Date: Wed, 19 Jul 2000 14:07:07 +0930 From: Greg Lehey <grog@lemis.com> To: Mike Smith <msmith@FreeBSD.ORG> Cc: Alfred Perlstein <bright@wintelcom.net>, arch@FreeBSD.ORG, smp@FreeBSD.ORG Subject: Re: Tidying up the interrupt registration process Message-ID: <20000719140707.K12072@wantadilla.lemis.com> In-Reply-To: <200007190415.VAA21470@mass.osd.bsdi.com> References: <20000718205756.Q13979@fw.wintelcom.net> <200007190415.VAA21470@mass.osd.bsdi.com>
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On Tuesday, 18 July 2000 at 21:15:53 -0700, Mike Smith wrote: >> * Mike Smith <msmith@FreeBSD.ORG> [000718 20:55] wrote: >>> >>> Sharing a 'fast' interrupt completely defeats the point of making it >>> 'fast'. You should not be able to register a 'fast' handler on any >>> source with anything else attached, nor anything else on a source that >>> has a 'fast' handler already registered. Yes, this does impose some >>> configuration constraints on the system, but there are few viable >>> alternatives. >> >> Just wondering, could a device fall back to non-fast mode if the >> hardware forced this sort of situation but still complain about it? > > You don't typically bother requesting a 'fast' interrupt unless you > really need it. This decision would have to be left up to the > device driver - some might be OK accepting the tradeoff (eg. sio), > wheras for others this might constitute a fatal error. In fact, unless I'm missing something, it looks as if there's no code there to stop you from sharing fast interrupts. I could have sworn there was, but the code in intr_machdep.c doesn't check. The cy driver also sets INTR_EXCL, which is checked for, but nexus_setup_intr doesn't. If you share a fast interrupt and a slow interrupt, the first-level handler becomes the mux, and so it appears that the "fast" attribute would just go away, *without* any warning. I don't know if there's something else that would stop it from working at all. Greg -- Finger grog@lemis.com for PGP public key See complete headers for address and phone numbers To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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