Date: Sat, 27 Jun 1998 07:15:31 +0000 (GMT) From: Terry Lambert <tlambert@primenet.com> To: dg@root.com Cc: rivers@dignus.com, hackers@FreeBSD.ORG Subject: Re: Heads up: block devices to disappear! Message-ID: <199806270715.AAA22822@usr08.primenet.com> In-Reply-To: <199806261400.HAA10810@implode.root.com> from "David Greenman" at Jun 26, 98 07:00:25 am
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> All caching in Unix used to be device-based and the block device was the > thing being cached (as opposed to the character device which is uncached). > Starting with 4.4BSD, the cache is file-based, making the main reason for > the existence of the block device obsolete. Say I controlled a device by mapping it and then writing two values to the same offset. A device that exposes the I/O address space using unmapped pages, and handles them by examination of the fault, then fixes up the fault. One might see a similar approach taken for hardware emulation to make the hardware appear to match the driver... For instance, a device that emulated inb/outb/inw/outw/etc. on an Alpha platform to allow a user space XFree86 to talk to nominally PC hardware, or a VMM for managing multiple virtual x86's. Will the new character interface be uncached, or will it "gather" the writes, preventing me from talking to such a device? Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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