Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262742AbUCWR6s (ORCPT ); Tue, 23 Mar 2004 12:58:48 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262752AbUCWR6s (ORCPT ); Tue, 23 Mar 2004 12:58:48 -0500 Received: from pentafluge.infradead.org ([213.86.99.235]:43651 "EHLO pentafluge.infradead.org") by vger.kernel.org with ESMTP id S262742AbUCWR6p (ORCPT ); Tue, 23 Mar 2004 12:58:45 -0500 Subject: Re: can device drivers return non-ram via vm_ops->nopage? From: David Woodhouse To: Andy Whitcroft Cc: Russell King , Linus Torvalds , Jeff Garzik , Christoph Hellwig , William Lee Irwin III , Andrew Morton , Andrea Arcangeli , linux-kernel@vger.kernel.org In-Reply-To: <28313883.1080064760@42.150.104.212.access.eclipse.net.uk> References: <1079901914.17681.317.camel@imladris.demon.co.uk> <20040321204931.A11519@infradead.org> <1079902670.17681.324.camel@imladris.demon.co.uk> <20040321222327.D26708@flint.arm.linux.org.uk> <405E1859.5030906@pobox.com> <20040321225117.F26708@flint.arm.linux.org.uk> <405E23A5.7080903@pobox.com> <20040321235854.H26708@flint.arm.linux.org.uk> <28313883.1080064760@42.150.104.212.access.eclipse.net.uk> Content-Type: text/plain Message-Id: <1080064710.16509.297.camel@hades.cambridge.redhat.com> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.5 (1.4.5-8.dwmw2.2) Date: Tue, 23 Mar 2004 17:58:31 +0000 Content-Transfer-Encoding: 7bit X-Spam-Score: 0.0 (/) X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 878 Lines: 22 On Tue, 2004-03-23 at 17:59 +0000, Andy Whitcroft wrote: > Would it not be possible to allocate struct page's for these special areas > of memory? Worst, worst, worst case could they not represent pages in a > memory only node in the NUMA sense? I am sure there is some way they could > be 'tacked' onto the end of the cmap in reality? It would be possible. But why? What benefit do we gain from this pretence? Just hide it all from the driver with dma_coherent_mmap() and forget about it. Let the arch deal with it -- the _common_ case will be that we use nopage for the actual mapping, perhaps. But why mandate it? -- dwmw2 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/