Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753200AbaGYOrG (ORCPT ); Fri, 25 Jul 2014 10:47:06 -0400 Received: from bedivere.hansenpartnership.com ([66.63.167.143]:49791 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751618AbaGYOrD (ORCPT ); Fri, 25 Jul 2014 10:47:03 -0400 Message-ID: <1406299616.1789.13.camel@jarvis.lan> Subject: Re: [PATCH 4/5] [SCSI] Do not use platform_bus as a parent From: James Bottomley To: Pawel Moll Cc: Greg Kroah-Hartman , Olof Johansson , Stephen Warren , Catalin Marinas , paul@pwsan.com, Arnd Bergmann , Peter De Schrijver , arm@kernel.org, linux-tegra@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org Date: Fri, 25 Jul 2014 07:46:56 -0700 In-Reply-To: <1406298233-27876-4-git-send-email-pawel.moll@arm.com> References: <1406298233-27876-1-git-send-email-pawel.moll@arm.com> <1406298233-27876-4-git-send-email-pawel.moll@arm.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2014-07-25 at 15:23 +0100, Pawel Moll wrote: > The host devices without a parent were "forcefully adopted" > by platform bus. This patch removes this assignment. In > effect the dev_dev may be NULL now, which means ISA. > > Cc: James E.J. Bottomley > Cc: linux-scsi@vger.kernel.org > Signed-off-by: Pawel Moll > --- > > This patch is a part of effort to remove references to platform_bus > and make it static. > > James, could you please have a look and advice if the change is > correct? Would you happen to know the "real reasons" behind > using the root platform_bus device a parent? Yes, for DMA purposes, the parent cannot now be NULL; we'll get a panic in the DMA transfers if it is. A lot of the legacy ISA device on x86 and I thought some ARM SOC devices don't pass in the parent device, so we hang them off a known parent. You can grep for it; these are the devices that will begin to panic if you apply this patch: arch/ia64/hp/sim/simscsi.c: error = scsi_add_host(host, NULL); drivers/scsi/a2091.c: error = scsi_add_host(instance, NULL); drivers/scsi/a3000.c: error = scsi_add_host(instance, NULL); drivers/scsi/aha152x.c: if( scsi_add_host(shpnt, NULL) ) { drivers/scsi/gdth.c: error = scsi_add_host(shp, NULL); drivers/scsi/gdth.c: error = scsi_add_host(shp, NULL); drivers/scsi/gvp11.c: error = scsi_add_host(instance, NULL); drivers/scsi/imm.c: err = scsi_add_host(host, NULL); drivers/scsi/pcmcia/fdomain_stub.c: if (scsi_add_host(host, NULL)) drivers/scsi/pcmcia/nsp_cs.c: ret = scsi_add_host (host, NULL); drivers/scsi/pcmcia/qlogic_stub.c: if (scsi_add_host(shost, NULL)) drivers/scsi/pcmcia/sym53c500_cs.c: if (scsi_add_host(host, NULL)) drivers/scsi/ppa.c: err = scsi_add_host(host, NULL); drivers/scsi/qlogicfas.c: if (scsi_add_host(hreg, NULL)) drivers/scsi/scsi_module.c: error = scsi_add_host(shost, NULL); drivers/scsi/sgiwd93.c: err = scsi_add_host(host, NULL); Note I've picked up scsi_module, so anything that uses the SCSI module interface also has this problem. James -- 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/