On Thu, Apr 13, 2017 at 03:40:08PM +0000, Mario.Limonciello@xxxxxxxx wrote: > > -----Original Message----- > > From: Andy Lutomirski [mailto:luto@xxxxxxxxxx] > > Sent: Thursday, April 13, 2017 10:35 AM > > To: Pali Rohár <pali.rohar@xxxxxxxxx> > > Cc: Limonciello, Mario <Mario_Limonciello@xxxxxxxx>; Hans de Goede > > <hdegoede@xxxxxxxxxx>; Michał Kępień <kernel@xxxxxxxxxx>; Darren Hart > > <dvhart@xxxxxxxxxxxxx>; Rafael J. Wysocki <rjw@xxxxxxxxxxxxx>; Len Brown > > <len.brown@xxxxxxxxx>; corentin.chary@xxxxxxxxx; Andrew Lutomirski > > <luto@xxxxxxxxxx>; Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>; > > linux-kernel@xxxxxxxxxxxxxxx; platform-driver-x86@xxxxxxxxxxxxxxx; linux- > > pm@xxxxxxxxxxxxxxx > > Subject: Re: RFC: WMI Enhancements > > > > On Thu, Apr 13, 2017 at 6:51 AM, Pali Rohár <pali.rohar@xxxxxxxxx> wrote: > > > On Thursday 13 April 2017 13:29:41 Mario.Limonciello@xxxxxxxx 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
