From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752670AbdI3Bwf (ORCPT ); Fri, 29 Sep 2017 21:52:35 -0400 Received: from bombadil.infradead.org ([65.50.211.133]:39425 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752639AbdI3Bwd (ORCPT ); Fri, 29 Sep 2017 21:52:33 -0400 Date: Fri, 29 Sep 2017 18:52:28 -0700 From: Darren Hart To: Mario Limonciello Cc: Andy Shevchenko , LKML , platform-driver-x86@vger.kernel.org, Andy Lutomirski , quasisec@google.com, pali.rohar@gmail.com, Greg Kroah-Hartman , Rafael Wysocki , Matthew Garrett , Christoph Hellwig Subject: Re: [PATCH v3 4/8] platform/x86: wmi: create character devices when requested by drivers Message-ID: <20170930015228.GC13307@fury> References: <17fcf9748e83ede2751a00d8248cb32cbdc610d6.1506571188.git.mario.limonciello@dell.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <17fcf9748e83ede2751a00d8248cb32cbdc610d6.1506571188.git.mario.limonciello@dell.com> User-Agent: Mutt/1.8.0 (2017-02-23) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 27, 2017 at 11:02:16PM -0500, Mario Limonciello wrote: > For WMI operations that are only Set or Query read or write sysfs > attributes created by WMI vendor drivers make sense. > > For other WMI operations that are run on Method, there needs to be a > way to guarantee to userspace that the results from the method call > belong to the data request to the method call. Sysfs attributes don't > work well in this scenario because two userspace processes may be > competing at reading/writing an attribute and step on each other's > data. > > When a WMI vendor driver declares a set of functions in a > file_operations object the WMI bus driver will create a character > device that maps to those file operations. > > That character device will correspond to this path: > /dev/wmi/$driver > > This policy is selected as one driver may map and use multiple > GUIDs and it would be better to only expose a single character > device. > > The WMI vendor drivers will be responsible for managing access to > this character device and proper locking on it. > > When a WMI vendor driver is unloaded the WMI bus driver will clean > up the character device. > > Signed-off-by: Mario Limonciello > --- > drivers/platform/x86/wmi.c | 98 +++++++++++++++++++++++++++++++++++++++++++--- > include/linux/wmi.h | 1 + > 2 files changed, 94 insertions(+), 5 deletions(-) +Greg, Rafael, Matthew, and Christoph You each provided feedback regarding the method of exposing WMI methods to userspace. This and subsequent patches from Mario lay some of the core groundwork. They implement an implicit whitelist as only drivers requesting the char dev will see it created. https://lkml.org/lkml/2017/9/28/8 -- Darren Hart VMware Open Source Technology Center