Date: Thu, 6 Mar 1997 13:12:17 -0700 (MST) From: Terry Lambert <terry@lambert.org> To: bmcgover@cisco.com (Brian McGovern) Cc: hackers@freebsd.org Subject: Re: Porting device drivers... Message-ID: <199703062012.NAA13898@phaeton.artisoft.com> In-Reply-To: <199703061912.OAA02242@bmcgover-pc.cisco.com> from "Brian McGovern" at Mar 6, 97 02:12:45 pm
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> I'm curious if anyone has any comments on the feasability of "porting" > Linux device drivers to FreeBSD. I'm looking at doing a driver for the > Cyclom Z card, and there is one that currently works for Linux. I'm > wondering if its worth my time trying to recode it, or whether I should > just start from scratch. Linus treats the kernel services exported to drivers as if the kernel were a library distributed under the LGPL. This lets him get away with a GPL'ed kernel that does not cause commercial drivers to become GPL'ed. The Linux statement of license makes this very clear. Because of this, I believe that any driver that can be loaded as an LKM satisfies both the LPGL relink clause, and the GPL agregation clause. Several lawyers have agreed with this intepretation at various commercial companies (hence the availability of commercial drivers for Linux). Conversely, then, any driver that can be LKM'ed will satisfy those clauses in the BSD environment as well. The one problem you will have is with boot-critical devices: drivers for them must be loaded as part of the kernel load. You should attempt to convince the driver authors to reclassify their drivers under LGPL, if you can, if they are boot-critical drivers (disk controllers, and so on), or, ideally, release them under UCB license as well. This is actually one of the driving factors in my advocacy of VM86() fallback drivers: boot critical devices can all have specific drivers LKM'ed, as long as you can get to the point where you can load modules at all before you need them, so the Linux drivers under GPL can still be safely used by BSD via post-boot loading using the fallback drivers. Unless this card is used for a serial console (ie: it's boot-critical), there's no reason you can't make it an LKM, and allow users to locally create statically linked kernels, which would be non-redistributable because of the conflict between the GPL "no additional restrictions" and the UCB "claim credit" clauses. My opinion, Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers.
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