Re: patent on O_ATOMICLOOKUP [Re: [PATCH] loopable tmpfs (2.4.17)]

[Robert Schwebel]

On Fri, May 24, 2002 at 08:25:38PM -0700, Linus Torvalds wrote:
> With RTLinux, you have to split the app up into the "hard realtime" part
> (which ends up being in kernel space) and the "rest".
> 
> Which is, in my opinion, the only sane way to handle hard realtime. No
> confusion about priority inversions, no crap. Clear borders between what
> is "has to happen _now_" and "this can do with the regular soft realtime".

... which in turn results in the situation that applications must be
implemented as kernel modules. 

> Your claim was that RTLinux made realtime hard to do with licensing
> concerns. MY claim is that if you actually were to use RTLinux, you
> wouldn't _have_ any licensing concerns: the kernel module would have to
> be GPL (both because the kernel wants it that way _and_ because you get
> the liences to the patent that way), and the user-level code that uses
> whatever data the RT module produces is no longer hard realtime at all.

This is only correct for open-loop applications. Most real life apps are
closed-loop. 

Robert
-- 
 +--------------------------------------------------------+
 | Dipl.-Ing. Robert Schwebel | http://www.pengutronix.de |
 | Pengutronix - Linux Solutions for Science and Industry |
 |   Braunschweiger Str. 79,  31134 Hildesheim, Germany   |
 |    Phone: [phone] |  Fax: [phone]    |
 +--------------------------------------------------------+