From owner-freebsd-hackers Sat Jun 27 00:15:40 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id AAA26736 for freebsd-hackers-outgoing; Sat, 27 Jun 1998 00:15:40 -0700 (PDT) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from smtp02.primenet.com (daemon@smtp02.primenet.com [206.165.6.132]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id AAA26728 for ; Sat, 27 Jun 1998 00:15:38 -0700 (PDT) (envelope-from tlambert@usr08.primenet.com) Received: (from daemon@localhost) by smtp02.primenet.com (8.8.8/8.8.8) id AAA28009; Sat, 27 Jun 1998 00:15:38 -0700 (MST) Received: from usr08.primenet.com(206.165.6.208) via SMTP by smtp02.primenet.com, id smtpd027993; Sat Jun 27 00:15:35 1998 Received: (from tlambert@localhost) by usr08.primenet.com (8.8.5/8.8.5) id AAA22822; Sat, 27 Jun 1998 00:15:31 -0700 (MST) From: Terry Lambert Message-Id: <199806270715.AAA22822@usr08.primenet.com> Subject: Re: Heads up: block devices to disappear! To: dg@root.com Date: Sat, 27 Jun 1998 07:15:31 +0000 (GMT) Cc: rivers@dignus.com, hackers@FreeBSD.ORG In-Reply-To: <199806261400.HAA10810@implode.root.com> from "David Greenman" at Jun 26, 98 07:00:25 am X-Mailer: ELM [version 2.4 PL25] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG > 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