Date: Wed, 16 Apr 1997 00:48:51 +0200 From: j@uriah.heep.sax.de (J Wunsch) To: hackers@freebsd.org Cc: krygier@kph.uni-mainz.de (Klaus Werner Krygier) Subject: Re: special memory device Message-ID: <19970416004851.LL04161@uriah.heep.sax.de> In-Reply-To: <Pine.BSF.3.95q.970415095626.15027A-100000@krygierpc.kph.uni-mainz.de>; from Klaus Werner Krygier on Apr 15, 1997 09:57:39 %2B0200 References: <Pine.BSF.3.95q.970415095626.15027A-100000@krygierpc.kph.uni-mainz.de>
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As Klaus Werner Krygier wrote: > Now I want to install a similar device which is compatible to the Sun > solution. It will never be used by read/write i/o but only by mmaped i/o. > It shall be able to do a dynamic remapping of the VMEbus window every time > an address is accessed which is out of the current 64 KB window using the > page fault mechanism. Is this possible? This sounds hard to do. Is your card using a real bus system (EISA, PCI), so that you could map the entire memory at once? This would be the simplest solution. Otherwise, i guess you gotta play VM games, by invalidating the pages for the currently invisible device memory. You have to be notified about the page fault (no idea how this might be done, but i'm sure David or John could chime in here), invalidate the pages for the currently visible window, reprogram your card, and validate the pages for the now visible window. Returning from the page fault handler will continue the application. -- cheers, J"org joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE Never trust an operating system you don't have sources for. ;-)
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