From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755359AbcARO4w (ORCPT ); Mon, 18 Jan 2016 09:56:52 -0500 Received: from v094114.home.net.pl ([79.96.170.134]:52996 "HELO v094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752626AbcARO4t (ORCPT ); Mon, 18 Jan 2016 09:56:49 -0500 From: "Rafael J. Wysocki" To: Ankitprasad Sharma Cc: intel-gfx@lists.freedesktop.org, akash.goel@intel.com, shashidhar.hiremath@intel.com, tvrtko.ursulin@linux.intel.com, Len Brown , linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 10/11] acpi: Export acpi_bus_type Date: Mon, 18 Jan 2016 15:57:29 +0100 Message-ID: <2702251.zg6zbsLF6s@vostro.rjw.lan> User-Agent: KMail/4.11.5 (Linux/4.4.0; KDE/4.11.5; x86_64; ; ) In-Reply-To: <1453107660.10582.31.camel@ankitprasad-desktop> References: <1452752207-30382-1-git-send-email-ankitprasad.r.sharma@intel.com> <19135964.pq7BquODL6@vostro.rjw.lan> <1453107660.10582.31.camel@ankitprasad-desktop> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday, January 18, 2016 02:31:00 PM Ankitprasad Sharma wrote: > On Fri, 2016-01-15 at 15:51 +0100, Rafael J. Wysocki wrote: > > On Thursday, January 14, 2016 11:46:46 AM ankitprasad.r.sharma@intel.com wrote: > > > From: Ankitprasad Sharma > > > > > > Some modules, like i915.ko, needs to detect when certain ACPI features > > > are active inorder to prevent corruption on contended resources. > > > In particular, use of BIOS RapidStart Technology may corrupt the contents > > > of the reserved graphics memory, due to unalarmed hibernation. In which > > > case i915.ko cannot assume that it (reserved gfx memory) remains > > > unmodified and must recreate teh contents and importantly not use it to > > > store unrecoverable user data. > > > > > > Signed-off-by: Ankitprasad Sharma > > > Cc: "Rafael J. Wysocki" > > > Cc: Len Brown > > > Cc: linux-acpi@vger.kernel.org > > > Cc: linux-kernel@vger.kernel.org > > > --- > > > drivers/acpi/bus.c | 1 + > > > 1 file changed, 1 insertion(+) > > > > > > diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c > > > index a212cef..69509c7 100644 > > > --- a/drivers/acpi/bus.c > > > +++ b/drivers/acpi/bus.c > > > @@ -814,6 +814,7 @@ struct bus_type acpi_bus_type = { > > > .remove = acpi_device_remove, > > > .uevent = acpi_device_uevent, > > > }; > > > +EXPORT_SYMBOL_GPL(acpi_bus_type); > > > > > > /* -------------------------------------------------------------------------- > > > Initialization/Cleanup > > > > > > > No. > > > > I see no reason whatsoever for doing this. > > > > Thanks, > > Rafael > Hi Rafael, > > Thanks for the response. > > Can you please help me with, how to detect the presence of a certain > acpi device using its id (for example, INT3392 for Intel RST device)? If you want to check if the device ir present at all, you cen use acpi_device_is_present() introduced recently (although that would need to be exported if you want to use it from a driver). > As you might have seen (in the next patch in this series), that we use > this symbol (acpi_bus_type) to iterate over all the devices registered > on acpi bus, to check if there is a device with id INT3392 present or > not. Please don't do that this way. I'll have a look at the other patch later. Thanks, Rafael