[alsa-devel] [PATCH 1/2] thinkpad-acpi: Try to use full software mute control

[Henrique de Moraes Holschuh]

On Thu, 16 Oct 2014, Andy Lutomirski wrote:
> > On IBM ThinkPads, the "generates KEY_foo" thing is controlable by the
> > driver.  In fact, thinkpad_acpi defaults to NOT send these, all breakage
> > is entirely the fault of userspace that enables it instead of doing OSD
> > out of the extra mixer, and then fails to deal with the side-effects.
> 
> Are you sure?  I'm reasonably confident that the KEY_MUTE comes from

Yes.

> i8042, not from an ACPI GPE.  Even without this patch, pressing the

The EC *is* the i8042 in a ThinkPad.  Really.  You talk to the same chip and
to the same firmware over the ACPI EC ports, the i8042 ports, and the
Renesas extra LPC3 channel (used by HDAPS and SBS).

That said, on a **IBM** ThinkPad, _nothing_ related to the digital volume
control comes from the i8042 port.  In fact, with older BIOSes, you couldn't
even get it from ACPI unless you hooked the GPE directly because the
required ACPI L/E methods were missing and were added by later versions of
the T4x/R4x/X3x BIOS.

The EC firmware in a thinkpad is often more capable than what the BIOS
exposes.

KEY_MUTE comes from the i8042 in Lenovo Thinkpads, only.  And they started
doing that when they removed the hardware volume control chip.  It was
retrofitted in later versions of the T60 BIOS (v2.x), I don't know how well
though.

> > On Lenovo ThinkPads, it depends on BIOS/EC version for the X60/T60.  Later
> > versions will behave like the X61/T61. Since family 200 you can tell the
> > EC to switch modes (latch, toggle, none), but Lenovo didn't test it well
> > enough.
> 
> "none" seems to work well on all ThinkPads that I've tried.  The other
> modes seem to have spotty support.

I am fine that we go with "none" and emulate everything in the driver where
supported, yes.

> >> This behavior is unfortunate, since modern userspace will also
> >> handle the hotkeys and change the other mixer.  If the software
> >
> > Like I said, we disable that by default, and userspace enables them back
> > because they want to use it as a keyboard.  We could override it entirely
> > on the IBM thinkpads, and refuse to issue any key events no matter what, I
> > suppose.
> 
> How?  The only way I ever found to do that was using the i8042_filter
> in the older incarnations of this driver, and that was incredibly

You didn't try it on a IBM thinkpad, just on Lenovo thinkpads, then...

> >> This should also allow us to remove _OSI(Linux) for all ThinkPads.
> >
> > No, it doesn't.  Only after an exaustive search for what _OSI(Linux)
> > changes across a brickload of thinkpad ACPI dumps could we say that for
> > sure.
> 
> I think we only need that for the four models in question.  Also, all
> the commit messages for those quirk additions seem to suggest that
> they were done to improve volume controls.  And I'm pretty sure I
> already checked at least one of those models (that's how I discovered
> HAUM/SAUM in the first place).
> 
> Anyway, patch 2 is optional.

Since you did due diligency, I'm fine with that.  It is already in a
separate patch, so it is easy to bissect and revert anyway.

> >> + * The EC or perhaps SMM firmware can optionally automatically change
> >> + * the volume in response to user input.  Unfortunately, this rarely
> >
> > It is the EC, which also emulates the i8042 KBC.
> >
> > I don't see any problems with the code, will have to test it in a IBM
> > thinkpad, though (I have one).
> 
> Please test v2 instead. :)

I will only be able to do that during the weekend anyway, so feel free to
send a v3 if you need :-)

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh