Re: RFC: WMI Enhancements

From	Pali Rohár <pali.rohar@gmail.com>
Newsgroups	linux.kernel
Subject	Re: RFC: WMI Enhancements
Date	2017-04-18 10:00 +0200
Message-ID	<txwdj-3uy-7@gated-at.bofh.it> (permalink)
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On Thursday 13 April 2017 17:39:56 Mario.Limonciello@dell.com wrote:
> > > No more than exists today with the dcdbas SMI interface (which
> > > only if you manually run userspace tools that manipulate the same
> > > data you can do that technically).
> > >
> > > We're all reasonable folks, if there is an instance of this that comes
> > > up we can make changes to userspace to fix it.
> > 
> > Right. As Pali pointed out previously, if there is an existing class driver /
> > subsystem which supports this functionality we should use that.
> > 
> > I suppose one risk will be one GUID exposing both types of methods. Those which
> > are used by kernel drivers, and those which have no kernel support. Or worse,
> > methods which have multiple behaviors depending on their input arguments.
> > 
> > --
> 
> Well the "most" interesting to me is the SMBIOS calling interface on the
> regular Dell GUID (WMBA IIRC).  That's what is used to manipulate keyboard
> LED timeouts in dell-laptop (although through direct SMI today).
> 
> It's also what is used for other SMBIOS calls like changing random BIOS settings
> that shouldn't be generically exposed in sysfs but should be controlled by
> manageability tools.
> 
> Example: turning on/off legacy option ROM or changing legacy boot order.

Which basically means that new WMI /dev/ files does not help for Dell.

Kernel needs to manipulate with SMBIOS for implementing rfkill, keyboard
backlight, display brightness and also needs to receive WMI events for
hotkeys. So kernel modules would lock WMI interface for receiving events
& sending SMBIOS calls, and userspace would be blocked from usage of
this WMI GUID.

I do not think that we can solve this problem easily in vendor-neutral
interface. There was argument that WMI API was designed to allow
userspace applications call firmware functions directly... But we are
using WMI in kernel and we should not allow both kernel and userspace to
fight on some WMI API.

So for Dell we need for sure some Dell specific interface which covers
all needed functionality. I'm not sure what everything Dell software
needs, so what about specifying current usage of Dell SMBIOS/WMI
functions from existing userspace applications and also planned usage in
future? Then from this information we can design kernel and userspace
API which can fit for Dell usage.

About other vendor WMI's functions... I'm not sure, but there is again
possibility that rfkill, leds or hotkeys would exists on same WMI GUID
as other maintenance functions (which userspace wants), so export would
be again blocked by kernel module for rfkill/leds/hotkeys.

Therefore I'm not really sure if some /dev/wmi* API would be usefull,
and not always blocked by kernel module which implements rfkill support.

-- 
Pali Rohár
pali.rohar@gmail.com

Thread

RFC: WMI Enhancements Darren Hart <dvhart@infradead.org> - 2017-04-13 01:10 +0200
  Re: RFC: WMI Enhancements Pali Rohár <pali.rohar@gmail.com> - 2017-04-13 09:40 +0200
    Re: RFC: WMI Enhancements Darren Hart <dvhart@infradead.org> - 2017-04-13 19:00 +0200
      RE: RFC: WMI Enhancements <Mario.Limonciello@dell.com> - 2017-04-13 22:40 +0200
        Re: RFC: WMI Enhancements Darren Hart <dvhart@infradead.org> - 2017-04-14 02:00 +0200
          RE: RFC: WMI Enhancements <Mario.Limonciello@dell.com> - 2017-04-14 19:50 +0200
            Re: RFC: WMI Enhancements Darren Hart <dvhart@infradead.org> - 2017-04-14 20:30 +0200
              RE: RFC: WMI Enhancements <Mario.Limonciello@dell.com> - 2017-04-14 21:10 +0200
  Re: RFC: WMI Enhancements Michał Kępień <kernel@kempniu.pl> - 2017-04-13 09:40 +0200
    RE: RFC: WMI Enhancements <Mario.Limonciello@dell.com> - 2017-04-13 15:50 +0200
      Re: RFC: WMI Enhancements Pali Rohár <pali.rohar@gmail.com> - 2017-04-13 16:00 +0200
        Re: RFC: WMI Enhancements Andy Lutomirski <luto@kernel.org> - 2017-04-13 17:40 +0200
          RE: RFC: WMI Enhancements <Mario.Limonciello@dell.com> - 2017-04-13 18:00 +0200
            Re: RFC: WMI Enhancements Darren Hart <dvhart@infradead.org> - 2017-04-13 18:10 +0200
        RE: RFC: WMI Enhancements <Mario.Limonciello@dell.com> - 2017-04-13 17:50 +0200
          Re: RFC: WMI Enhancements Andy Shevchenko <andriy.shevchenko@linux.intel.com> - 2017-04-18 12:00 +0200
            RE: RFC: WMI Enhancements <Mario.Limonciello@dell.com> - 2017-04-18 16:10 +0200
    Re: RFC: WMI Enhancements Andy Lutomirski <luto@kernel.org> - 2017-04-13 17:40 +0200
      Re: RFC: WMI Enhancements Andy Lutomirski <luto@kernel.org> - 2017-04-13 17:50 +0200
        Re: RFC: WMI Enhancements Darren Hart <dvhart@infradead.org> - 2017-04-13 18:20 +0200
      Re: RFC: WMI Enhancements Pali Rohár <pali.rohar@gmail.com> - 2017-04-13 17:50 +0200
      Re: RFC: WMI Enhancements Andy Lutomirski <luto@kernel.org> - 2017-04-13 18:00 +0200
        RE: RFC: WMI Enhancements <Mario.Limonciello@dell.com> - 2017-04-13 19:00 +0200
          Re: RFC: WMI Enhancements Darren Hart <dvhart@infradead.org> - 2017-04-13 19:10 +0200
            Re: RFC: WMI Enhancements Andy Lutomirski <luto@kernel.org> - 2017-04-13 19:50 +0200
              RE: RFC: WMI Enhancements <Mario.Limonciello@dell.com> - 2017-04-13 20:00 +0200
            RE: RFC: WMI Enhancements <Mario.Limonciello@dell.com> - 2017-04-13 19:50 +0200
              Re: RFC: WMI Enhancements Pali Rohár <pali.rohar@gmail.com> - 2017-04-18 10:00 +0200
                Re: RFC: WMI Enhancements Darren Hart <dvhart@infradead.org> - 2017-04-18 19:00 +0200
                Re: RFC: WMI Enhancements Pali Rohár <pali.rohar@gmail.com> - 2017-04-18 21:30 +0200
      RE: RFC: WMI Enhancements <Mario.Limonciello@dell.com> - 2017-04-13 18:00 +0200
        Re: RFC: WMI Enhancements Darren Hart <dvhart@infradead.org> - 2017-04-13 19:10 +0200
          Re: RFC: WMI Enhancements Andy Lutomirski <luto@kernel.org> - 2017-04-13 19:40 +0200
            RE: RFC: WMI Enhancements <Mario.Limonciello@dell.com> - 2017-04-13 19:50 +0200
      Re: RFC: WMI Enhancements Darren Hart <dvhart@infradead.org> - 2017-04-13 18:10 +0200
  Re: RFC: WMI Enhancements "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-04-15 01:00 +0200
    Re: RFC: WMI Enhancements Darren Hart <dvhart@infradead.org> - 2017-04-15 01:10 +0200
      Re: RFC: WMI Enhancements Andy Lutomirski <luto@amacapital.net> - 2017-04-18 00:10 +0200
        Re: RFC: WMI Enhancements Darren Hart <dvhart@infradead.org> - 2017-04-18 01:20 +0200
          Re: RFC: WMI Enhancements "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-04-18 15:20 +0200
            Re: RFC: WMI Enhancements Darren Hart <dvhart@infradead.org> - 2017-04-18 18:40 +0200
              Re: RFC: WMI Enhancements Pali Rohár <pali.rohar@gmail.com> - 2017-04-18 21:30 +0200
                Re: RFC: WMI Enhancements Darren Hart <dvhart@infradead.org> - 2017-04-19 00:50 +0200
                Re: RFC: WMI Enhancements Pali Rohár <pali.rohar@gmail.com> - 2017-04-19 10:00 +0200
                RE: RFC: WMI Enhancements <Mario.Limonciello@dell.com> - 2017-04-19 18:40 +0200
                Re: RFC: WMI Enhancements Pali Rohár <pali.rohar@gmail.com> - 2017-04-19 19:00 +0200
                RE: RFC: WMI Enhancements <Mario.Limonciello@dell.com> - 2017-04-19 19:30 +0200
                Re: RFC: WMI Enhancements Pali Rohár <pali.rohar@gmail.com> - 2017-04-20 15:20 +0200
                Re: RFC: WMI Enhancements Darren Hart <dvhart@infradead.org> - 2017-04-20 22:50 +0200
                Re: RFC: WMI Enhancements Christoph Hellwig <hch@infradead.org> - 2017-04-20 16:20 +0200
              Re: RFC: WMI Enhancements "Rafael J. Wysocki" <rafael@kernel.org> - 2017-04-18 23:20 +0200

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