Porting linux drivers [was: Re: [RFC] sema_wait_sig]

[Oleksandr Tymoshenko]

On 2012-11-25, at 11:18 AM, Ian Lepore <freebsd at damnhippie.dyndns.org> wrote:

> On Thu, 2012-11-22 at 22:12 -0800, Oleksandr Tymoshenko wrote:
>> Hello,
>> 
>> Is there any particular reason FreeBSD does not have sema_wait_sig
>> function? It seems to be easily implementable using cv_wait_sig
>> function. 
>> 
>> The reason I'm asking is that I'm getting some Linux drivers
>> ported to FreeBSD and the code in question relies on semaphores
>> and there is no obvious alternative to down_interruptible function.
>> I realize that not all approaches to driver development are easily
>> mappable from OS to OS but in this case lack of cv_wait_sig seems 
>> like gap in API. Unless of course there is strong rationale behind it.
> 
> As if this thread weren't contentious enough already, it seems to me to
> be the perfect lead-in to a question I've long wondered about...
> 
> Given that linux drivers are pretty much universally GPL licensed,
> what's the legality of "porting" them (whatever that means) to freebsd?
> Just how much can you cobble from a GPL'd linux driver in creating a
> BSD-licensed freebsd driver?
> 
> I've done my best to avoid EVER looking at linux driver code when
> working on freebsd drivers, because I don't know the legalistic answers
> to such questions.  I know the "what feels right to my moral sense"
> answer, which is if you study the linux driver and then write
> essentially the same driver for freebsd, it doesn't matter if you've
> re-typed the code with different variable names, you've copied it.
> 
> I've peeked at the linux code from time to time, mostly to confirm my
> understanding of poorly-written chip datasheets, or to find the meaning
> of some status register bit that doesn't seem to be documented
> elsewhere.  But it would be nice to know where the proper lines are that
> should not be crossed.

Just to be clear - the drivers in question are going to be relicensed 
to BSD (actually, double-licensed) by upstream. And if it's not happening
FreeBSD version will remain GPL.