Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756304AbcCaMCw (ORCPT ); Thu, 31 Mar 2016 08:02:52 -0400 Received: from mail-lf0-f67.google.com ([209.85.215.67]:36828 "EHLO mail-lf0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751884AbcCaMCu (ORCPT ); Thu, 31 Mar 2016 08:02:50 -0400 MIME-Version: 1.0 In-Reply-To: <1459423425-1220-2-git-send-email-zhaoshenglong@huawei.com> References: <1459423425-1220-1-git-send-email-zhaoshenglong@huawei.com> <1459423425-1220-2-git-send-email-zhaoshenglong@huawei.com> Date: Thu, 31 Mar 2016 14:02:47 +0200 X-Google-Sender-Auth: FKLEHceTCymsDDC-CIAj-zecMow Message-ID: Subject: Re: [PATCH v9 01/17] Xen: ACPI: Hide UART used by Xen From: "Rafael J. Wysocki" To: Shannon Zhao Cc: "linux-arm-kernel@lists.infradead.org" , stefano.stabellini@citrix.com, david.vrabel@citrix.com, Catalin Marinas , Will Deacon , sstabellini@kernel.org, julien.grall@arm.com, xen-devel@lists.xen.org, "devicetree@vger.kernel.org" , linux-efi@vger.kernel.org, Linux Kernel Mailing List , Shannon Zhao , peter.huangpeng@huawei.com, "Rafael J. Wysocki" , Len Brown , "open list:ACPI" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2782 Lines: 87 On Thu, Mar 31, 2016 at 1:23 PM, 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. > > CC: "Rafael J. Wysocki" (supporter:ACPI) > CC: Len Brown (supporter:ACPI) > CC: linux-acpi@vger.kernel.org (open list:ACPI) > Signed-off-by: Shannon Zhao > --- > drivers/acpi/scan.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 69 insertions(+) > > diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c > index 5f28cf7..29f26fc 100644 > --- a/drivers/acpi/scan.c > +++ b/drivers/acpi/scan.c > @@ -45,6 +45,7 @@ static LIST_HEAD(acpi_scan_handlers_list); > DEFINE_MUTEX(acpi_device_lock); > LIST_HEAD(acpi_wakeup_device_list); > static DEFINE_MUTEX(acpi_hp_context_lock); > +static u64 spcr_uart_addr; > > struct acpi_dep_data { > struct list_head node; > @@ -1453,6 +1454,42 @@ static int acpi_add_single_object(struct acpi_device **child, > return 0; > } > > +static acpi_status acpi_get_resource_memory(struct acpi_resource *ares, > + void *context) > +{ > + struct resource *res = context; > + > + if (acpi_dev_resource_memory(ares, res)) > + return AE_CTRL_TERMINATE; > + > + return AE_OK; > +} > + > +static bool acpi_device_should_be_hidden(acpi_handle handle) > +{ > + acpi_status status; > + struct resource res; > + > + /* Check if it should ignore the UART device */ > + if (spcr_uart_addr != 0) { Why not to write this as if (spcr_uart_addr) { Or even if (!spcr_uart_addr) return false; and then the indentation level of the rest will be reduced. > + if (!acpi_has_method(handle, METHOD_NAME__CRS)) > + return false; > + I'd like to see a comment here that the devices in question are assumed to have only one memory resource present which is why we only look for the first one. > + status = acpi_walk_resources(handle, METHOD_NAME__CRS, > + acpi_get_resource_memory, &res); > + if (ACPI_FAILURE(status)) > + return false; > + > + if (res.start == spcr_uart_addr) { > + printk(KERN_INFO PREFIX "The UART device @%pa in SPCR table will be hidden\n", > + &res.start); > + return true; > + } > + } > + > + return false; > +} > + Thanks, Rafael