From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754138Ab2KLXN5 (ORCPT ); Mon, 12 Nov 2012 18:13:57 -0500 Received: from mail132.messagelabs.com ([216.82.242.115]:19837 "EHLO mail132.messagelabs.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754081Ab2KLXNz convert rfc822-to-8bit (ORCPT ); Mon, 12 Nov 2012 18:13:55 -0500 X-Env-Sender: hartleys@visionengravers.com X-Msg-Ref: server-11.tower-132.messagelabs.com!1352762034!11910074!1 X-Originating-IP: [216.166.12.99] X-StarScan-Received: X-StarScan-Version: 6.6.1.8; banners=-,-,- X-VirusChecked: Checked From: H Hartley Sweeten To: Bjorn Helgaas CC: "linux-kernel@vger.kernel.org" , Stephen Rothwell Date: Mon, 12 Nov 2012 17:13:52 -0600 Subject: RE: Q: Kconfig option VIRT_TO_BUS Thread-Topic: Q: Kconfig option VIRT_TO_BUS Thread-Index: Ac3BBUzmbt8PdCmHQNC0fHLCsBwJ2gAJd2UA Message-ID: References: In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday, November 12, 2012 11:41 AM, Bjorn Helgaas wrote: > On Mon, Nov 12, 2012 at 9:18 AM, H Hartley Sweeten wrote: >> Does anyone know what the Kconfig option VIRT_TO_BUS does? >> There are a number of "depends on" that option but it does not >> seem to directly enable any code in the kernel. > > virt_to_bus() is a deprecated interface for converting a kernel > virtual address to a bus address. It's deprecated because it's > impossible to implement correctly when there are multiple bus address > spaces, because you don't know which bus address space the caller has > in mind. Thanks for the info. So if a driver does not use virt_to_bus() then the "depends on VIRT_TO_BUS" is not necessary. Correct? Thanks, Hartley