From owner-freebsd-current Tue Jun 1 23:17:42 1999 Delivered-To: freebsd-current@freebsd.org Received: from godzilla.zeta.org.au (godzilla.zeta.org.au [203.26.10.9]) by hub.freebsd.org (Postfix) with ESMTP id B8FCD15179 for ; Tue, 1 Jun 1999 23:17:38 -0700 (PDT) (envelope-from bde@godzilla.zeta.org.au) Received: (from bde@localhost) by godzilla.zeta.org.au (8.8.7/8.8.7) id QAA17171; Wed, 2 Jun 1999 16:17:36 +1000 Date: Wed, 2 Jun 1999 16:17:36 +1000 From: Bruce Evans Message-Id: <199906020617.QAA17171@godzilla.zeta.org.au> To: dfr@nlsystems.com, wollman@khavrinen.lcs.mit.edu Subject: Re: IRQ sharing with newbus Cc: bde@zeta.org.au, current@FreeBSD.ORG, newton@atdot.dotat.org Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG >> I don't think the sio multiport stuff needs to use RF_SHAREABLE - the >> master device knows how to field interrupts for the slaves (at least thats >> how I understood it). > >But the sio non-multiport stuff should be able to use RF_TIMESHARE. -- >If I'm not using my serial port, I should be able to use my >infrared.... Preemptive timesharing would be hard to implement reasonably for irqs. A uniform timeslice would have to be 86 usec to work properly for unbuffered sio devices at 115200 bps. This is not reasonable, so the interrupt system would have to guess which device you are using and only switch irqs away from it every few [hundred] msec. This would work better for slower and output-mostly devices, mainly for printers. Bruce To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message