From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from caramon.arm.linux.org.uk ([212.18.232.186]:45321 "EHLO caramon.arm.linux.org.uk") by vger.kernel.org with ESMTP id S262522AbUCWMkj (ORCPT ); Tue, 23 Mar 2004 07:40:39 -0500 Date: Tue, 23 Mar 2004 12:40:27 +0000 From: Russell King Subject: Re: can device drivers return non-ram via vm_ops->nopage? Message-ID: <20040323124027.D25134@flint.arm.linux.org.uk> References: <20040322151533.C11212@flint.arm.linux.org.uk> <1079969221.1759.25.camel@mulgrave> <1079992229.22190.29.camel@gaston> <405F6636.2090609@pobox.com> <20040322223509.GO2045@holomorphy.com> <1079999839.23205.40.camel@gaston> <20040323020756.GS2045@holomorphy.com> <20040323113534.GD22639@dualathlon.random> <20040323114452.GE2045@holomorphy.com> <20040323123439.GJ22639@dualathlon.random> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040323123439.GJ22639@dualathlon.random>; from andrea@suse.de on Tue, Mar 23, 2004 at 01:34:39PM +0100 Sender: Russell King To: Andrea Arcangeli Cc: William Lee Irwin III , Benjamin Herrenschmidt , Jeff Garzik , James Bottomley , Linux Arch list , Linus Torvalds , David Woodhouse , Christoph Hellwig , Andrew Morton List-ID: On Tue, Mar 23, 2004 at 01:34:39PM +0100, Andrea Arcangeli wrote: > anyways Linus vetoed the lazy approch so we probably should give it up > (the one thing I like most is to avoid the branch in the fast path). I don't think he did - he vetoed adding another special condition to the fast path, or returning non-RAM pages via ->nopage. However, I do not believe he has vetoed an architecture implementing dma_coherent_mmap() in such a way that it uses the ->nopage method, _provided_ ->nopage returns valid struct pages. -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: 2.6 PCMCIA - http://pcmcia.arm.linux.org.uk/ 2.6 Serial core