From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752872AbdDMQGS (ORCPT ); Thu, 13 Apr 2017 12:06:18 -0400 Received: from bombadil.infradead.org ([65.50.211.133]:40558 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751119AbdDMQGP (ORCPT ); Thu, 13 Apr 2017 12:06:15 -0400 Date: Thu, 13 Apr 2017 09:06:06 -0700 From: Darren Hart To: Mario.Limonciello@dell.com Cc: luto@kernel.org, pali.rohar@gmail.com, hdegoede@redhat.com, kernel@kempniu.pl, rjw@rjwysocki.net, len.brown@intel.com, corentin.chary@gmail.com, andriy.shevchenko@linux.intel.com, linux-kernel@vger.kernel.org, platform-driver-x86@vger.kernel.org, linux-pm@vger.kernel.org Subject: Re: RFC: WMI Enhancements Message-ID: <20170413160606.GA2064@fury> References: <20170412230854.GA11963@fury> <20170413073228.GB1462@ozzy.nask.waw.pl> <3370431810bd4bc09fd9eb16eb9abea5@ausx13mpc120.AMER.DELL.COM> <20170413135102.GL3090@pali> <5bdfff4f72a941d086eeebba71557f19@ausx13mpc120.AMER.DELL.COM> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <5bdfff4f72a941d086eeebba71557f19@ausx13mpc120.AMER.DELL.COM> User-Agent: Mutt/1.7.1 (2016-10-04) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 13, 2017 at 03:40:08PM +0000, Mario.Limonciello@dell.com wrote: > > -----Original Message----- > > From: Andy Lutomirski [mailto:luto@kernel.org] > > Sent: Thursday, April 13, 2017 10:35 AM > > To: Pali Rohár > > Cc: Limonciello, Mario ; Hans de Goede > > ; Michał Kępień ; Darren Hart > > ; Rafael J. Wysocki ; Len Brown > > ; corentin.chary@gmail.com; Andrew Lutomirski > > ; Andy Shevchenko ; > > linux-kernel@vger.kernel.org; platform-driver-x86@vger.kernel.org; linux- > > pm@vger.kernel.org > > Subject: Re: RFC: WMI Enhancements > > > > On Thu, Apr 13, 2017 at 6:51 AM, Pali Rohár wrote: > > > On Thursday 13 April 2017 13:29:41 Mario.Limonciello@dell.com wrote: > > >> > Please pardon my ignorance, but what do we actually gain by > > >> > exposing WMI to userspace? Enabling applications to fetch SMBIOS > > >> > data? We already have an interface for that. Enabling applications to > > receive input events? Likewise. > > >> > > >> Input notifications are just one aspect that received over WMI. I > > >> don't see any reason to move the notifications out of the kernel. > > >> > > >> In terms of userspace applications, once a WMI interface to userspace > > >> is available libsmbios would change over to that. Applications using > > libsmbios would benefit. > > > > > > Really libsmbios matters here? Hans (added to thread) wrote that > > > libsmbios is a relic, something of ages long gone by and a normal user > > > should never use it. > > > > > > If this is truth and libsmbios should not be used, then we probably do > > > not need to care about it in changes for WMI. > > > > > > Hans, Mario, any comment/clarification about it? > > > > > >> > You mentioned WMI's efficiency compared to SMI/SMM, but is it a > > >> > difference significant enough for anyone to notice? > > >> > > >> At least for Dell there are optimizations being made when data is > > >> requested over the WMI-ACPI wrapper instead of directly via SMI/SMM. > > >> > > >> For example if the data is a "static" table or the request is to > > >> something that is passed thru to the EC it's a big waste of effort to put the > > CPU in SMM. > > >> > > >> The savings there is significant. > > > > > > Maybe we can use this Dell WMI-ACPI wrapper for kernel drivers instead > > > of current SMI/SMM direct access? > > > > > > > This would make sense to me. IIRC the only functional difference is the way > > that pointers are handled. It shouldn't be that hard to make it work for both > > variants, though. It could look like: > > > > buf = dell_smbios_alloc(...); > > dell_smbios_put_pointer(buf, offset of pointer, offset of pointee); > > dell_smbios_call(buf); > > > > or similar. > > Yes, I was going to encourage that kernel change after this WMI discussion > had some conclusions. Agreed on this point as well. -- Darren Hart VMware Open Source Technology Center