From owner-freebsd-hackers Fri Feb 28 09:19:31 1997 Return-Path: Received: (from root@localhost) by freefall.freebsd.org (8.8.5/8.8.5) id JAA06422 for hackers-outgoing; Fri, 28 Feb 1997 09:19:31 -0800 (PST) Received: from phaeton.artisoft.com (phaeton.Artisoft.COM [198.17.250.50]) by freefall.freebsd.org (8.8.5/8.8.5) with SMTP id JAA06415 for ; Fri, 28 Feb 1997 09:19:29 -0800 (PST) Received: (from terry@localhost) by phaeton.artisoft.com (8.6.11/8.6.9) id KAA02143; Fri, 28 Feb 1997 10:15:22 -0700 From: Terry Lambert Message-Id: <199702281715.KAA02143@phaeton.artisoft.com> Subject: Re: Assumptions about kmem_malloc()... To: dg@root.com Date: Fri, 28 Feb 1997 10:15:22 -0700 (MST) Cc: jpt@msc.edu, hackers@FreeBSD.ORG In-Reply-To: <199702280129.RAA05746@root.com> from "David Greenman" at Feb 27, 97 05:29:28 pm X-Mailer: ELM [version 2.4 PL24] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-hackers@FreeBSD.ORG X-Loop: FreeBSD.org Precedence: bulk > > o What other hidden gotchas are there in working with DMA and > >device drivers? > > Well, contiguous allocation is always the most common thing to get people. > :-) The only other thing you should be aware of is that allocation of > contiguous memory during normal system operation isn't guaranteed (in fact, > will likely fail)...so you should allocate whatever you need contiguous > during the device attach and olny release it later if you know you won't > need it. Why doesn't it push pages around to get a contiguous space so that it won't fail? Regards, Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers.