From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933070AbcBILT3 (ORCPT ); Tue, 9 Feb 2016 06:19:29 -0500 Received: from smtp.citrix.com ([66.165.176.89]:1473 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932911AbcBILT0 (ORCPT ); Tue, 9 Feb 2016 06:19:26 -0500 X-IronPort-AV: E=Sophos;i="5.22,420,1449532800"; d="scan'208";a="330530225" Date: Tue, 9 Feb 2016 11:19:02 +0000 From: Stefano Stabellini X-X-Sender: sstabellini@kaball.uk.xensource.com To: "Rafael J. Wysocki" CC: Stefano Stabellini , "Rafael J. Wysocki" , Shannon Zhao , "linux-arm-kernel@lists.infradead.org" , , , , Catalin Marinas , Will Deacon , Mark Rutland , , , "devicetree@vger.kernel.org" , , Linux Kernel Mailing List , , Shannon Zhao , , Len Brown , "open list:ACPI" Subject: Re: [PATCH v4 01/17] Xen: ACPI: Hide UART used by Xen In-Reply-To: <2213954.ztOe55fprN@vostro.rjw.lan> Message-ID: References: <1454641552-12576-1-git-send-email-zhaoshenglong@huawei.com> <2213954.ztOe55fprN@vostro.rjw.lan> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" X-DLP: MIA2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 8 Feb 2016, Rafael J. Wysocki wrote: > On Monday, February 08, 2016 10:57:01 AM Stefano Stabellini wrote: > > On Sat, 6 Feb 2016, Rafael J. Wysocki wrote: > > > On Fri, Feb 5, 2016 at 4:05 AM, Shannon Zhao wrote: > > > > From: Shannon Zhao > > > > > > > > ACPI 6.0 introduces a new table STAO to list the devices which are used > > > > by Xen and can't be used by Dom0. On Xen virtual platforms, the physical > > > > UART is used by Xen. So here it hides UART from Dom0. > > > > > > > > Signed-off-by: Shannon Zhao > > > > Reviewed-by: Stefano Stabellini > > > > > > Well, this doesn't look right to me. > > > > > > We need to find a nicer way to achieve what you want. > > > > I take that you are talking about how to honor the STAO table in Linux. > > Do you have any concrete suggestions? > > I do. > > The last hunk of the patch is likely what it needs to be, although I'm > not sure if the place it is added to is the right one. That's a minor thing, > though. > > The other part is problematic. Not that as it doesn't work, but because of > how it works. With these changes the device will be visible to the OS (in > fact to user space even), but will never be "present". I'm not sure if > that's what you want? > > It might be better to add a check to acpi_bus_type_and_status() that will > evaluate the "should ignore?" thing and return -ENODEV if this is true. This > way the device won't be visible at all. Something like below? Actually your suggestion is better, thank you! diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c index 78d5f02..4778c51 100644 --- a/drivers/acpi/scan.c +++ b/drivers/acpi/scan.c @@ -1455,6 +1455,9 @@ static int acpi_bus_type_and_status(acpi_handle handle, int *type, if (ACPI_FAILURE(status)) return -ENODEV; + if (acpi_check_device_is_ignored(handle)) + return -ENODEV; + switch (acpi_type) { case ACPI_TYPE_ANY: /* for ACPI_ROOT_OBJECT */ case ACPI_TYPE_DEVICE: