RE: RFC: WMI Enhancements

[<Mario.Limonciello@dell.com>]

> -----Original Message-----
> From: Pali Rohár [mailto:pali.rohar@gmail.com]
> Sent: Thursday, April 13, 2017 8:51 AM
> To: Limonciello, Mario <Mario_Limonciello@Dell.com>; Hans de Goede
> <hdegoede@redhat.com>
> Cc: kernel@kempniu.pl; dvhart@infradead.org; rjw@rjwysocki.net;
> len.brown@intel.com; corentin.chary@gmail.com; luto@kernel.org;
> 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
> 
> 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.
> 	

A normal user shouldn't be using it directly, but libsmbios is used by a few open 
source tools as a dependency.  It's also used in many Dell manageability tools.

> 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?
> 
> --
> Pali Rohár
> pali.rohar@gmail.com