Re: Dell Vostro V131 hotkeys revisited

From: "Pali Rohár" <pali.rohar@gmail.com>
To: "Michał Kępień" <kernel@kempniu.pl>
Cc: Matthew Garrett <mjg@redhat.com>,
	Rezwanul Kabir <Rezwanul_Kabir@dell.com>,
	Alex Hung <alex.hung@canonical.com>,
	Darren Hart <dvhart@infradead.org>,
	platform-driver-x86@vger.kernel.org
Subject: Re: Dell Vostro V131 hotkeys revisited
Date: Wed, 1 Jul 2015 12:55:44 +0200	[thread overview]
Message-ID: <20150701105544.GD17577@pali> (raw)
In-Reply-To: <20150701101146.GA3421@eudyptula.hq.kempniu.pl>

On Wednesday 01 July 2015 12:11:46 Michał Kępień wrote:
> > Ok, I do not know all these windows internals, but it would be cool to
> > check if WMI event is really received with correct mask in that NEVT
> > method. No idea if this is possible to debug/test on windows...
> 
> That was my first idea after analyzing the NEVT method, but after
> skimming through the AMLI Debugger and KD docs, I got the impression
> that setting up an ACPI debugging session in Windows is so much of a
> hassle [1] for someone with no experience in Windows kernel-mode
> debugging that I'd rather hack the hell out of the DSDT in Linux and get
> on with my life.
> 
> > > Well, here's the catch: there is no PNP0C09 device in the DSDT and thus
> > > the EC driver isn't even loaded in Linux and I can't dump EC registers.
> > > Yet Windows tools seem to be able to do it, using ports 0x66/0x62. I'm
> > > confused.
> > > 
> > 
> > Hm... could be this reason? And windows read pressed hotkeys from EC
> > registers?
> > 
> > Can you ask acpi guys what could *not* work if acpi ec driver is not
> > loaded?
> 
> Maybe I am missing something here, but even if the above turns out to be
> the case, how would such knowledge help in solving the issue? Suppose we
> learn that some magic command needs to be sent to the EC to enable event
> reporting via WMI, but we cannot do that as the kernel doesn't even see
> the EC.
> 

It would mean that we need to write new driver for it (or extend some).

> If I'm reading the DSDT dump correctly, it seems the Vostro V131 makes
> heavy use of SMIs. \SB.SMII is an alias for the 0xB2 I/O port, which is
> written to by the WMI and SXX6 methods. A call to the latter is made
> inside ECG1 (from SX11, specifically). IOW, an SMI is generated to get
> the event code. My guess would be that some magic SMI has to be
> generated if events are to be reported via WMI or something among the
> lines. Which gets us back to hearing from Dell as trying random values
> doesn't sound like a sane thing to do.
> 

Yes, I'm still thinking about some missing init call. And for that we
need documentation: what and how.

> [1] Another Windows machine is needed, debugging over a network cable is
> only supported since Windows 8, the Vostro V131 doesn't have any
> Firewire or serial ports, so I'd need to buy a USB debug cable, then get
> get my hands on a checked version of Acpi.sys and pray it all works. Now
> compare all that to recompiling the kernel with
> CONFIG_ACPI_CUSTOM_METHOD and CONFIG_ACPI_DEBUG enabled.
> 

I know, debugging windows kernel is hard and only sometimes is possible.

-- 
Pali Rohár
pali.rohar@gmail.com