Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756703AbYLEU2I (ORCPT ); Fri, 5 Dec 2008 15:28:08 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751121AbYLEU1y (ORCPT ); Fri, 5 Dec 2008 15:27:54 -0500 Received: from mx1.redhat.com ([66.187.233.31]:59995 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750852AbYLEU1y (ORCPT ); Fri, 5 Dec 2008 15:27:54 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit From: Roland McGrath To: "Dave Airlie" X-Fcc: ~/Mail/linus Cc: "linux-kernel@vger.kernel.org" , libc-alpha@sources.redhat.com Subject: Re: IO space memcpy support for userspace. In-Reply-To: Dave Airlie's message of Friday, 5 December 2008 13:40:43 +1000 <21d7e9970812041940h29994c60w3e7bcf20b96efe04@mail.gmail.com> References: <21d7e9970812041940h29994c60w3e7bcf20b96efe04@mail.gmail.com> X-Zippy-Says: I know how to get the hostesses released! Give them their own television series! Message-Id: <20081205202746.7DB20FC379@magilla.sf.frob.com> Date: Fri, 5 Dec 2008 12:27:46 -0800 (PST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 762 Lines: 17 There is never going to be something in memcpy that makes any magical kernel calls to find out about an address. That's just loony, sorry. memcpy is inlined away by the compiler in good cases. It's like you'd asked for "*ptr" to have magical constraints by the compiler generating code to ask the kernel if "ptr" is a special address. Uh, really? If you can think of an efficient way to determine it and do what you need, then you could write optimized routines that do that in the vDSO perhaps. Thanks, Roland -- 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/