Message-ID: <4530570B.7030500@comcast.net>
Date:	Fri, 13 Oct 2006 23:18:35 -0400
From:	John Richard Moser <nigelenki@...cast.net>
To:	linux-kernel@...r.kernel.org
Subject: Driver model.. expel legacy drivers?

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Here's a silly thought I had a while ago.  Linux has no static ABI for
device drivers, I think the general argument was between "it's slower"
and "different hardware will have different requirements."  Putting
aside design difficulties, I've come up with an example case of a useful
hardware driver ABI.

As kernel development goes on, some infrastructure changes require
drivers to be updated.  Eventually some drivers become buggy and
ill-maintained, even when they used to be legitimately working ones; and
then developers have to take some of their time to fix them, or eject
them from the tree.

  (I can't think of any specific cases where a driver has actually
become buggy enough that it became a notable hazard.  OSS eventually was
deprecated and pulled out of the tree because its architecture was old
and it wasn't worth keeping since we have ALSA now.)

The drivers have to be shipped in the main tree as well, and the kernel
tarballs are getting bigger.  2.6.14 was in a 37M .tar.bz2; .15 was in a
38M; .16 and .17 in a 39M; .18 is in a 40M tarball.  The size keeps
piling up, that's more and more code that's got to be maintained and
shipped.

Writing Linux into a microkernel isn't going to happen.  Linus isn't hot
on the idea; and besides, what would the developers DO with that kind of
disruption?  Tons of projects would drop off because basement coders
can't all rewrite their code for a new architecture (hey why not port
your new Linux memory management patch to FreeBSD while you're at it?).
 So the only other way to isolate parts of the kernel off the main tree
is, obviously, by making a way to move drivers out of it.

This brings up a few potential questions:

  - Will this eventually be necessary to an absolute?  Will 100M
    tarballs and hundreds of thousands of drivers be unmanageable in a
    tight, ABI-unstable monolith 10 years from now?

  - Would it ACTUALLY be worthwhile, given such a scenario, to expel
    drivers out of the tree to glue on by a static, somewhat slower but
    workable ABI so nobody has to touch the code ever?

  - Is there actually a benefit -now- to ejecting drivers from the tree,
    or are the developers pretty much comfortable polishing the stuff
    nobody normally touches here and there?

Just curious.


- --
    We will enslave their women, eat their children and rape their
    cattle!
                  -- Bosc, Evil alien overlord from the fifth dimension
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