCBM) will have difficulties in keeping up with changes to the
internal kernel interfaces.
I hope that I can be proven wrong about the difficulty of getting
additional drivers accepted to Linus' Linux kernel tree. It is a pity
that implementing and deploying low-level system programs is so hard in
the age of MMUs and multi-tasking.
Marko
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