Date: Sun, 14 Jun 1998 14:44:23 -0700 (PDT) From: Julian Elischer <julian@whistle.com> To: Brian Somers <brian@Awfulhak.org> Cc: current@FreeBSD.ORG Subject: Re: RFC: Change to the device interface Message-ID: <Pine.BSF.3.95.980614143541.6528A-100000@current1.whistle.com> In-Reply-To: <199806142130.WAA27843@awfulhak.org>
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On Sun, 14 Jun 1998, Brian Somers wrote: > > As PHK and others have noted the device interface is broken in a number of > > ways: > > > > Here is a set of suggestions for fixing it > > (hopefully in a way that will be minimal impact.) > > The message was originally on another topic.. > [.....] > > A second change would be to make each FILE structure in the kernel > > store a cookie that is returned by the open() call to the driver. > > this would allow the driver to associate an IO request with a particular > > open(). it would be an added arguent to all the devsw[] entrypoints. > [.....] > > I vote for this option. It's the intuitive place to hold state > information, despite it not being required by every driver. > I wasn't suggesting that one be done without the other, but rather splitting up the work into 2 'phases'. They are somewhat order independent. the first 'phase' can be done without editing any drivers, but becomes a lot more useful with the addition of the second change. reminder phase 1.. add devsw[] entrypoint for all status changes (RDONLY->RDWR close etc) phase 2.. associate every IO request with an 'open' using a cookie. this way a driver can know who is asking for an IO and how many clients it actuually has (which it doesn't know at the moment.) (at the moment it knows 0 or "more than 0") Justin in particular is asking for that ability for CAM. julian To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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